Adding upstream version 4.19.249.upstream/4.19.249

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

1 files changed, 5868 insertions, 0 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
new file mode 100644
index 000000000..b1bb6cb58
--- /dev/null
+++ b/kernel/workqueue.c
@@ -0,0 +1,5868 @@
+/*
+ * kernel/workqueue.c - generic async execution with shared worker pool
+ *
+ * Copyright (C) 2002		Ingo Molnar
+ *
+ *   Derived from the taskqueue/keventd code by:
+ *     David Woodhouse <dwmw2@infradead.org>
+ *     Andrew Morton
+ *     Kai Petzke <wpp@marie.physik.tu-berlin.de>
+ *     Theodore Ts'o <tytso@mit.edu>
+ *
+ * Made to use alloc_percpu by Christoph Lameter.
+ *
+ * Copyright (C) 2010		SUSE Linux Products GmbH
+ * Copyright (C) 2010		Tejun Heo <tj@kernel.org>
+ *
+ * This is the generic async execution mechanism.  Work items as are
+ * executed in process context.  The worker pool is shared and
+ * automatically managed.  There are two worker pools for each CPU (one for
+ * normal work items and the other for high priority ones) and some extra
+ * pools for workqueues which are not bound to any specific CPU - the
+ * number of these backing pools is dynamic.
+ *
+ * Please read Documentation/core-api/workqueue.rst for details.
+ */
+
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/signal.h>
+#include <linux/completion.h>
+#include <linux/workqueue.h>
+#include <linux/slab.h>
+#include <linux/cpu.h>
+#include <linux/notifier.h>
+#include <linux/kthread.h>
+#include <linux/hardirq.h>
+#include <linux/mempolicy.h>
+#include <linux/freezer.h>
+#include <linux/debug_locks.h>
+#include <linux/lockdep.h>
+#include <linux/idr.h>
+#include <linux/jhash.h>
+#include <linux/hashtable.h>
+#include <linux/rculist.h>
+#include <linux/nodemask.h>
+#include <linux/moduleparam.h>
+#include <linux/uaccess.h>
+#include <linux/sched/isolation.h>
+#include <linux/nmi.h>
+#include <linux/kvm_para.h>
+
+#include "workqueue_internal.h"
+
+enum {
+	/*
+	 * worker_pool flags
+	 *
+	 * A bound pool is either associated or disassociated with its CPU.
+	 * While associated (!DISASSOCIATED), all workers are bound to the
+	 * CPU and none has %WORKER_UNBOUND set and concurrency management
+	 * is in effect.
+	 *
+	 * While DISASSOCIATED, the cpu may be offline and all workers have
+	 * %WORKER_UNBOUND set and concurrency management disabled, and may
+	 * be executing on any CPU.  The pool behaves as an unbound one.
+	 *
+	 * Note that DISASSOCIATED should be flipped only while holding
+	 * wq_pool_attach_mutex to avoid changing binding state while
+	 * worker_attach_to_pool() is in progress.
+	 */
+	POOL_MANAGER_ACTIVE	= 1 << 0,	/* being managed */
+	POOL_DISASSOCIATED	= 1 << 2,	/* cpu can't serve workers */
+
+	/* worker flags */
+	WORKER_DIE		= 1 << 1,	/* die die die */
+	WORKER_IDLE		= 1 << 2,	/* is idle */
+	WORKER_PREP		= 1 << 3,	/* preparing to run works */
+	WORKER_CPU_INTENSIVE	= 1 << 6,	/* cpu intensive */
+	WORKER_UNBOUND		= 1 << 7,	/* worker is unbound */
+	WORKER_REBOUND		= 1 << 8,	/* worker was rebound */
+
+	WORKER_NOT_RUNNING	= WORKER_PREP | WORKER_CPU_INTENSIVE |
+				  WORKER_UNBOUND | WORKER_REBOUND,
+
+	NR_STD_WORKER_POOLS	= 2,		/* # standard pools per cpu */
+
+	UNBOUND_POOL_HASH_ORDER	= 6,		/* hashed by pool->attrs */
+	BUSY_WORKER_HASH_ORDER	= 6,		/* 64 pointers */
+
+	MAX_IDLE_WORKERS_RATIO	= 4,		/* 1/4 of busy can be idle */
+	IDLE_WORKER_TIMEOUT	= 300 * HZ,	/* keep idle ones for 5 mins */
+
+	MAYDAY_INITIAL_TIMEOUT  = HZ / 100 >= 2 ? HZ / 100 : 2,
+						/* call for help after 10ms
+						   (min two ticks) */
+	MAYDAY_INTERVAL		= HZ / 10,	/* and then every 100ms */
+	CREATE_COOLDOWN		= HZ,		/* time to breath after fail */
+
+	/*
+	 * Rescue workers are used only on emergencies and shared by
+	 * all cpus.  Give MIN_NICE.
+	 */
+	RESCUER_NICE_LEVEL	= MIN_NICE,
+	HIGHPRI_NICE_LEVEL	= MIN_NICE,
+
+	WQ_NAME_LEN		= 24,
+};
+
+/*
+ * Structure fields follow one of the following exclusion rules.
+ *
+ * I: Modifiable by initialization/destruction paths and read-only for
+ *    everyone else.
+ *
+ * P: Preemption protected.  Disabling preemption is enough and should
+ *    only be modified and accessed from the local cpu.
+ *
+ * L: pool->lock protected.  Access with pool->lock held.
+ *
+ * X: During normal operation, modification requires pool->lock and should
+ *    be done only from local cpu.  Either disabling preemption on local
+ *    cpu or grabbing pool->lock is enough for read access.  If
+ *    POOL_DISASSOCIATED is set, it's identical to L.
+ *
+ * A: wq_pool_attach_mutex protected.
+ *
+ * PL: wq_pool_mutex protected.
+ *
+ * PR: wq_pool_mutex protected for writes.  Sched-RCU protected for reads.
+ *
+ * PW: wq_pool_mutex and wq->mutex protected for writes.  Either for reads.
+ *
+ * PWR: wq_pool_mutex and wq->mutex protected for writes.  Either or
+ *      sched-RCU for reads.
+ *
+ * WQ: wq->mutex protected.
+ *
+ * WR: wq->mutex protected for writes.  Sched-RCU protected for reads.
+ *
+ * MD: wq_mayday_lock protected.
+ */
+
+/* struct worker is defined in workqueue_internal.h */
+
+struct worker_pool {
+	spinlock_t		lock;		/* the pool lock */
+	int			cpu;		/* I: the associated cpu */
+	int			node;		/* I: the associated node ID */
+	int			id;		/* I: pool ID */
+	unsigned int		flags;		/* X: flags */
+
+	unsigned long		watchdog_ts;	/* L: watchdog timestamp */
+
+	struct list_head	worklist;	/* L: list of pending works */
+
+	int			nr_workers;	/* L: total number of workers */
+	int			nr_idle;	/* L: currently idle workers */
+
+	struct list_head	idle_list;	/* X: list of idle workers */
+	struct timer_list	idle_timer;	/* L: worker idle timeout */
+	struct timer_list	mayday_timer;	/* L: SOS timer for workers */
+
+	/* a workers is either on busy_hash or idle_list, or the manager */
+	DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
+						/* L: hash of busy workers */
+
+	struct worker		*manager;	/* L: purely informational */
+	struct list_head	workers;	/* A: attached workers */
+	struct completion	*detach_completion; /* all workers detached */
+
+	struct ida		worker_ida;	/* worker IDs for task name */
+
+	struct workqueue_attrs	*attrs;		/* I: worker attributes */
+	struct hlist_node	hash_node;	/* PL: unbound_pool_hash node */
+	int			refcnt;		/* PL: refcnt for unbound pools */
+
+	/*
+	 * The current concurrency level.  As it's likely to be accessed
+	 * from other CPUs during try_to_wake_up(), put it in a separate
+	 * cacheline.
+	 */
+	atomic_t		nr_running ____cacheline_aligned_in_smp;
+
+	/*
+	 * Destruction of pool is sched-RCU protected to allow dereferences
+	 * from get_work_pool().
+	 */
+	struct rcu_head		rcu;
+} ____cacheline_aligned_in_smp;
+
+/*
+ * The per-pool workqueue.  While queued, the lower WORK_STRUCT_FLAG_BITS
+ * of work_struct->data are used for flags and the remaining high bits
+ * point to the pwq; thus, pwqs need to be aligned at two's power of the
+ * number of flag bits.
+ */
+struct pool_workqueue {
+	struct worker_pool	*pool;		/* I: the associated pool */
+	struct workqueue_struct *wq;		/* I: the owning workqueue */
+	int			work_color;	/* L: current color */
+	int			flush_color;	/* L: flushing color */
+	int			refcnt;		/* L: reference count */
+	int			nr_in_flight[WORK_NR_COLORS];
+						/* L: nr of in_flight works */
+	int			nr_active;	/* L: nr of active works */
+	int			max_active;	/* L: max active works */
+	struct list_head	delayed_works;	/* L: delayed works */
+	struct list_head	pwqs_node;	/* WR: node on wq->pwqs */
+	struct list_head	mayday_node;	/* MD: node on wq->maydays */
+
+	/*
+	 * Release of unbound pwq is punted to system_wq.  See put_pwq()
+	 * and pwq_unbound_release_workfn() for details.  pool_workqueue
+	 * itself is also sched-RCU protected so that the first pwq can be
+	 * determined without grabbing wq->mutex.
+	 */
+	struct work_struct	unbound_release_work;
+	struct rcu_head		rcu;
+} __aligned(1 << WORK_STRUCT_FLAG_BITS);
+
+/*
+ * Structure used to wait for workqueue flush.
+ */
+struct wq_flusher {
+	struct list_head	list;		/* WQ: list of flushers */
+	int			flush_color;	/* WQ: flush color waiting for */
+	struct completion	done;		/* flush completion */
+};
+
+struct wq_device;
+
+/*
+ * The externally visible workqueue.  It relays the issued work items to
+ * the appropriate worker_pool through its pool_workqueues.
+ */
+struct workqueue_struct {
+	struct list_head	pwqs;		/* WR: all pwqs of this wq */
+	struct list_head	list;		/* PR: list of all workqueues */
+
+	struct mutex		mutex;		/* protects this wq */
+	int			work_color;	/* WQ: current work color */
+	int			flush_color;	/* WQ: current flush color */
+	atomic_t		nr_pwqs_to_flush; /* flush in progress */
+	struct wq_flusher	*first_flusher;	/* WQ: first flusher */
+	struct list_head	flusher_queue;	/* WQ: flush waiters */
+	struct list_head	flusher_overflow; /* WQ: flush overflow list */
+
+	struct list_head	maydays;	/* MD: pwqs requesting rescue */
+	struct worker		*rescuer;	/* I: rescue worker */
+
+	int			nr_drainers;	/* WQ: drain in progress */
+	int			saved_max_active; /* WQ: saved pwq max_active */
+
+	struct workqueue_attrs	*unbound_attrs;	/* PW: only for unbound wqs */
+	struct pool_workqueue	*dfl_pwq;	/* PW: only for unbound wqs */
+
+#ifdef CONFIG_SYSFS
+	struct wq_device	*wq_dev;	/* I: for sysfs interface */
+#endif
+#ifdef CONFIG_LOCKDEP
+	struct lockdep_map	lockdep_map;
+#endif
+	char			name[WQ_NAME_LEN]; /* I: workqueue name */
+
+	/*
+	 * Destruction of workqueue_struct is sched-RCU protected to allow
+	 * walking the workqueues list without grabbing wq_pool_mutex.
