Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 6494 insertions, 0 deletions

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
new file mode 100644
index 000000000..7471d85f5
--- /dev/null
+++ b/kernel/locking/lockdep.c
@@ -0,0 +1,6494 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * kernel/lockdep.c
+ *
+ * Runtime locking correctness validator
+ *
+ * Started by Ingo Molnar:
+ *
+ *  Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
+ *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
+ *
+ * this code maps all the lock dependencies as they occur in a live kernel
+ * and will warn about the following classes of locking bugs:
+ *
+ * - lock inversion scenarios
+ * - circular lock dependencies
+ * - hardirq/softirq safe/unsafe locking bugs
+ *
+ * Bugs are reported even if the current locking scenario does not cause
+ * any deadlock at this point.
+ *
+ * I.e. if anytime in the past two locks were taken in a different order,
+ * even if it happened for another task, even if those were different
+ * locks (but of the same class as this lock), this code will detect it.
+ *
+ * Thanks to Arjan van de Ven for coming up with the initial idea of
+ * mapping lock dependencies runtime.
+ */
+#define DISABLE_BRANCH_PROFILING
+#include <linux/mutex.h>
+#include <linux/sched.h>
+#include <linux/sched/clock.h>
+#include <linux/sched/task.h>
+#include <linux/sched/mm.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/spinlock.h>
+#include <linux/kallsyms.h>
+#include <linux/interrupt.h>
+#include <linux/stacktrace.h>
+#include <linux/debug_locks.h>
+#include <linux/irqflags.h>
+#include <linux/utsname.h>
+#include <linux/hash.h>
+#include <linux/ftrace.h>
+#include <linux/stringify.h>
+#include <linux/bitmap.h>
+#include <linux/bitops.h>
+#include <linux/gfp.h>
+#include <linux/random.h>
+#include <linux/jhash.h>
+#include <linux/nmi.h>
+#include <linux/rcupdate.h>
+#include <linux/kprobes.h>
+
+#include <asm/sections.h>
+
+#include "lockdep_internals.h"
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/lock.h>
+
+#ifdef CONFIG_PROVE_LOCKING
+int prove_locking = 1;
+module_param(prove_locking, int, 0644);
+#else
+#define prove_locking 0
+#endif
+
+#ifdef CONFIG_LOCK_STAT
+int lock_stat = 1;
+module_param(lock_stat, int, 0644);
+#else
+#define lock_stat 0
+#endif
+
+DEFINE_PER_CPU(unsigned int, lockdep_recursion);
+EXPORT_PER_CPU_SYMBOL_GPL(lockdep_recursion);
+
+static __always_inline bool lockdep_enabled(void)
+{
+	if (!debug_locks)
+		return false;
+
+	if (this_cpu_read(lockdep_recursion))
+		return false;
+
+	if (current->lockdep_recursion)
+		return false;
+
+	return true;
+}
+
+/*
+ * lockdep_lock: protects the lockdep graph, the hashes and the
+ *               class/list/hash allocators.
+ *
+ * This is one of the rare exceptions where it's justified
+ * to use a raw spinlock - we really dont want the spinlock
+ * code to recurse back into the lockdep code...
+ */
+static arch_spinlock_t __lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
+static struct task_struct *__owner;
+
+static inline void lockdep_lock(void)
+{
+	DEBUG_LOCKS_WARN_ON(!irqs_disabled());
+
+	__this_cpu_inc(lockdep_recursion);
+	arch_spin_lock(&__lock);
+	__owner = current;
+}
+
+static inline void lockdep_unlock(void)
+{
+	DEBUG_LOCKS_WARN_ON(!irqs_disabled());
+
+	if (debug_locks && DEBUG_LOCKS_WARN_ON(__owner != current))
+		return;
+
+	__owner = NULL;
+	arch_spin_unlock(&__lock);
+	__this_cpu_dec(lockdep_recursion);
+}
+
+static inline bool lockdep_assert_locked(void)
+{
+	return DEBUG_LOCKS_WARN_ON(__owner != current);
+}
+
+static struct task_struct *lockdep_selftest_task_struct;
+
+
+static int graph_lock(void)
+{
+	lockdep_lock();
+	/*
+	 * Make sure that if another CPU detected a bug while
+	 * walking the graph we dont change it (while the other
+	 * CPU is busy printing out stuff with the graph lock
+	 * dropped already)
+	 */
+	if (!debug_locks) {
+		lockdep_unlock();
+		return 0;
+	}
+	return 1;
+}
+
+static inline void graph_unlock(void)
+{
+	lockdep_unlock();
+}
+
+/*
+ * Turn lock debugging off and return with 0 if it was off already,
+ * and also release the graph lock:
+ */
+static inline int debug_locks_off_graph_unlock(void)
+{
+	int ret = debug_locks_off();
+
+	lockdep_unlock();
+
+	return ret;
+}
+
+unsigned long nr_list_entries;
+static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
+static DECLARE_BITMAP(list_entries_in_use, MAX_LOCKDEP_ENTRIES);
+
+/*
+ * All data structures here are protected by the global debug_lock.
+ *
+ * nr_lock_classes is the number of elements of lock_classes[] that is
+ * in use.
+ */
+#define KEYHASH_BITS		(MAX_LOCKDEP_KEYS_BITS - 1)
+#define KEYHASH_SIZE		(1UL << KEYHASH_BITS)
+static struct hlist_head lock_keys_hash[KEYHASH_SIZE];
+unsigned long nr_lock_classes;
+unsigned long nr_zapped_classes;
+unsigned long max_lock_class_idx;
+struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
+DECLARE_BITMAP(lock_classes_in_use, MAX_LOCKDEP_KEYS);
+
+static inline struct lock_class *hlock_class(struct held_lock *hlock)
+{
+	unsigned int class_idx = hlock->class_idx;
+
+	/* Don't re-read hlock->class_idx, can't use READ_ONCE() on bitfield */
+	barrier();
+
+	if (!test_bit(class_idx, lock_classes_in_use)) {
+		/*
+		 * Someone passed in garbage, we give up.
+		 */
+		DEBUG_LOCKS_WARN_ON(1);
+		return NULL;
+	}
+
+	/*
+	 * At this point, if the passed hlock->class_idx is still garbage,
+	 * we just have to live with it
+	 */
+	return lock_classes + class_idx;
+}
+
+#ifdef CONFIG_LOCK_STAT
+static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], cpu_lock_stats);
+
+static inline u64 lockstat_clock(void)
+{
+	return local_clock();
+}
+
+static int lock_point(unsigned long points[], unsigned long ip)
+{
+	int i;
+
+	for (i = 0; i < LOCKSTAT_POINTS; i++) {
+		if (points[i] == 0) {
+			points[i] = ip;
+			break;
+		}
+		if (points[i] == ip)
+			break;
+	}
+
+	return i;
+}
+
+static void lock_time_inc(struct lock_time *lt, u64 time)
+{
+	if (time > lt->max)
+		lt->max = time;
+
+	if (time < lt->min || !lt->nr)
+		lt->min = time;
+
+	lt->total += time;
+	lt->nr++;
+}
+
+static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
+{
+	if (!src->nr)
+		return;
+
+	if (src->max > dst->max)
+		dst->max = src->max;
+
+	if (src->min < dst->min || !dst->nr)
+		dst->min = src->min;
+
+	dst->total += src->total;
+	dst->nr += src->nr;
+}
+
+struct lock_class_stats lock_stats(struct lock_class *class)
+{
+	struct lock_class_stats stats;
+	int cpu, i;
+
+	memset(&stats, 0, sizeof(struct lock_class_stats));
+	for_each_possible_cpu(cpu) {
+		struct lock_class_stats *pcs =
+			&per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
+
+		for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
+			stats.contention_point[i] += pcs->contention_point[i];
+
+		for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
+			stats.contending_point[i] += pcs->contending_point[i];
+
+		lock_time_add(&pcs->read_waittime, &stats.read_waittime);
+		lock_time_add(&pcs->write_waittime, &stats.write_waittime);
+
+		lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
+		lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
+
+		for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
+			stats.bounces[i] += pcs->bounces[i];
+	}
+
+	return stats;
+}
+
+void clear_lock_stats(struct lock_class *class)
+{
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		struct lock_class_stats *cpu_stats =
+			&per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
+
+		memset(cpu_stats, 0, sizeof(struct lock_class_stats));
+	}
+	memset(class->contention_point, 0, sizeof(class->contention_point));
+	memset(class->contending_point, 0, sizeof(class->contending_point));
+}
+
+static struct lock_class_stats *get_lock_stats(struct lock_class *class)
+{
+	return &this_cpu_ptr(cpu_lock_stats)[class - lock_classes];
+}
+
+static void lock_release_holdtime(struct held_lock *hlock)
+{
+	struct lock_class_stats *stats;
+	u64 holdtime;
+
+	if (!lock_stat)
+		return;
+
+	holdtime = lockstat_clock() - hlock->holdtime_stamp;
+
+	stats = get_lock_stats(hlock_class(hlock));
+	if (hlock->read)
+		lock_time_inc(&stats->read_holdtime, holdtime);
+	else
+		lock_time_inc(&stats->write_holdtime, holdtime);
+}
+#else
+static inline void lock_release_holdtime(struct held_lock *hlock)
+{
+}
+#endif
+
+/*
+ * We keep a global list of all lock classes. The list is only accessed with
+ * the lockdep spinlock lock held. free_lock_classes is a list with free
+ * elements. These elements are linked together by the lock_entry member in
+ * struct lock_class.
+ */
+static LIST_HEAD(all_lock_classes);
+static LIST_HEAD(free_lock_classes);
+
+/**
+ * struct pending_free - information about data structures about to be freed
+ * @zapped: Head of a list with struct lock_class elements.
+ * @lock_chains_being_freed: Bitmap that indicates which lock_chains[] elements
+ *	are about to be freed.
+ */
+struct pending_free {
+	struct list_head zapped;
+	DECLARE_BITMAP(lock_chains_being_freed, MAX_LOCKDEP_CHAINS);
+};
+
+/**
+ * struct delayed_free - data structures used for delayed freeing
+ *
+ * A data structure for delayed freeing of data structures that may be
+ * accessed by RCU readers at the time these were freed.
+ *
+ * @rcu_head:  Used to schedule an RCU callback for freeing data structures.
+ * @index:     Index of @pf to which freed data structures are added.
+ * @scheduled: Whether or not an RCU callback has been scheduled.
+ * @pf:        Array with information about data structures about to be freed.
+ */
+static struct delayed_free {
+	struct rcu_head		rcu_head;
+	int			index;
+	int			scheduled;
+	struct pending_free	pf[2];
+} delayed_free;
+
+/*
+ * The lockdep classes are in a hash-table as well, for fast lookup:
+ */
+#define CLASSHASH_BITS		(MAX_LOCKDEP_KEYS_BITS - 1)
+#define CLASSHASH_SIZE		(1UL << CLASSHASH_BITS)
+#define __classhashfn(key)	hash_long((unsigned long)key, CLASSHASH_BITS)
+#define classhashentry(key)	(classhash_table + __classhashfn((key)))
+
+static struct hlist_head classhash_table[CLASSHASH_SIZE];
+
+/*
+ * We put the lock dependency chains into a hash-table as well, to cache
+ * their existence:
+ */
+#define CHAINHASH_BITS		(MAX_LOCKDEP_CHAINS_BITS-1)
+#define CHAINHASH_SIZE		(1UL << CHAINHASH_BITS)
+#define __chainhashfn(chain)	hash_long(chain, CHAINHASH_BITS)
+#define chainhashentry(chain)	(chainhash_table + __chainhashfn((chain)))
+
+static struct hlist_head chainhash_table[CHAINHASH_SIZE];
+
+/*
+ * the id of held_lock
+ */
+static inline u16 hlock_id(struct held_lock *hlock)
+{
+	BUILD_BUG_ON(MAX_LOCKDEP_KEYS_BITS + 2 > 16);
+
+	return (hlock->class_idx | (hlock->read << MAX_LOCKDEP_KEYS_BITS));
+}
+
+static inline unsigned int chain_hlock_class_idx(u16 hlock_id)
+{
+	return hlock_id & (MAX_LOCKDEP_KEYS - 1);
+}
+
+/*
+ * The hash key of the lock dependency chains is a hash itself too:
+ * it's a hash of all locks taken up to that lock, including that lock.
+ * It's a 64-bit hash, because it's important for the keys to be
+ * unique.
+ */
+static inline u64 iterate_chain_key(u64 key, u32 idx)
+{
+	u32 k0 = key, k1 = key >> 32;
+
+	__jhash_mix(idx, k0, k1); /* Macro that modifies arguments! */
+
+	return k0 | (u64)k1 << 32;
+}
+
+void lockdep_init_task(struct task_struct *task)
+{
+	task->lockdep_depth = 0; /* no locks held yet */
+	task->curr_chain_key = INITIAL_CHAIN_KEY;
+	task->lockdep_recursion = 0;
+}
+
+static __always_inline void lockdep_recursion_inc(void)
+{
+	__this_cpu_inc(lockdep_recursion);
+}
+
+static __always_inline void lockdep_recursion_finish(void)
+{
+	if (WARN_ON_ONCE(__this_cpu_dec_return(lockdep_recursion)))
+		__this_cpu_write(lockdep_recursion, 0);
+}
+
+void lockdep_set_selftest_task(struct task_struct *task)
+{
+	lockdep_selftest_task_struct = task;
+}
+
+/*
+ * Debugging switches:
+ */
+
+#define VERBOSE			0
+#define VERY_VERBOSE		0
+
+#if VERBOSE
+# define HARDIRQ_VERBOSE	1
+# define SOFTIRQ_VERBOSE	1
+#else
+# define HARDIRQ_VERBOSE	0
+# define SOFTIRQ_VERBOSE	0
+#endif
+
+#if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE
+/*
+ * Quick filtering for interesting events:
+ */
+static int class_filter(struct lock_class *class)
+{
+#if 0
+	/* Example */
+	if (class->name_version == 1 &&
+			!strcmp(class->name, "lockname"))
+		return 1;
+	if (class->name_version == 1 &&
+			!strcmp(class->name, "&struct->lockfield"))
+		return 1;
+#endif
+	/* Filter everything else. 1 would be to allow everything else */
+	return 0;
+}
+#endif
+
+static int verbose(struct lock_class *class)
+{
+#if VERBOSE
+	return class_filter(class);
+#endif
+	return 0;
+}
+
+static void print_lockdep_off(const char *bug_msg)
+{
+	printk(KERN_DEBUG "%s\n", bug_msg);
+	printk(KERN_DEBUG "turning off the locking correctness validator.\n");
+#ifdef CONFIG_LOCK_STAT
+	printk(KERN_DEBUG "Please attach the output of /proc/lock_stat to the bug report\n");
+#endif
+}
+
+unsigned long nr_stack_trace_entries;
+
+#ifdef CONFIG_PROVE_LOCKING
+/**
+ * struct lock_trace - single stack backtrace
+ * @hash_entry:	Entry in a stack_trace_hash[] list.
+ * @hash:	jhash() of @entries.
+ * @nr_entries:	Number of entries in @entries.
+ * @entries:	Actual stack backtrace.
+ */
+struct lock_trace {
+	struct hlist_node	hash_entry;
+	u32			hash;
+	u32			nr_entries;
+	unsigned long		entries[] __aligned(sizeof(unsigned long));
+};
+#define LOCK_TRACE_SIZE_IN_LONGS				\
+	(sizeof(struct lock_trace) / sizeof(unsigned long))
+/*
+ * Stack-trace: sequence of lock_trace structures. Protected by the graph_lock.
+ */
+static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
+static struct hlist_head stack_trace_hash[STACK_TRACE_HASH_SIZE];
+
+static bool traces_identical(struct lock_trace *t1, struct lock_trace *t2)
+{
+	return t1->hash == t2->hash && t1->nr_entries == t2->nr_entries &&
+		memcmp(t1->entries, t2->entries,
+		       t1->nr_entries * sizeof(t1->entries[0])) == 0;
+}
+
+static struct lock_trace *save_trace(void)
+{
+	struct lock_trace *trace, *t2;
+	struct hlist_head *hash_head;
+	u32 hash;
+	int max_entries;
+
+	BUILD_BUG_ON_NOT_POWER_OF_2(STACK_TRACE_HASH_SIZE);
+	BUILD_BUG_ON(LOCK_TRACE_SIZE_IN_LONGS >= MAX_STACK_TRACE_ENTRIES);
+
+	trace = (struct lock_trace *)(stack_trace + nr_stack_trace_entries);
+	max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries -
+		LOCK_TRACE_SIZE_IN_LONGS;
+
+	if (max_entries <= 0) {
+		if (!debug_locks_off_graph_unlock())
+			return NULL;
+
+		print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!");
+		dump_stack();
+
+		return NULL;
+	}
+	trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3);
+
+	hash = jhash(trace->entries, trace->nr_entries *
+		     sizeof(trace->entries[0]), 0);
+	trace->hash = hash;
+	hash_head = stack_trace_hash + (hash & (STACK_TRACE_HASH_SIZE - 1));
+	hlist_for_each_entry(t2, hash_head, hash_entry) {
+		if (traces_identical(trace, t2))
+			return t2;
+	}
+	nr_stack_trace_entries += LOCK_TRACE_SIZE_IN_LONGS + trace->nr_entries;
+	hlist_add_head(&trace->hash_entry, hash_head);
+
+	return trace;
+}
+
+/* Return the number of stack traces in the stack_trace[] array. */
+u64 lockdep_stack_trace_count(void)
+{
+	struct lock_trace *trace;
+	u64 c = 0;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++) {
+		hlist_for_each_entry(trace, &stack_trace_hash[i], hash_entry) {
+			c++;
+		}
+	}
+
+	return c;
+}
+
+/* Return the number of stack hash chains that have at least one stack trace. */
+u64 lockdep_stack_hash_count(void)
+{
+	u64 c = 0;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++)
+		if (!hlist_empty(&stack_trace_hash[i]))
+			c++;
+
+	return c;
+}
+#endif
+
+unsigned int nr_hardirq_chains;
+unsigned int nr_softirq_chains;
+unsigned int nr_process_chains;
+unsigned int max_lockdep_depth;
+
+#ifdef CONFIG_DEBUG_LOCKDEP
+/*
+ * Various lockdep statistics:
+ */
+DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
+#endif
+
+#ifdef CONFIG_PROVE_LOCKING
+/*
+ * Locking printouts:
+ */
+
+#define __USAGE(__STATE)						\
+	[LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W",	\
+	[LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W",		\
+	[LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
+	[LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
+
+static const char *usage_str[] =
+{
+#define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
+#include "lockdep_states.h"
+#undef LOCKDEP_STATE
+	[LOCK_USED] = "INITIAL USE",
+	[LOCK_USED_READ] = "INITIAL READ USE",
+	/* abused as string storage for verify_lock_unused() */
+	[LOCK_USAGE_STATES] = "IN-NMI",
+};
+#endif
+
+const char *__get_key_name(const struct lockdep_subclass_key *key, char *str)
+{
+	return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
+}
+
+static inline unsigned long lock_flag(enum lock_usage_bit bit)
+{
+	return 1UL << bit;
+}
+
+static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
+{
+	/*
+	 * The usage character defaults to '.' (i.e., irqs disabled and not in
+	 * irq context), which is the safest usage category.
+	 */
+	char c = '.';
+
+	/*
+	 * The order of the following usage checks matters, which will
+	 * result in the outcome character as follows:
+	 *
+	 * - '+': irq is enabled and not in irq context
+	 * - '-': in irq context and irq is disabled
+	 * - '?': in irq context and irq is enabled
+	 */
+	if (class->usage_mask & lock_flag(bit + LOCK_USAGE_DIR_MASK)) {
+		c = '+';
+		if (class->usage_mask & lock_flag(bit))
+			c = '?';
+	} else if (class->usage_mask & lock_flag(bit))
+		c = '-';
+
+	return c;
+}
+
+void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
+{
+	int i = 0;
+
+#define LOCKDEP_STATE(__STATE) 						\
+	usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE);	\
+	usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
+#include "lockdep_states.h"
+#undef LOCKDEP_STATE
+
+	usage[i] = '\0';
+}
+
+static void __print_lock_name(struct lock_class *class)
+{
+	char str[KSYM_NAME_LEN];
+	const char *name;
+
+	name = class->name;
+	if (!name) {
+		name = __get_key_name(class->key, str);
+		printk(KERN_CONT "%s", name);
+	} else {
+		printk(KERN_CONT "%s", name);
+		if (class->name_version > 1)
+			printk(KERN_CONT "#%d", class->name_version);
+		if (class->subclass)
+			printk(KERN_CONT "/%d", class->subclass);
+	}
+}
+
+static void print_lock_name(struct lock_class *class)
+{
+	char usage[LOCK_USAGE_CHARS];
+
+	get_usage_chars(class, usage);
+
+	printk(KERN_CONT " (");
+	__print_lock_name(class);
+	printk(KERN_CONT "){%s}-{%d:%d}", usage,
+			class->wait_type_outer ?: class->wait_type_inner,
+			class->wait_type_inner);
+}
+
+static void print_lockdep_cache(struct lockdep_map *lock)
+{
+	const char *name;
+	char str[KSYM_NAME_LEN];
+
+	name = lock->name;
+	if (!name)
+		name = __get_key_name(lock->key->subkeys, str);
+
+	printk(KERN_CONT "%s", name);
+}
+
+static void print_lock(struct held_lock *hlock)
+{
+	/*
+	 * We can be called locklessly through debug_show_all_locks() so be
+	 * extra careful, the hlock might have been released and cleared.
+	 *
+	 * If this indeed happens, lets pretend it does not hurt to continue
+	 * to print the lock unless the hlock class_idx does not point to a
+	 * registered class. The rationale here is: since we don't attempt
+	 * to distinguish whether we are in this situation, if it just
+	 * happened we can't count on class_idx to tell either.
+	 */
+	struct lock_class *lock = hlock_class(hlock);
+
+	if (!lock) {
+		printk(KERN_CONT "<RELEASED>\n");
+		return;
+	}
+
+	printk(KERN_CONT "%px", hlock->instance);
+	print_lock_name(lock);
+	printk(KERN_CONT ", at: %pS\n", (void *)hlock->acquire_ip);
+}
+
+static void lockdep_print_held_locks(struct task_struct *p)
+{
+	int i, depth = READ_ONCE(p->lockdep_depth);
+
+	if (!depth)
+		printk("no locks held by %s/%d.\n", p->comm, task_pid_nr(p));
+	else
+		printk("%d lock%s held by %s/%d:\n", depth,
+		       depth > 1 ? "s" : "", p->comm, task_pid_nr(p));
+	/*
+	 * It's not reliable to print a task's held locks if it's not sleeping
+	 * and it's not the current task.
+	 */
+	if (p->state == TASK_RUNNING && p != current)
+		return;
+	for (i = 0; i < depth; i++) {
+		printk(" #%d: ", i);
+		print_lock(p->held_locks + i);
+	}
+}
+
+static void print_kernel_ident(void)
+{
+	printk("%s %.*s %s\n", init_utsname()->release,
+		(int)strcspn(init_utsname()->version, " "),
+		init_utsname()->version,
+		print_tainted());
+}
+
+static int very_verbose(struct lock_class *class)
+{
+#if VERY_VERBOSE
+	return class_filter(class);
+#endif
+	return 0;
+}
+
+/*
+ * Is this the address of a static object:
+ */
+#ifdef __KERNEL__
+static int static_obj(const void *obj)
+{
+	unsigned long start = (unsigned long) &_stext,
+		      end   = (unsigned long) &_end,
+		      addr  = (unsigned long) obj;
+
+	if (arch_is_kernel_initmem_freed(addr))
+		return 0;
+
+	/*
+	 * static variable?
+	 */
+	if ((addr >= start) && (addr < end))
+		return 1;
+
+	if (arch_is_kernel_data(addr))
+		return 1;
+
+	/*
+	 * in-kernel percpu var?
+	 */
+	if (is_kernel_percpu_address(addr))
+		return 1;
+
+	/*
+	 * module static or percpu var?
+	 */
+	return is_module_address(addr) || is_module_percpu_address(addr);
+}
+#endif
+
+/*
+ * To make lock name printouts unique, we calculate a unique
+ * class->name_version generation counter. The caller must hold the graph
+ * lock.
+ */
+static int count_matching_names(struct lock_class *new_class)
+{
+	struct lock_class *class;
+	int count = 0;
+
+	if (!new_class->name)
+		return 0;
+
+	list_for_each_entry(class, &all_lock_classes, lock_entry) {
+		if (new_class->key - new_class->subclass == class->key)
+			return class->name_version;
+		if (class->name && !strcmp(class->name, new_class->name))
+			count = max(count, class->name_version);
+	}
+
+	return count + 1;
+}
+
+/* used from NMI context -- must be lockless */
+static noinstr struct lock_class *
+look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass)
+{
+	struct lockdep_subclass_key *key;
+	struct hlist_head *hash_head;
+	struct lock_class *class;
+
+	if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
+		instrumentation_begin();
+		debug_locks_off();
+		printk(KERN_ERR
+			"BUG: looking up invalid subclass: %u\n", subclass);
+		printk(KERN_ERR
+			"turning off the locking correctness validator.\n");
+		dump_stack();
+		instrumentation_end();
+		return NULL;
+	}
+
+	/*
+	 * If it is not initialised then it has never been locked,
+	 * so it won't be present in the hash table.