+	 * This is used to dump all workqueues from sysrq.
+	 */
+	struct rcu_head		rcu;
+
+	/* hot fields used during command issue, aligned to cacheline */
+	unsigned int		flags ____cacheline_aligned; /* WQ: WQ_* flags */
+	struct pool_workqueue __percpu *cpu_pwqs; /* I: per-cpu pwqs */
+	struct pool_workqueue __rcu *numa_pwq_tbl[]; /* PWR: unbound pwqs indexed by node */
+};
+
+static struct kmem_cache *pwq_cache;
+
+static cpumask_var_t *wq_numa_possible_cpumask;
+					/* possible CPUs of each node */
+
+static bool wq_disable_numa;
+module_param_named(disable_numa, wq_disable_numa, bool, 0444);
+
+/* see the comment above the definition of WQ_POWER_EFFICIENT */
+static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
+module_param_named(power_efficient, wq_power_efficient, bool, 0444);
+
+static bool wq_online;			/* can kworkers be created yet? */
+
+static bool wq_numa_enabled;		/* unbound NUMA affinity enabled */
+
+/* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */
+static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf;
+
+static DEFINE_MUTEX(wq_pool_mutex);	/* protects pools and workqueues list */
+static DEFINE_MUTEX(wq_pool_attach_mutex); /* protects worker attach/detach */
+static DEFINE_SPINLOCK(wq_mayday_lock);	/* protects wq->maydays list */
+static DECLARE_WAIT_QUEUE_HEAD(wq_manager_wait); /* wait for manager to go away */
+
+static LIST_HEAD(workqueues);		/* PR: list of all workqueues */
+static bool workqueue_freezing;		/* PL: have wqs started freezing? */
+
+/* PL: allowable cpus for unbound wqs and work items */
+static cpumask_var_t wq_unbound_cpumask;
+
+/* CPU where unbound work was last round robin scheduled from this CPU */
+static DEFINE_PER_CPU(int, wq_rr_cpu_last);
+
+/*
+ * Local execution of unbound work items is no longer guaranteed.  The
+ * following always forces round-robin CPU selection on unbound work items
+ * to uncover usages which depend on it.
+ */
+#ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU
+static bool wq_debug_force_rr_cpu = true;
+#else
+static bool wq_debug_force_rr_cpu = false;
+#endif
+module_param_named(debug_force_rr_cpu, wq_debug_force_rr_cpu, bool, 0644);
+
+/* the per-cpu worker pools */
+static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], cpu_worker_pools);
+
+static DEFINE_IDR(worker_pool_idr);	/* PR: idr of all pools */
+
+/* PL: hash of all unbound pools keyed by pool->attrs */
+static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);
+
+/* I: attributes used when instantiating standard unbound pools on demand */
+static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];
+
+/* I: attributes used when instantiating ordered pools on demand */
+static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];
+
+struct workqueue_struct *system_wq __read_mostly;
+EXPORT_SYMBOL(system_wq);
+struct workqueue_struct *system_highpri_wq __read_mostly;
+EXPORT_SYMBOL_GPL(system_highpri_wq);
+struct workqueue_struct *system_long_wq __read_mostly;
+EXPORT_SYMBOL_GPL(system_long_wq);
+struct workqueue_struct *system_unbound_wq __read_mostly;
+EXPORT_SYMBOL_GPL(system_unbound_wq);
+struct workqueue_struct *system_freezable_wq __read_mostly;
+EXPORT_SYMBOL_GPL(system_freezable_wq);
+struct workqueue_struct *system_power_efficient_wq __read_mostly;
+EXPORT_SYMBOL_GPL(system_power_efficient_wq);
+struct workqueue_struct *system_freezable_power_efficient_wq __read_mostly;
+EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
+
+static int worker_thread(void *__worker);
+static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/workqueue.h>
+
+#define assert_rcu_or_pool_mutex()					\
+	RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() &&			\
+			 !lockdep_is_held(&wq_pool_mutex),		\
+			 "sched RCU or wq_pool_mutex should be held")
+
+#define assert_rcu_or_wq_mutex(wq)					\
+	RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() &&			\
+			 !lockdep_is_held(&wq->mutex),			\
+			 "sched RCU or wq->mutex should be held")
+
+#define assert_rcu_or_wq_mutex_or_pool_mutex(wq)			\
+	RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() &&			\
+			 !lockdep_is_held(&wq->mutex) &&		\
+			 !lockdep_is_held(&wq_pool_mutex),		\
+			 "sched RCU, wq->mutex or wq_pool_mutex should be held")
+
+#define for_each_cpu_worker_pool(pool, cpu)				\
+	for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0];		\
+	     (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
+	     (pool)++)
+
+/**
+ * for_each_pool - iterate through all worker_pools in the system
+ * @pool: iteration cursor
+ * @pi: integer used for iteration
+ *
+ * This must be called either with wq_pool_mutex held or sched RCU read
+ * locked.  If the pool needs to be used beyond the locking in effect, the
+ * caller is responsible for guaranteeing that the pool stays online.
+ *
+ * The if/else clause exists only for the lockdep assertion and can be
+ * ignored.
+ */
+#define for_each_pool(pool, pi)						\
+	idr_for_each_entry(&worker_pool_idr, pool, pi)			\
+		if (({ assert_rcu_or_pool_mutex(); false; })) { }	\
+		else
+
+/**
+ * for_each_pool_worker - iterate through all workers of a worker_pool
+ * @worker: iteration cursor
+ * @pool: worker_pool to iterate workers of
+ *
+ * This must be called with wq_pool_attach_mutex.
+ *
+ * The if/else clause exists only for the lockdep assertion and can be
+ * ignored.
+ */
+#define for_each_pool_worker(worker, pool)				\
+	list_for_each_entry((worker), &(pool)->workers, node)		\
+		if (({ lockdep_assert_held(&wq_pool_attach_mutex); false; })) { } \
+		else
+
+/**
+ * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
+ * @pwq: iteration cursor
+ * @wq: the target workqueue
+ *
+ * This must be called either with wq->mutex held or sched RCU read locked.
+ * If the pwq needs to be used beyond the locking in effect, the caller is
+ * responsible for guaranteeing that the pwq stays online.
+ *
+ * The if/else clause exists only for the lockdep assertion and can be
+ * ignored.
+ */
+#define for_each_pwq(pwq, wq)						\
+	list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node)		\
+		if (({ assert_rcu_or_wq_mutex(wq); false; })) { }	\
+		else
+
+#ifdef CONFIG_DEBUG_OBJECTS_WORK
+
+static struct debug_obj_descr work_debug_descr;
+
+static void *work_debug_hint(void *addr)
+{
+	return ((struct work_struct *) addr)->func;
+}
+
+static bool work_is_static_object(void *addr)
+{
+	struct work_struct *work = addr;
+
+	return test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work));
+}
+
+/*
+ * fixup_init is called when:
+ * - an active object is initialized
+ */
+static bool work_fixup_init(void *addr, enum debug_obj_state state)
+{
+	struct work_struct *work = addr;
+
+	switch (state) {
+	case ODEBUG_STATE_ACTIVE:
+		cancel_work_sync(work);
+		debug_object_init(work, &work_debug_descr);
+		return true;
+	default:
+		return false;
+	}
+}
+
+/*
+ * fixup_free is called when:
+ * - an active object is freed
+ */
+static bool work_fixup_free(void *addr, enum debug_obj_state state)
+{
+	struct work_struct *work = addr;
+
+	switch (state) {
+	case ODEBUG_STATE_ACTIVE:
+		cancel_work_sync(work);
+		debug_object_free(work, &work_debug_descr);
+		return true;
+	default:
+		return false;
+	}
+}
+
+static struct debug_obj_descr work_debug_descr = {
+	.name		= "work_struct",
+	.debug_hint	= work_debug_hint,
+	.is_static_object = work_is_static_object,
+	.fixup_init	= work_fixup_init,
+	.fixup_free	= work_fixup_free,
+};
+
+static inline void debug_work_activate(struct work_struct *work)
+{
+	debug_object_activate(work, &work_debug_descr);
+}
+
+static inline void debug_work_deactivate(struct work_struct *work)
+{
+	debug_object_deactivate(work, &work_debug_descr);
+}
+
+void __init_work(struct work_struct *work, int onstack)
+{
+	if (onstack)
+		debug_object_init_on_stack(work, &work_debug_descr);
+	else
+		debug_object_init(work, &work_debug_descr);
+}
+EXPORT_SYMBOL_GPL(__init_work);
+
+void destroy_work_on_stack(struct work_struct *work)
+{
+	debug_object_free(work, &work_debug_descr);
+}
+EXPORT_SYMBOL_GPL(destroy_work_on_stack);
+
+void destroy_delayed_work_on_stack(struct delayed_work *work)
+{
+	destroy_timer_on_stack(&work->timer);
+	debug_object_free(&work->work, &work_debug_descr);
+}
+EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack);
+
+#else
+static inline void debug_work_activate(struct work_struct *work) { }
+static inline void debug_work_deactivate(struct work_struct *work) { }
+#endif
+
+/**
+ * worker_pool_assign_id - allocate ID and assing it to @pool
+ * @pool: the pool pointer of interest
+ *
+ * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
+ * successfully, -errno on failure.
+ */
+static int worker_pool_assign_id(struct worker_pool *pool)
+{
+	int ret;
+
+	lockdep_assert_held(&wq_pool_mutex);
+
+	ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE,
+			GFP_KERNEL);
+	if (ret >= 0) {
+		pool->id = ret;
+		return 0;
+	}
+	return ret;
+}
+
+/**
+ * unbound_pwq_by_node - return the unbound pool_workqueue for the given node
+ * @wq: the target workqueue
+ * @node: the node ID
+ *
+ * This must be called with any of wq_pool_mutex, wq->mutex or sched RCU
+ * read locked.
+ * If the pwq needs to be used beyond the locking in effect, the caller is
+ * responsible for guaranteeing that the pwq stays online.
+ *
+ * Return: The unbound pool_workqueue for @node.
+ */
+static struct pool_workqueue *unbound_pwq_by_node(struct workqueue_struct *wq,
+						  int node)
+{
+	assert_rcu_or_wq_mutex_or_pool_mutex(wq);
+
+	/*
+	 * XXX: @node can be NUMA_NO_NODE if CPU goes offline while a
+	 * delayed item is pending.  The plan is to keep CPU -> NODE
+	 * mapping valid and stable across CPU on/offlines.  Once that
+	 * happens, this workaround can be removed.
+	 */
+	if (unlikely(node == NUMA_NO_NODE))
+		return wq->dfl_pwq;
+
+	return rcu_dereference_raw(wq->numa_pwq_tbl[node]);
+}
+
+static unsigned int work_color_to_flags(int color)
+{
+	return color << WORK_STRUCT_COLOR_SHIFT;
+}
+
+static int get_work_color(struct work_struct *work)
+{
+	return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) &
+		((1 << WORK_STRUCT_COLOR_BITS) - 1);
+}
+
+static int work_next_color(int color)
+{
+	return (color + 1) % WORK_NR_COLORS;
+}
+
+/*
+ * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
+ * contain the pointer to the queued pwq.  Once execution starts, the flag
+ * is cleared and the high bits contain OFFQ flags and pool ID.
+ *
+ * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
+ * and clear_work_data() can be used to set the pwq, pool or clear
+ * work->data.  These functions should only be called while the work is
+ * owned - ie. while the PENDING bit is set.
+ *
+ * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
+ * corresponding to a work.  Pool is available once the work has been
+ * queued anywhere after initialization until it is sync canceled.  pwq is
+ * available only while the work item is queued.
+ *
+ * %WORK_OFFQ_CANCELING is used to mark a work item which is being
+ * canceled.  While being canceled, a work item may have its PENDING set
+ * but stay off timer and worklist for arbitrarily long and nobody should
+ * try to steal the PENDING bit.
+ */
+static inline void set_work_data(struct work_struct *work, unsigned long data,
+				 unsigned long flags)
+{
+	WARN_ON_ONCE(!work_pending(work));
+	atomic_long_set(&work->data, data | flags | work_static(work));
+}
+
+static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq,
+			 unsigned long extra_flags)
+{
+	set_work_data(work, (unsigned long)pwq,
+		      WORK_STRUCT_PENDING | WORK_STRUCT_PWQ | extra_flags);
+}
+
+static void set_work_pool_and_keep_pending(struct work_struct *work,
+					   int pool_id)
+{
+	set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT,
+		      WORK_STRUCT_PENDING);
+}
+
+static void set_work_pool_and_clear_pending(struct work_struct *work,
+					    int pool_id)
+{
+	/*
+	 * The following wmb is paired with the implied mb in
+	 * test_and_set_bit(PENDING) and ensures all updates to @work made
+	 * here are visible to and precede any updates by the next PENDING
+	 * owner.
+	 */
+	smp_wmb();
+	set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0);
+	/*
+	 * The following mb guarantees that previous clear of a PENDING bit
+	 * will not be reordered with any speculative LOADS or STORES from
+	 * work->current_func, which is executed afterwards.  This possible
+	 * reordering can lead to a missed execution on attempt to qeueue
+	 * the same @work.  E.g. consider this case:
+	 *
+	 *   CPU#0                         CPU#1
+	 *   ----------------------------  --------------------------------
+	 *
+	 * 1  STORE event_indicated
+	 * 2  queue_work_on() {
+	 * 3    test_and_set_bit(PENDING)
+	 * 4 }                             set_..._and_clear_pending() {
+	 * 5                                 set_work_data() # clear bit
+	 * 6                                 smp_mb()
+	 * 7                               work->current_func() {
+	 * 8				      LOAD event_indicated
+	 *				   }
+	 *
+	 * Without an explicit full barrier speculative LOAD on line 8 can
+	 * be executed before CPU#0 does STORE on line 1.  If that happens,
+	 * CPU#0 observes the PENDING bit is still set and new execution of
+	 * a @work is not queued in a hope, that CPU#1 will eventually
+	 * finish the queued @work.  Meanwhile CPU#1 does not see
+	 * event_indicated is set, because speculative LOAD was executed
+	 * before actual STORE.
+	 */
+	smp_mb();
+}
+
+static void clear_work_data(struct work_struct *work)
+{
+	smp_wmb();	/* see set_work_pool_and_clear_pending() */
+	set_work_data(work, WORK_STRUCT_NO_POOL, 0);
+}
+
+static struct pool_workqueue *get_work_pwq(struct work_struct *work)
+{
+	unsigned long data = atomic_long_read(&work->data);
+
+	if (data & WORK_STRUCT_PWQ)
+		return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
+	else
+		return NULL;
+}
+
+/**
+ * get_work_pool - return the worker_pool a given work was associated with
+ * @work: the work item of interest
+ *
+ * Pools are created and destroyed under wq_pool_mutex, and allows read
+ * access under sched-RCU read lock.  As such, this function should be
+ * called under wq_pool_mutex or with preemption disabled.
+ *
+ * All fields of the returned pool are accessible as long as the above
+ * mentioned locking is in effect.  If the returned pool needs to be used
+ * beyond the critical section, the caller is responsible for ensuring the
+ * returned pool is and stays online.
+ *
+ * Return: The worker_pool @work was last associated with.  %NULL if none.
+ */
+static struct worker_pool *get_work_pool(struct work_struct *work)
+{
+	unsigned long data = atomic_long_read(&work->data);
+	int pool_id;
+
+	assert_rcu_or_pool_mutex();
+
+	if (data & WORK_STRUCT_PWQ)
+		return ((struct pool_workqueue *)
+			(data & WORK_STRUCT_WQ_DATA_MASK))->pool;
+
+	pool_id = data >> WORK_OFFQ_POOL_SHIFT;
+	if (pool_id == WORK_OFFQ_POOL_NONE)
+		return NULL;
+
+	return idr_find(&worker_pool_idr, pool_id);
+}
+
+/**
+ * get_work_pool_id - return the worker pool ID a given work is associated with
+ * @work: the work item of interest
+ *
+ * Return: The worker_pool ID @work was last associated with.
+ * %WORK_OFFQ_POOL_NONE if none.
+ */
+static int get_work_pool_id(struct work_struct *work)
+{
+	unsigned long data = atomic_long_read(&work->data);
+
+	if (data & WORK_STRUCT_PWQ)
+		return ((struct pool_workqueue *)
+			(data & WORK_STRUCT_WQ_DATA_MASK))->pool->id;
+
+	return data >> WORK_OFFQ_POOL_SHIFT;
+}
+
+static void mark_work_canceling(struct work_struct *work)
+{
+	unsigned long pool_id = get_work_pool_id(work);
+
+	pool_id <<= WORK_OFFQ_POOL_SHIFT;
+	set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING);
+}
+
+static bool work_is_canceling(struct work_struct *work)
+{
+	unsigned long data = atomic_long_read(&work->data);
+
+	return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING);
+}
+
+/*
+ * Policy functions.  These define the policies on how the global worker
+ * pools are managed.  Unless noted otherwise, these functions assume that
+ * they're being called with pool->lock held.
+ */
+
+static bool __need_more_worker(struct worker_pool *pool)
+{
+	return !atomic_read(&pool->nr_running);
+}
+
+/*
+ * Need to wake up a worker?  Called from anything but currently
+ * running workers.
+ *
+ * Note that, because unbound workers never contribute to nr_running, this
+ * function will always return %true for unbound pools as long as the
+ * worklist isn't empty.
+ */
+static bool need_more_worker(struct worker_pool *pool)
+{
+	return !list_empty(&pool->worklist) && __need_more_worker(pool);
+}
+
+/* Can I start working?  Called from busy but !running workers. */
+static bool may_start_working(struct worker_pool *pool)
+{
+	return pool->nr_idle;
+}
+
+/* Do I need to keep working?  Called from currently running workers. */
+static bool keep_working(struct worker_pool *pool)
+{
+	return !list_empty(&pool->worklist) &&
+		atomic_read(&pool->nr_running) <= 1;
+}
+
+/* Do we need a new worker?  Called from manager. */
+static bool need_to_create_worker(struct worker_pool *pool)
+{
+	return need_more_worker(pool) && !may_start_working(pool);
+}
+
+/* Do we have too many workers and should some go away? */
+static bool too_many_workers(struct worker_pool *pool)
+{
+	bool managing = pool->flags & POOL_MANAGER_ACTIVE;
+	int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
+	int nr_busy = pool->nr_workers - nr_idle;
+
+	return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
+}
+
+/*
+ * Wake up functions.
+ */
+
+/* Return the first idle worker.  Safe with preemption disabled */
+static struct worker *first_idle_worker(struct worker_pool *pool)
+{
+	if (unlikely(list_empty(&pool->idle_list)))
+		return NULL;
+
+	return list_first_entry(&pool->idle_list, struct worker, entry);
+}
+
+/**
+ * wake_up_worker - wake up an idle worker
+ * @pool: worker pool to wake worker from
+ *
+ * Wake up the first idle worker of @pool.
+ *
+ * CONTEXT:
+ * spin_lock_irq(pool->lock).
+ */
+static void wake_up_worker(struct worker_pool *pool)
+{
+	struct worker *worker = first_idle_worker(pool);
+
+	if (likely(worker))
+		wake_up_process(worker->task);
+}
+
+/**
+ * wq_worker_waking_up - a worker is waking up
+ * @task: task waking up
+ * @cpu: CPU @task is waking up to
+ *
+ * This function is called during try_to_wake_up() when a worker is
+ * being awoken.
+ *
+ * CONTEXT:
+ * spin_lock_irq(rq->lock)
+ */
+void wq_worker_waking_up(struct task_struct *task, int cpu)
+{
+	struct worker *worker = kthread_data(task);
+
+	if (!(worker->flags & WORKER_NOT_RUNNING)) {
+		WARN_ON_ONCE(worker->pool->cpu != cpu);
+		atomic_inc(&worker->pool->nr_running);
+	}
+}
+
+/**
+ * wq_worker_sleeping - a worker is going to sleep
+ * @task: task going to sleep
+ *
+ * This function is called during schedule() when a busy worker is
+ * going to sleep.  Worker on the same cpu can be woken up by
+ * returning pointer to its task.
+ *
+ * CONTEXT:
+ * spin_lock_irq(rq->lock)
+ *
+ * Return:
+ * Worker task on @cpu to wake up, %NULL if none.
+ */
+struct task_struct *wq_worker_sleeping(struct task_struct *task)
+{
+	struct worker *worker = kthread_data(task), *to_wakeup = NULL;
+	struct worker_pool *pool;
+
+	/*
+	 * Rescuers, which may not have all the fields set up like normal
+	 * workers, also reach here, let's not access anything before
+	 * checking NOT_RUNNING.