+	 */
+	if (unlikely(!lock->key))
+		return NULL;
+
+	/*
+	 * NOTE: the class-key must be unique. For dynamic locks, a static
+	 * lock_class_key variable is passed in through the mutex_init()
+	 * (or spin_lock_init()) call - which acts as the key. For static
+	 * locks we use the lock object itself as the key.
+	 */
+	BUILD_BUG_ON(sizeof(struct lock_class_key) >
+			sizeof(struct lockdep_map));
+
+	key = lock->key->subkeys + subclass;
+
+	hash_head = classhashentry(key);
+
+	/*
+	 * We do an RCU walk of the hash, see lockdep_free_key_range().
+	 */
+	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
+		return NULL;
+
+	hlist_for_each_entry_rcu_notrace(class, hash_head, hash_entry) {
+		if (class->key == key) {
+			/*
+			 * Huh! same key, different name? Did someone trample
+			 * on some memory? We're most confused.
+			 */
+			WARN_ON_ONCE(class->name != lock->name &&
+				     lock->key != &__lockdep_no_validate__);
+			return class;
+		}
+	}
+
+	return NULL;
+}
+
+/*
+ * Static locks do not have their class-keys yet - for them the key is
+ * the lock object itself. If the lock is in the per cpu area, the
+ * canonical address of the lock (per cpu offset removed) is used.
+ */
+static bool assign_lock_key(struct lockdep_map *lock)
+{
+	unsigned long can_addr, addr = (unsigned long)lock;
+
+#ifdef __KERNEL__
+	/*
+	 * lockdep_free_key_range() assumes that struct lock_class_key
+	 * objects do not overlap. Since we use the address of lock
+	 * objects as class key for static objects, check whether the
+	 * size of lock_class_key objects does not exceed the size of
+	 * the smallest lock object.
+	 */
+	BUILD_BUG_ON(sizeof(struct lock_class_key) > sizeof(raw_spinlock_t));
+#endif
+
+	if (__is_kernel_percpu_address(addr, &can_addr))
+		lock->key = (void *)can_addr;
+	else if (__is_module_percpu_address(addr, &can_addr))
+		lock->key = (void *)can_addr;
+	else if (static_obj(lock))
+		lock->key = (void *)lock;
+	else {
+		/* Debug-check: all keys must be persistent! */
+		debug_locks_off();
+		pr_err("INFO: trying to register non-static key.\n");
+		pr_err("The code is fine but needs lockdep annotation, or maybe\n");
+		pr_err("you didn't initialize this object before use?\n");
+		pr_err("turning off the locking correctness validator.\n");
+		dump_stack();
+		return false;
+	}
+
+	return true;
+}
+
+#ifdef CONFIG_DEBUG_LOCKDEP
+
+/* Check whether element @e occurs in list @h */
+static bool in_list(struct list_head *e, struct list_head *h)
+{
+	struct list_head *f;
+
+	list_for_each(f, h) {
+		if (e == f)
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ * Check whether entry @e occurs in any of the locks_after or locks_before
+ * lists.
+ */
+static bool in_any_class_list(struct list_head *e)
+{
+	struct lock_class *class;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
+		class = &lock_classes[i];
+		if (in_list(e, &class->locks_after) ||
+		    in_list(e, &class->locks_before))
+			return true;
+	}
+	return false;
+}
+
+static bool class_lock_list_valid(struct lock_class *c, struct list_head *h)
+{
+	struct lock_list *e;
+
+	list_for_each_entry(e, h, entry) {
+		if (e->links_to != c) {
+			printk(KERN_INFO "class %s: mismatch for lock entry %ld; class %s <> %s",
+			       c->name ? : "(?)",
+			       (unsigned long)(e - list_entries),
+			       e->links_to && e->links_to->name ?
+			       e->links_to->name : "(?)",
+			       e->class && e->class->name ? e->class->name :
+			       "(?)");
+			return false;
+		}
+	}
+	return true;
+}
+
+#ifdef CONFIG_PROVE_LOCKING
+static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
+#endif
+
+static bool check_lock_chain_key(struct lock_chain *chain)
+{
+#ifdef CONFIG_PROVE_LOCKING
+	u64 chain_key = INITIAL_CHAIN_KEY;
+	int i;
+
+	for (i = chain->base; i < chain->base + chain->depth; i++)
+		chain_key = iterate_chain_key(chain_key, chain_hlocks[i]);
+	/*
+	 * The 'unsigned long long' casts avoid that a compiler warning
+	 * is reported when building tools/lib/lockdep.
+	 */
+	if (chain->chain_key != chain_key) {
+		printk(KERN_INFO "chain %lld: key %#llx <> %#llx\n",
+		       (unsigned long long)(chain - lock_chains),
+		       (unsigned long long)chain->chain_key,
+		       (unsigned long long)chain_key);
+		return false;
+	}
+#endif
+	return true;
+}
+
+static bool in_any_zapped_class_list(struct lock_class *class)
+{
+	struct pending_free *pf;
+	int i;
+
+	for (i = 0, pf = delayed_free.pf; i < ARRAY_SIZE(delayed_free.pf); i++, pf++) {
+		if (in_list(&class->lock_entry, &pf->zapped))
+			return true;
+	}
+
+	return false;
+}
+
+static bool __check_data_structures(void)
+{
+	struct lock_class *class;
+	struct lock_chain *chain;
+	struct hlist_head *head;
+	struct lock_list *e;
+	int i;
+
+	/* Check whether all classes occur in a lock list. */
+	for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
+		class = &lock_classes[i];
+		if (!in_list(&class->lock_entry, &all_lock_classes) &&
+		    !in_list(&class->lock_entry, &free_lock_classes) &&
+		    !in_any_zapped_class_list(class)) {
+			printk(KERN_INFO "class %px/%s is not in any class list\n",
+			       class, class->name ? : "(?)");
+			return false;
+		}
+	}
+
+	/* Check whether all classes have valid lock lists. */
+	for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
+		class = &lock_classes[i];
+		if (!class_lock_list_valid(class, &class->locks_before))
+			return false;
+		if (!class_lock_list_valid(class, &class->locks_after))
+			return false;
+	}
+
+	/* Check the chain_key of all lock chains. */
+	for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
+		head = chainhash_table + i;
+		hlist_for_each_entry_rcu(chain, head, entry) {
+			if (!check_lock_chain_key(chain))
+				return false;
+		}
+	}
+
+	/*
+	 * Check whether all list entries that are in use occur in a class
+	 * lock list.
+	 */
+	for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
+		e = list_entries + i;
+		if (!in_any_class_list(&e->entry)) {
+			printk(KERN_INFO "list entry %d is not in any class list; class %s <> %s\n",
+			       (unsigned int)(e - list_entries),
+			       e->class->name ? : "(?)",
+			       e->links_to->name ? : "(?)");
+			return false;
+		}
+	}
+
+	/*
+	 * Check whether all list entries that are not in use do not occur in
+	 * a class lock list.
+	 */
+	for_each_clear_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
+		e = list_entries + i;
+		if (in_any_class_list(&e->entry)) {
+			printk(KERN_INFO "list entry %d occurs in a class list; class %s <> %s\n",
+			       (unsigned int)(e - list_entries),
+			       e->class && e->class->name ? e->class->name :
+			       "(?)",
+			       e->links_to && e->links_to->name ?
+			       e->links_to->name : "(?)");
+			return false;
+		}
+	}
+
+	return true;
+}
+
+int check_consistency = 0;
+module_param(check_consistency, int, 0644);
+
+static void check_data_structures(void)
+{
+	static bool once = false;
+
+	if (check_consistency && !once) {
+		if (!__check_data_structures()) {
+			once = true;
+			WARN_ON(once);
+		}
+	}
+}
+
+#else /* CONFIG_DEBUG_LOCKDEP */
+
+static inline void check_data_structures(void) { }
+
+#endif /* CONFIG_DEBUG_LOCKDEP */
+
+static void init_chain_block_buckets(void);
+
+/*
+ * Initialize the lock_classes[] array elements, the free_lock_classes list
+ * and also the delayed_free structure.
+ */
+static void init_data_structures_once(void)
+{
+	static bool __read_mostly ds_initialized, rcu_head_initialized;
+	int i;
+
+	if (likely(rcu_head_initialized))
+		return;
+
+	if (system_state >= SYSTEM_SCHEDULING) {
+		init_rcu_head(&delayed_free.rcu_head);
+		rcu_head_initialized = true;
+	}
+
+	if (ds_initialized)
+		return;
+
+	ds_initialized = true;
+
+	INIT_LIST_HEAD(&delayed_free.pf[0].zapped);
+	INIT_LIST_HEAD(&delayed_free.pf[1].zapped);
+
+	for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
+		list_add_tail(&lock_classes[i].lock_entry, &free_lock_classes);
+		INIT_LIST_HEAD(&lock_classes[i].locks_after);
+		INIT_LIST_HEAD(&lock_classes[i].locks_before);
+	}
+	init_chain_block_buckets();
+}
+
+static inline struct hlist_head *keyhashentry(const struct lock_class_key *key)
+{
+	unsigned long hash = hash_long((uintptr_t)key, KEYHASH_BITS);
+
+	return lock_keys_hash + hash;
+}
+
+/* Register a dynamically allocated key. */
+void lockdep_register_key(struct lock_class_key *key)
+{
+	struct hlist_head *hash_head;
+	struct lock_class_key *k;
+	unsigned long flags;
+
+	if (WARN_ON_ONCE(static_obj(key)))
+		return;
+	hash_head = keyhashentry(key);
+
+	raw_local_irq_save(flags);
+	if (!graph_lock())
+		goto restore_irqs;
+	hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
+		if (WARN_ON_ONCE(k == key))
+			goto out_unlock;
+	}
+	hlist_add_head_rcu(&key->hash_entry, hash_head);
+out_unlock:
+	graph_unlock();
+restore_irqs:
+	raw_local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(lockdep_register_key);
+
+/* Check whether a key has been registered as a dynamic key. */
+static bool is_dynamic_key(const struct lock_class_key *key)
+{
+	struct hlist_head *hash_head;
+	struct lock_class_key *k;
+	bool found = false;
+
+	if (WARN_ON_ONCE(static_obj(key)))
+		return false;
+
+	/*
+	 * If lock debugging is disabled lock_keys_hash[] may contain
+	 * pointers to memory that has already been freed. Avoid triggering
+	 * a use-after-free in that case by returning early.
+	 */
+	if (!debug_locks)
+		return true;
+
+	hash_head = keyhashentry(key);
+
+	rcu_read_lock();
+	hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
+		if (k == key) {
+			found = true;
+			break;
+		}
+	}
+	rcu_read_unlock();
+
+	return found;
+}
+
+/*
+ * Register a lock's class in the hash-table, if the class is not present
+ * yet. Otherwise we look it up. We cache the result in the lock object
+ * itself, so actual lookup of the hash should be once per lock object.
+ */
+static struct lock_class *
+register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
+{
+	struct lockdep_subclass_key *key;
+	struct hlist_head *hash_head;
+	struct lock_class *class;
+	int idx;
+
+	DEBUG_LOCKS_WARN_ON(!irqs_disabled());
+
+	class = look_up_lock_class(lock, subclass);
+	if (likely(class))
+		goto out_set_class_cache;
+
+	if (!lock->key) {
+		if (!assign_lock_key(lock))
+			return NULL;
+	} else if (!static_obj(lock->key) && !is_dynamic_key(lock->key)) {
+		return NULL;
+	}
+
+	key = lock->key->subkeys + subclass;
+	hash_head = classhashentry(key);
+
+	if (!graph_lock()) {
+		return NULL;
+	}
+	/*
+	 * We have to do the hash-walk again, to avoid races
+	 * with another CPU:
+	 */
+	hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
+		if (class->key == key)
+			goto out_unlock_set;
+	}
+
+	init_data_structures_once();
+
+	/* Allocate a new lock class and add it to the hash. */
+	class = list_first_entry_or_null(&free_lock_classes, typeof(*class),
+					 lock_entry);
+	if (!class) {
+		if (!debug_locks_off_graph_unlock()) {
+			return NULL;
+		}
+
+		print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!");
+		dump_stack();
+		return NULL;
+	}
+	nr_lock_classes++;
+	__set_bit(class - lock_classes, lock_classes_in_use);
+	debug_atomic_inc(nr_unused_locks);
+	class->key = key;
+	class->name = lock->name;
+	class->subclass = subclass;
+	WARN_ON_ONCE(!list_empty(&class->locks_before));
+	WARN_ON_ONCE(!list_empty(&class->locks_after));
+	class->name_version = count_matching_names(class);
+	class->wait_type_inner = lock->wait_type_inner;
+	class->wait_type_outer = lock->wait_type_outer;
+	class->lock_type = lock->lock_type;
+	/*
+	 * We use RCU's safe list-add method to make
+	 * parallel walking of the hash-list safe:
+	 */
+	hlist_add_head_rcu(&class->hash_entry, hash_head);
+	/*
+	 * Remove the class from the free list and add it to the global list
+	 * of classes.
+	 */
+	list_move_tail(&class->lock_entry, &all_lock_classes);
+	idx = class - lock_classes;
+	if (idx > max_lock_class_idx)
+		max_lock_class_idx = idx;
+
+	if (verbose(class)) {
+		graph_unlock();
+
+		printk("\nnew class %px: %s", class->key, class->name);
+		if (class->name_version > 1)
+			printk(KERN_CONT "#%d", class->name_version);
+		printk(KERN_CONT "\n");
+		dump_stack();
+
+		if (!graph_lock()) {
+			return NULL;
+		}
+	}
+out_unlock_set:
+	graph_unlock();
+
+out_set_class_cache:
+	if (!subclass || force)
+		lock->class_cache[0] = class;
+	else if (subclass < NR_LOCKDEP_CACHING_CLASSES)
+		lock->class_cache[subclass] = class;
+
+	/*
+	 * Hash collision, did we smoke some? We found a class with a matching
+	 * hash but the subclass -- which is hashed in -- didn't match.
+	 */
+	if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
+		return NULL;
+
+	return class;
+}
+
+#ifdef CONFIG_PROVE_LOCKING
+/*
+ * Allocate a lockdep entry. (assumes the graph_lock held, returns
+ * with NULL on failure)
+ */
+static struct lock_list *alloc_list_entry(void)
+{
+	int idx = find_first_zero_bit(list_entries_in_use,
+				      ARRAY_SIZE(list_entries));
+
+	if (idx >= ARRAY_SIZE(list_entries)) {
+		if (!debug_locks_off_graph_unlock())
+			return NULL;
+
+		print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!");
+		dump_stack();
+		return NULL;
+	}
+	nr_list_entries++;
+	__set_bit(idx, list_entries_in_use);
+	return list_entries + idx;
+}
+
+/*
+ * Add a new dependency to the head of the list:
+ */
+static int add_lock_to_list(struct lock_class *this,
+			    struct lock_class *links_to, struct list_head *head,
+			    unsigned long ip, u16 distance, u8 dep,
+			    const struct lock_trace *trace)
+{
+	struct lock_list *entry;
+	/*
+	 * Lock not present yet - get a new dependency struct and
+	 * add it to the list:
+	 */
+	entry = alloc_list_entry();
+	if (!entry)
+		return 0;
+
+	entry->class = this;
+	entry->links_to = links_to;
+	entry->dep = dep;
+	entry->distance = distance;
+	entry->trace = trace;
+	/*
+	 * Both allocation and removal are done under the graph lock; but
+	 * iteration is under RCU-sched; see look_up_lock_class() and
+	 * lockdep_free_key_range().
+	 */
+	list_add_tail_rcu(&entry->entry, head);
+
+	return 1;
+}
+
+/*
+ * For good efficiency of modular, we use power of 2
+ */
+#define MAX_CIRCULAR_QUEUE_SIZE		(1UL << CONFIG_LOCKDEP_CIRCULAR_QUEUE_BITS)
+#define CQ_MASK				(MAX_CIRCULAR_QUEUE_SIZE-1)
+
+/*
+ * The circular_queue and helpers are used to implement graph
+ * breadth-first search (BFS) algorithm, by which we can determine
+ * whether there is a path from a lock to another. In deadlock checks,
+ * a path from the next lock to be acquired to a previous held lock
+ * indicates that adding the <prev> -> <next> lock dependency will
+ * produce a circle in the graph. Breadth-first search instead of
+ * depth-first search is used in order to find the shortest (circular)
+ * path.
+ */
+struct circular_queue {
+	struct lock_list *element[MAX_CIRCULAR_QUEUE_SIZE];
+	unsigned int  front, rear;
+};
+
+static struct circular_queue lock_cq;
+
+unsigned int max_bfs_queue_depth;
+
+static unsigned int lockdep_dependency_gen_id;
+
+static inline void __cq_init(struct circular_queue *cq)
+{
+	cq->front = cq->rear = 0;
+	lockdep_dependency_gen_id++;
+}
+
+static inline int __cq_empty(struct circular_queue *cq)
+{
+	return (cq->front == cq->rear);
+}
+
+static inline int __cq_full(struct circular_queue *cq)
+{
+	return ((cq->rear + 1) & CQ_MASK) == cq->front;
+}
+
+static inline int __cq_enqueue(struct circular_queue *cq, struct lock_list *elem)
+{
+	if (__cq_full(cq))
+		return -1;
+
+	cq->element[cq->rear] = elem;
+	cq->rear = (cq->rear + 1) & CQ_MASK;
+	return 0;
+}
+
+/*
+ * Dequeue an element from the circular_queue, return a lock_list if
+ * the queue is not empty, or NULL if otherwise.
+ */
+static inline struct lock_list * __cq_dequeue(struct circular_queue *cq)
+{
+	struct lock_list * lock;
+
+	if (__cq_empty(cq))
+		return NULL;
+
+	lock = cq->element[cq->front];
+	cq->front = (cq->front + 1) & CQ_MASK;
+
+	return lock;
+}
+
+static inline unsigned int  __cq_get_elem_count(struct circular_queue *cq)
+{
+	return (cq->rear - cq->front) & CQ_MASK;
+}
+
+static inline void mark_lock_accessed(struct lock_list *lock)
+{
+	lock->class->dep_gen_id = lockdep_dependency_gen_id;
+}
+
+static inline void visit_lock_entry(struct lock_list *lock,
+				    struct lock_list *parent)
+{
+	lock->parent = parent;
+}
+
+static inline unsigned long lock_accessed(struct lock_list *lock)
+{
+	return lock->class->dep_gen_id == lockdep_dependency_gen_id;
+}
+
+static inline struct lock_list *get_lock_parent(struct lock_list *child)
+{
+	return child->parent;
+}
+
+static inline int get_lock_depth(struct lock_list *child)
+{
+	int depth = 0;
+	struct lock_list *parent;
+
+	while ((parent = get_lock_parent(child))) {
+		child = parent;
+		depth++;
+	}
+	return depth;
+}
+
+/*
+ * Return the forward or backward dependency list.
+ *
+ * @lock:   the lock_list to get its class's dependency list
+ * @offset: the offset to struct lock_class to determine whether it is
+ *          locks_after or locks_before
+ */
+static inline struct list_head *get_dep_list(struct lock_list *lock, int offset)
+{
+	void *lock_class = lock->class;
+
+	return lock_class + offset;
+}
+/*
+ * Return values of a bfs search:
+ *
+ * BFS_E* indicates an error
+ * BFS_R* indicates a result (match or not)
+ *
+ * BFS_EINVALIDNODE: Find a invalid node in the graph.
+ *
+ * BFS_EQUEUEFULL: The queue is full while doing the bfs.
+ *
+ * BFS_RMATCH: Find the matched node in the graph, and put that node into
+ *             *@target_entry.
+ *
+ * BFS_RNOMATCH: Haven't found the matched node and keep *@target_entry
+ *               _unchanged_.
+ */
+enum bfs_result {
+	BFS_EINVALIDNODE = -2,
+	BFS_EQUEUEFULL = -1,
+	BFS_RMATCH = 0,
+	BFS_RNOMATCH = 1,
+};
+
+/*
+ * bfs_result < 0 means error
+ */
+static inline bool bfs_error(enum bfs_result res)
+{
+	return res < 0;
+}
+
+/*
+ * DEP_*_BIT in lock_list::dep
+ *
+ * For dependency @prev -> @next:
+ *
+ *   SR: @prev is shared reader (->read != 0) and @next is recursive reader
+ *       (->read == 2)
+ *   ER: @prev is exclusive locker (->read == 0) and @next is recursive reader
+ *   SN: @prev is shared reader and @next is non-recursive locker (->read != 2)
+ *   EN: @prev is exclusive locker and @next is non-recursive locker
+ *
+ * Note that we define the value of DEP_*_BITs so that:
+ *   bit0 is prev->read == 0
+ *   bit1 is next->read != 2
+ */
+#define DEP_SR_BIT (0 + (0 << 1)) /* 0 */
+#define DEP_ER_BIT (1 + (0 << 1)) /* 1 */
+#define DEP_SN_BIT (0 + (1 << 1)) /* 2 */
+#define DEP_EN_BIT (1 + (1 << 1)) /* 3 */
+
+#define DEP_SR_MASK (1U << (DEP_SR_BIT))
+#define DEP_ER_MASK (1U << (DEP_ER_BIT))
+#define DEP_SN_MASK (1U << (DEP_SN_BIT))
+#define DEP_EN_MASK (1U << (DEP_EN_BIT))
+
+static inline unsigned int
+__calc_dep_bit(struct held_lock *prev, struct held_lock *next)
+{
+	return (prev->read == 0) + ((next->read != 2) << 1);
+}
+
+static inline u8 calc_dep(struct held_lock *prev, struct held_lock *next)
+{
+	return 1U << __calc_dep_bit(prev, next);
+}
+
+/*
+ * calculate the dep_bit for backwards edges. We care about whether @prev is
+ * shared and whether @next is recursive.
+ */
+static inline unsigned int
+__calc_dep_bitb(struct held_lock *prev, struct held_lock *next)
+{
+	return (next->read != 2) + ((prev->read == 0) << 1);
+}
+
+static inline u8 calc_depb(struct held_lock *prev, struct held_lock *next)
+{
+	return 1U << __calc_dep_bitb(prev, next);
+}
+
+/*
+ * Initialize a lock_list entry @lock belonging to @class as the root for a BFS
+ * search.
+ */
+static inline void __bfs_init_root(struct lock_list *lock,
+				   struct lock_class *class)
+{
+	lock->class = class;
+	lock->parent = NULL;
+	lock->only_xr = 0;
+}
+
+/*
+ * Initialize a lock_list entry @lock based on a lock acquisition @hlock as the
+ * root for a BFS search.
+ *
+ * ->only_xr of the initial lock node is set to @hlock->read == 2, to make sure
+ * that <prev> -> @hlock and @hlock -> <whatever __bfs() found> is not -(*R)->
+ * and -(S*)->.
+ */
+static inline void bfs_init_root(struct lock_list *lock,
+				 struct held_lock *hlock)
+{
+	__bfs_init_root(lock, hlock_class(hlock));
+	lock->only_xr = (hlock->read == 2);
+}
+
+/*
+ * Similar to bfs_init_root() but initialize the root for backwards BFS.
+ *
+ * ->only_xr of the initial lock node is set to @hlock->read != 0, to make sure
+ * that <next> -> @hlock and @hlock -> <whatever backwards BFS found> is not
+ * -(*S)-> and -(R*)-> (reverse order of -(*R)-> and -(S*)->).
+ */
+static inline void bfs_init_rootb(struct lock_list *lock,
+				  struct held_lock *hlock)
+{
+	__bfs_init_root(lock, hlock_class(hlock));
+	lock->only_xr = (hlock->read != 0);
+}
+
+static inline struct lock_list *__bfs_next(struct lock_list *lock, int offset)
+{
+	if (!lock || !lock->parent)
+		return NULL;
+
+	return list_next_or_null_rcu(get_dep_list(lock->parent, offset),
+				     &lock->entry, struct lock_list, entry);
+}
+
+/*
+ * Breadth-First Search to find a strong path in the dependency graph.
+ *
+ * @source_entry: the source of the path we are searching for.
+ * @data: data used for the second parameter of @match function
+ * @match: match function for the search
+ * @target_entry: pointer to the target of a matched path
+ * @offset: the offset to struct lock_class to determine whether it is
+ *          locks_after or locks_before
+ *
+ * We may have multiple edges (considering different kinds of dependencies,
+ * e.g. ER and SN) between two nodes in the dependency graph. But
+ * only the strong dependency path in the graph is relevant to deadlocks. A
+ * strong dependency path is a dependency path that doesn't have two adjacent
+ * dependencies as -(*R)-> -(S*)->, please see:
+ *
+ *         Documentation/locking/lockdep-design.rst
+ *
+ * for more explanation of the definition of strong dependency paths
+ *
+ * In __bfs(), we only traverse in the strong dependency path:
+ *
+ *     In lock_list::only_xr, we record whether the previous dependency only
+ *     has -(*R)-> in the search, and if it does (prev only has -(*R)->), we
+ *     filter out any -(S*)-> in the current dependency and after that, the
+ *     ->only_xr is set according to whether we only have -(*R)-> left.