+	 */
+	if (worker->flags & WORKER_NOT_RUNNING)
+		return NULL;
+
+	pool = worker->pool;
+
+	/* this can only happen on the local cpu */
+	if (WARN_ON_ONCE(pool->cpu != raw_smp_processor_id()))
+		return NULL;
+
+	/*
+	 * The counterpart of the following dec_and_test, implied mb,
+	 * worklist not empty test sequence is in insert_work().
+	 * Please read comment there.
+	 *
+	 * NOT_RUNNING is clear.  This means that we're bound to and
+	 * running on the local cpu w/ rq lock held and preemption
+	 * disabled, which in turn means that none else could be
+	 * manipulating idle_list, so dereferencing idle_list without pool
+	 * lock is safe.
+	 */
+	if (atomic_dec_and_test(&pool->nr_running) &&
+	    !list_empty(&pool->worklist))
+		to_wakeup = first_idle_worker(pool);
+	return to_wakeup ? to_wakeup->task : NULL;
+}
+
+/**
+ * worker_set_flags - set worker flags and adjust nr_running accordingly
+ * @worker: self
+ * @flags: flags to set
+ *
+ * Set @flags in @worker->flags and adjust nr_running accordingly.
+ *
+ * CONTEXT:
+ * spin_lock_irq(pool->lock)
+ */
+static inline void worker_set_flags(struct worker *worker, unsigned int flags)
+{
+	struct worker_pool *pool = worker->pool;
+
+	WARN_ON_ONCE(worker->task != current);
+
+	/* If transitioning into NOT_RUNNING, adjust nr_running. */
+	if ((flags & WORKER_NOT_RUNNING) &&
+	    !(worker->flags & WORKER_NOT_RUNNING)) {
+		atomic_dec(&pool->nr_running);
+	}
+
+	worker->flags |= flags;
+}
+
+/**
+ * worker_clr_flags - clear worker flags and adjust nr_running accordingly
+ * @worker: self
+ * @flags: flags to clear
+ *
+ * Clear @flags in @worker->flags and adjust nr_running accordingly.
+ *
+ * CONTEXT:
+ * spin_lock_irq(pool->lock)
+ */
+static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
+{
+	struct worker_pool *pool = worker->pool;
+	unsigned int oflags = worker->flags;
+
+	WARN_ON_ONCE(worker->task != current);
+
+	worker->flags &= ~flags;
+
+	/*
+	 * If transitioning out of NOT_RUNNING, increment nr_running.  Note
+	 * that the nested NOT_RUNNING is not a noop.  NOT_RUNNING is mask
+	 * of multiple flags, not a single flag.
+	 */
+	if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
+		if (!(worker->flags & WORKER_NOT_RUNNING))
+			atomic_inc(&pool->nr_running);
+}
+
+/**
+ * find_worker_executing_work - find worker which is executing a work
+ * @pool: pool of interest
+ * @work: work to find worker for
+ *
+ * Find a worker which is executing @work on @pool by searching
+ * @pool->busy_hash which is keyed by the address of @work.  For a worker
+ * to match, its current execution should match the address of @work and
+ * its work function.  This is to avoid unwanted dependency between
+ * unrelated work executions through a work item being recycled while still
+ * being executed.
+ *
+ * This is a bit tricky.  A work item may be freed once its execution
+ * starts and nothing prevents the freed area from being recycled for
+ * another work item.  If the same work item address ends up being reused
+ * before the original execution finishes, workqueue will identify the
+ * recycled work item as currently executing and make it wait until the
+ * current execution finishes, introducing an unwanted dependency.
+ *
+ * This function checks the work item address and work function to avoid
+ * false positives.  Note that this isn't complete as one may construct a
+ * work function which can introduce dependency onto itself through a
+ * recycled work item.  Well, if somebody wants to shoot oneself in the
+ * foot that badly, there's only so much we can do, and if such deadlock
+ * actually occurs, it should be easy to locate the culprit work function.
+ *
+ * CONTEXT:
+ * spin_lock_irq(pool->lock).
+ *
+ * Return:
+ * Pointer to worker which is executing @work if found, %NULL
+ * otherwise.
+ */
+static struct worker *find_worker_executing_work(struct worker_pool *pool,
+						 struct work_struct *work)
+{
+	struct worker *worker;
+
+	hash_for_each_possible(pool->busy_hash, worker, hentry,
+			       (unsigned long)work)
+		if (worker->current_work == work &&
+		    worker->current_func == work->func)
+			return worker;
+
+	return NULL;
+}
+
+/**
+ * move_linked_works - move linked works to a list
+ * @work: start of series of works to be scheduled
+ * @head: target list to append @work to
+ * @nextp: out parameter for nested worklist walking
+ *
+ * Schedule linked works starting from @work to @head.  Work series to
+ * be scheduled starts at @work and includes any consecutive work with
+ * WORK_STRUCT_LINKED set in its predecessor.
+ *
+ * If @nextp is not NULL, it's updated to point to the next work of
+ * the last scheduled work.  This allows move_linked_works() to be
+ * nested inside outer list_for_each_entry_safe().
+ *
+ * CONTEXT:
+ * spin_lock_irq(pool->lock).
+ */
+static void move_linked_works(struct work_struct *work, struct list_head *head,
+			      struct work_struct **nextp)
+{
+	struct work_struct *n;
+
+	/*
+	 * Linked worklist will always end before the end of the list,
+	 * use NULL for list head.
+	 */
+	list_for_each_entry_safe_from(work, n, NULL, entry) {
+		list_move_tail(&work->entry, head);
+		if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
+			break;
+	}
+
+	/*
+	 * If we're already inside safe list traversal and have moved
+	 * multiple works to the scheduled queue, the next position
+	 * needs to be updated.
+	 */
+	if (nextp)
+		*nextp = n;
+}
+
+/**
+ * get_pwq - get an extra reference on the specified pool_workqueue
+ * @pwq: pool_workqueue to get
+ *
+ * Obtain an extra reference on @pwq.  The caller should guarantee that
+ * @pwq has positive refcnt and be holding the matching pool->lock.
+ */
+static void get_pwq(struct pool_workqueue *pwq)
+{
+	lockdep_assert_held(&pwq->pool->lock);
+	WARN_ON_ONCE(pwq->refcnt <= 0);
+	pwq->refcnt++;
+}
+
+/**
+ * put_pwq - put a pool_workqueue reference
+ * @pwq: pool_workqueue to put
+ *
+ * Drop a reference of @pwq.  If its refcnt reaches zero, schedule its
+ * destruction.  The caller should be holding the matching pool->lock.
+ */
+static void put_pwq(struct pool_workqueue *pwq)
+{
+	lockdep_assert_held(&pwq->pool->lock);
+	if (likely(--pwq->refcnt))
+		return;
+	if (WARN_ON_ONCE(!(pwq->wq->flags & WQ_UNBOUND)))
+		return;
+	/*
+	 * @pwq can't be released under pool->lock, bounce to
+	 * pwq_unbound_release_workfn().  This never recurses on the same
+	 * pool->lock as this path is taken only for unbound workqueues and
+	 * the release work item is scheduled on a per-cpu workqueue.  To
+	 * avoid lockdep warning, unbound pool->locks are given lockdep
+	 * subclass of 1 in get_unbound_pool().
+	 */
+	schedule_work(&pwq->unbound_release_work);
+}
+
+/**
+ * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
+ * @pwq: pool_workqueue to put (can be %NULL)
+ *
+ * put_pwq() with locking.  This function also allows %NULL @pwq.
+ */
+static void put_pwq_unlocked(struct pool_workqueue *pwq)
+{
+	if (pwq) {
+		/*
+		 * As both pwqs and pools are sched-RCU protected, the
+		 * following lock operations are safe.
+		 */
+		spin_lock_irq(&pwq->pool->lock);
+		put_pwq(pwq);
+		spin_unlock_irq(&pwq->pool->lock);
+	}
+}
+
+static void pwq_activate_delayed_work(struct work_struct *work)
+{
+	struct pool_workqueue *pwq = get_work_pwq(work);
+
+	trace_workqueue_activate_work(work);
+	if (list_empty(&pwq->pool->worklist))
+		pwq->pool->watchdog_ts = jiffies;
+	move_linked_works(work, &pwq->pool->worklist, NULL);
+	__clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
+	pwq->nr_active++;
+}
+
+static void pwq_activate_first_delayed(struct pool_workqueue *pwq)
+{
+	struct work_struct *work = list_first_entry(&pwq->delayed_works,
+						    struct work_struct, entry);
+
+	pwq_activate_delayed_work(work);
+}
+
+/**
+ * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
+ * @pwq: pwq of interest
+ * @color: color of work which left the queue
+ *
+ * A work either has completed or is removed from pending queue,
+ * decrement nr_in_flight of its pwq and handle workqueue flushing.
+ *
+ * CONTEXT:
+ * spin_lock_irq(pool->lock).
+ */
+static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, int color)
+{
+	/* uncolored work items don't participate in flushing or nr_active */
+	if (color == WORK_NO_COLOR)
+		goto out_put;
+
+	pwq->nr_in_flight[color]--;
+
+	pwq->nr_active--;
+	if (!list_empty(&pwq->delayed_works)) {
+		/* one down, submit a delayed one */
+		if (pwq->nr_active < pwq->max_active)
+			pwq_activate_first_delayed(pwq);
+	}
+
+	/* is flush in progress and are we at the flushing tip? */
+	if (likely(pwq->flush_color != color))
+		goto out_put;
+
+	/* are there still in-flight works? */
+	if (pwq->nr_in_flight[color])
+		goto out_put;
+
+	/* this pwq is done, clear flush_color */
+	pwq->flush_color = -1;
+
+	/*
+	 * If this was the last pwq, wake up the first flusher.  It
+	 * will handle the rest.
+	 */
+	if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
+		complete(&pwq->wq->first_flusher->done);
+out_put:
+	put_pwq(pwq);
+}
+
+/**
+ * try_to_grab_pending - steal work item from worklist and disable irq
+ * @work: work item to steal
+ * @is_dwork: @work is a delayed_work
+ * @flags: place to store irq state
+ *
+ * Try to grab PENDING bit of @work.  This function can handle @work in any
+ * stable state - idle, on timer or on worklist.
+ *
+ * Return:
+ *  1		if @work was pending and we successfully stole PENDING
+ *  0		if @work was idle and we claimed PENDING
+ *  -EAGAIN	if PENDING couldn't be grabbed at the moment, safe to busy-retry
+ *  -ENOENT	if someone else is canceling @work, this state may persist
+ *		for arbitrarily long
+ *
+ * Note:
+ * On >= 0 return, the caller owns @work's PENDING bit.  To avoid getting
+ * interrupted while holding PENDING and @work off queue, irq must be
+ * disabled on entry.  This, combined with delayed_work->timer being
+ * irqsafe, ensures that we return -EAGAIN for finite short period of time.
+ *
+ * On successful return, >= 0, irq is disabled and the caller is
+ * responsible for releasing it using local_irq_restore(*@flags).
+ *
+ * This function is safe to call from any context including IRQ handler.
+ */
+static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
+			       unsigned long *flags)
+{
+	struct worker_pool *pool;
+	struct pool_workqueue *pwq;
+
+	local_irq_save(*flags);
+
+	/* try to steal the timer if it exists */
+	if (is_dwork) {
+		struct delayed_work *dwork = to_delayed_work(work);
+
+		/*
+		 * dwork->timer is irqsafe.  If del_timer() fails, it's
+		 * guaranteed that the timer is not queued anywhere and not
+		 * running on the local CPU.
+		 */
+		if (likely(del_timer(&dwork->timer)))
+			return 1;
+	}
+
+	/* try to claim PENDING the normal way */
+	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
+		return 0;
+
+	/*
+	 * The queueing is in progress, or it is already queued. Try to
+	 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
+	 */
+	pool = get_work_pool(work);
+	if (!pool)
+		goto fail;
+
+	spin_lock(&pool->lock);
+	/*
+	 * work->data is guaranteed to point to pwq only while the work
+	 * item is queued on pwq->wq, and both updating work->data to point
+	 * to pwq on queueing and to pool on dequeueing are done under
+	 * pwq->pool->lock.  This in turn guarantees that, if work->data
+	 * points to pwq which is associated with a locked pool, the work
+	 * item is currently queued on that pool.
+	 */
+	pwq = get_work_pwq(work);
+	if (pwq && pwq->pool == pool) {
+		debug_work_deactivate(work);
+
+		/*
+		 * A delayed work item cannot be grabbed directly because
+		 * it might have linked NO_COLOR work items which, if left
+		 * on the delayed_list, will confuse pwq->nr_active
+		 * management later on and cause stall.  Make sure the work
+		 * item is activated before grabbing.
+		 */
+		if (*work_data_bits(work) & WORK_STRUCT_DELAYED)
+			pwq_activate_delayed_work(work);
+
+		list_del_init(&work->entry);
+		pwq_dec_nr_in_flight(pwq, get_work_color(work));
+
+		/* work->data points to pwq iff queued, point to pool */
+		set_work_pool_and_keep_pending(work, pool->id);
+
+		spin_unlock(&pool->lock);
+		return 1;
+	}
+	spin_unlock(&pool->lock);
+fail:
+	local_irq_restore(*flags);
+	if (work_is_canceling(work))
+		return -ENOENT;
+	cpu_relax();
+	return -EAGAIN;
+}
+
+/**
+ * insert_work - insert a work into a pool
+ * @pwq: pwq @work belongs to
+ * @work: work to insert
+ * @head: insertion point
+ * @extra_flags: extra WORK_STRUCT_* flags to set
+ *
+ * Insert @work which belongs to @pwq after @head.  @extra_flags is or'd to
+ * work_struct flags.
+ *
+ * CONTEXT:
+ * spin_lock_irq(pool->lock).
+ */
+static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
+			struct list_head *head, unsigned int extra_flags)
+{
+	struct worker_pool *pool = pwq->pool;
+
+	/* we own @work, set data and link */
+	set_work_pwq(work, pwq, extra_flags);
+	list_add_tail(&work->entry, head);
+	get_pwq(pwq);
+
+	/*
+	 * Ensure either wq_worker_sleeping() sees the above
+	 * list_add_tail() or we see zero nr_running to avoid workers lying
+	 * around lazily while there are works to be processed.
+	 */
+	smp_mb();
+
+	if (__need_more_worker(pool))
+		wake_up_worker(pool);
+}
+
+/*
+ * Test whether @work is being queued from another work executing on the
+ * same workqueue.
+ */
+static bool is_chained_work(struct workqueue_struct *wq)
+{
+	struct worker *worker;
+
+	worker = current_wq_worker();
+	/*
+	 * Return %true iff I'm a worker execuing a work item on @wq.  If
+	 * I'm @worker, it's safe to dereference it without locking.
+	 */
+	return worker && worker->current_pwq->wq == wq;
+}
+
+/*
+ * When queueing an unbound work item to a wq, prefer local CPU if allowed
+ * by wq_unbound_cpumask.  Otherwise, round robin among the allowed ones to
+ * avoid perturbing sensitive tasks.
+ */
+static int wq_select_unbound_cpu(int cpu)
+{
+	static bool printed_dbg_warning;
+	int new_cpu;
+
+	if (likely(!wq_debug_force_rr_cpu)) {
+		if (cpumask_test_cpu(cpu, wq_unbound_cpumask))
+			return cpu;
+	} else if (!printed_dbg_warning) {
+		pr_warn("workqueue: round-robin CPU selection forced, expect performance impact\n");
+		printed_dbg_warning = true;
+	}
+
+	if (cpumask_empty(wq_unbound_cpumask))
+		return cpu;
+
+	new_cpu = __this_cpu_read(wq_rr_cpu_last);
+	new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask);
+	if (unlikely(new_cpu >= nr_cpu_ids)) {
+		new_cpu = cpumask_first_and(wq_unbound_cpumask, cpu_online_mask);
+		if (unlikely(new_cpu >= nr_cpu_ids))
+			return cpu;
+	}
+	__this_cpu_write(wq_rr_cpu_last, new_cpu);
+
+	return new_cpu;
+}
+
+static void __queue_work(int cpu, struct workqueue_struct *wq,
+			 struct work_struct *work)
+{
+	struct pool_workqueue *pwq;
+	struct worker_pool *last_pool;
+	struct list_head *worklist;
+	unsigned int work_flags;
+	unsigned int req_cpu = cpu;
+
+	/*
+	 * While a work item is PENDING && off queue, a task trying to
+	 * steal the PENDING will busy-loop waiting for it to either get
+	 * queued or lose PENDING.  Grabbing PENDING and queueing should
+	 * happen with IRQ disabled.
+	 */
+	lockdep_assert_irqs_disabled();
+
+
+	/* if draining, only works from the same workqueue are allowed */
+	if (unlikely(wq->flags & __WQ_DRAINING) &&
+	    WARN_ON_ONCE(!is_chained_work(wq)))
+		return;
+retry:
+	/* pwq which will be used unless @work is executing elsewhere */
+	if (wq->flags & WQ_UNBOUND) {
+		if (req_cpu == WORK_CPU_UNBOUND)
+			cpu = wq_select_unbound_cpu(raw_smp_processor_id());
+		pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
+	} else {
+		if (req_cpu == WORK_CPU_UNBOUND)
+			cpu = raw_smp_processor_id();
+		pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
+	}
+
+	/*
+	 * If @work was previously on a different pool, it might still be
+	 * running there, in which case the work needs to be queued on that
+	 * pool to guarantee non-reentrancy.
+	 */
+	last_pool = get_work_pool(work);
+	if (last_pool && last_pool != pwq->pool) {
+		struct worker *worker;
+
+		spin_lock(&last_pool->lock);
+
+		worker = find_worker_executing_work(last_pool, work);
+
+		if (worker && worker->current_pwq->wq == wq) {
+			pwq = worker->current_pwq;
+		} else {
+			/* meh... not running there, queue here */
+			spin_unlock(&last_pool->lock);
+			spin_lock(&pwq->pool->lock);
+		}
+	} else {
+		spin_lock(&pwq->pool->lock);
+	}
+
+	/*
+	 * pwq is determined and locked.  For unbound pools, we could have
+	 * raced with pwq release and it could already be dead.  If its
+	 * refcnt is zero, repeat pwq selection.  Note that pwqs never die
+	 * without another pwq replacing it in the numa_pwq_tbl or while
+	 * work items are executing on it, so the retrying is guaranteed to
+	 * make forward-progress.
+	 */
+	if (unlikely(!pwq->refcnt)) {
+		if (wq->flags & WQ_UNBOUND) {
+			spin_unlock(&pwq->pool->lock);
+			cpu_relax();
+			goto retry;
+		}
+		/* oops */
+		WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
+			  wq->name, cpu);
+	}
+
+	/* pwq determined, queue */
+	trace_workqueue_queue_work(req_cpu, pwq, work);
+
+	if (WARN_ON(!list_empty(&work->entry))) {
+		spin_unlock(&pwq->pool->lock);
+		return;
+	}
+
+	pwq->nr_in_flight[pwq->work_color]++;
+	work_flags = work_color_to_flags(pwq->work_color);
+
+	if (likely(pwq->nr_active < pwq->max_active)) {
+		trace_workqueue_activate_work(work);
+		pwq->nr_active++;
+		worklist = &pwq->pool->worklist;
+		if (list_empty(worklist))
+			pwq->pool->watchdog_ts = jiffies;
+	} else {
+		work_flags |= WORK_STRUCT_DELAYED;
+		worklist = &pwq->delayed_works;
+	}
+
+	debug_work_activate(work);
+	insert_work(pwq, work, worklist, work_flags);
+
+	spin_unlock(&pwq->pool->lock);
+}
+
+/**
+ * queue_work_on - queue work on specific cpu
+ * @cpu: CPU number to execute work on
+ * @wq: workqueue to use
+ * @work: work to queue
+ *
+ * We queue the work to a specific CPU, the caller must ensure it
+ * can't go away.
+ *
+ * Return: %false if @work was already on a queue, %true otherwise.
+ */
+bool queue_work_on(int cpu, struct workqueue_struct *wq,
+		   struct work_struct *work)
+{
+	bool ret = false;
+	unsigned long flags;
+
+	local_irq_save(flags);
+
+	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
+		__queue_work(cpu, wq, work);
+		ret = true;
+	}
+
+	local_irq_restore(flags);
+	return ret;
+}
+EXPORT_SYMBOL(queue_work_on);
+
+void delayed_work_timer_fn(struct timer_list *t)
+{
+	struct delayed_work *dwork = from_timer(dwork, t, timer);
+
+	/* should have been called from irqsafe timer with irq already off */
+	__queue_work(dwork->cpu, dwork->wq, &dwork->work);
+}
+EXPORT_SYMBOL(delayed_work_timer_fn);
+
+static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
+				struct delayed_work *dwork, unsigned long delay)
+{
+	struct timer_list *timer = &dwork->timer;
+	struct work_struct *work = &dwork->work;
+
+	WARN_ON_ONCE(!wq);
+	WARN_ON_ONCE(timer->function != delayed_work_timer_fn);
+	WARN_ON_ONCE(timer_pending(timer));
+	WARN_ON_ONCE(!list_empty(&work->entry));
+
+	/*
+	 * If @delay is 0, queue @dwork->work immediately.  This is for
+	 * both optimization and correctness.  The earliest @timer can
+	 * expire is on the closest next tick and delayed_work users depend
+	 * on that there's no such delay when @delay is 0.