+ */
+static enum bfs_result __bfs(struct lock_list *source_entry,
+			     void *data,
+			     bool (*match)(struct lock_list *entry, void *data),
+			     struct lock_list **target_entry,
+			     int offset)
+{
+	struct circular_queue *cq = &lock_cq;
+	struct lock_list *lock = NULL;
+	struct lock_list *entry;
+	struct list_head *head;
+	unsigned int cq_depth;
+	bool first;
+
+	lockdep_assert_locked();
+
+	__cq_init(cq);
+	__cq_enqueue(cq, source_entry);
+
+	while ((lock = __bfs_next(lock, offset)) || (lock = __cq_dequeue(cq))) {
+		if (!lock->class)
+			return BFS_EINVALIDNODE;
+
+		/*
+		 * Step 1: check whether we already finish on this one.
+		 *
+		 * If we have visited all the dependencies from this @lock to
+		 * others (iow, if we have visited all lock_list entries in
+		 * @lock->class->locks_{after,before}) we skip, otherwise go
+		 * and visit all the dependencies in the list and mark this
+		 * list accessed.
+		 */
+		if (lock_accessed(lock))
+			continue;
+		else
+			mark_lock_accessed(lock);
+
+		/*
+		 * Step 2: check whether prev dependency and this form a strong
+		 *         dependency path.
+		 */
+		if (lock->parent) { /* Parent exists, check prev dependency */
+			u8 dep = lock->dep;
+			bool prev_only_xr = lock->parent->only_xr;
+
+			/*
+			 * Mask out all -(S*)-> if we only have *R in previous
+			 * step, because -(*R)-> -(S*)-> don't make up a strong
+			 * dependency.
+			 */
+			if (prev_only_xr)
+				dep &= ~(DEP_SR_MASK | DEP_SN_MASK);
+
+			/* If nothing left, we skip */
+			if (!dep)
+				continue;
+
+			/* If there are only -(*R)-> left, set that for the next step */
+			lock->only_xr = !(dep & (DEP_SN_MASK | DEP_EN_MASK));
+		}
+
+		/*
+		 * Step 3: we haven't visited this and there is a strong
+		 *         dependency path to this, so check with @match.
+		 */
+		if (match(lock, data)) {
+			*target_entry = lock;
+			return BFS_RMATCH;
+		}
+
+		/*
+		 * Step 4: if not match, expand the path by adding the
+		 *         forward or backwards dependencis in the search
+		 *
+		 */
+		first = true;
+		head = get_dep_list(lock, offset);
+		list_for_each_entry_rcu(entry, head, entry) {
+			visit_lock_entry(entry, lock);
+
+			/*
+			 * Note we only enqueue the first of the list into the
+			 * queue, because we can always find a sibling
+			 * dependency from one (see __bfs_next()), as a result
+			 * the space of queue is saved.
+			 */
+			if (!first)
+				continue;
+
+			first = false;
+
+			if (__cq_enqueue(cq, entry))
+				return BFS_EQUEUEFULL;
+
+			cq_depth = __cq_get_elem_count(cq);
+			if (max_bfs_queue_depth < cq_depth)
+				max_bfs_queue_depth = cq_depth;
+		}
+	}
+
+	return BFS_RNOMATCH;
+}
+
+static inline enum bfs_result
+__bfs_forwards(struct lock_list *src_entry,
+	       void *data,
+	       bool (*match)(struct lock_list *entry, void *data),
+	       struct lock_list **target_entry)
+{
+	return __bfs(src_entry, data, match, target_entry,
+		     offsetof(struct lock_class, locks_after));
+
+}
+
+static inline enum bfs_result
+__bfs_backwards(struct lock_list *src_entry,
+		void *data,
+		bool (*match)(struct lock_list *entry, void *data),
+		struct lock_list **target_entry)
+{
+	return __bfs(src_entry, data, match, target_entry,
+		     offsetof(struct lock_class, locks_before));
+
+}
+
+static void print_lock_trace(const struct lock_trace *trace,
+			     unsigned int spaces)
+{
+	stack_trace_print(trace->entries, trace->nr_entries, spaces);
+}
+
+/*
+ * Print a dependency chain entry (this is only done when a deadlock
+ * has been detected):
+ */
+static noinline void
+print_circular_bug_entry(struct lock_list *target, int depth)
+{
+	if (debug_locks_silent)
+		return;
+	printk("\n-> #%u", depth);
+	print_lock_name(target->class);
+	printk(KERN_CONT ":\n");
+	print_lock_trace(target->trace, 6);
+}
+
+static void
+print_circular_lock_scenario(struct held_lock *src,
+			     struct held_lock *tgt,
+			     struct lock_list *prt)
+{
+	struct lock_class *source = hlock_class(src);
+	struct lock_class *target = hlock_class(tgt);
+	struct lock_class *parent = prt->class;
+
+	/*
+	 * A direct locking problem where unsafe_class lock is taken
+	 * directly by safe_class lock, then all we need to show
+	 * is the deadlock scenario, as it is obvious that the
+	 * unsafe lock is taken under the safe lock.
+	 *
+	 * But if there is a chain instead, where the safe lock takes
+	 * an intermediate lock (middle_class) where this lock is
+	 * not the same as the safe lock, then the lock chain is
+	 * used to describe the problem. Otherwise we would need
+	 * to show a different CPU case for each link in the chain
+	 * from the safe_class lock to the unsafe_class lock.
+	 */
+	if (parent != source) {
+		printk("Chain exists of:\n  ");
+		__print_lock_name(source);
+		printk(KERN_CONT " --> ");
+		__print_lock_name(parent);
+		printk(KERN_CONT " --> ");
+		__print_lock_name(target);
+		printk(KERN_CONT "\n\n");
+	}
+
+	printk(" Possible unsafe locking scenario:\n\n");
+	printk("       CPU0                    CPU1\n");
+	printk("       ----                    ----\n");
+	printk("  lock(");
+	__print_lock_name(target);
+	printk(KERN_CONT ");\n");
+	printk("                               lock(");
+	__print_lock_name(parent);
+	printk(KERN_CONT ");\n");
+	printk("                               lock(");
+	__print_lock_name(target);
+	printk(KERN_CONT ");\n");
+	printk("  lock(");
+	__print_lock_name(source);
+	printk(KERN_CONT ");\n");
+	printk("\n *** DEADLOCK ***\n\n");
+}
+
+/*
+ * When a circular dependency is detected, print the
+ * header first:
+ */
+static noinline void
+print_circular_bug_header(struct lock_list *entry, unsigned int depth,
+			struct held_lock *check_src,
+			struct held_lock *check_tgt)
+{
+	struct task_struct *curr = current;
+
+	if (debug_locks_silent)
+		return;
+
+	pr_warn("\n");
+	pr_warn("======================================================\n");
+	pr_warn("WARNING: possible circular locking dependency detected\n");
+	print_kernel_ident();
+	pr_warn("------------------------------------------------------\n");
+	pr_warn("%s/%d is trying to acquire lock:\n",
+		curr->comm, task_pid_nr(curr));
+	print_lock(check_src);
+
+	pr_warn("\nbut task is already holding lock:\n");
+
+	print_lock(check_tgt);
+	pr_warn("\nwhich lock already depends on the new lock.\n\n");
+	pr_warn("\nthe existing dependency chain (in reverse order) is:\n");
+
+	print_circular_bug_entry(entry, depth);
+}
+
+/*
+ * We are about to add A -> B into the dependency graph, and in __bfs() a
+ * strong dependency path A -> .. -> B is found: hlock_class equals
+ * entry->class.
+ *
+ * If A -> .. -> B can replace A -> B in any __bfs() search (means the former
+ * is _stronger_ than or equal to the latter), we consider A -> B as redundant.
+ * For example if A -> .. -> B is -(EN)-> (i.e. A -(E*)-> .. -(*N)-> B), and A
+ * -> B is -(ER)-> or -(EN)->, then we don't need to add A -> B into the
+ * dependency graph, as any strong path ..-> A -> B ->.. we can get with
+ * having dependency A -> B, we could already get a equivalent path ..-> A ->
+ * .. -> B -> .. with A -> .. -> B. Therefore A -> B is reduntant.
+ *
+ * We need to make sure both the start and the end of A -> .. -> B is not
+ * weaker than A -> B. For the start part, please see the comment in
+ * check_redundant(). For the end part, we need:
+ *
+ * Either
+ *
+ *     a) A -> B is -(*R)-> (everything is not weaker than that)
+ *
+ * or
+ *
+ *     b) A -> .. -> B is -(*N)-> (nothing is stronger than this)
+ *
+ */
+static inline bool hlock_equal(struct lock_list *entry, void *data)
+{
+	struct held_lock *hlock = (struct held_lock *)data;
+
+	return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
+	       (hlock->read == 2 ||  /* A -> B is -(*R)-> */
+		!entry->only_xr); /* A -> .. -> B is -(*N)-> */
+}
+
+/*
+ * We are about to add B -> A into the dependency graph, and in __bfs() a
+ * strong dependency path A -> .. -> B is found: hlock_class equals
+ * entry->class.
+ *
+ * We will have a deadlock case (conflict) if A -> .. -> B -> A is a strong
+ * dependency cycle, that means:
+ *
+ * Either
+ *
+ *     a) B -> A is -(E*)->
+ *
+ * or
+ *
+ *     b) A -> .. -> B is -(*N)-> (i.e. A -> .. -(*N)-> B)
+ *
+ * as then we don't have -(*R)-> -(S*)-> in the cycle.
+ */
+static inline bool hlock_conflict(struct lock_list *entry, void *data)
+{
+	struct held_lock *hlock = (struct held_lock *)data;
+
+	return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
+	       (hlock->read == 0 || /* B -> A is -(E*)-> */
+		!entry->only_xr); /* A -> .. -> B is -(*N)-> */
+}
+
+static noinline void print_circular_bug(struct lock_list *this,
+				struct lock_list *target,
+				struct held_lock *check_src,
+				struct held_lock *check_tgt)
+{
+	struct task_struct *curr = current;
+	struct lock_list *parent;
+	struct lock_list *first_parent;
+	int depth;
+
+	if (!debug_locks_off_graph_unlock() || debug_locks_silent)
+		return;
+
+	this->trace = save_trace();
+	if (!this->trace)
+		return;
+
+	depth = get_lock_depth(target);
+
+	print_circular_bug_header(target, depth, check_src, check_tgt);
+
+	parent = get_lock_parent(target);
+	first_parent = parent;
+
+	while (parent) {
+		print_circular_bug_entry(parent, --depth);
+		parent = get_lock_parent(parent);
+	}
+
+	printk("\nother info that might help us debug this:\n\n");
+	print_circular_lock_scenario(check_src, check_tgt,
+				     first_parent);
+
+	lockdep_print_held_locks(curr);
+
+	printk("\nstack backtrace:\n");
+	dump_stack();
+}
+
+static noinline void print_bfs_bug(int ret)
+{
+	if (!debug_locks_off_graph_unlock())
+		return;
+
+	/*
+	 * Breadth-first-search failed, graph got corrupted?
+	 */
+	WARN(1, "lockdep bfs error:%d\n", ret);
+}
+
+static bool noop_count(struct lock_list *entry, void *data)
+{
+	(*(unsigned long *)data)++;
+	return false;
+}
+
+static unsigned long __lockdep_count_forward_deps(struct lock_list *this)
+{
+	unsigned long  count = 0;
+	struct lock_list *target_entry;
+
+	__bfs_forwards(this, (void *)&count, noop_count, &target_entry);
+
+	return count;
+}
+unsigned long lockdep_count_forward_deps(struct lock_class *class)
+{
+	unsigned long ret, flags;
+	struct lock_list this;
+
+	__bfs_init_root(&this, class);
+
+	raw_local_irq_save(flags);
+	lockdep_lock();
+	ret = __lockdep_count_forward_deps(&this);
+	lockdep_unlock();
+	raw_local_irq_restore(flags);
+
+	return ret;
+}
+
+static unsigned long __lockdep_count_backward_deps(struct lock_list *this)
+{
+	unsigned long  count = 0;
+	struct lock_list *target_entry;
+
+	__bfs_backwards(this, (void *)&count, noop_count, &target_entry);
+
+	return count;
+}
+
+unsigned long lockdep_count_backward_deps(struct lock_class *class)
+{
+	unsigned long ret, flags;
+	struct lock_list this;
+
+	__bfs_init_root(&this, class);
+
+	raw_local_irq_save(flags);
+	lockdep_lock();
+	ret = __lockdep_count_backward_deps(&this);
+	lockdep_unlock();
+	raw_local_irq_restore(flags);
+
+	return ret;
+}
+
+/*
+ * Check that the dependency graph starting at <src> can lead to
+ * <target> or not.
+ */
+static noinline enum bfs_result
+check_path(struct held_lock *target, struct lock_list *src_entry,
+	   bool (*match)(struct lock_list *entry, void *data),
+	   struct lock_list **target_entry)
+{
+	enum bfs_result ret;
+
+	ret = __bfs_forwards(src_entry, target, match, target_entry);
+
+	if (unlikely(bfs_error(ret)))
+		print_bfs_bug(ret);
+
+	return ret;
+}
+
+/*
+ * Prove that the dependency graph starting at <src> can not
+ * lead to <target>. If it can, there is a circle when adding
+ * <target> -> <src> dependency.
+ *
+ * Print an error and return BFS_RMATCH if it does.
+ */
+static noinline enum bfs_result
+check_noncircular(struct held_lock *src, struct held_lock *target,
+		  struct lock_trace **const trace)
+{
+	enum bfs_result ret;
+	struct lock_list *target_entry;
+	struct lock_list src_entry;
+
+	bfs_init_root(&src_entry, src);
+
+	debug_atomic_inc(nr_cyclic_checks);
+
+	ret = check_path(target, &src_entry, hlock_conflict, &target_entry);
+
+	if (unlikely(ret == BFS_RMATCH)) {
+		if (!*trace) {
+			/*
+			 * If save_trace fails here, the printing might
+			 * trigger a WARN but because of the !nr_entries it
+			 * should not do bad things.
+			 */
+			*trace = save_trace();
+		}
+
+		print_circular_bug(&src_entry, target_entry, src, target);
+	}
+
+	return ret;
+}
+
+#ifdef CONFIG_LOCKDEP_SMALL
+/*
+ * Check that the dependency graph starting at <src> can lead to
+ * <target> or not. If it can, <src> -> <target> dependency is already
+ * in the graph.
+ *
+ * Return BFS_RMATCH if it does, or BFS_RMATCH if it does not, return BFS_E* if
+ * any error appears in the bfs search.
+ */
+static noinline enum bfs_result
+check_redundant(struct held_lock *src, struct held_lock *target)
+{
+	enum bfs_result ret;
+	struct lock_list *target_entry;
+	struct lock_list src_entry;
+
+	bfs_init_root(&src_entry, src);
+	/*
+	 * Special setup for check_redundant().
+	 *
+	 * To report redundant, we need to find a strong dependency path that
+	 * is equal to or stronger than <src> -> <target>. So if <src> is E,
+	 * we need to let __bfs() only search for a path starting at a -(E*)->,
+	 * we achieve this by setting the initial node's ->only_xr to true in
+	 * that case. And if <prev> is S, we set initial ->only_xr to false
+	 * because both -(S*)-> (equal) and -(E*)-> (stronger) are redundant.
+	 */
+	src_entry.only_xr = src->read == 0;
+
+	debug_atomic_inc(nr_redundant_checks);
+
+	ret = check_path(target, &src_entry, hlock_equal, &target_entry);
+
+	if (ret == BFS_RMATCH)
+		debug_atomic_inc(nr_redundant);
+
+	return ret;
+}
+#endif
+
+#ifdef CONFIG_TRACE_IRQFLAGS
+
+/*
+ * Forwards and backwards subgraph searching, for the purposes of
+ * proving that two subgraphs can be connected by a new dependency
+ * without creating any illegal irq-safe -> irq-unsafe lock dependency.
+ *
+ * A irq safe->unsafe deadlock happens with the following conditions:
+ *
+ * 1) We have a strong dependency path A -> ... -> B
+ *
+ * 2) and we have ENABLED_IRQ usage of B and USED_IN_IRQ usage of A, therefore
+ *    irq can create a new dependency B -> A (consider the case that a holder
+ *    of B gets interrupted by an irq whose handler will try to acquire A).
+ *
+ * 3) the dependency circle A -> ... -> B -> A we get from 1) and 2) is a
+ *    strong circle:
+ *
+ *      For the usage bits of B:
+ *        a) if A -> B is -(*N)->, then B -> A could be any type, so any
+ *           ENABLED_IRQ usage suffices.
+ *        b) if A -> B is -(*R)->, then B -> A must be -(E*)->, so only
+ *           ENABLED_IRQ_*_READ usage suffices.
+ *
+ *      For the usage bits of A:
+ *        c) if A -> B is -(E*)->, then B -> A could be any type, so any
+ *           USED_IN_IRQ usage suffices.
+ *        d) if A -> B is -(S*)->, then B -> A must be -(*N)->, so only
+ *           USED_IN_IRQ_*_READ usage suffices.
+ */
+
+/*
+ * There is a strong dependency path in the dependency graph: A -> B, and now
+ * we need to decide which usage bit of A should be accumulated to detect
+ * safe->unsafe bugs.
+ *
+ * Note that usage_accumulate() is used in backwards search, so ->only_xr
+ * stands for whether A -> B only has -(S*)-> (in this case ->only_xr is true).
+ *
+ * As above, if only_xr is false, which means A -> B has -(E*)-> dependency
+ * path, any usage of A should be considered. Otherwise, we should only
+ * consider _READ usage.
+ */
+static inline bool usage_accumulate(struct lock_list *entry, void *mask)
+{
+	if (!entry->only_xr)
+		*(unsigned long *)mask |= entry->class->usage_mask;
+	else /* Mask out _READ usage bits */
+		*(unsigned long *)mask |= (entry->class->usage_mask & LOCKF_IRQ);
+
+	return false;
+}
+
+/*
+ * There is a strong dependency path in the dependency graph: A -> B, and now
+ * we need to decide which usage bit of B conflicts with the usage bits of A,
+ * i.e. which usage bit of B may introduce safe->unsafe deadlocks.
+ *
+ * As above, if only_xr is false, which means A -> B has -(*N)-> dependency
+ * path, any usage of B should be considered. Otherwise, we should only
+ * consider _READ usage.
+ */
+static inline bool usage_match(struct lock_list *entry, void *mask)
+{
+	if (!entry->only_xr)
+		return !!(entry->class->usage_mask & *(unsigned long *)mask);
+	else /* Mask out _READ usage bits */
+		return !!((entry->class->usage_mask & LOCKF_IRQ) & *(unsigned long *)mask);
+}
+
+/*
+ * Find a node in the forwards-direction dependency sub-graph starting
+ * at @root->class that matches @bit.
+ *
+ * Return BFS_MATCH if such a node exists in the subgraph, and put that node
+ * into *@target_entry.
+ */
+static enum bfs_result
+find_usage_forwards(struct lock_list *root, unsigned long usage_mask,
+			struct lock_list **target_entry)
+{
+	enum bfs_result result;
+
+	debug_atomic_inc(nr_find_usage_forwards_checks);
+
+	result = __bfs_forwards(root, &usage_mask, usage_match, target_entry);
+
+	return result;
+}
+
+/*
+ * Find a node in the backwards-direction dependency sub-graph starting
+ * at @root->class that matches @bit.
+ */
+static enum bfs_result
+find_usage_backwards(struct lock_list *root, unsigned long usage_mask,
+			struct lock_list **target_entry)
+{
+	enum bfs_result result;
+
+	debug_atomic_inc(nr_find_usage_backwards_checks);
+
+	result = __bfs_backwards(root, &usage_mask, usage_match, target_entry);
+
+	return result;
+}
+
+static void print_lock_class_header(struct lock_class *class, int depth)
+{
+	int bit;
+
+	printk("%*s->", depth, "");
+	print_lock_name(class);
+#ifdef CONFIG_DEBUG_LOCKDEP
+	printk(KERN_CONT " ops: %lu", debug_class_ops_read(class));
+#endif
+	printk(KERN_CONT " {\n");
+
+	for (bit = 0; bit < LOCK_TRACE_STATES; bit++) {
+		if (class->usage_mask & (1 << bit)) {
+			int len = depth;
+
+			len += printk("%*s   %s", depth, "", usage_str[bit]);
+			len += printk(KERN_CONT " at:\n");
+			print_lock_trace(class->usage_traces[bit], len);
+		}
+	}
+	printk("%*s }\n", depth, "");
+
+	printk("%*s ... key      at: [<%px>] %pS\n",
+		depth, "", class->key, class->key);
+}
+
+/*
+ * Dependency path printing:
+ *
+ * After BFS we get a lock dependency path (linked via ->parent of lock_list),
+ * printing out each lock in the dependency path will help on understanding how
+ * the deadlock could happen. Here are some details about dependency path
+ * printing:
+ *
+ * 1)	A lock_list can be either forwards or backwards for a lock dependency,
+ * 	for a lock dependency A -> B, there are two lock_lists:
+ *
+ * 	a)	lock_list in the ->locks_after list of A, whose ->class is B and
+ * 		->links_to is A. In this case, we can say the lock_list is
+ * 		"A -> B" (forwards case).
+ *
+ * 	b)	lock_list in the ->locks_before list of B, whose ->class is A
+ * 		and ->links_to is B. In this case, we can say the lock_list is
+ * 		"B <- A" (bacwards case).
+ *
+ * 	The ->trace of both a) and b) point to the call trace where B was
+ * 	acquired with A held.
+ *
+ * 2)	A "helper" lock_list is introduced during BFS, this lock_list doesn't
+ * 	represent a certain lock dependency, it only provides an initial entry
+ * 	for BFS. For example, BFS may introduce a "helper" lock_list whose
+ * 	->class is A, as a result BFS will search all dependencies starting with
+ * 	A, e.g. A -> B or A -> C.
+ *
+ * 	The notation of a forwards helper lock_list is like "-> A", which means
+ * 	we should search the forwards dependencies starting with "A", e.g A -> B
+ * 	or A -> C.
+ *
+ * 	The notation of a bacwards helper lock_list is like "<- B", which means
+ * 	we should search the backwards dependencies ending with "B", e.g.
+ * 	B <- A or B <- C.
+ */
+
+/*
+ * printk the shortest lock dependencies from @root to @leaf in reverse order.
+ *
+ * We have a lock dependency path as follow:
+ *
+ *    @root                                                                 @leaf
+ *      |                                                                     |
+ *      V                                                                     V
+ *	          ->parent                                   ->parent
+ * | lock_list | <--------- | lock_list | ... | lock_list  | <--------- | lock_list |
+ * |    -> L1  |            | L1 -> L2  | ... |Ln-2 -> Ln-1|            | Ln-1 -> Ln|
+ *
+ * , so it's natural that we start from @leaf and print every ->class and
+ * ->trace until we reach the @root.
+ */
+static void __used
+print_shortest_lock_dependencies(struct lock_list *leaf,
+				 struct lock_list *root)
+{
+	struct lock_list *entry = leaf;
+	int depth;
+
+	/*compute depth from generated tree by BFS*/
+	depth = get_lock_depth(leaf);
+
+	do {
+		print_lock_class_header(entry->class, depth);
+		printk("%*s ... acquired at:\n", depth, "");
+		print_lock_trace(entry->trace, 2);
+		printk("\n");
+
+		if (depth == 0 && (entry != root)) {
+			printk("lockdep:%s bad path found in chain graph\n", __func__);
+			break;
+		}
+
+		entry = get_lock_parent(entry);
+		depth--;
+	} while (entry && (depth >= 0));
+}
+
+/*
+ * printk the shortest lock dependencies from @leaf to @root.
+ *
+ * We have a lock dependency path (from a backwards search) as follow:
+ *
+ *    @leaf                                                                 @root
+ *      |                                                                     |
+ *      V                                                                     V
+ *	          ->parent                                   ->parent
+ * | lock_list | ---------> | lock_list | ... | lock_list  | ---------> | lock_list |
+ * | L2 <- L1  |            | L3 <- L2  | ... | Ln <- Ln-1 |            |    <- Ln  |
+ *
+ * , so when we iterate from @leaf to @root, we actually print the lock
+ * dependency path L1 -> L2 -> .. -> Ln in the non-reverse order.
+ *
+ * Another thing to notice here is that ->class of L2 <- L1 is L1, while the
+ * ->trace of L2 <- L1 is the call trace of L2, in fact we don't have the call
+ * trace of L1 in the dependency path, which is alright, because most of the
+ * time we can figure out where L1 is held from the call trace of L2.
+ */
+static void __used
+print_shortest_lock_dependencies_backwards(struct lock_list *leaf,
+					   struct lock_list *root)
+{
+	struct lock_list *entry = leaf;
+	const struct lock_trace *trace = NULL;
+	int depth;
+
+	/*compute depth from generated tree by BFS*/
+	depth = get_lock_depth(leaf);
+
+	do {
+		print_lock_class_header(entry->class, depth);
+		if (trace) {
+			printk("%*s ... acquired at:\n", depth, "");
+			print_lock_trace(trace, 2);
+			printk("\n");
+		}
+
+		/*
+		 * Record the pointer to the trace for the next lock_list
+		 * entry, see the comments for the function.