+	 */
+	if (!delay) {
+		__queue_work(cpu, wq, &dwork->work);
+		return;
+	}
+
+	dwork->wq = wq;
+	dwork->cpu = cpu;
+	timer->expires = jiffies + delay;
+
+	if (unlikely(cpu != WORK_CPU_UNBOUND))
+		add_timer_on(timer, cpu);
+	else
+		add_timer(timer);
+}
+
+/**
+ * queue_delayed_work_on - queue work on specific CPU after delay
+ * @cpu: CPU number to execute work on
+ * @wq: workqueue to use
+ * @dwork: work to queue
+ * @delay: number of jiffies to wait before queueing
+ *
+ * Return: %false if @work was already on a queue, %true otherwise.  If
+ * @delay is zero and @dwork is idle, it will be scheduled for immediate
+ * execution.
+ */
+bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
+			   struct delayed_work *dwork, unsigned long delay)
+{
+	struct work_struct *work = &dwork->work;
+	bool ret = false;
+	unsigned long flags;
+
+	/* read the comment in __queue_work() */
+	local_irq_save(flags);
+
+	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
+		__queue_delayed_work(cpu, wq, dwork, delay);
+		ret = true;
+	}
+
+	local_irq_restore(flags);
+	return ret;
+}
+EXPORT_SYMBOL(queue_delayed_work_on);
+
+/**
+ * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
+ * @cpu: CPU number to execute work on
+ * @wq: workqueue to use
+ * @dwork: work to queue
+ * @delay: number of jiffies to wait before queueing
+ *
+ * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
+ * modify @dwork's timer so that it expires after @delay.  If @delay is
+ * zero, @work is guaranteed to be scheduled immediately regardless of its
+ * current state.
+ *
+ * Return: %false if @dwork was idle and queued, %true if @dwork was
+ * pending and its timer was modified.
+ *
+ * This function is safe to call from any context including IRQ handler.
+ * See try_to_grab_pending() for details.
+ */
+bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
+			 struct delayed_work *dwork, unsigned long delay)
+{
+	unsigned long flags;
+	int ret;
+
+	do {
+		ret = try_to_grab_pending(&dwork->work, true, &flags);
+	} while (unlikely(ret == -EAGAIN));
+
+	if (likely(ret >= 0)) {
+		__queue_delayed_work(cpu, wq, dwork, delay);
+		local_irq_restore(flags);
+	}
+
+	/* -ENOENT from try_to_grab_pending() becomes %true */
+	return ret;
+}
+EXPORT_SYMBOL_GPL(mod_delayed_work_on);
+
+static void rcu_work_rcufn(struct rcu_head *rcu)
+{
+	struct rcu_work *rwork = container_of(rcu, struct rcu_work, rcu);
+
+	/* read the comment in __queue_work() */
+	local_irq_disable();
+	__queue_work(WORK_CPU_UNBOUND, rwork->wq, &rwork->work);
+	local_irq_enable();
+}
+
+/**
+ * queue_rcu_work - queue work after a RCU grace period
+ * @wq: workqueue to use
+ * @rwork: work to queue
+ *
+ * Return: %false if @rwork was already pending, %true otherwise.  Note
+ * that a full RCU grace period is guaranteed only after a %true return.
+ * While @rwork is guarnateed to be executed after a %false return, the
+ * execution may happen before a full RCU grace period has passed.
+ */
+bool queue_rcu_work(struct workqueue_struct *wq, struct rcu_work *rwork)
+{
+	struct work_struct *work = &rwork->work;
+
+	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
+		rwork->wq = wq;
+		call_rcu(&rwork->rcu, rcu_work_rcufn);
+		return true;
+	}
+
+	return false;
+}
+EXPORT_SYMBOL(queue_rcu_work);
+
+/**
+ * worker_enter_idle - enter idle state
+ * @worker: worker which is entering idle state
+ *
+ * @worker is entering idle state.  Update stats and idle timer if
+ * necessary.
+ *
+ * LOCKING:
+ * spin_lock_irq(pool->lock).
+ */
+static void worker_enter_idle(struct worker *worker)
+{
+	struct worker_pool *pool = worker->pool;
+
+	if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
+	    WARN_ON_ONCE(!list_empty(&worker->entry) &&
+			 (worker->hentry.next || worker->hentry.pprev)))
+		return;
+
+	/* can't use worker_set_flags(), also called from create_worker() */
+	worker->flags |= WORKER_IDLE;
+	pool->nr_idle++;
+	worker->last_active = jiffies;
+
+	/* idle_list is LIFO */
+	list_add(&worker->entry, &pool->idle_list);
+
+	if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
+		mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
+
+	/*
+	 * Sanity check nr_running.  Because unbind_workers() releases
+	 * pool->lock between setting %WORKER_UNBOUND and zapping
+	 * nr_running, the warning may trigger spuriously.  Check iff
+	 * unbind is not in progress.
+	 */
+	WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
+		     pool->nr_workers == pool->nr_idle &&
+		     atomic_read(&pool->nr_running));
+}
+
+/**
+ * worker_leave_idle - leave idle state
+ * @worker: worker which is leaving idle state
+ *
+ * @worker is leaving idle state.  Update stats.
+ *
+ * LOCKING:
+ * spin_lock_irq(pool->lock).
+ */
+static void worker_leave_idle(struct worker *worker)
+{
+	struct worker_pool *pool = worker->pool;
+
+	if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
+		return;
+	worker_clr_flags(worker, WORKER_IDLE);
+	pool->nr_idle--;
+	list_del_init(&worker->entry);
+}
+
+static struct worker *alloc_worker(int node)
+{
+	struct worker *worker;
+
+	worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node);
+	if (worker) {
+		INIT_LIST_HEAD(&worker->entry);
+		INIT_LIST_HEAD(&worker->scheduled);
+		INIT_LIST_HEAD(&worker->node);
+		/* on creation a worker is in !idle && prep state */
+		worker->flags = WORKER_PREP;
+	}
+	return worker;
+}
+
+/**
+ * worker_attach_to_pool() - attach a worker to a pool
+ * @worker: worker to be attached
+ * @pool: the target pool
+ *
+ * Attach @worker to @pool.  Once attached, the %WORKER_UNBOUND flag and
+ * cpu-binding of @worker are kept coordinated with the pool across
+ * cpu-[un]hotplugs.
+ */
+static void worker_attach_to_pool(struct worker *worker,
+				   struct worker_pool *pool)
+{
+	mutex_lock(&wq_pool_attach_mutex);
+
+	/*
+	 * The wq_pool_attach_mutex ensures %POOL_DISASSOCIATED remains
+	 * stable across this function.  See the comments above the flag
+	 * definition for details.
+	 */
+	if (pool->flags & POOL_DISASSOCIATED)
+		worker->flags |= WORKER_UNBOUND;
+
+	if (worker->rescue_wq)
+		set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);
+
+	list_add_tail(&worker->node, &pool->workers);
+	worker->pool = pool;
+
+	mutex_unlock(&wq_pool_attach_mutex);
+}
+
+/**
+ * worker_detach_from_pool() - detach a worker from its pool
+ * @worker: worker which is attached to its pool
+ *
+ * Undo the attaching which had been done in worker_attach_to_pool().  The
+ * caller worker shouldn't access to the pool after detached except it has
+ * other reference to the pool.
+ */
+static void worker_detach_from_pool(struct worker *worker)
+{
+	struct worker_pool *pool = worker->pool;
+	struct completion *detach_completion = NULL;
+
+	mutex_lock(&wq_pool_attach_mutex);
+
+	list_del(&worker->node);
+	worker->pool = NULL;
+
+	if (list_empty(&pool->workers))
+		detach_completion = pool->detach_completion;
+	mutex_unlock(&wq_pool_attach_mutex);
+
+	/* clear leftover flags without pool->lock after it is detached */
+	worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);
+
+	if (detach_completion)
+		complete(detach_completion);
+}
+
+/**
+ * create_worker - create a new workqueue worker
+ * @pool: pool the new worker will belong to
+ *
+ * Create and start a new worker which is attached to @pool.
+ *
+ * CONTEXT:
+ * Might sleep.  Does GFP_KERNEL allocations.
+ *
+ * Return:
+ * Pointer to the newly created worker.
+ */
+static struct worker *create_worker(struct worker_pool *pool)
+{
+	struct worker *worker = NULL;
+	int id = -1;
+	char id_buf[16];
+
+	/* ID is needed to determine kthread name */
+	id = ida_simple_get(&pool->worker_ida, 0, 0, GFP_KERNEL);
+	if (id < 0)
+		goto fail;
+
+	worker = alloc_worker(pool->node);
+	if (!worker)
+		goto fail;
+
+	worker->id = id;
+
+	if (pool->cpu >= 0)
+		snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id,
+			 pool->attrs->nice < 0  ? "H" : "");
+	else
+		snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id);
+
+	worker->task = kthread_create_on_node(worker_thread, worker, pool->node,
+					      "kworker/%s", id_buf);
+	if (IS_ERR(worker->task))
+		goto fail;
+
+	set_user_nice(worker->task, pool->attrs->nice);
+	kthread_bind_mask(worker->task, pool->attrs->cpumask);
+
+	/* successful, attach the worker to the pool */
+	worker_attach_to_pool(worker, pool);
+
+	/* start the newly created worker */
+	spin_lock_irq(&pool->lock);
+	worker->pool->nr_workers++;
+	worker_enter_idle(worker);
+	wake_up_process(worker->task);
+	spin_unlock_irq(&pool->lock);
+
+	return worker;
+
+fail:
+	if (id >= 0)
+		ida_simple_remove(&pool->worker_ida, id);
+	kfree(worker);
+	return NULL;
+}
+
+/**
+ * destroy_worker - destroy a workqueue worker
+ * @worker: worker to be destroyed
+ *
+ * Destroy @worker and adjust @pool stats accordingly.  The worker should
+ * be idle.
+ *
+ * CONTEXT:
+ * spin_lock_irq(pool->lock).
+ */
+static void destroy_worker(struct worker *worker)
+{
+	struct worker_pool *pool = worker->pool;
+
+	lockdep_assert_held(&pool->lock);
+
+	/* sanity check frenzy */
+	if (WARN_ON(worker->current_work) ||
+	    WARN_ON(!list_empty(&worker->scheduled)) ||
+	    WARN_ON(!(worker->flags & WORKER_IDLE)))
+		return;
+
+	pool->nr_workers--;
+	pool->nr_idle--;
+
+	list_del_init(&worker->entry);
+	worker->flags |= WORKER_DIE;
+	wake_up_process(worker->task);
+}
+
+static void idle_worker_timeout(struct timer_list *t)
+{
+	struct worker_pool *pool = from_timer(pool, t, idle_timer);
+
+	spin_lock_irq(&pool->lock);
+
+	while (too_many_workers(pool)) {
+		struct worker *worker;
+		unsigned long expires;
+
+		/* idle_list is kept in LIFO order, check the last one */
+		worker = list_entry(pool->idle_list.prev, struct worker, entry);
+		expires = worker->last_active + IDLE_WORKER_TIMEOUT;
+
+		if (time_before(jiffies, expires)) {
+			mod_timer(&pool->idle_timer, expires);
+			break;
+		}
+
+		destroy_worker(worker);
+	}
+
+	spin_unlock_irq(&pool->lock);
+}
+
+static void send_mayday(struct work_struct *work)
+{
+	struct pool_workqueue *pwq = get_work_pwq(work);
+	struct workqueue_struct *wq = pwq->wq;
+
+	lockdep_assert_held(&wq_mayday_lock);
+
+	if (!wq->rescuer)
+		return;
+
+	/* mayday mayday mayday */
+	if (list_empty(&pwq->mayday_node)) {
+		/*
+		 * If @pwq is for an unbound wq, its base ref may be put at
+		 * any time due to an attribute change.  Pin @pwq until the
+		 * rescuer is done with it.
+		 */
+		get_pwq(pwq);
+		list_add_tail(&pwq->mayday_node, &wq->maydays);
+		wake_up_process(wq->rescuer->task);
+	}
+}
+
+static void pool_mayday_timeout(struct timer_list *t)
+{
+	struct worker_pool *pool = from_timer(pool, t, mayday_timer);
+	struct work_struct *work;
+
+	spin_lock_irq(&pool->lock);
+	spin_lock(&wq_mayday_lock);		/* for wq->maydays */
+
+	if (need_to_create_worker(pool)) {
+		/*
+		 * We've been trying to create a new worker but
+		 * haven't been successful.  We might be hitting an
+		 * allocation deadlock.  Send distress signals to
+		 * rescuers.
+		 */
+		list_for_each_entry(work, &pool->worklist, entry)
+			send_mayday(work);
+	}
+
+	spin_unlock(&wq_mayday_lock);
+	spin_unlock_irq(&pool->lock);
+
+	mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
+}
+
+/**
+ * maybe_create_worker - create a new worker if necessary
+ * @pool: pool to create a new worker for
+ *
+ * Create a new worker for @pool if necessary.  @pool is guaranteed to
+ * have at least one idle worker on return from this function.  If
+ * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
+ * sent to all rescuers with works scheduled on @pool to resolve
+ * possible allocation deadlock.
+ *
+ * On return, need_to_create_worker() is guaranteed to be %false and
+ * may_start_working() %true.
+ *
+ * LOCKING:
+ * spin_lock_irq(pool->lock) which may be released and regrabbed
+ * multiple times.  Does GFP_KERNEL allocations.  Called only from
+ * manager.
+ */
+static void maybe_create_worker(struct worker_pool *pool)
+__releases(&pool->lock)
+__acquires(&pool->lock)
+{
+restart:
+	spin_unlock_irq(&pool->lock);
+
+	/* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
+	mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
+
+	while (true) {
+		if (create_worker(pool) || !need_to_create_worker(pool))
+			break;
+
+		schedule_timeout_interruptible(CREATE_COOLDOWN);
+
+		if (!need_to_create_worker(pool))
+			break;
+	}
+
+	del_timer_sync(&pool->mayday_timer);
+	spin_lock_irq(&pool->lock);
+	/*
+	 * This is necessary even after a new worker was just successfully
+	 * created as @pool->lock was dropped and the new worker might have
+	 * already become busy.
+	 */
+	if (need_to_create_worker(pool))
+		goto restart;
+}
+
+/**
+ * manage_workers - manage worker pool
+ * @worker: self
+ *
+ * Assume the manager role and manage the worker pool @worker belongs
+ * to.  At any given time, there can be only zero or one manager per
+ * pool.  The exclusion is handled automatically by this function.
+ *
+ * The caller can safely start processing works on false return.  On
+ * true return, it's guaranteed that need_to_create_worker() is false
+ * and may_start_working() is true.
+ *
+ * CONTEXT:
+ * spin_lock_irq(pool->lock) which may be released and regrabbed
+ * multiple times.  Does GFP_KERNEL allocations.
+ *
+ * Return:
+ * %false if the pool doesn't need management and the caller can safely
+ * start processing works, %true if management function was performed and
+ * the conditions that the caller verified before calling the function may
+ * no longer be true.
+ */
+static bool manage_workers(struct worker *worker)
+{
+	struct worker_pool *pool = worker->pool;
+
+	if (pool->flags & POOL_MANAGER_ACTIVE)
+		return false;
+
+	pool->flags |= POOL_MANAGER_ACTIVE;
+	pool->manager = worker;
+
+	maybe_create_worker(pool);
+
+	pool->manager = NULL;
+	pool->flags &= ~POOL_MANAGER_ACTIVE;
+	wake_up(&wq_manager_wait);
+	return true;
+}
+
+/**
+ * process_one_work - process single work
+ * @worker: self
+ * @work: work to process
+ *
+ * Process @work.  This function contains all the logics necessary to
+ * process a single work including synchronization against and
+ * interaction with other workers on the same cpu, queueing and
+ * flushing.  As long as context requirement is met, any worker can
+ * call this function to process a work.
+ *
+ * CONTEXT:
+ * spin_lock_irq(pool->lock) which is released and regrabbed.
+ */
+static void process_one_work(struct worker *worker, struct work_struct *work)
+__releases(&pool->lock)
+__acquires(&pool->lock)
+{
+	struct pool_workqueue *pwq = get_work_pwq(work);
+	struct worker_pool *pool = worker->pool;
+	bool cpu_intensive = pwq->wq->flags & WQ_CPU_INTENSIVE;
+	int work_color;
+	struct worker *collision;
+#ifdef CONFIG_LOCKDEP
+	/*
+	 * It is permissible to free the struct work_struct from
+	 * inside the function that is called from it, this we need to
+	 * take into account for lockdep too.  To avoid bogus "held
+	 * lock freed" warnings as well as problems when looking into
+	 * work->lockdep_map, make a copy and use that here.
+	 */
+	struct lockdep_map lockdep_map;
+
+	lockdep_copy_map(&lockdep_map, &work->lockdep_map);
+#endif
+	/* ensure we're on the correct CPU */
+	WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
+		     raw_smp_processor_id() != pool->cpu);
+
+	/*
+	 * A single work shouldn't be executed concurrently by
+	 * multiple workers on a single cpu.  Check whether anyone is
+	 * already processing the work.  If so, defer the work to the
+	 * currently executing one.
+	 */
+	collision = find_worker_executing_work(pool, work);
+	if (unlikely(collision)) {
+		move_linked_works(work, &collision->scheduled, NULL);
+		return;
+	}
+
+	/* claim and dequeue */
+	debug_work_deactivate(work);
+	hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
+	worker->current_work = work;
+	worker->current_func = work->func;
+	worker->current_pwq = pwq;
+	work_color = get_work_color(work);
+
+	/*
+	 * Record wq name for cmdline and debug reporting, may get
+	 * overridden through set_worker_desc().
+	 */
+	strscpy(worker->desc, pwq->wq->name, WORKER_DESC_LEN);
+
+	list_del_init(&work->entry);
+
+	/*
+	 * CPU intensive works don't participate in concurrency management.
+	 * They're the scheduler's responsibility.  This takes @worker out
+	 * of concurrency management and the next code block will chain
+	 * execution of the pending work items.
+	 */
+	if (unlikely(cpu_intensive))
+		worker_set_flags(worker, WORKER_CPU_INTENSIVE);
+
+	/*
+	 * Wake up another worker if necessary.  The condition is always
+	 * false for normal per-cpu workers since nr_running would always
+	 * be >= 1 at this point.  This is used to chain execution of the
+	 * pending work items for WORKER_NOT_RUNNING workers such as the
+	 * UNBOUND and CPU_INTENSIVE ones.
+	 */
+	if (need_more_worker(pool))
+		wake_up_worker(pool);
+
+	/*
+	 * Record the last pool and clear PENDING which should be the last
+	 * update to @work.  Also, do this inside @pool->lock so that
+	 * PENDING and queued state changes happen together while IRQ is
+	 * disabled.
+	 */
+	set_work_pool_and_clear_pending(work, pool->id);
+
+	spin_unlock_irq(&pool->lock);
+
+	lock_map_acquire(&pwq->wq->lockdep_map);
+	lock_map_acquire(&lockdep_map);
+	/*
+	 * Strictly speaking we should mark the invariant state without holding
+	 * any locks, that is, before these two lock_map_acquire()'s.
+	 *
+	 * However, that would result in:
+	 *
+	 *   A(W1)
+	 *   WFC(C)
+	 *		A(W1)
+	 *		C(C)
+	 *
+	 * Which would create W1->C->W1 dependencies, even though there is no
+	 * actual deadlock possible. There are two solutions, using a
+	 * read-recursive acquire on the work(queue) 'locks', but this will then
+	 * hit the lockdep limitation on recursive locks, or simply discard
+	 * these locks.
+	 *
+	 * AFAICT there is no possible deadlock scenario between the
+	 * flush_work() and complete() primitives (except for single-threaded
+	 * workqueues), so hiding them isn't a problem.
+	 */
+	lockdep_invariant_state(true);
+	trace_workqueue_execute_start(work);
+	worker->current_func(work);
+	/*
+	 * While we must be careful to not use "work" after this, the trace
+	 * point will only record its address.
+	 */
+	trace_workqueue_execute_end(work);
+	lock_map_release(&lockdep_map);
+	lock_map_release(&pwq->wq->lockdep_map);
+
+	if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
+		pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
+		       "     last function: %pf\n",
+		       current->comm, preempt_count(), task_pid_nr(current),
+		       worker->current_func);
+		debug_show_held_locks(current);
+		dump_stack();
+	}
+
+	/*
+	 * The following prevents a kworker from hogging CPU on !PREEMPT
+	 * kernels, where a requeueing work item waiting for something to
+	 * happen could deadlock with stop_machine as such work item could
+	 * indefinitely requeue itself while all other CPUs are trapped in
+	 * stop_machine. At the same time, report a quiescent RCU state so
+	 * the same condition doesn't freeze RCU.
+	 */
+	cond_resched();
+
+	spin_lock_irq(&pool->lock);
+
+	/* clear cpu intensive status */
+	if (unlikely(cpu_intensive))
+		worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
+
+	/* we're done with it, release */
+	hash_del(&worker->hentry);
+	worker->current_work = NULL;
+	worker->current_func = NULL;
+	worker->current_pwq = NULL;
+	pwq_dec_nr_in_flight(pwq, work_color);
+}
+
+/**
+ * process_scheduled_works - process scheduled works
+ * @worker: self
+ *
+ * Process all scheduled works.  Please note that the scheduled list
+ * may change while processing a work, so this function repeatedly
+ * fetches a work from the top and executes it.
+ *
+ * CONTEXT:
+ * spin_lock_irq(pool->lock) which may be released and regrabbed
+ * multiple times.