+		 */
+		trace = entry->trace;
+
+		if (depth == 0 && (entry != root)) {
+			printk("lockdep:%s bad path found in chain graph\n", __func__);
+			break;
+		}
+
+		entry = get_lock_parent(entry);
+		depth--;
+	} while (entry && (depth >= 0));
+}
+
+static void
+print_irq_lock_scenario(struct lock_list *safe_entry,
+			struct lock_list *unsafe_entry,
+			struct lock_class *prev_class,
+			struct lock_class *next_class)
+{
+	struct lock_class *safe_class = safe_entry->class;
+	struct lock_class *unsafe_class = unsafe_entry->class;
+	struct lock_class *middle_class = prev_class;
+
+	if (middle_class == safe_class)
+		middle_class = next_class;
+
+	/*
+	 * A direct locking problem where unsafe_class lock is taken
+	 * directly by safe_class lock, then all we need to show
+	 * is the deadlock scenario, as it is obvious that the
+	 * unsafe lock is taken under the safe lock.
+	 *
+	 * But if there is a chain instead, where the safe lock takes
+	 * an intermediate lock (middle_class) where this lock is
+	 * not the same as the safe lock, then the lock chain is
+	 * used to describe the problem. Otherwise we would need
+	 * to show a different CPU case for each link in the chain
+	 * from the safe_class lock to the unsafe_class lock.
+	 */
+	if (middle_class != unsafe_class) {
+		printk("Chain exists of:\n  ");
+		__print_lock_name(safe_class);
+		printk(KERN_CONT " --> ");
+		__print_lock_name(middle_class);
+		printk(KERN_CONT " --> ");
+		__print_lock_name(unsafe_class);
+		printk(KERN_CONT "\n\n");
+	}
+
+	printk(" Possible interrupt unsafe locking scenario:\n\n");
+	printk("       CPU0                    CPU1\n");
+	printk("       ----                    ----\n");
+	printk("  lock(");
+	__print_lock_name(unsafe_class);
+	printk(KERN_CONT ");\n");
+	printk("                               local_irq_disable();\n");
+	printk("                               lock(");
+	__print_lock_name(safe_class);
+	printk(KERN_CONT ");\n");
+	printk("                               lock(");
+	__print_lock_name(middle_class);
+	printk(KERN_CONT ");\n");
+	printk("  <Interrupt>\n");
+	printk("    lock(");
+	__print_lock_name(safe_class);
+	printk(KERN_CONT ");\n");
+	printk("\n *** DEADLOCK ***\n\n");
+}
+
+static void
+print_bad_irq_dependency(struct task_struct *curr,
+			 struct lock_list *prev_root,
+			 struct lock_list *next_root,
+			 struct lock_list *backwards_entry,
+			 struct lock_list *forwards_entry,
+			 struct held_lock *prev,
+			 struct held_lock *next,
+			 enum lock_usage_bit bit1,
+			 enum lock_usage_bit bit2,
+			 const char *irqclass)
+{
+	if (!debug_locks_off_graph_unlock() || debug_locks_silent)
+		return;
+
+	pr_warn("\n");
+	pr_warn("=====================================================\n");
+	pr_warn("WARNING: %s-safe -> %s-unsafe lock order detected\n",
+		irqclass, irqclass);
+	print_kernel_ident();
+	pr_warn("-----------------------------------------------------\n");
+	pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
+		curr->comm, task_pid_nr(curr),
+		lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT,
+		curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
+		lockdep_hardirqs_enabled(),
+		curr->softirqs_enabled);
+	print_lock(next);
+
+	pr_warn("\nand this task is already holding:\n");
+	print_lock(prev);
+	pr_warn("which would create a new lock dependency:\n");
+	print_lock_name(hlock_class(prev));
+	pr_cont(" ->");
+	print_lock_name(hlock_class(next));
+	pr_cont("\n");
+
+	pr_warn("\nbut this new dependency connects a %s-irq-safe lock:\n",
+		irqclass);
+	print_lock_name(backwards_entry->class);
+	pr_warn("\n... which became %s-irq-safe at:\n", irqclass);
+
+	print_lock_trace(backwards_entry->class->usage_traces[bit1], 1);
+
+	pr_warn("\nto a %s-irq-unsafe lock:\n", irqclass);
+	print_lock_name(forwards_entry->class);
+	pr_warn("\n... which became %s-irq-unsafe at:\n", irqclass);
+	pr_warn("...");
+
+	print_lock_trace(forwards_entry->class->usage_traces[bit2], 1);
+
+	pr_warn("\nother info that might help us debug this:\n\n");
+	print_irq_lock_scenario(backwards_entry, forwards_entry,
+				hlock_class(prev), hlock_class(next));
+
+	lockdep_print_held_locks(curr);
+
+	pr_warn("\nthe dependencies between %s-irq-safe lock and the holding lock:\n", irqclass);
+	prev_root->trace = save_trace();
+	if (!prev_root->trace)
+		return;
+	print_shortest_lock_dependencies_backwards(backwards_entry, prev_root);
+
+	pr_warn("\nthe dependencies between the lock to be acquired");
+	pr_warn(" and %s-irq-unsafe lock:\n", irqclass);
+	next_root->trace = save_trace();
+	if (!next_root->trace)
+		return;
+	print_shortest_lock_dependencies(forwards_entry, next_root);
+
+	pr_warn("\nstack backtrace:\n");
+	dump_stack();
+}
+
+static const char *state_names[] = {
+#define LOCKDEP_STATE(__STATE) \
+	__stringify(__STATE),
+#include "lockdep_states.h"
+#undef LOCKDEP_STATE
+};
+
+static const char *state_rnames[] = {
+#define LOCKDEP_STATE(__STATE) \
+	__stringify(__STATE)"-READ",
+#include "lockdep_states.h"
+#undef LOCKDEP_STATE
+};
+
+static inline const char *state_name(enum lock_usage_bit bit)
+{
+	if (bit & LOCK_USAGE_READ_MASK)
+		return state_rnames[bit >> LOCK_USAGE_DIR_MASK];
+	else
+		return state_names[bit >> LOCK_USAGE_DIR_MASK];
+}
+
+/*
+ * The bit number is encoded like:
+ *
+ *  bit0: 0 exclusive, 1 read lock
+ *  bit1: 0 used in irq, 1 irq enabled
+ *  bit2-n: state
+ */
+static int exclusive_bit(int new_bit)
+{
+	int state = new_bit & LOCK_USAGE_STATE_MASK;
+	int dir = new_bit & LOCK_USAGE_DIR_MASK;
+
+	/*
+	 * keep state, bit flip the direction and strip read.
+	 */
+	return state | (dir ^ LOCK_USAGE_DIR_MASK);
+}
+
+/*
+ * Observe that when given a bitmask where each bitnr is encoded as above, a
+ * right shift of the mask transforms the individual bitnrs as -1 and
+ * conversely, a left shift transforms into +1 for the individual bitnrs.
+ *
+ * So for all bits whose number have LOCK_ENABLED_* set (bitnr1 == 1), we can
+ * create the mask with those bit numbers using LOCK_USED_IN_* (bitnr1 == 0)
+ * instead by subtracting the bit number by 2, or shifting the mask right by 2.
+ *
+ * Similarly, bitnr1 == 0 becomes bitnr1 == 1 by adding 2, or shifting left 2.
+ *
+ * So split the mask (note that LOCKF_ENABLED_IRQ_ALL|LOCKF_USED_IN_IRQ_ALL is
+ * all bits set) and recompose with bitnr1 flipped.
+ */
+static unsigned long invert_dir_mask(unsigned long mask)
+{
+	unsigned long excl = 0;
+
+	/* Invert dir */
+	excl |= (mask & LOCKF_ENABLED_IRQ_ALL) >> LOCK_USAGE_DIR_MASK;
+	excl |= (mask & LOCKF_USED_IN_IRQ_ALL) << LOCK_USAGE_DIR_MASK;
+
+	return excl;
+}
+
+/*
+ * Note that a LOCK_ENABLED_IRQ_*_READ usage and a LOCK_USED_IN_IRQ_*_READ
+ * usage may cause deadlock too, for example:
+ *
+ * P1				P2
+ * <irq disabled>
+ * write_lock(l1);		<irq enabled>
+ *				read_lock(l2);
+ * write_lock(l2);
+ * 				<in irq>
+ * 				read_lock(l1);
+ *
+ * , in above case, l1 will be marked as LOCK_USED_IN_IRQ_HARDIRQ_READ and l2
+ * will marked as LOCK_ENABLE_IRQ_HARDIRQ_READ, and this is a possible
+ * deadlock.
+ *
+ * In fact, all of the following cases may cause deadlocks:
+ *
+ * 	 LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*
+ * 	 LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*
+ * 	 LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*_READ
+ * 	 LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*_READ
+ *
+ * As a result, to calculate the "exclusive mask", first we invert the
+ * direction (USED_IN/ENABLED) of the original mask, and 1) for all bits with
+ * bitnr0 set (LOCK_*_READ), add those with bitnr0 cleared (LOCK_*). 2) for all
+ * bits with bitnr0 cleared (LOCK_*_READ), add those with bitnr0 set (LOCK_*).
+ */
+static unsigned long exclusive_mask(unsigned long mask)
+{
+	unsigned long excl = invert_dir_mask(mask);
+
+	excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
+	excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
+
+	return excl;
+}
+
+/*
+ * Retrieve the _possible_ original mask to which @mask is
+ * exclusive. Ie: this is the opposite of exclusive_mask().
+ * Note that 2 possible original bits can match an exclusive
+ * bit: one has LOCK_USAGE_READ_MASK set, the other has it
+ * cleared. So both are returned for each exclusive bit.
+ */
+static unsigned long original_mask(unsigned long mask)
+{
+	unsigned long excl = invert_dir_mask(mask);
+
+	/* Include read in existing usages */
+	excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
+	excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
+
+	return excl;
+}
+
+/*
+ * Find the first pair of bit match between an original
+ * usage mask and an exclusive usage mask.
+ */
+static int find_exclusive_match(unsigned long mask,
+				unsigned long excl_mask,
+				enum lock_usage_bit *bitp,
+				enum lock_usage_bit *excl_bitp)
+{
+	int bit, excl, excl_read;
+
+	for_each_set_bit(bit, &mask, LOCK_USED) {
+		/*
+		 * exclusive_bit() strips the read bit, however,
+		 * LOCK_ENABLED_IRQ_*_READ may cause deadlocks too, so we need
+		 * to search excl | LOCK_USAGE_READ_MASK as well.
+		 */
+		excl = exclusive_bit(bit);
+		excl_read = excl | LOCK_USAGE_READ_MASK;
+		if (excl_mask & lock_flag(excl)) {
+			*bitp = bit;
+			*excl_bitp = excl;
+			return 0;
+		} else if (excl_mask & lock_flag(excl_read)) {
+			*bitp = bit;
+			*excl_bitp = excl_read;
+			return 0;
+		}
+	}
+	return -1;
+}
+
+/*
+ * Prove that the new dependency does not connect a hardirq-safe(-read)
+ * lock with a hardirq-unsafe lock - to achieve this we search
+ * the backwards-subgraph starting at <prev>, and the
+ * forwards-subgraph starting at <next>:
+ */
+static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
+			   struct held_lock *next)
+{
+	unsigned long usage_mask = 0, forward_mask, backward_mask;
+	enum lock_usage_bit forward_bit = 0, backward_bit = 0;
+	struct lock_list *target_entry1;
+	struct lock_list *target_entry;
+	struct lock_list this, that;
+	enum bfs_result ret;
+
+	/*
+	 * Step 1: gather all hard/soft IRQs usages backward in an
+	 * accumulated usage mask.
+	 */
+	bfs_init_rootb(&this, prev);
+
+	ret = __bfs_backwards(&this, &usage_mask, usage_accumulate, NULL);
+	if (bfs_error(ret)) {
+		print_bfs_bug(ret);
+		return 0;
+	}
+
+	usage_mask &= LOCKF_USED_IN_IRQ_ALL;
+	if (!usage_mask)
+		return 1;
+
+	/*
+	 * Step 2: find exclusive uses forward that match the previous
+	 * backward accumulated mask.
+	 */
+	forward_mask = exclusive_mask(usage_mask);
+
+	bfs_init_root(&that, next);
+
+	ret = find_usage_forwards(&that, forward_mask, &target_entry1);
+	if (bfs_error(ret)) {
+		print_bfs_bug(ret);
+		return 0;
+	}
+	if (ret == BFS_RNOMATCH)
+		return 1;
+
+	/*
+	 * Step 3: we found a bad match! Now retrieve a lock from the backward
+	 * list whose usage mask matches the exclusive usage mask from the
+	 * lock found on the forward list.
+	 *
+	 * Note, we should only keep the LOCKF_ENABLED_IRQ_ALL bits, considering
+	 * the follow case:
+	 *
+	 * When trying to add A -> B to the graph, we find that there is a
+	 * hardirq-safe L, that L -> ... -> A, and another hardirq-unsafe M,
+	 * that B -> ... -> M. However M is **softirq-safe**, if we use exact
+	 * invert bits of M's usage_mask, we will find another lock N that is
+	 * **softirq-unsafe** and N -> ... -> A, however N -> .. -> M will not
+	 * cause a inversion deadlock.
+	 */
+	backward_mask = original_mask(target_entry1->class->usage_mask & LOCKF_ENABLED_IRQ_ALL);
+
+	ret = find_usage_backwards(&this, backward_mask, &target_entry);
+	if (bfs_error(ret)) {
+		print_bfs_bug(ret);
+		return 0;
+	}
+	if (DEBUG_LOCKS_WARN_ON(ret == BFS_RNOMATCH))
+		return 1;
+
+	/*
+	 * Step 4: narrow down to a pair of incompatible usage bits
+	 * and report it.
+	 */
+	ret = find_exclusive_match(target_entry->class->usage_mask,
+				   target_entry1->class->usage_mask,
+				   &backward_bit, &forward_bit);
+	if (DEBUG_LOCKS_WARN_ON(ret == -1))
+		return 1;
+
+	print_bad_irq_dependency(curr, &this, &that,
+				 target_entry, target_entry1,
+				 prev, next,
+				 backward_bit, forward_bit,
+				 state_name(backward_bit));
+
+	return 0;
+}
+
+#else
+
+static inline int check_irq_usage(struct task_struct *curr,
+				  struct held_lock *prev, struct held_lock *next)
+{
+	return 1;
+}
+#endif /* CONFIG_TRACE_IRQFLAGS */
+
+static void inc_chains(int irq_context)
+{
+	if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
+		nr_hardirq_chains++;
+	else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
+		nr_softirq_chains++;
+	else
+		nr_process_chains++;
+}
+
+static void dec_chains(int irq_context)
+{
+	if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
+		nr_hardirq_chains--;
+	else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
+		nr_softirq_chains--;
+	else
+		nr_process_chains--;
+}
+
+static void
+print_deadlock_scenario(struct held_lock *nxt, struct held_lock *prv)
+{
+	struct lock_class *next = hlock_class(nxt);
+	struct lock_class *prev = hlock_class(prv);
+
+	printk(" Possible unsafe locking scenario:\n\n");
+	printk("       CPU0\n");
+	printk("       ----\n");
+	printk("  lock(");
+	__print_lock_name(prev);
+	printk(KERN_CONT ");\n");
+	printk("  lock(");
+	__print_lock_name(next);
+	printk(KERN_CONT ");\n");
+	printk("\n *** DEADLOCK ***\n\n");
+	printk(" May be due to missing lock nesting notation\n\n");
+}
+
+static void
+print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
+		   struct held_lock *next)
+{
+	if (!debug_locks_off_graph_unlock() || debug_locks_silent)
+		return;
+
+	pr_warn("\n");
+	pr_warn("============================================\n");
+	pr_warn("WARNING: possible recursive locking detected\n");
+	print_kernel_ident();
+	pr_warn("--------------------------------------------\n");
+	pr_warn("%s/%d is trying to acquire lock:\n",
+		curr->comm, task_pid_nr(curr));
+	print_lock(next);
+	pr_warn("\nbut task is already holding lock:\n");
+	print_lock(prev);
+
+	pr_warn("\nother info that might help us debug this:\n");
+	print_deadlock_scenario(next, prev);
+	lockdep_print_held_locks(curr);
+
+	pr_warn("\nstack backtrace:\n");
+	dump_stack();
+}
+
+/*
+ * Check whether we are holding such a class already.
+ *
+ * (Note that this has to be done separately, because the graph cannot
+ * detect such classes of deadlocks.)
+ *
+ * Returns: 0 on deadlock detected, 1 on OK, 2 if another lock with the same
+ * lock class is held but nest_lock is also held, i.e. we rely on the
+ * nest_lock to avoid the deadlock.
+ */
+static int
+check_deadlock(struct task_struct *curr, struct held_lock *next)
+{
+	struct held_lock *prev;
+	struct held_lock *nest = NULL;
+	int i;
+
+	for (i = 0; i < curr->lockdep_depth; i++) {
+		prev = curr->held_locks + i;
+
+		if (prev->instance == next->nest_lock)
+			nest = prev;
+
+		if (hlock_class(prev) != hlock_class(next))
+			continue;
+
+		/*
+		 * Allow read-after-read recursion of the same
+		 * lock class (i.e. read_lock(lock)+read_lock(lock)):
+		 */
+		if ((next->read == 2) && prev->read)
+			continue;
+
+		/*
+		 * We're holding the nest_lock, which serializes this lock's
+		 * nesting behaviour.
+		 */
+		if (nest)
+			return 2;
+
+		print_deadlock_bug(curr, prev, next);
+		return 0;
+	}
+	return 1;
+}
+
+/*
+ * There was a chain-cache miss, and we are about to add a new dependency
+ * to a previous lock. We validate the following rules:
+ *
+ *  - would the adding of the <prev> -> <next> dependency create a
+ *    circular dependency in the graph? [== circular deadlock]
+ *
+ *  - does the new prev->next dependency connect any hardirq-safe lock
+ *    (in the full backwards-subgraph starting at <prev>) with any
+ *    hardirq-unsafe lock (in the full forwards-subgraph starting at
+ *    <next>)? [== illegal lock inversion with hardirq contexts]
+ *
+ *  - does the new prev->next dependency connect any softirq-safe lock
+ *    (in the full backwards-subgraph starting at <prev>) with any
+ *    softirq-unsafe lock (in the full forwards-subgraph starting at
+ *    <next>)? [== illegal lock inversion with softirq contexts]
+ *
+ * any of these scenarios could lead to a deadlock.
+ *
+ * Then if all the validations pass, we add the forwards and backwards
+ * dependency.
+ */
+static int
+check_prev_add(struct task_struct *curr, struct held_lock *prev,
+	       struct held_lock *next, u16 distance,
+	       struct lock_trace **const trace)
+{
+	struct lock_list *entry;
+	enum bfs_result ret;
+
+	if (!hlock_class(prev)->key || !hlock_class(next)->key) {
+		/*
+		 * The warning statements below may trigger a use-after-free
+		 * of the class name. It is better to trigger a use-after free
+		 * and to have the class name most of the time instead of not
+		 * having the class name available.
+		 */
+		WARN_ONCE(!debug_locks_silent && !hlock_class(prev)->key,
+			  "Detected use-after-free of lock class %px/%s\n",
+			  hlock_class(prev),
+			  hlock_class(prev)->name);
+		WARN_ONCE(!debug_locks_silent && !hlock_class(next)->key,
+			  "Detected use-after-free of lock class %px/%s\n",
+			  hlock_class(next),
+			  hlock_class(next)->name);
+		return 2;
+	}
+
+	/*
+	 * Prove that the new <prev> -> <next> dependency would not
+	 * create a circular dependency in the graph. (We do this by
+	 * a breadth-first search into the graph starting at <next>,
+	 * and check whether we can reach <prev>.)
+	 *
+	 * The search is limited by the size of the circular queue (i.e.,
+	 * MAX_CIRCULAR_QUEUE_SIZE) which keeps track of a breadth of nodes
+	 * in the graph whose neighbours are to be checked.
+	 */
+	ret = check_noncircular(next, prev, trace);
+	if (unlikely(bfs_error(ret) || ret == BFS_RMATCH))
+		return 0;
+
+	if (!check_irq_usage(curr, prev, next))
+		return 0;
+
+	/*
+	 * Is the <prev> -> <next> dependency already present?
+	 *
+	 * (this may occur even though this is a new chain: consider
+	 *  e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
+	 *  chains - the second one will be new, but L1 already has
+	 *  L2 added to its dependency list, due to the first chain.)
+	 */
+	list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
+		if (entry->class == hlock_class(next)) {
+			if (distance == 1)
+				entry->distance = 1;
+			entry->dep |= calc_dep(prev, next);
+
+			/*
+			 * Also, update the reverse dependency in @next's
+			 * ->locks_before list.
+			 *
+			 *  Here we reuse @entry as the cursor, which is fine
+			 *  because we won't go to the next iteration of the
+			 *  outer loop:
+			 *
+			 *  For normal cases, we return in the inner loop.
+			 *
+			 *  If we fail to return, we have inconsistency, i.e.
+			 *  <prev>::locks_after contains <next> while
+			 *  <next>::locks_before doesn't contain <prev>. In
+			 *  that case, we return after the inner and indicate
+			 *  something is wrong.
+			 */
+			list_for_each_entry(entry, &hlock_class(next)->locks_before, entry) {
+				if (entry->class == hlock_class(prev)) {
+					if (distance == 1)
+						entry->distance = 1;
+					entry->dep |= calc_depb(prev, next);
+					return 1;
+				}
+			}
+
+			/* <prev> is not found in <next>::locks_before */
+			return 0;
+		}
+	}
+
+#ifdef CONFIG_LOCKDEP_SMALL
+	/*
+	 * Is the <prev> -> <next> link redundant?
+	 */
+	ret = check_redundant(prev, next);
+	if (bfs_error(ret))
+		return 0;
+	else if (ret == BFS_RMATCH)
+		return 2;
+#endif
+
+	if (!*trace) {
+		*trace = save_trace();
+		if (!*trace)
+			return 0;
+	}
+
+	/*
+	 * Ok, all validations passed, add the new lock
+	 * to the previous lock's dependency list:
+	 */
+	ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
+			       &hlock_class(prev)->locks_after,
+			       next->acquire_ip, distance,
+			       calc_dep(prev, next),
+			       *trace);
+
+	if (!ret)
+		return 0;
+
+	ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
+			       &hlock_class(next)->locks_before,
+			       next->acquire_ip, distance,
+			       calc_depb(prev, next),
+			       *trace);
+	if (!ret)
+		return 0;
+
+	return 2;
+}
+
+/*
+ * Add the dependency to all directly-previous locks that are 'relevant'.
+ * The ones that are relevant are (in increasing distance from curr):
+ * all consecutive trylock entries and the final non-trylock entry - or
+ * the end of this context's lock-chain - whichever comes first.
+ */
+static int
+check_prevs_add(struct task_struct *curr, struct held_lock *next)
+{
+	struct lock_trace *trace = NULL;
+	int depth = curr->lockdep_depth;
+	struct held_lock *hlock;
+
+	/*
+	 * Debugging checks.
+	 *
+	 * Depth must not be zero for a non-head lock:
+	 */
+	if (!depth)
+		goto out_bug;
+	/*
+	 * At least two relevant locks must exist for this
+	 * to be a head:
+	 */
+	if (curr->held_locks[depth].irq_context !=
+			curr->held_locks[depth-1].irq_context)
+		goto out_bug;
+
+	for (;;) {
+		u16 distance = curr->lockdep_depth - depth + 1;
+		hlock = curr->held_locks + depth - 1;
+
+		if (hlock->check) {
+			int ret = check_prev_add(curr, hlock, next, distance, &trace);
+			if (!ret)
+				return 0;
+
+			/*
+			 * Stop after the first non-trylock entry,
+			 * as non-trylock entries have added their
+			 * own direct dependencies already, so this
+			 * lock is connected to them indirectly:
+			 */
+			if (!hlock->trylock)
+				break;
+		}
+
+		depth--;
+		/*
+		 * End of lock-stack?
+		 */
+		if (!depth)
+			break;
+		/*
+		 * Stop the search if we cross into another context:
+		 */
+		if (curr->held_locks[depth].irq_context !=
+				curr->held_locks[depth-1].irq_context)
+			break;
+	}
+	return 1;
+out_bug:
+	if (!debug_locks_off_graph_unlock())
+		return 0;
+
+	/*
+	 * Clearly we all shouldn't be here, but since we made it we
+	 * can reliable say we messed up our state. See the above two
+	 * gotos for reasons why we could possibly end up here.
+	 */
+	WARN_ON(1);
+
+	return 0;
+}
+
+struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
+static DECLARE_BITMAP(lock_chains_in_use, MAX_LOCKDEP_CHAINS);
+static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
+unsigned long nr_zapped_lock_chains;
+unsigned int nr_free_chain_hlocks;	/* Free chain_hlocks in buckets */
+unsigned int nr_lost_chain_hlocks;	/* Lost chain_hlocks */
+unsigned int nr_large_chain_blocks;	/* size > MAX_CHAIN_BUCKETS */
+
+/*
+ * The first 2 chain_hlocks entries in the chain block in the bucket
+ * list contains the following meta data:
+ *
+ *   entry[0]:
+ *     Bit    15 - always set to 1 (it is not a class index)
+ *     Bits 0-14 - upper 15 bits of the next block index
+ *   entry[1]    - lower 16 bits of next block index
+ *
+ * A next block index of all 1 bits means it is the end of the list.
+ *
+ * On the unsized bucket (bucket-0), the 3rd and 4th entries contain
+ * the chain block size:
+ *
+ *   entry[2] - upper 16 bits of the chain block size
+ *   entry[3] - lower 16 bits of the chain block size
+ */
+#define MAX_CHAIN_BUCKETS	16
+#define CHAIN_BLK_FLAG		(1U << 15)
+#define CHAIN_BLK_LIST_END	0xFFFFU
+
+static int chain_block_buckets[MAX_CHAIN_BUCKETS];
+
+static inline int size_to_bucket(int size)
+{
+	if (size > MAX_CHAIN_BUCKETS)
+		return 0;
+
+	return size - 1;
+}
+
+/*
+ * Iterate all the chain blocks in a bucket.
+ */
+#define for_each_chain_block(bucket, prev, curr)		\
+	for ((prev) = -1, (curr) = chain_block_buckets[bucket];	\
+	     (curr) >= 0;					\
+	     (prev) = (curr), (curr) = chain_block_next(curr))
+
+/*
+ * next block or -1
+ */
+static inline int chain_block_next(int offset)
+{
+	int next = chain_hlocks[offset];
+
+	WARN_ON_ONCE(!(next & CHAIN_BLK_FLAG));
+
+	if (next == CHAIN_BLK_LIST_END)
+		return -1;
+
+	next &= ~CHAIN_BLK_FLAG;
+	next <<= 16;
+	next |= chain_hlocks[offset + 1];
+
+	return next;
+}
+
+/*
+ * bucket-0 only
+ */
+static inline int chain_block_size(int offset)
+{
+	return (chain_hlocks[offset + 2] << 16) | chain_hlocks[offset + 3];
+}
+
+static inline void init_chain_block(int offset, int next, int bucket, int size)
+{
+	chain_hlocks[offset] = (next >> 16) | CHAIN_BLK_FLAG;
+	chain_hlocks[offset + 1] = (u16)next;
+
+	if (size && !bucket) {
+		chain_hlocks[offset + 2] = size >> 16;
+		chain_hlocks[offset + 3] = (u16)size;
+	}
+}
+
+static inline void add_chain_block(int offset, int size)
+{
+	int bucket = size_to_bucket(size);
+	int next = chain_block_buckets[bucket];
+	int prev, curr;
+
+	if (unlikely(size < 2)) {
+		/*
+		 * We can't store single entries on the freelist. Leak them.
+		 *
+		 * One possible way out would be to uniquely mark them, other
+		 * than with CHAIN_BLK_FLAG, such that we can recover them when
+		 * the block before it is re-added.
+		 */
+		if (size)
+			nr_lost_chain_hlocks++;
+		return;
+	}
+
+	nr_free_chain_hlocks += size;
+	if (!bucket) {
+		nr_large_chain_blocks++;
+
+		/*
+		 * Variable sized, sort large to small.
+		 */
+		for_each_chain_block(0, prev, curr) {
+			if (size >= chain_block_size(curr))
+				break;
+		}
+		init_chain_block(offset, curr, 0, size);
+		if (prev < 0)
+			chain_block_buckets[0] = offset;
+		else
+			init_chain_block(prev, offset, 0, 0);
+		return;
+	}
+	/*
+	 * Fixed size, add to head.
+	 */
+	init_chain_block(offset, next, bucket, size);
+	chain_block_buckets[bucket] = offset;
+}
+
+/*
+ * Only the first block in the list can be deleted.
+ *
+ * For the variable size bucket[0], the first block (the largest one) is
+ * returned, broken up and put back into the pool. So if a chain block of
+ * length > MAX_CHAIN_BUCKETS is ever used and zapped, it will just be
+ * queued up after the primordial chain block and never be used until the
+ * hlock entries in the primordial chain block is almost used up. That
+ * causes fragmentation and reduce allocation efficiency. That can be
+ * monitored by looking at the "large chain blocks" number in lockdep_stats.
+ */
+static inline void del_chain_block(int bucket, int size, int next)
+{
+	nr_free_chain_hlocks -= size;
+	chain_block_buckets[bucket] = next;
+
+	if (!bucket)
+		nr_large_chain_blocks--;
+}
+
+static void init_chain_block_buckets(void)
+{
+	int i;
+
+	for (i = 0; i < MAX_CHAIN_BUCKETS; i++)
+		chain_block_buckets[i] = -1;
+
+	add_chain_block(0, ARRAY_SIZE(chain_hlocks));
+}
+
+/*
+ * Return offset of a chain block of the right size or -1 if not found.
+ *
+ * Fairly simple worst-fit allocator with the addition of a number of size
+ * specific free lists.
+ */
+static int alloc_chain_hlocks(int req)
+{
+	int bucket, curr, size;
+
+	/*
+	 * We rely on the MSB to act as an escape bit to denote freelist
+	 * pointers. Make sure this bit isn't set in 'normal' class_idx usage.
+	 */
+	BUILD_BUG_ON((MAX_LOCKDEP_KEYS-1) & CHAIN_BLK_FLAG);
+
+	init_data_structures_once();
+
+	if (nr_free_chain_hlocks < req)
+		return -1;
+
+	/*
+	 * We require a minimum of 2 (u16) entries to encode a freelist
+	 * 'pointer'.
+	 */
+	req = max(req, 2);
+	bucket = size_to_bucket(req);
+	curr = chain_block_buckets[bucket];
+
+	if (bucket) {
+		if (curr >= 0) {
+			del_chain_block(bucket, req, chain_block_next(curr));
+			return curr;
+		}
+		/* Try bucket 0 */
+		curr = chain_block_buckets[0];
+	}
+
+	/*
+	 * The variable sized freelist is sorted by size; the first entry is
+	 * the largest. Use it if it fits.
+	 */
+	if (curr >= 0) {
+		size = chain_block_size(curr);
+		if (likely(size >= req)) {
+			del_chain_block(0, size, chain_block_next(curr));
+			if (size > req)
+				add_chain_block(curr + req, size - req);
+			return curr;
+		}
+	}
+
+	/*
+	 * Last resort, split a block in a larger sized bucket.
+	 */
+	for (size = MAX_CHAIN_BUCKETS; size > req; size--) {
+		bucket = size_to_bucket(size);
+		curr = chain_block_buckets[bucket];
+		if (curr < 0)
+			continue;
+
+		del_chain_block(bucket, size, chain_block_next(curr));
+		add_chain_block(curr + req, size - req);
+		return curr;
+	}
+
+	return -1;
+}
+
+static inline void free_chain_hlocks(int base, int size)
+{
+	add_chain_block(base, max(size, 2));
+}
+
+struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
+{
+	u16 chain_hlock = chain_hlocks[chain->base + i];
+	unsigned int class_idx = chain_hlock_class_idx(chain_hlock);
+
+	return lock_classes + class_idx;
+}
+
+/*
+ * Returns the index of the first held_lock of the current chain
+ */
+static inline int get_first_held_lock(struct task_struct *curr,
+					struct held_lock *hlock)
+{
+	int i;
+	struct held_lock *hlock_curr;
+
+	for (i = curr->lockdep_depth - 1; i >= 0; i--) {
+		hlock_curr = curr->held_locks + i;
+		if (hlock_curr->irq_context != hlock->irq_context)
+			break;
+
+	}
+
+	return ++i;
+}
+
+#ifdef CONFIG_DEBUG_LOCKDEP
+/*
+ * Returns the next chain_key iteration
+ */
+static u64 print_chain_key_iteration(u16 hlock_id, u64 chain_key)
+{
+	u64 new_chain_key = iterate_chain_key(chain_key, hlock_id);
+
+	printk(" hlock_id:%d -> chain_key:%016Lx",
+		(unsigned int)hlock_id,
+		(unsigned long long)new_chain_key);
+	return new_chain_key;
+}
+
+static void
+print_chain_keys_held_locks(struct task_struct *curr, struct held_lock *hlock_next)
+{
+	struct held_lock *hlock;
+	u64 chain_key = INITIAL_CHAIN_KEY;
+	int depth = curr->lockdep_depth;
+	int i = get_first_held_lock(curr, hlock_next);
+
+	printk("depth: %u (irq_context %u)\n", depth - i + 1,
+		hlock_next->irq_context);
+	for (; i < depth; i++) {
+		hlock = curr->held_locks + i;
+		chain_key = print_chain_key_iteration(hlock_id(hlock), chain_key);
+
+		print_lock(hlock);
+	}
+
+	print_chain_key_iteration(hlock_id(hlock_next), chain_key);
+	print_lock(hlock_next);
+}
+
+static void print_chain_keys_chain(struct lock_chain *chain)
+{
+	int i;
+	u64 chain_key = INITIAL_CHAIN_KEY;
+	u16 hlock_id;
+
+	printk("depth: %u\n", chain->depth);
+	for (i = 0; i < chain->depth; i++) {
+		hlock_id = chain_hlocks[chain->base + i];
+		chain_key = print_chain_key_iteration(hlock_id, chain_key);
+
+		print_lock_name(lock_classes + chain_hlock_class_idx(hlock_id));
+		printk("\n");
+	}
+}
+
+static void print_collision(struct task_struct *curr,
+			struct held_lock *hlock_next,
+			struct lock_chain *chain)
+{
+	pr_warn("\n");
+	pr_warn("============================\n");
+	pr_warn("WARNING: chain_key collision\n");
+	print_kernel_ident();
+	pr_warn("----------------------------\n");
+	pr_warn("%s/%d: ", current->comm, task_pid_nr(current));
+	pr_warn("Hash chain already cached but the contents don't match!\n");
+
+	pr_warn("Held locks:");
+	print_chain_keys_held_locks(curr, hlock_next);
+
+	pr_warn("Locks in cached chain:");
+	print_chain_keys_chain(chain);
+
+	pr_warn("\nstack backtrace:\n");
+	dump_stack();
+}
+#endif
+
+/*
+ * Checks whether the chain and the current held locks are consistent
+ * in depth and also in content. If they are not it most likely means
+ * that there was a collision during the calculation of the chain_key.
+ * Returns: 0 not passed, 1 passed
+ */
+static int check_no_collision(struct task_struct *curr,
+			struct held_lock *hlock,
+			struct lock_chain *chain)
+{
+#ifdef CONFIG_DEBUG_LOCKDEP
+	int i, j, id;
+
+	i = get_first_held_lock(curr, hlock);
+
+	if (DEBUG_LOCKS_WARN_ON(chain->depth != curr->lockdep_depth - (i - 1))) {
+		print_collision(curr, hlock, chain);
+		return 0;
+	}
+
+	for (j = 0; j < chain->depth - 1; j++, i++) {
+		id = hlock_id(&curr->held_locks[i]);
+
+		if (DEBUG_LOCKS_WARN_ON(chain_hlocks[chain->base + j] != id)) {
+			print_collision(curr, hlock, chain);
+			return 0;
+		}
+	}
+#endif
+	return 1;
+}
+
+/*
+ * Given an index that is >= -1, return the index of the next lock chain.
+ * Return -2 if there is no next lock chain.
+ */
+long lockdep_next_lockchain(long i)
+{
+	i = find_next_bit(lock_chains_in_use, ARRAY_SIZE(lock_chains), i + 1);
+	return i < ARRAY_SIZE(lock_chains) ? i : -2;
+}
+
+unsigned long lock_chain_count(void)
+{
+	return bitmap_weight(lock_chains_in_use, ARRAY_SIZE(lock_chains));
+}
+
+/* Must be called with the graph lock held. */
+static struct lock_chain *alloc_lock_chain(void)
+{
+	int idx = find_first_zero_bit(lock_chains_in_use,
+				      ARRAY_SIZE(lock_chains));
+
+	if (unlikely(idx >= ARRAY_SIZE(lock_chains)))
+		return NULL;
+	__set_bit(idx, lock_chains_in_use);
+	return lock_chains + idx;
+}
+
+/*
+ * Adds a dependency chain into chain hashtable. And must be called with
+ * graph_lock held.
+ *
+ * Return 0 if fail, and graph_lock is released.
+ * Return 1 if succeed, with graph_lock held.
+ */
+static inline int add_chain_cache(struct task_struct *curr,
+				  struct held_lock *hlock,
+				  u64 chain_key)
+{
+	struct hlist_head *hash_head = chainhashentry(chain_key);
+	struct lock_chain *chain;
+	int i, j;
+
+	/*
+	 * The caller must hold the graph lock, ensure we've got IRQs
+	 * disabled to make this an IRQ-safe lock.. for recursion reasons
+	 * lockdep won't complain about its own locking errors.
+	 */
+	if (lockdep_assert_locked())
+		return 0;
+
+	chain = alloc_lock_chain();
+	if (!chain) {
+		if (!debug_locks_off_graph_unlock())
+			return 0;
+
+		print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!");
+		dump_stack();
+		return 0;
+	}
+	chain->chain_key = chain_key;
+	chain->irq_context = hlock->irq_context;
+	i = get_first_held_lock(curr, hlock);
+	chain->depth = curr->lockdep_depth + 1 - i;
+
+	BUILD_BUG_ON((1UL << 24) <= ARRAY_SIZE(chain_hlocks));
+	BUILD_BUG_ON((1UL << 6)  <= ARRAY_SIZE(curr->held_locks));
+	BUILD_BUG_ON((1UL << 8*sizeof(chain_hlocks[0])) <= ARRAY_SIZE(lock_classes));
+
+	j = alloc_chain_hlocks(chain->depth);
+	if (j < 0) {
+		if (!debug_locks_off_graph_unlock())
+			return 0;
+
+		print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!");
+		dump_stack();
+		return 0;
+	}
+
+	chain->base = j;
+	for (j = 0; j < chain->depth - 1; j++, i++) {
+		int lock_id = hlock_id(curr->held_locks + i);
+
+		chain_hlocks[chain->base + j] = lock_id;
+	}
+	chain_hlocks[chain->base + j] = hlock_id(hlock);
+	hlist_add_head_rcu(&chain->entry, hash_head);
+	debug_atomic_inc(chain_lookup_misses);
+	inc_chains(chain->irq_context);
+
+	return 1;
+}
+
+/*
+ * Look up a dependency chain. Must be called with either the graph lock or
+ * the RCU read lock held.
+ */
+static inline struct lock_chain *lookup_chain_cache(u64 chain_key)
+{
+	struct hlist_head *hash_head = chainhashentry(chain_key);
+	struct lock_chain *chain;
+
+	hlist_for_each_entry_rcu(chain, hash_head, entry) {
+		if (READ_ONCE(chain->chain_key) == chain_key) {
+			debug_atomic_inc(chain_lookup_hits);
+			return chain;
+		}
+	}
+	return NULL;
+}
+
+/*
+ * If the key is not present yet in dependency chain cache then
+ * add it and return 1 - in this case the new dependency chain is
+ * validated. If the key is already hashed, return 0.
+ * (On return with 1 graph_lock is held.)
+ */
+static inline int lookup_chain_cache_add(struct task_struct *curr,
+					 struct held_lock *hlock,
+					 u64 chain_key)
+{
+	struct lock_class *class = hlock_class(hlock);
+	struct lock_chain *chain = lookup_chain_cache(chain_key);
+
+	if (chain) {
+cache_hit:
+		if (!check_no_collision(curr, hlock, chain))
+			return 0;
+
+		if (very_verbose(class)) {
+			printk("\nhash chain already cached, key: "
+					"%016Lx tail class: [%px] %s\n",
+					(unsigned long long)chain_key,
+					class->key, class->name);
+		}
+
+		return 0;
+	}
+
+	if (very_verbose(class)) {
+		printk("\nnew hash chain, key: %016Lx tail class: [%px] %s\n",
+			(unsigned long long)chain_key, class->key, class->name);
+	}
+
+	if (!graph_lock())
+		return 0;
+
+	/*
+	 * We have to walk the chain again locked - to avoid duplicates:
+	 */
+	chain = lookup_chain_cache(chain_key);
+	if (chain) {
+		graph_unlock();
+		goto cache_hit;
+	}
+
+	if (!add_chain_cache(curr, hlock, chain_key))
+		return 0;
+
+	return 1;
+}
+
+static int validate_chain(struct task_struct *curr,
+			  struct held_lock *hlock,
+			  int chain_head, u64 chain_key)
+{
+	/*
+	 * Trylock needs to maintain the stack of held locks, but it
+	 * does not add new dependencies, because trylock can be done
+	 * in any order.
+	 *
+	 * We look up the chain_key and do the O(N^2) check and update of
+	 * the dependencies only if this is a new dependency chain.
+	 * (If lookup_chain_cache_add() return with 1 it acquires
+	 * graph_lock for us)
+	 */
+	if (!hlock->trylock && hlock->check &&
+	    lookup_chain_cache_add(curr, hlock, chain_key)) {
+		/*
+		 * Check whether last held lock:
+		 *
+		 * - is irq-safe, if this lock is irq-unsafe
+		 * - is softirq-safe, if this lock is hardirq-unsafe
+		 *
+		 * And check whether the new lock's dependency graph
+		 * could lead back to the previous lock:
+		 *
+		 * - within the current held-lock stack
+		 * - across our accumulated lock dependency records
+		 *
+		 * any of these scenarios could lead to a deadlock.
+		 */
+		/*
+		 * The simple case: does the current hold the same lock
+		 * already?
+		 */
+		int ret = check_deadlock(curr, hlock);
+
+		if (!ret)
+			return 0;
+		/*
+		 * Add dependency only if this lock is not the head
+		 * of the chain, and if the new lock introduces no more
+		 * lock dependency (because we already hold a lock with the
+		 * same lock class) nor deadlock (because the nest_lock
+		 * serializes nesting locks), see the comments for
+		 * check_deadlock().
+		 */
+		if (!chain_head && ret != 2) {
+			if (!check_prevs_add(curr, hlock))
+				return 0;
+		}
+
+		graph_unlock();
+	} else {
+		/* after lookup_chain_cache_add(): */
+		if (unlikely(!debug_locks))
+			return 0;
+	}
+
+	return 1;
+}
+#else
+static inline int validate_chain(struct task_struct *curr,
+				 struct held_lock *hlock,
+				 int chain_head, u64 chain_key)
+{
+	return 1;
+}
+
+static void init_chain_block_buckets(void)	{ }
+#endif /* CONFIG_PROVE_LOCKING */
+
+/*
+ * We are building curr_chain_key incrementally, so double-check
+ * it from scratch, to make sure that it's done correctly:
+ */
+static void check_chain_key(struct task_struct *curr)
+{
+#ifdef CONFIG_DEBUG_LOCKDEP
+	struct held_lock *hlock, *prev_hlock = NULL;
+	unsigned int i;
+	u64 chain_key = INITIAL_CHAIN_KEY;
+
+	for (i = 0; i < curr->lockdep_depth; i++) {
+		hlock = curr->held_locks + i;
+		if (chain_key != hlock->prev_chain_key) {
+			debug_locks_off();
+			/*
+			 * We got mighty confused, our chain keys don't match
+			 * with what we expect, someone trample on our task state?
+			 */
+			WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
+				curr->lockdep_depth, i,
+				(unsigned long long)chain_key,
+				(unsigned long long)hlock->prev_chain_key);
+			return;
+		}
+
+		/*
+		 * hlock->class_idx can't go beyond MAX_LOCKDEP_KEYS, but is
+		 * it registered lock class index?
+		 */
+		if (DEBUG_LOCKS_WARN_ON(!test_bit(hlock->class_idx, lock_classes_in_use)))
+			return;
+
+		if (prev_hlock && (prev_hlock->irq_context !=
+							hlock->irq_context))
+			chain_key = INITIAL_CHAIN_KEY;
+		chain_key = iterate_chain_key(chain_key, hlock_id(hlock));
+		prev_hlock = hlock;
+	}
+	if (chain_key != curr->curr_chain_key) {
+		debug_locks_off();
+		/*
+		 * More smoking hash instead of calculating it, damn see these
+		 * numbers float.. I bet that a pink elephant stepped on my memory.
+		 */
+		WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
+			curr->lockdep_depth, i,
+			(unsigned long long)chain_key,
+			(unsigned long long)curr->curr_chain_key);
+	}
+#endif
+}
+
+#ifdef CONFIG_PROVE_LOCKING
+static int mark_lock(struct task_struct *curr, struct held_lock *this,
+		     enum lock_usage_bit new_bit);
+
+static void print_usage_bug_scenario(struct held_lock *lock)
+{
+	struct lock_class *class = hlock_class(lock);
+
+	printk(" Possible unsafe locking scenario:\n\n");
+	printk("       CPU0\n");
+	printk("       ----\n");
+	printk("  lock(");
+	__print_lock_name(class);
+	printk(KERN_CONT ");\n");
+	printk("  <Interrupt>\n");
+	printk("    lock(");
+	__print_lock_name(class);
+	printk(KERN_CONT ");\n");
+	printk("\n *** DEADLOCK ***\n\n");
+}
+
+static void
+print_usage_bug(struct task_struct *curr, struct held_lock *this,
+		enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
+{
+	if (!debug_locks_off() || debug_locks_silent)
+		return;
+
+	pr_warn("\n");
+	pr_warn("================================\n");
+	pr_warn("WARNING: inconsistent lock state\n");
+	print_kernel_ident();
+	pr_warn("--------------------------------\n");
+
+	pr_warn("inconsistent {%s} -> {%s} usage.\n",
+		usage_str[prev_bit], usage_str[new_bit]);
+
+	pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
+		curr->comm, task_pid_nr(curr),
+		lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT,
+		lockdep_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
+		lockdep_hardirqs_enabled(),
+		lockdep_softirqs_enabled(curr));
+	print_lock(this);
+
+	pr_warn("{%s} state was registered at:\n", usage_str[prev_bit]);
+	print_lock_trace(hlock_class(this)->usage_traces[prev_bit], 1);
+
+	print_irqtrace_events(curr);
+	pr_warn("\nother info that might help us debug this:\n");
+	print_usage_bug_scenario(this);
+
+	lockdep_print_held_locks(curr);
+
+	pr_warn("\nstack backtrace:\n");
+	dump_stack();
+}
+
+/*
+ * Print out an error if an invalid bit is set:
+ */
+static inline int
+valid_state(struct task_struct *curr, struct held_lock *this,
+	    enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
+{
+	if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit))) {
+		graph_unlock();
+		print_usage_bug(curr, this, bad_bit, new_bit);
+		return 0;
+	}
+	return 1;
+}
+
+
+/*
+ * print irq inversion bug:
+ */
+static void
+print_irq_inversion_bug(struct task_struct *curr,
+			struct lock_list *root, struct lock_list *other,
+			struct held_lock *this, int forwards,
+			const char *irqclass)
+{
+	struct lock_list *entry = other;
+	struct lock_list *middle = NULL;
+	int depth;
+
+	if (!debug_locks_off_graph_unlock() || debug_locks_silent)
+		return;
+
+	pr_warn("\n");
+	pr_warn("========================================================\n");
+	pr_warn("WARNING: possible irq lock inversion dependency detected\n");
+	print_kernel_ident();
+	pr_warn("--------------------------------------------------------\n");
+	pr_warn("%s/%d just changed the state of lock:\n",
+		curr->comm, task_pid_nr(curr));
+	print_lock(this);
+	if (forwards)
+		pr_warn("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
+	else
+		pr_warn("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
+	print_lock_name(other->class);
+	pr_warn("\n\nand interrupts could create inverse lock ordering between them.\n\n");
+
+	pr_warn("\nother info that might help us debug this:\n");
+
+	/* Find a middle lock (if one exists) */
+	depth = get_lock_depth(other);
+	do {
+		if (depth == 0 && (entry != root)) {
+			pr_warn("lockdep:%s bad path found in chain graph\n", __func__);
+			break;
+		}
+		middle = entry;
+		entry = get_lock_parent(entry);
+		depth--;
+	} while (entry && entry != root && (depth >= 0));
+	if (forwards)
+		print_irq_lock_scenario(root, other,
+			middle ? middle->class : root->class, other->class);
+	else
+		print_irq_lock_scenario(other, root,
+			middle ? middle->class : other->class, root->class);
+
+	lockdep_print_held_locks(curr);
+
+	pr_warn("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
+	root->trace = save_trace();
+	if (!root->trace)
+		return;
+	print_shortest_lock_dependencies(other, root);
+
+	pr_warn("\nstack backtrace:\n");
+	dump_stack();
+}
+
+/*
+ * Prove that in the forwards-direction subgraph starting at <this>
+ * there is no lock matching <mask>:
+ */
+static int
+check_usage_forwards(struct task_struct *curr, struct held_lock *this,
+		     enum lock_usage_bit bit)
+{
+	enum bfs_result ret;
+	struct lock_list root;
+	struct lock_list *target_entry;
+	enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK;
+	unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit);
+
+	bfs_init_root(&root, this);
+	ret = find_usage_forwards(&root, usage_mask, &target_entry);
+	if (bfs_error(ret)) {
+		print_bfs_bug(ret);
+		return 0;
+	}
+	if (ret == BFS_RNOMATCH)
+		return 1;
+
+	/* Check whether write or read usage is the match */
+	if (target_entry->class->usage_mask & lock_flag(bit)) {
+		print_irq_inversion_bug(curr, &root, target_entry,
+					this, 1, state_name(bit));
+	} else {
+		print_irq_inversion_bug(curr, &root, target_entry,
+					this, 1, state_name(read_bit));
+	}
+
+	return 0;
+}
+
+/*
+ * Prove that in the backwards-direction subgraph starting at <this>
+ * there is no lock matching <mask>:
+ */
+static int
+check_usage_backwards(struct task_struct *curr, struct held_lock *this,
+		      enum lock_usage_bit bit)
+{
+	enum bfs_result ret;
+	struct lock_list root;
+	struct lock_list *target_entry;
+	enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK;
+	unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit);
+
+	bfs_init_rootb(&root, this);
+	ret = find_usage_backwards(&root, usage_mask, &target_entry);
+	if (bfs_error(ret)) {
+		print_bfs_bug(ret);
+		return 0;
+	}
+	if (ret == BFS_RNOMATCH)
+		return 1;
+
+	/* Check whether write or read usage is the match */
+	if (target_entry->class->usage_mask & lock_flag(bit)) {
+		print_irq_inversion_bug(curr, &root, target_entry,
+					this, 0, state_name(bit));
+	} else {
+		print_irq_inversion_bug(curr, &root, target_entry,
+					this, 0, state_name(read_bit));
+	}
+
+	return 0;
+}
+
+void print_irqtrace_events(struct task_struct *curr)
+{
+	const struct irqtrace_events *trace = &curr->irqtrace;
+
+	printk("irq event stamp: %u\n", trace->irq_events);
+	printk("hardirqs last  enabled at (%u): [<%px>] %pS\n",
+		trace->hardirq_enable_event, (void *)trace->hardirq_enable_ip,
+		(void *)trace->hardirq_enable_ip);
+	printk("hardirqs last disabled at (%u): [<%px>] %pS\n",
+		trace->hardirq_disable_event, (void *)trace->hardirq_disable_ip,
+		(void *)trace->hardirq_disable_ip);
+	printk("softirqs last  enabled at (%u): [<%px>] %pS\n",
+		trace->softirq_enable_event, (void *)trace->softirq_enable_ip,
+		(void *)trace->softirq_enable_ip);
+	printk("softirqs last disabled at (%u): [<%px>] %pS\n",
+		trace->softirq_disable_event, (void *)trace->softirq_disable_ip,
+		(void *)trace->softirq_disable_ip);
+}
+
+static int HARDIRQ_verbose(struct lock_class *class)
+{
+#if HARDIRQ_VERBOSE
+	return class_filter(class);
+#endif
+	return 0;
+}
+
+static int SOFTIRQ_verbose(struct lock_class *class)
+{
+#if SOFTIRQ_VERBOSE
+	return class_filter(class);
+#endif
+	return 0;
+}
+
+static int (*state_verbose_f[])(struct lock_class *class) = {
+#define LOCKDEP_STATE(__STATE) \
+	__STATE##_verbose,
+#include "lockdep_states.h"
+#undef LOCKDEP_STATE
+};
+
+static inline int state_verbose(enum lock_usage_bit bit,
+				struct lock_class *class)
+{
+	return state_verbose_f[bit >> LOCK_USAGE_DIR_MASK](class);
+}
+
+typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
+			     enum lock_usage_bit bit, const char *name);
+
+static int
+mark_lock_irq(struct task_struct *curr, struct held_lock *this,
+		enum lock_usage_bit new_bit)
+{
+	int excl_bit = exclusive_bit(new_bit);
+	int read = new_bit & LOCK_USAGE_READ_MASK;
+	int dir = new_bit & LOCK_USAGE_DIR_MASK;
+
+	/*
+	 * Validate that this particular lock does not have conflicting
+	 * usage states.
+	 */
+	if (!valid_state(curr, this, new_bit, excl_bit))
+		return 0;
+
+	/*
+	 * Check for read in write conflicts
+	 */
+	if (!read && !valid_state(curr, this, new_bit,
+				  excl_bit + LOCK_USAGE_READ_MASK))
+		return 0;
+
+
+	/*
+	 * Validate that the lock dependencies don't have conflicting usage
+	 * states.
+	 */
+	if (dir) {
+		/*
+		 * mark ENABLED has to look backwards -- to ensure no dependee
+		 * has USED_IN state, which, again, would allow  recursion deadlocks.
+		 */
+		if (!check_usage_backwards(curr, this, excl_bit))
+			return 0;
+	} else {
+		/*
+		 * mark USED_IN has to look forwards -- to ensure no dependency
+		 * has ENABLED state, which would allow recursion deadlocks.
+		 */
+		if (!check_usage_forwards(curr, this, excl_bit))
+			return 0;
+	}
+
+	if (state_verbose(new_bit, hlock_class(this)))
+		return 2;
+
+	return 1;
+}
+
+/*
+ * Mark all held locks with a usage bit:
+ */
+static int
+mark_held_locks(struct task_struct *curr, enum lock_usage_bit base_bit)
+{
+	struct held_lock *hlock;
+	int i;
+
+	for (i = 0; i < curr->lockdep_depth; i++) {
+		enum lock_usage_bit hlock_bit = base_bit;
+		hlock = curr->held_locks + i;
+
+		if (hlock->read)
+			hlock_bit += LOCK_USAGE_READ_MASK;
+
+		BUG_ON(hlock_bit >= LOCK_USAGE_STATES);
+
+		if (!hlock->check)
+			continue;
+
+		if (!mark_lock(curr, hlock, hlock_bit))
+			return 0;
+	}
+
+	return 1;
+}
+
+/*
+ * Hardirqs will be enabled:
+ */
+static void __trace_hardirqs_on_caller(void)
+{
+	struct task_struct *curr = current;
+
+	/*
+	 * We are going to turn hardirqs on, so set the
+	 * usage bit for all held locks:
+	 */
+	if (!mark_held_locks(curr, LOCK_ENABLED_HARDIRQ))
+		return;
+	/*
+	 * If we have softirqs enabled, then set the usage
+	 * bit for all held locks. (disabled hardirqs prevented
+	 * this bit from being set before)
+	 */
+	if (curr->softirqs_enabled)
+		mark_held_locks(curr, LOCK_ENABLED_SOFTIRQ);
+}
+
+/**
+ * lockdep_hardirqs_on_prepare - Prepare for enabling interrupts
+ * @ip:		Caller address
+ *
+ * Invoked before a possible transition to RCU idle from exit to user or
+ * guest mode. This ensures that all RCU operations are done before RCU
+ * stops watching. After the RCU transition lockdep_hardirqs_on() has to be
+ * invoked to set the final state.
+ */
+void lockdep_hardirqs_on_prepare(unsigned long ip)
+{
+	if (unlikely(!debug_locks))
+		return;
+
+	/*
+	 * NMIs do not (and cannot) track lock dependencies, nothing to do.
+	 */
+	if (unlikely(in_nmi()))
+		return;
+
+	if (unlikely(this_cpu_read(lockdep_recursion)))
+		return;
+
+	if (unlikely(lockdep_hardirqs_enabled())) {
+		/*
+		 * Neither irq nor preemption are disabled here
+		 * so this is racy by nature but losing one hit
+		 * in a stat is not a big deal.
+		 */
+		__debug_atomic_inc(redundant_hardirqs_on);
+		return;
+	}
+
+	/*
+	 * We're enabling irqs and according to our state above irqs weren't
+	 * already enabled, yet we find the hardware thinks they are in fact
+	 * enabled.. someone messed up their IRQ state tracing.
+	 */
+	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
+		return;
+
+	/*
+	 * See the fine text that goes along with this variable definition.
+	 */
+	if (DEBUG_LOCKS_WARN_ON(early_boot_irqs_disabled))
+		return;
+
+	/*
+	 * Can't allow enabling interrupts while in an interrupt handler,
+	 * that's general bad form and such. Recursion, limited stack etc..
+	 */
+	if (DEBUG_LOCKS_WARN_ON(lockdep_hardirq_context()))
+		return;
+
+	current->hardirq_chain_key = current->curr_chain_key;
+
+	lockdep_recursion_inc();
+	__trace_hardirqs_on_caller();
+	lockdep_recursion_finish();
+}
+EXPORT_SYMBOL_GPL(lockdep_hardirqs_on_prepare);
+
+void noinstr lockdep_hardirqs_on(unsigned long ip)
+{
+	struct irqtrace_events *trace = &current->irqtrace;
+
+	if (unlikely(!debug_locks))
+		return;
+
+	/*
+	 * NMIs can happen in the middle of local_irq_{en,dis}able() where the
+	 * tracking state and hardware state are out of sync.
+	 *
+	 * NMIs must save lockdep_hardirqs_enabled() to restore IRQ state from,
+	 * and not rely on hardware state like normal interrupts.
+	 */
+	if (unlikely(in_nmi())) {
+		if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI))
+			return;
+
+		/*
+		 * Skip:
+		 *  - recursion check, because NMI can hit lockdep;
+		 *  - hardware state check, because above;
+		 *  - chain_key check, see lockdep_hardirqs_on_prepare().
+		 */
+		goto skip_checks;
+	}
+
+	if (unlikely(this_cpu_read(lockdep_recursion)))
+		return;
+
+	if (lockdep_hardirqs_enabled()) {
+		/*
+		 * Neither irq nor preemption are disabled here
+		 * so this is racy by nature but losing one hit
+		 * in a stat is not a big deal.
+		 */
+		__debug_atomic_inc(redundant_hardirqs_on);
+		return;
+	}
+
+	/*
+	 * We're enabling irqs and according to our state above irqs weren't
+	 * already enabled, yet we find the hardware thinks they are in fact
+	 * enabled.. someone messed up their IRQ state tracing.
+	 */
+	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
+		return;
+
+	/*
+	 * Ensure the lock stack remained unchanged between
+	 * lockdep_hardirqs_on_prepare() and lockdep_hardirqs_on().
+	 */
+	DEBUG_LOCKS_WARN_ON(current->hardirq_chain_key !=
+			    current->curr_chain_key);
+
+skip_checks:
+	/* we'll do an OFF -> ON transition: */
+	__this_cpu_write(hardirqs_enabled, 1);
+	trace->hardirq_enable_ip = ip;
+	trace->hardirq_enable_event = ++trace->irq_events;
+	debug_atomic_inc(hardirqs_on_events);
+}
+EXPORT_SYMBOL_GPL(lockdep_hardirqs_on);
+
+/*
+ * Hardirqs were disabled:
+ */
+void noinstr lockdep_hardirqs_off(unsigned long ip)
+{
+	if (unlikely(!debug_locks))
+		return;
+
+	/*
+	 * Matching lockdep_hardirqs_on(), allow NMIs in the middle of lockdep;
+	 * they will restore the software state. This ensures the software
+	 * state is consistent inside NMIs as well.
+	 */
+	if (in_nmi()) {
+		if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI))
+			return;
+	} else if (__this_cpu_read(lockdep_recursion))
+		return;
+
+	/*
+	 * So we're supposed to get called after you mask local IRQs, but for
+	 * some reason the hardware doesn't quite think you did a proper job.
+	 */
+	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
+		return;
+
+	if (lockdep_hardirqs_enabled()) {
+		struct irqtrace_events *trace = &current->irqtrace;
+
+		/*
+		 * We have done an ON -> OFF transition:
+		 */
+		__this_cpu_write(hardirqs_enabled, 0);
+		trace->hardirq_disable_ip = ip;
+		trace->hardirq_disable_event = ++trace->irq_events;
+		debug_atomic_inc(hardirqs_off_events);
+	} else {
+		debug_atomic_inc(redundant_hardirqs_off);
+	}
+}
+EXPORT_SYMBOL_GPL(lockdep_hardirqs_off);
+
+/*
+ * Softirqs will be enabled:
+ */
+void lockdep_softirqs_on(unsigned long ip)
+{
+	struct irqtrace_events *trace = &current->irqtrace;
+
+	if (unlikely(!lockdep_enabled()))
+		return;
+
+	/*
+	 * We fancy IRQs being disabled here, see softirq.c, avoids
+	 * funny state and nesting things.
+	 */
+	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
+		return;
+
+	if (current->softirqs_enabled) {
+		debug_atomic_inc(redundant_softirqs_on);
+		return;
+	}
+
+	lockdep_recursion_inc();
+	/*
+	 * We'll do an OFF -> ON transition:
+	 */
+	current->softirqs_enabled = 1;
+	trace->softirq_enable_ip = ip;
+	trace->softirq_enable_event = ++trace->irq_events;
+	debug_atomic_inc(softirqs_on_events);
+	/*
+	 * We are going to turn softirqs on, so set the
+	 * usage bit for all held locks, if hardirqs are
+	 * enabled too:
+	 */
+	if (lockdep_hardirqs_enabled())
+		mark_held_locks(current, LOCK_ENABLED_SOFTIRQ);
+	lockdep_recursion_finish();
+}
+
+/*
+ * Softirqs were disabled:
+ */
+void lockdep_softirqs_off(unsigned long ip)
+{
+	if (unlikely(!lockdep_enabled()))
+		return;
+
+	/*
+	 * We fancy IRQs being disabled here, see softirq.c
+	 */
+	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
+		return;
+
+	if (current->softirqs_enabled) {
+		struct irqtrace_events *trace = &current->irqtrace;
+
+		/*
+		 * We have done an ON -> OFF transition:
+		 */
+		current->softirqs_enabled = 0;
+		trace->softirq_disable_ip = ip;
+		trace->softirq_disable_event = ++trace->irq_events;
+		debug_atomic_inc(softirqs_off_events);
+		/*
+		 * Whoops, we wanted softirqs off, so why aren't they?
+		 */
+		DEBUG_LOCKS_WARN_ON(!softirq_count());
+	} else
+		debug_atomic_inc(redundant_softirqs_off);
+}
+
+static int
+mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
+{
+	if (!check)
+		goto lock_used;
+
+	/*
+	 * If non-trylock use in a hardirq or softirq context, then
+	 * mark the lock as used in these contexts:
+	 */
+	if (!hlock->trylock) {
+		if (hlock->read) {
+			if (lockdep_hardirq_context())
+				if (!mark_lock(curr, hlock,
+						LOCK_USED_IN_HARDIRQ_READ))
+					return 0;
+			if (curr->softirq_context)
+				if (!mark_lock(curr, hlock,
+						LOCK_USED_IN_SOFTIRQ_READ))
+					return 0;
+		} else {
+			if (lockdep_hardirq_context())
+				if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
+					return 0;
+			if (curr->softirq_context)
+				if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
+					return 0;
+		}
+	}
+	if (!hlock->hardirqs_off) {
+		if (hlock->read) {
+			if (!mark_lock(curr, hlock,
+					LOCK_ENABLED_HARDIRQ_READ))
+				return 0;
+			if (curr->softirqs_enabled)
+				if (!mark_lock(curr, hlock,
+						LOCK_ENABLED_SOFTIRQ_READ))
+					return 0;
+		} else {
+			if (!mark_lock(curr, hlock,
+					LOCK_ENABLED_HARDIRQ))
+				return 0;
+			if (curr->softirqs_enabled)
+				if (!mark_lock(curr, hlock,
+						LOCK_ENABLED_SOFTIRQ))
+					return 0;
+		}
+	}
+
+lock_used:
+	/* mark it as used: */
+	if (!mark_lock(curr, hlock, LOCK_USED))
+		return 0;
+
+	return 1;
+}
+
+static inline unsigned int task_irq_context(struct task_struct *task)
+{
+	return LOCK_CHAIN_HARDIRQ_CONTEXT * !!lockdep_hardirq_context() +
+	       LOCK_CHAIN_SOFTIRQ_CONTEXT * !!task->softirq_context;
+}
+
+static int separate_irq_context(struct task_struct *curr,
+		struct held_lock *hlock)
+{
+	unsigned int depth = curr->lockdep_depth;
+
+	/*
+	 * Keep track of points where we cross into an interrupt context:
+	 */
+	if (depth) {
+		struct held_lock *prev_hlock;
+
+		prev_hlock = curr->held_locks + depth-1;
+		/*
+		 * If we cross into another context, reset the
+		 * hash key (this also prevents the checking and the
+		 * adding of the dependency to 'prev'):
+		 */
+		if (prev_hlock->irq_context != hlock->irq_context)
+			return 1;
+	}
+	return 0;
+}
+
+/*
+ * Mark a lock with a usage bit, and validate the state transition:
+ */
+static int mark_lock(struct task_struct *curr, struct held_lock *this,
+			     enum lock_usage_bit new_bit)
+{
+	unsigned int new_mask, ret = 1;
+
+	if (new_bit >= LOCK_USAGE_STATES) {
+		DEBUG_LOCKS_WARN_ON(1);
+		return 0;
+	}
+
+	if (new_bit == LOCK_USED && this->read)
+		new_bit = LOCK_USED_READ;
+
+	new_mask = 1 << new_bit;
+
+	/*
+	 * If already set then do not dirty the cacheline,
+	 * nor do any checks:
+	 */
+	if (likely(hlock_class(this)->usage_mask & new_mask))
+		return 1;
+
+	if (!graph_lock())
+		return 0;
+	/*
+	 * Make sure we didn't race:
+	 */
+	if (unlikely(hlock_class(this)->usage_mask & new_mask))
+		goto unlock;
+
+	if (!hlock_class(this)->usage_mask)
+		debug_atomic_dec(nr_unused_locks);
+
+	hlock_class(this)->usage_mask |= new_mask;
+
+	if (new_bit < LOCK_TRACE_STATES) {
+		if (!(hlock_class(this)->usage_traces[new_bit] = save_trace()))
+			return 0;
+	}
+
+	if (new_bit < LOCK_USED) {
+		ret = mark_lock_irq(curr, this, new_bit);
+		if (!ret)
+			return 0;
+	}
+
+unlock:
+	graph_unlock();
+
+	/*
+	 * We must printk outside of the graph_lock:
+	 */
+	if (ret == 2) {
+		printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
+		print_lock(this);
+		print_irqtrace_events(curr);
+		dump_stack();
+	}
+
+	return ret;
+}
+
+static inline short task_wait_context(struct task_struct *curr)
+{
+	/*
+	 * Set appropriate wait type for the context; for IRQs we have to take
+	 * into account force_irqthread as that is implied by PREEMPT_RT.
+	 */
+	if (lockdep_hardirq_context()) {
+		/*
+		 * Check if force_irqthreads will run us threaded.
+		 */
+		if (curr->hardirq_threaded || curr->irq_config)
+			return LD_WAIT_CONFIG;
+
+		return LD_WAIT_SPIN;
+	} else if (curr->softirq_context) {
+		/*
+		 * Softirqs are always threaded.
+		 */
+		return LD_WAIT_CONFIG;
+	}
+
+	return LD_WAIT_MAX;
+}
+
+static int
+print_lock_invalid_wait_context(struct task_struct *curr,
+				struct held_lock *hlock)
+{
+	short curr_inner;
+
+	if (!debug_locks_off())
+		return 0;
+	if (debug_locks_silent)
+		return 0;
+
+	pr_warn("\n");
+	pr_warn("=============================\n");
+	pr_warn("[ BUG: Invalid wait context ]\n");
+	print_kernel_ident();
+	pr_warn("-----------------------------\n");
+
+	pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
+	print_lock(hlock);
+
+	pr_warn("other info that might help us debug this:\n");
+
+	curr_inner = task_wait_context(curr);
+	pr_warn("context-{%d:%d}\n", curr_inner, curr_inner);
+
+	lockdep_print_held_locks(curr);
+
+	pr_warn("stack backtrace:\n");
+	dump_stack();
+
+	return 0;
+}
+
+/*
+ * Verify the wait_type context.
+ *
+ * This check validates we takes locks in the right wait-type order; that is it
+ * ensures that we do not take mutexes inside spinlocks and do not attempt to
+ * acquire spinlocks inside raw_spinlocks and the sort.
+ *
+ * The entire thing is slightly more complex because of RCU, RCU is a lock that
+ * can be taken from (pretty much) any context but also has constraints.
+ * However when taken in a stricter environment the RCU lock does not loosen
+ * the constraints.
+ *
+ * Therefore we must look for the strictest environment in the lock stack and
+ * compare that to the lock we're trying to acquire.
+ */
+static int check_wait_context(struct task_struct *curr, struct held_lock *next)
+{
+	u8 next_inner = hlock_class(next)->wait_type_inner;
+	u8 next_outer = hlock_class(next)->wait_type_outer;
+	u8 curr_inner;
+	int depth;
+
+	if (!next_inner || next->trylock)
+		return 0;
+
+	if (!next_outer)
+		next_outer = next_inner;
+
+	/*
+	 * Find start of current irq_context..
+	 */
+	for (depth = curr->lockdep_depth - 1; depth >= 0; depth--) {
+		struct held_lock *prev = curr->held_locks + depth;
+		if (prev->irq_context != next->irq_context)
+			break;
+	}
+	depth++;
+
+	curr_inner = task_wait_context(curr);
+
+	for (; depth < curr->lockdep_depth; depth++) {
+		struct held_lock *prev = curr->held_locks + depth;
+		u8 prev_inner = hlock_class(prev)->wait_type_inner;
+
+		if (prev_inner) {
+			/*
+			 * We can have a bigger inner than a previous one
+			 * when outer is smaller than inner, as with RCU.
+			 *
+			 * Also due to trylocks.
+			 */
+			curr_inner = min(curr_inner, prev_inner);
+		}
+	}
+
+	if (next_outer > curr_inner)
+		return print_lock_invalid_wait_context(curr, next);
+
+	return 0;
+}
+
+#else /* CONFIG_PROVE_LOCKING */
+
+static inline int
+mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
+{
+	return 1;
+}
+
+static inline unsigned int task_irq_context(struct task_struct *task)
+{
+	return 0;
+}
+
+static inline int separate_irq_context(struct task_struct *curr,
+		struct held_lock *hlock)
+{
+	return 0;
+}
+
+static inline int check_wait_context(struct task_struct *curr,
+				     struct held_lock *next)
+{
+	return 0;
+}
+
+#endif /* CONFIG_PROVE_LOCKING */
+
+/*
+ * Initialize a lock instance's lock-class mapping info:
+ */
+void lockdep_init_map_type(struct lockdep_map *lock, const char *name,
+			    struct lock_class_key *key, int subclass,
+			    u8 inner, u8 outer, u8 lock_type)
+{
+	int i;
+
+	for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
+		lock->class_cache[i] = NULL;
+
+#ifdef CONFIG_LOCK_STAT
+	lock->cpu = raw_smp_processor_id();
+#endif
+
+	/*
+	 * Can't be having no nameless bastards around this place!
+	 */
+	if (DEBUG_LOCKS_WARN_ON(!name)) {
+		lock->name = "NULL";
+		return;
+	}
+
+	lock->name = name;
+
+	lock->wait_type_outer = outer;
+	lock->wait_type_inner = inner;
+	lock->lock_type = lock_type;
+
+	/*
+	 * No key, no joy, we need to hash something.
+	 */
+	if (DEBUG_LOCKS_WARN_ON(!key))
+		return;
+	/*
+	 * Sanity check, the lock-class key must either have been allocated
+	 * statically or must have been registered as a dynamic key.
+	 */
+	if (!static_obj(key) && !is_dynamic_key(key)) {
+		if (debug_locks)
+			printk(KERN_ERR "BUG: key %px has not been registered!\n", key);
+		DEBUG_LOCKS_WARN_ON(1);
+		return;
+	}
+	lock->key = key;
+
+	if (unlikely(!debug_locks))
+		return;
+
+	if (subclass) {
+		unsigned long flags;
+
+		if (DEBUG_LOCKS_WARN_ON(!lockdep_enabled()))
+			return;
+
+		raw_local_irq_save(flags);
+		lockdep_recursion_inc();
+		register_lock_class(lock, subclass, 1);
+		lockdep_recursion_finish();
+		raw_local_irq_restore(flags);
+	}
+}
+EXPORT_SYMBOL_GPL(lockdep_init_map_type);
+
+struct lock_class_key __lockdep_no_validate__;
+EXPORT_SYMBOL_GPL(__lockdep_no_validate__);
+
+static void
+print_lock_nested_lock_not_held(struct task_struct *curr,
+				struct held_lock *hlock,
+				unsigned long ip)
+{
+	if (!debug_locks_off())
+		return;
+	if (debug_locks_silent)
+		return;
+
+	pr_warn("\n");
+	pr_warn("==================================\n");
+	pr_warn("WARNING: Nested lock was not taken\n");
+	print_kernel_ident();
+	pr_warn("----------------------------------\n");
+
+	pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
+	print_lock(hlock);
+
+	pr_warn("\nbut this task is not holding:\n");
+	pr_warn("%s\n", hlock->nest_lock->name);
+
+	pr_warn("\nstack backtrace:\n");
+	dump_stack();
+
+	pr_warn("\nother info that might help us debug this:\n");
+	lockdep_print_held_locks(curr);
+
+	pr_warn("\nstack backtrace:\n");
+	dump_stack();
+}
+
+static int __lock_is_held(const struct lockdep_map *lock, int read);
+
+/*
+ * This gets called for every mutex_lock*()/spin_lock*() operation.
+ * We maintain the dependency maps and validate the locking attempt:
+ *
+ * The callers must make sure that IRQs are disabled before calling it,
+ * otherwise we could get an interrupt which would want to take locks,
+ * which would end up in lockdep again.
+ */
+static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
+			  int trylock, int read, int check, int hardirqs_off,
+			  struct lockdep_map *nest_lock, unsigned long ip,
+			  int references, int pin_count)
+{
+	struct task_struct *curr = current;
+	struct lock_class *class = NULL;
+	struct held_lock *hlock;
+	unsigned int depth;
+	int chain_head = 0;
+	int class_idx;
+	u64 chain_key;
+
+	if (unlikely(!debug_locks))
+		return 0;
+
+	if (!prove_locking || lock->key == &__lockdep_no_validate__)
+		check = 0;
+
+	if (subclass < NR_LOCKDEP_CACHING_CLASSES)
+		class = lock->class_cache[subclass];
+	/*
+	 * Not cached?
+	 */
+	if (unlikely(!class)) {
+		class = register_lock_class(lock, subclass, 0);
+		if (!class)
+			return 0;
+	}
+
+	debug_class_ops_inc(class);
+
+	if (very_verbose(class)) {
+		printk("\nacquire class [%px] %s", class->key, class->name);
+		if (class->name_version > 1)
+			printk(KERN_CONT "#%d", class->name_version);
+		printk(KERN_CONT "\n");
+		dump_stack();
+	}
+
+	/*
+	 * Add the lock to the list of currently held locks.
+	 * (we dont increase the depth just yet, up until the
+	 * dependency checks are done)
+	 */
+	depth = curr->lockdep_depth;
+	/*
+	 * Ran out of static storage for our per-task lock stack again have we?
+	 */
+	if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
+		return 0;
+
+	class_idx = class - lock_classes;
+
+	if (depth) { /* we're holding locks */
+		hlock = curr->held_locks + depth - 1;
+		if (hlock->class_idx == class_idx && nest_lock) {
+			if (!references)
+				references++;
+
+			if (!hlock->references)
+				hlock->references++;
+
+			hlock->references += references;
+
+			/* Overflow */
+			if (DEBUG_LOCKS_WARN_ON(hlock->references < references))
+				return 0;
+
+			return 2;
+		}
+	}
+
+	hlock = curr->held_locks + depth;
+	/*
+	 * Plain impossible, we just registered it and checked it weren't no
+	 * NULL like.. I bet this mushroom I ate was good!
+	 */
+	if (DEBUG_LOCKS_WARN_ON(!class))
+		return 0;
+	hlock->class_idx = class_idx;
+	hlock->acquire_ip = ip;
+	hlock->instance = lock;
+	hlock->nest_lock = nest_lock;
+	hlock->irq_context = task_irq_context(curr);
+	hlock->trylock = trylock;
+	hlock->read = read;
+	hlock->check = check;
+	hlock->hardirqs_off = !!hardirqs_off;
+	hlock->references = references;
+#ifdef CONFIG_LOCK_STAT
+	hlock->waittime_stamp = 0;
+	hlock->holdtime_stamp = lockstat_clock();
+#endif
+	hlock->pin_count = pin_count;
+
+	if (check_wait_context(curr, hlock))
+		return 0;
+
+	/* Initialize the lock usage bit */
+	if (!mark_usage(curr, hlock, check))
+		return 0;
+
+	/*
+	 * Calculate the chain hash: it's the combined hash of all the
+	 * lock keys along the dependency chain. We save the hash value
+	 * at every step so that we can get the current hash easily
+	 * after unlock. The chain hash is then used to cache dependency
+	 * results.
+	 *
+	 * The 'key ID' is what is the most compact key value to drive
+	 * the hash, not class->key.
+	 */
+	/*
+	 * Whoops, we did it again.. class_idx is invalid.
+	 */
+	if (DEBUG_LOCKS_WARN_ON(!test_bit(class_idx, lock_classes_in_use)))
+		return 0;
+
+	chain_key = curr->curr_chain_key;
+	if (!depth) {
+		/*
+		 * How can we have a chain hash when we ain't got no keys?!
+		 */
+		if (DEBUG_LOCKS_WARN_ON(chain_key != INITIAL_CHAIN_KEY))
+			return 0;
+		chain_head = 1;
+	}
+
+	hlock->prev_chain_key = chain_key;
+	if (separate_irq_context(curr, hlock)) {
+		chain_key = INITIAL_CHAIN_KEY;
+		chain_head = 1;
+	}
+	chain_key = iterate_chain_key(chain_key, hlock_id(hlock));
+
+	if (nest_lock && !__lock_is_held(nest_lock, -1)) {
+		print_lock_nested_lock_not_held(curr, hlock, ip);
+		return 0;
+	}
+
+	if (!debug_locks_silent) {
+		WARN_ON_ONCE(depth && !hlock_class(hlock - 1)->key);
+		WARN_ON_ONCE(!hlock_class(hlock)->key);
+	}
+
+	if (!validate_chain(curr, hlock, chain_head, chain_key))
+		return 0;
+
+	curr->curr_chain_key = chain_key;
+	curr->lockdep_depth++;
+	check_chain_key(curr);
+#ifdef CONFIG_DEBUG_LOCKDEP
+	if (unlikely(!debug_locks))
+		return 0;
+#endif
+	if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
+		debug_locks_off();
+		print_lockdep_off("BUG: MAX_LOCK_DEPTH too low!");
+		printk(KERN_DEBUG "depth: %i  max: %lu!\n",
+		       curr->lockdep_depth, MAX_LOCK_DEPTH);
+
+		lockdep_print_held_locks(current);
+		debug_show_all_locks();
+		dump_stack();
+
+		return 0;
+	}
+
+	if (unlikely(curr->lockdep_depth > max_lockdep_depth))
+		max_lockdep_depth = curr->lockdep_depth;
+
+	return 1;
+}
+
+static void print_unlock_imbalance_bug(struct task_struct *curr,
+				       struct lockdep_map *lock,
+				       unsigned long ip)
+{
+	if (!debug_locks_off())
+		return;
+	if (debug_locks_silent)
+		return;
+
+	pr_warn("\n");
+	pr_warn("=====================================\n");
+	pr_warn("WARNING: bad unlock balance detected!\n");
+	print_kernel_ident();
+	pr_warn("-------------------------------------\n");
+	pr_warn("%s/%d is trying to release lock (",
+		curr->comm, task_pid_nr(curr));
+	print_lockdep_cache(lock);
+	pr_cont(") at:\n");
+	print_ip_sym(KERN_WARNING, ip);
+	pr_warn("but there are no more locks to release!\n");
+	pr_warn("\nother info that might help us debug this:\n");
+	lockdep_print_held_locks(curr);
+
+	pr_warn("\nstack backtrace:\n");
+	dump_stack();
+}
+
+static noinstr int match_held_lock(const struct held_lock *hlock,
+				   const struct lockdep_map *lock)
+{
+	if (hlock->instance == lock)
+		return 1;
+
+	if (hlock->references) {
+		const struct lock_class *class = lock->class_cache[0];
+
+		if (!class)
+			class = look_up_lock_class(lock, 0);
+
+		/*
+		 * If look_up_lock_class() failed to find a class, we're trying
+		 * to test if we hold a lock that has never yet been acquired.
+		 * Clearly if the lock hasn't been acquired _ever_, we're not
+		 * holding it either, so report failure.
+		 */
+		if (!class)
+			return 0;
+
+		/*
+		 * References, but not a lock we're actually ref-counting?
+		 * State got messed up, follow the sites that change ->references
+		 * and try to make sense of it.
+		 */
+		if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock))
+			return 0;
+
+		if (hlock->class_idx == class - lock_classes)
+			return 1;
+	}
+
+	return 0;
+}
+
+/* @depth must not be zero */
+static struct held_lock *find_held_lock(struct task_struct *curr,
+					struct lockdep_map *lock,
+					unsigned int depth, int *idx)
+{
+	struct held_lock *ret, *hlock, *prev_hlock;
+	int i;
+
+	i = depth - 1;
+	hlock = curr->held_locks + i;
+	ret = hlock;
+	if (match_held_lock(hlock, lock))
+		goto out;
+
+	ret = NULL;
+	for (i--, prev_hlock = hlock--;
+	     i >= 0;
+	     i--, prev_hlock = hlock--) {
+		/*
+		 * We must not cross into another context:
+		 */
+		if (prev_hlock->irq_context != hlock->irq_context) {
+			ret = NULL;
+			break;
+		}
+		if (match_held_lock(hlock, lock)) {
+			ret = hlock;
+			break;
+		}
+	}
+
+out:
+	*idx = i;
+	return ret;
+}
+
+static int reacquire_held_locks(struct task_struct *curr, unsigned int depth,
+				int idx, unsigned int *merged)
+{
+	struct held_lock *hlock;
+	int first_idx = idx;
+
+	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
+		return 0;
+
+	for (hlock = curr->held_locks + idx; idx < depth; idx++, hlock++) {
+		switch (__lock_acquire(hlock->instance,
+				    hlock_class(hlock)->subclass,
+				    hlock->trylock,
+				    hlock->read, hlock->check,
+				    hlock->hardirqs_off,
+				    hlock->nest_lock, hlock->acquire_ip,
+				    hlock->references, hlock->pin_count)) {
+		case 0:
+			return 1;
+		case 1:
+			break;
+		case 2:
+			*merged += (idx == first_idx);
+			break;
+		default:
+			WARN_ON(1);
+			return 0;
+		}
+	}
+	return 0;
+}
+
+static int
+__lock_set_class(struct lockdep_map *lock, const char *name,
+		 struct lock_class_key *key, unsigned int subclass,
+		 unsigned long ip)
+{
+	struct task_struct *curr = current;
+	unsigned int depth, merged = 0;
+	struct held_lock *hlock;
+	struct lock_class *class;
+	int i;
+
+	if (unlikely(!debug_locks))
+		return 0;
+
+	depth = curr->lockdep_depth;
+	/*
+	 * This function is about (re)setting the class of a held lock,
+	 * yet we're not actually holding any locks. Naughty user!
+	 */
+	if (DEBUG_LOCKS_WARN_ON(!depth))
+		return 0;
+
+	hlock = find_held_lock(curr, lock, depth, &i);
+	if (!hlock) {
+		print_unlock_imbalance_bug(curr, lock, ip);
+		return 0;
+	}
+
+	lockdep_init_map_type(lock, name, key, 0,
+			      lock->wait_type_inner,
+			      lock->wait_type_outer,
+			      lock->lock_type);
+	class = register_lock_class(lock, subclass, 0);
+	hlock->class_idx = class - lock_classes;
+
+	curr->lockdep_depth = i;
+	curr->curr_chain_key = hlock->prev_chain_key;
+
+	if (reacquire_held_locks(curr, depth, i, &merged))
+		return 0;
+
+	/*
+	 * I took it apart and put it back together again, except now I have
+	 * these 'spare' parts.. where shall I put them.
+	 */
+	if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged))
+		return 0;
+	return 1;
+}
+
+static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip)
+{
+	struct task_struct *curr = current;
+	unsigned int depth, merged = 0;
+	struct held_lock *hlock;
+	int i;
+
+	if (unlikely(!debug_locks))
+		return 0;
+
+	depth = curr->lockdep_depth;
+	/*
+	 * This function is about (re)setting the class of a held lock,
+	 * yet we're not actually holding any locks. Naughty user!
+	 */
+	if (DEBUG_LOCKS_WARN_ON(!depth))
+		return 0;
+
+	hlock = find_held_lock(curr, lock, depth, &i);
+	if (!hlock) {
+		print_unlock_imbalance_bug(curr, lock, ip);
+		return 0;
+	}
+
+	curr->lockdep_depth = i;
+	curr->curr_chain_key = hlock->prev_chain_key;
+
+	WARN(hlock->read, "downgrading a read lock");
+	hlock->read = 1;
+	hlock->acquire_ip = ip;
+
+	if (reacquire_held_locks(curr, depth, i, &merged))
+		return 0;
+
+	/* Merging can't happen with unchanged classes.. */
+	if (DEBUG_LOCKS_WARN_ON(merged))
+		return 0;
+
+	/*
+	 * I took it apart and put it back together again, except now I have
+	 * these 'spare' parts.. where shall I put them.
+	 */
+	if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
+		return 0;
+
+	return 1;
+}
+
+/*
+ * Remove the lock from the list of currently held locks - this gets
+ * called on mutex_unlock()/spin_unlock*() (or on a failed
+ * mutex_lock_interruptible()).
+ */
+static int
+__lock_release(struct lockdep_map *lock, unsigned long ip)
+{
+	struct task_struct *curr = current;
+	unsigned int depth, merged = 1;
+	struct held_lock *hlock;
+	int i;
+
+	if (unlikely(!debug_locks))
+		return 0;
+
+	depth = curr->lockdep_depth;
+	/*
+	 * So we're all set to release this lock.. wait what lock? We don't
+	 * own any locks, you've been drinking again?
+	 */
+	if (depth <= 0) {
+		print_unlock_imbalance_bug(curr, lock, ip);
+		return 0;
+	}
+
+	/*
+	 * Check whether the lock exists in the current stack
+	 * of held locks:
+	 */
+	hlock = find_held_lock(curr, lock, depth, &i);
+	if (!hlock) {
+		print_unlock_imbalance_bug(curr, lock, ip);
+		return 0;
+	}
+
+	if (hlock->instance == lock)
+		lock_release_holdtime(hlock);
+
+	WARN(hlock->pin_count, "releasing a pinned lock\n");
+
+	if (hlock->references) {
+		hlock->references--;
+		if (hlock->references) {
+			/*
+			 * We had, and after removing one, still have
+			 * references, the current lock stack is still
+			 * valid. We're done!
+			 */
+			return 1;
+		}
+	}
+
+	/*
+	 * We have the right lock to unlock, 'hlock' points to it.
+	 * Now we remove it from the stack, and add back the other
+	 * entries (if any), recalculating the hash along the way:
+	 */
+
+	curr->lockdep_depth = i;
+	curr->curr_chain_key = hlock->prev_chain_key;
+
+	/*
+	 * The most likely case is when the unlock is on the innermost
+	 * lock. In this case, we are done!
+	 */
+	if (i == depth-1)
+		return 1;
+
+	if (reacquire_held_locks(curr, depth, i + 1, &merged))
+		return 0;
+
+	/*
+	 * We had N bottles of beer on the wall, we drank one, but now
+	 * there's not N-1 bottles of beer left on the wall...
+	 * Pouring two of the bottles together is acceptable.
+	 */
+	DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged);
+
+	/*
+	 * Since reacquire_held_locks() would have called check_chain_key()
+	 * indirectly via __lock_acquire(), we don't need to do it again
+	 * on return.
+	 */
+	return 0;
+}
+
+static __always_inline
+int __lock_is_held(const struct lockdep_map *lock, int read)
+{
+	struct task_struct *curr = current;
+	int i;
+
+	for (i = 0; i < curr->lockdep_depth; i++) {
+		struct held_lock *hlock = curr->held_locks + i;
+
+		if (match_held_lock(hlock, lock)) {
+			if (read == -1 || !!hlock->read == read)
+				return 1;
+
+			return 0;
+		}
+	}
+
+	return 0;
+}
+
+static struct pin_cookie __lock_pin_lock(struct lockdep_map *lock)
+{
+	struct pin_cookie cookie = NIL_COOKIE;
+	struct task_struct *curr = current;
+	int i;
+
+	if (unlikely(!debug_locks))
+		return cookie;
+
+	for (i = 0; i < curr->lockdep_depth; i++) {
+		struct held_lock *hlock = curr->held_locks + i;
+
+		if (match_held_lock(hlock, lock)) {
+			/*
+			 * Grab 16bits of randomness; this is sufficient to not
+			 * be guessable and still allows some pin nesting in
+			 * our u32 pin_count.
+			 */
+			cookie.val = 1 + (prandom_u32() >> 16);
+			hlock->pin_count += cookie.val;
+			return cookie;
+		}
+	}
+
+	WARN(1, "pinning an unheld lock\n");
+	return cookie;
+}
+
+static void __lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
+{
+	struct task_struct *curr = current;
+	int i;
+
+	if (unlikely(!debug_locks))
+		return;
+
+	for (i = 0; i < curr->lockdep_depth; i++) {
+		struct held_lock *hlock = curr->held_locks + i;
+
+		if (match_held_lock(hlock, lock)) {
+			hlock->pin_count += cookie.val;
+			return;
+		}
+	}
+
+	WARN(1, "pinning an unheld lock\n");
+}
+
+static void __lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
+{
+	struct task_struct *curr = current;
+	int i;
+
+	if (unlikely(!debug_locks))
+		return;
+
+	for (i = 0; i < curr->lockdep_depth; i++) {
+		struct held_lock *hlock = curr->held_locks + i;
+
+		if (match_held_lock(hlock, lock)) {
+			if (WARN(!hlock->pin_count, "unpinning an unpinned lock\n"))
+				return;
+
+			hlock->pin_count -= cookie.val;
+
+			if (WARN((int)hlock->pin_count < 0, "pin count corrupted\n"))
+				hlock->pin_count = 0;
+
+			return;
+		}
+	}
+
+	WARN(1, "unpinning an unheld lock\n");
+}
+
+/*
+ * Check whether we follow the irq-flags state precisely:
+ */
+static noinstr void check_flags(unsigned long flags)
+{
+#if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP)
+	if (!debug_locks)
+		return;
+
+	/* Get the warning out..  */
+	instrumentation_begin();
+
+	if (irqs_disabled_flags(flags)) {
+		if (DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled())) {
+			printk("possible reason: unannotated irqs-off.\n");
+		}
+	} else {
+		if (DEBUG_LOCKS_WARN_ON(!lockdep_hardirqs_enabled())) {
+			printk("possible reason: unannotated irqs-on.\n");
+		}
+	}
+
+	/*
+	 * We dont accurately track softirq state in e.g.
+	 * hardirq contexts (such as on 4KSTACKS), so only
+	 * check if not in hardirq contexts:
+	 */
+	if (!hardirq_count()) {
+		if (softirq_count()) {
+			/* like the above, but with softirqs */
+			DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
+		} else {
+			/* lick the above, does it taste good? */
+			DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
+		}
+	}
+
+	if (!debug_locks)
+		print_irqtrace_events(current);
+
+	instrumentation_end();
+#endif
+}
+
+void lock_set_class(struct lockdep_map *lock, const char *name,
+		    struct lock_class_key *key, unsigned int subclass,
+		    unsigned long ip)
+{
+	unsigned long flags;
+
+	if (unlikely(!lockdep_enabled()))
+		return;
+
+	raw_local_irq_save(flags);
+	lockdep_recursion_inc();
+	check_flags(flags);
+	if (__lock_set_class(lock, name, key, subclass, ip))
+		check_chain_key(current);
+	lockdep_recursion_finish();
+	raw_local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(lock_set_class);
+
+void lock_downgrade(struct lockdep_map *lock, unsigned long ip)
+{
+	unsigned long flags;
+
+	if (unlikely(!lockdep_enabled()))
+		return;
+
+	raw_local_irq_save(flags);
+	lockdep_recursion_inc();
+	check_flags(flags);
+	if (__lock_downgrade(lock, ip))
+		check_chain_key(current);
+	lockdep_recursion_finish();
+	raw_local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(lock_downgrade);
+
+/* NMI context !!! */
+static void verify_lock_unused(struct lockdep_map *lock, struct held_lock *hlock, int subclass)
+{
+#ifdef CONFIG_PROVE_LOCKING
+	struct lock_class *class = look_up_lock_class(lock, subclass);
+	unsigned long mask = LOCKF_USED;
+
+	/* if it doesn't have a class (yet), it certainly hasn't been used yet */
+	if (!class)
+		return;
+
+	/*
+	 * READ locks only conflict with USED, such that if we only ever use
+	 * READ locks, there is no deadlock possible -- RCU.
+	 */
+	if (!hlock->read)
+		mask |= LOCKF_USED_READ;
+
+	if (!(class->usage_mask & mask))
+		return;
+
+	hlock->class_idx = class - lock_classes;
+
+	print_usage_bug(current, hlock, LOCK_USED, LOCK_USAGE_STATES);
+#endif
+}
+
+static bool lockdep_nmi(void)
+{
+	if (raw_cpu_read(lockdep_recursion))
+		return false;
+
+	if (!in_nmi())
+		return false;
+
+	return true;
+}
+
+/*
+ * read_lock() is recursive if:
+ * 1. We force lockdep think this way in selftests or
+ * 2. The implementation is not queued read/write lock or
+ * 3. The locker is at an in_interrupt() context.
+ */
+bool read_lock_is_recursive(void)
+{
+	return force_read_lock_recursive ||
+	       !IS_ENABLED(CONFIG_QUEUED_RWLOCKS) ||
+	       in_interrupt();
+}
+EXPORT_SYMBOL_GPL(read_lock_is_recursive);
+
+/*
+ * We are not always called with irqs disabled - do that here,
+ * and also avoid lockdep recursion:
+ */
+void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
+			  int trylock, int read, int check,
+			  struct lockdep_map *nest_lock, unsigned long ip)
+{
+	unsigned long flags;
+
+	trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
+
+	if (!debug_locks)
+		return;
+
+	if (unlikely(!lockdep_enabled())) {
+		/* XXX allow trylock from NMI ?!? */
+		if (lockdep_nmi() && !trylock) {
+			struct held_lock hlock;
+
+			hlock.acquire_ip = ip;
+			hlock.instance = lock;
+			hlock.nest_lock = nest_lock;
+			hlock.irq_context = 2; // XXX
+			hlock.trylock = trylock;
+			hlock.read = read;
+			hlock.check = check;
+			hlock.hardirqs_off = true;
+			hlock.references = 0;
+
+			verify_lock_unused(lock, &hlock, subclass);
+		}
+		return;
+	}
+
+	raw_local_irq_save(flags);
+	check_flags(flags);
+
+	lockdep_recursion_inc();
+	__lock_acquire(lock, subclass, trylock, read, check,
+		       irqs_disabled_flags(flags), nest_lock, ip, 0, 0);
+	lockdep_recursion_finish();
+	raw_local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(lock_acquire);
+
+void lock_release(struct lockdep_map *lock, unsigned long ip)
+{
+	unsigned long flags;
+
+	trace_lock_release(lock, ip);
+
+	if (unlikely(!lockdep_enabled()))
+		return;
+
+	raw_local_irq_save(flags);
+	check_flags(flags);
+
+	lockdep_recursion_inc();
+	if (__lock_release(lock, ip))
+		check_chain_key(current);
+	lockdep_recursion_finish();
+	raw_local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(lock_release);
+
+noinstr int lock_is_held_type(const struct lockdep_map *lock, int read)
+{
+	unsigned long flags;
+	int ret = 0;
+
+	if (unlikely(!lockdep_enabled()))
+		return 1; /* avoid false negative lockdep_assert_held() */
+
+	raw_local_irq_save(flags);
+	check_flags(flags);
+
+	lockdep_recursion_inc();
+	ret = __lock_is_held(lock, read);
+	lockdep_recursion_finish();
+	raw_local_irq_restore(flags);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(lock_is_held_type);
+NOKPROBE_SYMBOL(lock_is_held_type);
+
+struct pin_cookie lock_pin_lock(struct lockdep_map *lock)
+{
+	struct pin_cookie cookie = NIL_COOKIE;
+	unsigned long flags;
+
+	if (unlikely(!lockdep_enabled()))
+		return cookie;
+
+	raw_local_irq_save(flags);
+	check_flags(flags);
+
+	lockdep_recursion_inc();
+	cookie = __lock_pin_lock(lock);
+	lockdep_recursion_finish();
+	raw_local_irq_restore(flags);
+
+	return cookie;
+}
+EXPORT_SYMBOL_GPL(lock_pin_lock);
+
+void lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
+{
+	unsigned long flags;
+
+	if (unlikely(!lockdep_enabled()))
+		return;
+
+	raw_local_irq_save(flags);
+	check_flags(flags);
+
+	lockdep_recursion_inc();
+	__lock_repin_lock(lock, cookie);
+	lockdep_recursion_finish();
+	raw_local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(lock_repin_lock);
+
+void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
+{
+	unsigned long flags;
+
+	if (unlikely(!lockdep_enabled()))
+		return;
+
+	raw_local_irq_save(flags);
+	check_flags(flags);
+
+	lockdep_recursion_inc();
+	__lock_unpin_lock(lock, cookie);
+	lockdep_recursion_finish();
+	raw_local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(lock_unpin_lock);
+
+#ifdef CONFIG_LOCK_STAT
+static void print_lock_contention_bug(struct task_struct *curr,
+				      struct lockdep_map *lock,
+				      unsigned long ip)
+{
+	if (!debug_locks_off())
+		return;
+	if (debug_locks_silent)
+		return;
+
+	pr_warn("\n");
+	pr_warn("=================================\n");
+	pr_warn("WARNING: bad contention detected!\n");
+	print_kernel_ident();
+	pr_warn("---------------------------------\n");
+	pr_warn("%s/%d is trying to contend lock (",
+		curr->comm, task_pid_nr(curr));
+	print_lockdep_cache(lock);
+	pr_cont(") at:\n");
+	print_ip_sym(KERN_WARNING, ip);
+	pr_warn("but there are no locks held!\n");
+	pr_warn("\nother info that might help us debug this:\n");
+	lockdep_print_held_locks(curr);
+
+	pr_warn("\nstack backtrace:\n");
+	dump_stack();
+}
+
+static void
+__lock_contended(struct lockdep_map *lock, unsigned long ip)
+{
+	struct task_struct *curr = current;
+	struct held_lock *hlock;
+	struct lock_class_stats *stats;
+	unsigned int depth;
+	int i, contention_point, contending_point;
+
+	depth = curr->lockdep_depth;
+	/*
+	 * Whee, we contended on this lock, except it seems we're not
+	 * actually trying to acquire anything much at all..
+	 */
+	if (DEBUG_LOCKS_WARN_ON(!depth))
+		return;
+
+	hlock = find_held_lock(curr, lock, depth, &i);
+	if (!hlock) {
+		print_lock_contention_bug(curr, lock, ip);
+		return;
+	}
+
+	if (hlock->instance != lock)
+		return;
+
+	hlock->waittime_stamp = lockstat_clock();
+
+	contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
+	contending_point = lock_point(hlock_class(hlock)->contending_point,
+				      lock->ip);
+
+	stats = get_lock_stats(hlock_class(hlock));
+	if (contention_point < LOCKSTAT_POINTS)
+		stats->contention_point[contention_point]++;
+	if (contending_point < LOCKSTAT_POINTS)
+		stats->contending_point[contending_point]++;
+	if (lock->cpu != smp_processor_id())
+		stats->bounces[bounce_contended + !!hlock->read]++;
+}
+
+static void
+__lock_acquired(struct lockdep_map *lock, unsigned long ip)
+{
+	struct task_struct *curr = current;
+	struct held_lock *hlock;
+	struct lock_class_stats *stats;
+	unsigned int depth;
+	u64 now, waittime = 0;
+	int i, cpu;
+
+	depth = curr->lockdep_depth;
+	/*
+	 * Yay, we acquired ownership of this lock we didn't try to
+	 * acquire, how the heck did that happen?
+	 */
+	if (DEBUG_LOCKS_WARN_ON(!depth))
+		return;
+
+	hlock = find_held_lock(curr, lock, depth, &i);
+	if (!hlock) {
+		print_lock_contention_bug(curr, lock, _RET_IP_);
+		return;
+	}
+
+	if (hlock->instance != lock)
+		return;
+
+	cpu = smp_processor_id();
+	if (hlock->waittime_stamp) {
+		now = lockstat_clock();
+		waittime = now - hlock->waittime_stamp;
+		hlock->holdtime_stamp = now;
+	}
+
+	stats = get_lock_stats(hlock_class(hlock));
+	if (waittime) {
+		if (hlock->read)
+			lock_time_inc(&stats->read_waittime, waittime);
+		else
+			lock_time_inc(&stats->write_waittime, waittime);
+	}
+	if (lock->cpu != cpu)
+		stats->bounces[bounce_acquired + !!hlock->read]++;
+
+	lock->cpu = cpu;
+	lock->ip = ip;
+}
+
+void lock_contended(struct lockdep_map *lock, unsigned long ip)
+{
+	unsigned long flags;
+
+	trace_lock_contended(lock, ip);
+
+	if (unlikely(!lock_stat || !lockdep_enabled()))
+		return;
+
+	raw_local_irq_save(flags);
+	check_flags(flags);
+	lockdep_recursion_inc();
+	__lock_contended(lock, ip);
+	lockdep_recursion_finish();
+	raw_local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(lock_contended);
+
+void lock_acquired(struct lockdep_map *lock, unsigned long ip)
+{
+	unsigned long flags;
+
+	trace_lock_acquired(lock, ip);
+
+	if (unlikely(!lock_stat || !lockdep_enabled()))
+		return;
+
+	raw_local_irq_save(flags);
+	check_flags(flags);
+	lockdep_recursion_inc();
+	__lock_acquired(lock, ip);
+	lockdep_recursion_finish();
+	raw_local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(lock_acquired);
+#endif
+
+/*
+ * Used by the testsuite, sanitize the validator state
+ * after a simulated failure:
+ */
+
+void lockdep_reset(void)
+{
+	unsigned long flags;
+	int i;
+
+	raw_local_irq_save(flags);
+	lockdep_init_task(current);
+	memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
+	nr_hardirq_chains = 0;
+	nr_softirq_chains = 0;
+	nr_process_chains = 0;
+	debug_locks = 1;
+	for (i = 0; i < CHAINHASH_SIZE; i++)
+		INIT_HLIST_HEAD(chainhash_table + i);
+	raw_local_irq_restore(flags);
+}
+
+/* Remove a class from a lock chain. Must be called with the graph lock held. */
+static void remove_class_from_lock_chain(struct pending_free *pf,
+					 struct lock_chain *chain,
+					 struct lock_class *class)
+{
+#ifdef CONFIG_PROVE_LOCKING
+	int i;
+
+	for (i = chain->base; i < chain->base + chain->depth; i++) {
+		if (chain_hlock_class_idx(chain_hlocks[i]) != class - lock_classes)
+			continue;
+		/*
+		 * Each lock class occurs at most once in a lock chain so once
+		 * we found a match we can break out of this loop.
+		 */
+		goto free_lock_chain;
+	}
+	/* Since the chain has not been modified, return. */
+	return;
+
+free_lock_chain:
+	free_chain_hlocks(chain->base, chain->depth);
+	/* Overwrite the chain key for concurrent RCU readers. */
+	WRITE_ONCE(chain->chain_key, INITIAL_CHAIN_KEY);
+	dec_chains(chain->irq_context);
+
+	/*
+	 * Note: calling hlist_del_rcu() from inside a
+	 * hlist_for_each_entry_rcu() loop is safe.
+	 */
+	hlist_del_rcu(&chain->entry);
+	__set_bit(chain - lock_chains, pf->lock_chains_being_freed);
+	nr_zapped_lock_chains++;
+#endif
+}
+
+/* Must be called with the graph lock held. */
+static void remove_class_from_lock_chains(struct pending_free *pf,
+					  struct lock_class *class)
+{
+	struct lock_chain *chain;
+	struct hlist_head *head;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
+		head = chainhash_table + i;
+		hlist_for_each_entry_rcu(chain, head, entry) {
+			remove_class_from_lock_chain(pf, chain, class);
+		}
+	}
+}
+
+/*
+ * Remove all references to a lock class. The caller must hold the graph lock.
+ */
+static void zap_class(struct pending_free *pf, struct lock_class *class)
+{
+	struct lock_list *entry;
+	int i;
+
+	WARN_ON_ONCE(!class->key);
+
+	/*
+	 * Remove all dependencies this lock is
+	 * involved in:
+	 */
+	for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
+		entry = list_entries + i;
+		if (entry->class != class && entry->links_to != class)
+			continue;
+		__clear_bit(i, list_entries_in_use);
+		nr_list_entries--;
+		list_del_rcu(&entry->entry);
+	}
+	if (list_empty(&class->locks_after) &&
+	    list_empty(&class->locks_before)) {
+		list_move_tail(&class->lock_entry, &pf->zapped);
+		hlist_del_rcu(&class->hash_entry);
+		WRITE_ONCE(class->key, NULL);
+		WRITE_ONCE(class->name, NULL);
+		nr_lock_classes--;
+		__clear_bit(class - lock_classes, lock_classes_in_use);
+		if (class - lock_classes == max_lock_class_idx)
+			max_lock_class_idx--;
+	} else {
+		WARN_ONCE(true, "%s() failed for class %s\n", __func__,
+			  class->name);
+	}
+
+	remove_class_from_lock_chains(pf, class);
+	nr_zapped_classes++;
+}
+
+static void reinit_class(struct lock_class *class)
+{
+	void *const p = class;
+	const unsigned int offset = offsetof(struct lock_class, key);
+
+	WARN_ON_ONCE(!class->lock_entry.next);
+	WARN_ON_ONCE(!list_empty(&class->locks_after));
+	WARN_ON_ONCE(!list_empty(&class->locks_before));
+	memset(p + offset, 0, sizeof(*class) - offset);
+	WARN_ON_ONCE(!class->lock_entry.next);
+	WARN_ON_ONCE(!list_empty(&class->locks_after));
+	WARN_ON_ONCE(!list_empty(&class->locks_before));
+}
+
+static inline int within(const void *addr, void *start, unsigned long size)
+{
+	return addr >= start && addr < start + size;
+}
+
+static bool inside_selftest(void)
+{
+	return current == lockdep_selftest_task_struct;
+}
+
+/* The caller must hold the graph lock. */
+static struct pending_free *get_pending_free(void)
+{
+	return delayed_free.pf + delayed_free.index;
+}
+
+static void free_zapped_rcu(struct rcu_head *cb);
+
+/*
+ * Schedule an RCU callback if no RCU callback is pending. Must be called with
+ * the graph lock held.
+ */
+static void call_rcu_zapped(struct pending_free *pf)
+{
+	WARN_ON_ONCE(inside_selftest());
+
+	if (list_empty(&pf->zapped))
+		return;
+
+	if (delayed_free.scheduled)
+		return;
+
+	delayed_free.scheduled = true;
+
+	WARN_ON_ONCE(delayed_free.pf + delayed_free.index != pf);
+	delayed_free.index ^= 1;
+
+	call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
+}
+
+/* The caller must hold the graph lock. May be called from RCU context. */
+static void __free_zapped_classes(struct pending_free *pf)
+{
+	struct lock_class *class;
+
+	check_data_structures();
+
+	list_for_each_entry(class, &pf->zapped, lock_entry)
+		reinit_class(class);
+
+	list_splice_init(&pf->zapped, &free_lock_classes);
+
+#ifdef CONFIG_PROVE_LOCKING
+	bitmap_andnot(lock_chains_in_use, lock_chains_in_use,
+		      pf->lock_chains_being_freed, ARRAY_SIZE(lock_chains));
+	bitmap_clear(pf->lock_chains_being_freed, 0, ARRAY_SIZE(lock_chains));
+#endif
+}
+
+static void free_zapped_rcu(struct rcu_head *ch)
+{
+	struct pending_free *pf;
+	unsigned long flags;
+
+	if (WARN_ON_ONCE(ch != &delayed_free.rcu_head))
+		return;
+
+	raw_local_irq_save(flags);
+	lockdep_lock();
+
+	/* closed head */
+	pf = delayed_free.pf + (delayed_free.index ^ 1);
+	__free_zapped_classes(pf);
+	delayed_free.scheduled = false;
+
+	/*
+	 * If there's anything on the open list, close and start a new callback.
+	 */
+	call_rcu_zapped(delayed_free.pf + delayed_free.index);
+
+	lockdep_unlock();
+	raw_local_irq_restore(flags);
+}
+
+/*
+ * Remove all lock classes from the class hash table and from the
+ * all_lock_classes list whose key or name is in the address range [start,
+ * start + size). Move these lock classes to the zapped_classes list. Must
+ * be called with the graph lock held.
+ */
+static void __lockdep_free_key_range(struct pending_free *pf, void *start,
+				     unsigned long size)
+{
+	struct lock_class *class;
+	struct hlist_head *head;
+	int i;
+
+	/* Unhash all classes that were created by a module. */
+	for (i = 0; i < CLASSHASH_SIZE; i++) {
+		head = classhash_table + i;
+		hlist_for_each_entry_rcu(class, head, hash_entry) {
+			if (!within(class->key, start, size) &&
+			    !within(class->name, start, size))
+				continue;
+			zap_class(pf, class);
+		}
+	}
+}
+
+/*
+ * Used in module.c to remove lock classes from memory that is going to be
+ * freed; and possibly re-used by other modules.
+ *
+ * We will have had one synchronize_rcu() before getting here, so we're
+ * guaranteed nobody will look up these exact classes -- they're properly dead
+ * but still allocated.
+ */
+static void lockdep_free_key_range_reg(void *start, unsigned long size)
+{
+	struct pending_free *pf;
+	unsigned long flags;
+
+	init_data_structures_once();
+
+	raw_local_irq_save(flags);
+	lockdep_lock();
+	pf = get_pending_free();
+	__lockdep_free_key_range(pf, start, size);
+	call_rcu_zapped(pf);
+	lockdep_unlock();
+	raw_local_irq_restore(flags);
+
+	/*
+	 * Wait for any possible iterators from look_up_lock_class() to pass
+	 * before continuing to free the memory they refer to.
+	 */
+	synchronize_rcu();
+}
+
+/*
+ * Free all lockdep keys in the range [start, start+size). Does not sleep.
+ * Ignores debug_locks. Must only be used by the lockdep selftests.
+ */
+static void lockdep_free_key_range_imm(void *start, unsigned long size)
+{
+	struct pending_free *pf = delayed_free.pf;
+	unsigned long flags;
+
+	init_data_structures_once();
+
+	raw_local_irq_save(flags);
+	lockdep_lock();
+	__lockdep_free_key_range(pf, start, size);
+	__free_zapped_classes(pf);
+	lockdep_unlock();
+	raw_local_irq_restore(flags);
+}
+
+void lockdep_free_key_range(void *start, unsigned long size)
+{
+	init_data_structures_once();
+
+	if (inside_selftest())
+		lockdep_free_key_range_imm(start, size);
+	else
+		lockdep_free_key_range_reg(start, size);
+}
+
+/*
+ * Check whether any element of the @lock->class_cache[] array refers to a
+ * registered lock class. The caller must hold either the graph lock or the
+ * RCU read lock.
+ */
+static bool lock_class_cache_is_registered(struct lockdep_map *lock)
+{
+	struct lock_class *class;
+	struct hlist_head *head;
+	int i, j;
+
+	for (i = 0; i < CLASSHASH_SIZE; i++) {
+		head = classhash_table + i;
+		hlist_for_each_entry_rcu(class, head, hash_entry) {
+			for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++)
+				if (lock->class_cache[j] == class)
+					return true;
+		}
+	}
+	return false;
+}
+
+/* The caller must hold the graph lock. Does not sleep. */
+static void __lockdep_reset_lock(struct pending_free *pf,
+				 struct lockdep_map *lock)
+{
+	struct lock_class *class;
+	int j;
+
+	/*
+	 * Remove all classes this lock might have:
+	 */
+	for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
+		/*
+		 * If the class exists we look it up and zap it:
+		 */
+		class = look_up_lock_class(lock, j);
+		if (class)
+			zap_class(pf, class);
+	}
+	/*
+	 * Debug check: in the end all mapped classes should
+	 * be gone.
+	 */
+	if (WARN_ON_ONCE(lock_class_cache_is_registered(lock)))
+		debug_locks_off();
+}
+
+/*
+ * Remove all information lockdep has about a lock if debug_locks == 1. Free
+ * released data structures from RCU context.
+ */
+static void lockdep_reset_lock_reg(struct lockdep_map *lock)
+{
+	struct pending_free *pf;
+	unsigned long flags;
+	int locked;
+
+	raw_local_irq_save(flags);
+	locked = graph_lock();
+	if (!locked)
+		goto out_irq;
+
+	pf = get_pending_free();
+	__lockdep_reset_lock(pf, lock);
+	call_rcu_zapped(pf);
+
+	graph_unlock();
+out_irq:
+	raw_local_irq_restore(flags);
+}
+
+/*
+ * Reset a lock. Does not sleep. Ignores debug_locks. Must only be used by the
+ * lockdep selftests.
+ */
+static void lockdep_reset_lock_imm(struct lockdep_map *lock)
+{
+	struct pending_free *pf = delayed_free.pf;
+	unsigned long flags;
+
+	raw_local_irq_save(flags);
+	lockdep_lock();
+	__lockdep_reset_lock(pf, lock);
+	__free_zapped_classes(pf);
+	lockdep_unlock();
+	raw_local_irq_restore(flags);
+}
+
+void lockdep_reset_lock(struct lockdep_map *lock)
+{
+	init_data_structures_once();
+
+	if (inside_selftest())
+		lockdep_reset_lock_imm(lock);
+	else
+		lockdep_reset_lock_reg(lock);
+}
+
+/*
+ * Unregister a dynamically allocated key.
+ *
+ * Unlike lockdep_register_key(), a search is always done to find a matching
+ * key irrespective of debug_locks to avoid potential invalid access to freed
+ * memory in lock_class entry.
+ */
+void lockdep_unregister_key(struct lock_class_key *key)
+{
+	struct hlist_head *hash_head = keyhashentry(key);
+	struct lock_class_key *k;
+	struct pending_free *pf;
+	unsigned long flags;
+	bool found = false;
+
+	might_sleep();
+
+	if (WARN_ON_ONCE(static_obj(key)))
+		return;
+
+	raw_local_irq_save(flags);
+	lockdep_lock();
+
+	hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
+		if (k == key) {
+			hlist_del_rcu(&k->hash_entry);
+			found = true;
+			break;
+		}
+	}
+	WARN_ON_ONCE(!found && debug_locks);
+	if (found) {
+		pf = get_pending_free();
+		__lockdep_free_key_range(pf, key, 1);
+		call_rcu_zapped(pf);
+	}
+	lockdep_unlock();
+	raw_local_irq_restore(flags);
+
+	/* Wait until is_dynamic_key() has finished accessing k->hash_entry. */
+	synchronize_rcu();
+}
+EXPORT_SYMBOL_GPL(lockdep_unregister_key);
+
+void __init lockdep_init(void)
+{
+	printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
+
+	printk("... MAX_LOCKDEP_SUBCLASSES:  %lu\n", MAX_LOCKDEP_SUBCLASSES);
+	printk("... MAX_LOCK_DEPTH:          %lu\n", MAX_LOCK_DEPTH);
+	printk("... MAX_LOCKDEP_KEYS:        %lu\n", MAX_LOCKDEP_KEYS);
+	printk("... CLASSHASH_SIZE:          %lu\n", CLASSHASH_SIZE);
+	printk("... MAX_LOCKDEP_ENTRIES:     %lu\n", MAX_LOCKDEP_ENTRIES);
+	printk("... MAX_LOCKDEP_CHAINS:      %lu\n", MAX_LOCKDEP_CHAINS);
+	printk("... CHAINHASH_SIZE:          %lu\n", CHAINHASH_SIZE);
+
+	printk(" memory used by lock dependency info: %zu kB\n",
+	       (sizeof(lock_classes) +
+		sizeof(lock_classes_in_use) +
+		sizeof(classhash_table) +
+		sizeof(list_entries) +
+		sizeof(list_entries_in_use) +
+		sizeof(chainhash_table) +
+		sizeof(delayed_free)
+#ifdef CONFIG_PROVE_LOCKING
+		+ sizeof(lock_cq)
+		+ sizeof(lock_chains)
+		+ sizeof(lock_chains_in_use)
+		+ sizeof(chain_hlocks)
+#endif
+		) / 1024
+		);
+
+#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
+	printk(" memory used for stack traces: %zu kB\n",
+	       (sizeof(stack_trace) + sizeof(stack_trace_hash)) / 1024
+	       );
+#endif
+
+	printk(" per task-struct memory footprint: %zu bytes\n",
+	       sizeof(((struct task_struct *)NULL)->held_locks));
+}
+
+static void
+print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
+		     const void *mem_to, struct held_lock *hlock)
+{
+	if (!debug_locks_off())
+		return;
+	if (debug_locks_silent)
+		return;
+
+	pr_warn("\n");
+	pr_warn("=========================\n");
+	pr_warn("WARNING: held lock freed!\n");
+	print_kernel_ident();
+	pr_warn("-------------------------\n");
+	pr_warn("%s/%d is freeing memory %px-%px, with a lock still held there!\n",
+		curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
+	print_lock(hlock);
+	lockdep_print_held_locks(curr);
+
+	pr_warn("\nstack backtrace:\n");
+	dump_stack();
+}
+
+static inline int not_in_range(const void* mem_from, unsigned long mem_len,
+				const void* lock_from, unsigned long lock_len)
+{
+	return lock_from + lock_len <= mem_from ||
+		mem_from + mem_len <= lock_from;
+}
+
+/*
+ * Called when kernel memory is freed (or unmapped), or if a lock
+ * is destroyed or reinitialized - this code checks whether there is
+ * any held lock in the memory range of <from> to <to>:
+ */
+void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
+{
+	struct task_struct *curr = current;
+	struct held_lock *hlock;
+	unsigned long flags;
+	int i;
+
+	if (unlikely(!debug_locks))
+		return;
+
+	raw_local_irq_save(flags);
+	for (i = 0; i < curr->lockdep_depth; i++) {
+		hlock = curr->held_locks + i;
+
+		if (not_in_range(mem_from, mem_len, hlock->instance,
+					sizeof(*hlock->instance)))
+			continue;
+
+		print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
+		break;
+	}
+	raw_local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
+
+static void print_held_locks_bug(void)
+{
+	if (!debug_locks_off())
+		return;
+	if (debug_locks_silent)
+		return;
+
+	pr_warn("\n");
+	pr_warn("====================================\n");
+	pr_warn("WARNING: %s/%d still has locks held!\n",
+	       current->comm, task_pid_nr(current));
+	print_kernel_ident();
+	pr_warn("------------------------------------\n");
+	lockdep_print_held_locks(current);
+	pr_warn("\nstack backtrace:\n");
+	dump_stack();
+}
+
+void debug_check_no_locks_held(void)
+{
+	if (unlikely(current->lockdep_depth > 0))
+		print_held_locks_bug();
+}
+EXPORT_SYMBOL_GPL(debug_check_no_locks_held);
+
+#ifdef __KERNEL__
+void debug_show_all_locks(void)
+{
+	struct task_struct *g, *p;
+
+	if (unlikely(!debug_locks)) {
+		pr_warn("INFO: lockdep is turned off.\n");
+		return;
+	}
+	pr_warn("\nShowing all locks held in the system:\n");
+
+	rcu_read_lock();
+	for_each_process_thread(g, p) {
+		if (!p->lockdep_depth)
+			continue;
+		lockdep_print_held_locks(p);
+		touch_nmi_watchdog();
+		touch_all_softlockup_watchdogs();
+	}
+	rcu_read_unlock();
+
+	pr_warn("\n");
+	pr_warn("=============================================\n\n");
+}
+EXPORT_SYMBOL_GPL(debug_show_all_locks);
+#endif
+
+/*
+ * Careful: only use this function if you are sure that
+ * the task cannot run in parallel!
+ */
+void debug_show_held_locks(struct task_struct *task)
+{
+	if (unlikely(!debug_locks)) {
+		printk("INFO: lockdep is turned off.\n");
+		return;
+	}
+	lockdep_print_held_locks(task);
+}
+EXPORT_SYMBOL_GPL(debug_show_held_locks);
+
+asmlinkage __visible void lockdep_sys_exit(void)
+{
+	struct task_struct *curr = current;
+
+	if (unlikely(curr->lockdep_depth)) {
+		if (!debug_locks_off())
+			return;
+		pr_warn("\n");
+		pr_warn("================================================\n");
+		pr_warn("WARNING: lock held when returning to user space!\n");
+		print_kernel_ident();
+		pr_warn("------------------------------------------------\n");
+		pr_warn("%s/%d is leaving the kernel with locks still held!\n",
+				curr->comm, curr->pid);
+		lockdep_print_held_locks(curr);
+	}
+
+	/*
+	 * The lock history for each syscall should be independent. So wipe the
+	 * slate clean on return to userspace.
+	 */
+	lockdep_invariant_state(false);
+}
+
+void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
+{
+	struct task_struct *curr = current;
+
+	/* Note: the following can be executed concurrently, so be careful. */
+	pr_warn("\n");
+	pr_warn("=============================\n");
+	pr_warn("WARNING: suspicious RCU usage\n");
+	print_kernel_ident();
+	pr_warn("-----------------------------\n");
+	pr_warn("%s:%d %s!\n", file, line, s);
+	pr_warn("\nother info that might help us debug this:\n\n");
+	pr_warn("\n%srcu_scheduler_active = %d, debug_locks = %d\n",
+	       !rcu_lockdep_current_cpu_online()
+			? "RCU used illegally from offline CPU!\n"
+			: "",
+	       rcu_scheduler_active, debug_locks);
+
+	/*
+	 * If a CPU is in the RCU-free window in idle (ie: in the section
+	 * between rcu_idle_enter() and rcu_idle_exit(), then RCU
+	 * considers that CPU to be in an "extended quiescent state",
+	 * which means that RCU will be completely ignoring that CPU.
+	 * Therefore, rcu_read_lock() and friends have absolutely no
+	 * effect on a CPU running in that state. In other words, even if
+	 * such an RCU-idle CPU has called rcu_read_lock(), RCU might well
+	 * delete data structures out from under it.  RCU really has no
+	 * choice here: we need to keep an RCU-free window in idle where
+	 * the CPU may possibly enter into low power mode. This way we can
+	 * notice an extended quiescent state to other CPUs that started a grace
+	 * period. Otherwise we would delay any grace period as long as we run
+	 * in the idle task.
+	 *
+	 * So complain bitterly if someone does call rcu_read_lock(),
+	 * rcu_read_lock_bh() and so on from extended quiescent states.
+	 */
+	if (!rcu_is_watching())
+		pr_warn("RCU used illegally from extended quiescent state!\n");
+
+	lockdep_print_held_locks(curr);
+	pr_warn("\nstack backtrace:\n");
+	dump_stack();
+}
+EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);