+ */
+static void process_scheduled_works(struct worker *worker)
+{
+	while (!list_empty(&worker->scheduled)) {
+		struct work_struct *work = list_first_entry(&worker->scheduled,
+						struct work_struct, entry);
+		process_one_work(worker, work);
+	}
+}
+
+static void set_pf_worker(bool val)
+{
+	mutex_lock(&wq_pool_attach_mutex);
+	if (val)
+		current->flags |= PF_WQ_WORKER;
+	else
+		current->flags &= ~PF_WQ_WORKER;
+	mutex_unlock(&wq_pool_attach_mutex);
+}
+
+/**
+ * worker_thread - the worker thread function
+ * @__worker: self
+ *
+ * The worker thread function.  All workers belong to a worker_pool -
+ * either a per-cpu one or dynamic unbound one.  These workers process all
+ * work items regardless of their specific target workqueue.  The only
+ * exception is work items which belong to workqueues with a rescuer which
+ * will be explained in rescuer_thread().
+ *
+ * Return: 0
+ */
+static int worker_thread(void *__worker)
+{
+	struct worker *worker = __worker;
+	struct worker_pool *pool = worker->pool;
+
+	/* tell the scheduler that this is a workqueue worker */
+	set_pf_worker(true);
+woke_up:
+	spin_lock_irq(&pool->lock);
+
+	/* am I supposed to die? */
+	if (unlikely(worker->flags & WORKER_DIE)) {
+		spin_unlock_irq(&pool->lock);
+		WARN_ON_ONCE(!list_empty(&worker->entry));
+		set_pf_worker(false);
+
+		set_task_comm(worker->task, "kworker/dying");
+		ida_simple_remove(&pool->worker_ida, worker->id);
+		worker_detach_from_pool(worker);
+		kfree(worker);
+		return 0;
+	}
+
+	worker_leave_idle(worker);
+recheck:
+	/* no more worker necessary? */
+	if (!need_more_worker(pool))
+		goto sleep;
+
+	/* do we need to manage? */
+	if (unlikely(!may_start_working(pool)) && manage_workers(worker))
+		goto recheck;
+
+	/*
+	 * ->scheduled list can only be filled while a worker is
+	 * preparing to process a work or actually processing it.
+	 * Make sure nobody diddled with it while I was sleeping.
+	 */
+	WARN_ON_ONCE(!list_empty(&worker->scheduled));
+
+	/*
+	 * Finish PREP stage.  We're guaranteed to have at least one idle
+	 * worker or that someone else has already assumed the manager
+	 * role.  This is where @worker starts participating in concurrency
+	 * management if applicable and concurrency management is restored
+	 * after being rebound.  See rebind_workers() for details.
+	 */
+	worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
+
+	do {
+		struct work_struct *work =
+			list_first_entry(&pool->worklist,
+					 struct work_struct, entry);
+
+		pool->watchdog_ts = jiffies;
+
+		if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
+			/* optimization path, not strictly necessary */
+			process_one_work(worker, work);
+			if (unlikely(!list_empty(&worker->scheduled)))
+				process_scheduled_works(worker);
+		} else {
+			move_linked_works(work, &worker->scheduled, NULL);
+			process_scheduled_works(worker);
+		}
+	} while (keep_working(pool));
+
+	worker_set_flags(worker, WORKER_PREP);
+sleep:
+	/*
+	 * pool->lock is held and there's no work to process and no need to
+	 * manage, sleep.  Workers are woken up only while holding
+	 * pool->lock or from local cpu, so setting the current state
+	 * before releasing pool->lock is enough to prevent losing any
+	 * event.
+	 */
+	worker_enter_idle(worker);
+	__set_current_state(TASK_IDLE);
+	spin_unlock_irq(&pool->lock);
+	schedule();
+	goto woke_up;
+}
+
+/**
+ * rescuer_thread - the rescuer thread function
+ * @__rescuer: self
+ *
+ * Workqueue rescuer thread function.  There's one rescuer for each
+ * workqueue which has WQ_MEM_RECLAIM set.
+ *
+ * Regular work processing on a pool may block trying to create a new
+ * worker which uses GFP_KERNEL allocation which has slight chance of
+ * developing into deadlock if some works currently on the same queue
+ * need to be processed to satisfy the GFP_KERNEL allocation.  This is
+ * the problem rescuer solves.
+ *
+ * When such condition is possible, the pool summons rescuers of all
+ * workqueues which have works queued on the pool and let them process
+ * those works so that forward progress can be guaranteed.
+ *
+ * This should happen rarely.
+ *
+ * Return: 0
+ */
+static int rescuer_thread(void *__rescuer)
+{
+	struct worker *rescuer = __rescuer;
+	struct workqueue_struct *wq = rescuer->rescue_wq;
+	struct list_head *scheduled = &rescuer->scheduled;
+	bool should_stop;
+
+	set_user_nice(current, RESCUER_NICE_LEVEL);
+
+	/*
+	 * Mark rescuer as worker too.  As WORKER_PREP is never cleared, it
+	 * doesn't participate in concurrency management.
+	 */
+	set_pf_worker(true);
+repeat:
+	set_current_state(TASK_IDLE);
+
+	/*
+	 * By the time the rescuer is requested to stop, the workqueue
+	 * shouldn't have any work pending, but @wq->maydays may still have
+	 * pwq(s) queued.  This can happen by non-rescuer workers consuming
+	 * all the work items before the rescuer got to them.  Go through
+	 * @wq->maydays processing before acting on should_stop so that the
+	 * list is always empty on exit.
+	 */
+	should_stop = kthread_should_stop();
+
+	/* see whether any pwq is asking for help */
+	spin_lock_irq(&wq_mayday_lock);
+
+	while (!list_empty(&wq->maydays)) {
+		struct pool_workqueue *pwq = list_first_entry(&wq->maydays,
+					struct pool_workqueue, mayday_node);
+		struct worker_pool *pool = pwq->pool;
+		struct work_struct *work, *n;
+		bool first = true;
+
+		__set_current_state(TASK_RUNNING);
+		list_del_init(&pwq->mayday_node);
+
+		spin_unlock_irq(&wq_mayday_lock);
+
+		worker_attach_to_pool(rescuer, pool);
+
+		spin_lock_irq(&pool->lock);
+
+		/*
+		 * Slurp in all works issued via this workqueue and
+		 * process'em.
+		 */
+		WARN_ON_ONCE(!list_empty(scheduled));
+		list_for_each_entry_safe(work, n, &pool->worklist, entry) {
+			if (get_work_pwq(work) == pwq) {
+				if (first)
+					pool->watchdog_ts = jiffies;
+				move_linked_works(work, scheduled, &n);
+			}
+			first = false;
+		}
+
+		if (!list_empty(scheduled)) {
+			process_scheduled_works(rescuer);
+
+			/*
+			 * The above execution of rescued work items could
+			 * have created more to rescue through
+			 * pwq_activate_first_delayed() or chained
+			 * queueing.  Let's put @pwq back on mayday list so
+			 * that such back-to-back work items, which may be
+			 * being used to relieve memory pressure, don't
+			 * incur MAYDAY_INTERVAL delay inbetween.
+			 */
+			if (need_to_create_worker(pool)) {
+				spin_lock(&wq_mayday_lock);
+				/*
+				 * Queue iff we aren't racing destruction
+				 * and somebody else hasn't queued it already.
+				 */
+				if (wq->rescuer && list_empty(&pwq->mayday_node)) {
+					get_pwq(pwq);
+					list_add_tail(&pwq->mayday_node, &wq->maydays);
+				}
+				spin_unlock(&wq_mayday_lock);
+			}
+		}
+
+		/*
+		 * Put the reference grabbed by send_mayday().  @pool won't
+		 * go away while we're still attached to it.
+		 */
+		put_pwq(pwq);
+
+		/*
+		 * Leave this pool.  If need_more_worker() is %true, notify a
+		 * regular worker; otherwise, we end up with 0 concurrency
+		 * and stalling the execution.
+		 */
+		if (need_more_worker(pool))
+			wake_up_worker(pool);
+
+		spin_unlock_irq(&pool->lock);
+
+		worker_detach_from_pool(rescuer);
+
+		spin_lock_irq(&wq_mayday_lock);
+	}
+
+	spin_unlock_irq(&wq_mayday_lock);
+
+	if (should_stop) {
+		__set_current_state(TASK_RUNNING);
+		set_pf_worker(false);
+		return 0;
+	}
+
+	/* rescuers should never participate in concurrency management */
+	WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
+	schedule();
+	goto repeat;
+}
+
+/**
+ * check_flush_dependency - check for flush dependency sanity
+ * @target_wq: workqueue being flushed
+ * @target_work: work item being flushed (NULL for workqueue flushes)
+ *
+ * %current is trying to flush the whole @target_wq or @target_work on it.
+ * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not
+ * reclaiming memory or running on a workqueue which doesn't have
+ * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to
+ * a deadlock.
+ */
+static void check_flush_dependency(struct workqueue_struct *target_wq,
+				   struct work_struct *target_work)
+{
+	work_func_t target_func = target_work ? target_work->func : NULL;
+	struct worker *worker;
+
+	if (target_wq->flags & WQ_MEM_RECLAIM)
+		return;
+
+	worker = current_wq_worker();
+
+	WARN_ONCE(current->flags & PF_MEMALLOC,
+		  "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%pf",
+		  current->pid, current->comm, target_wq->name, target_func);
+	WARN_ONCE(worker && ((worker->current_pwq->wq->flags &
+			      (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM),
+		  "workqueue: WQ_MEM_RECLAIM %s:%pf is flushing !WQ_MEM_RECLAIM %s:%pf",
+		  worker->current_pwq->wq->name, worker->current_func,
+		  target_wq->name, target_func);
+}
+
+struct wq_barrier {
+	struct work_struct	work;
+	struct completion	done;
+	struct task_struct	*task;	/* purely informational */
+};
+
+static void wq_barrier_func(struct work_struct *work)
+{
+	struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
+	complete(&barr->done);
+}
+
+/**
+ * insert_wq_barrier - insert a barrier work
+ * @pwq: pwq to insert barrier into
+ * @barr: wq_barrier to insert
+ * @target: target work to attach @barr to
+ * @worker: worker currently executing @target, NULL if @target is not executing
+ *
+ * @barr is linked to @target such that @barr is completed only after
+ * @target finishes execution.  Please note that the ordering
+ * guarantee is observed only with respect to @target and on the local
+ * cpu.
+ *
+ * Currently, a queued barrier can't be canceled.  This is because
+ * try_to_grab_pending() can't determine whether the work to be
+ * grabbed is at the head of the queue and thus can't clear LINKED
+ * flag of the previous work while there must be a valid next work
+ * after a work with LINKED flag set.
+ *
+ * Note that when @worker is non-NULL, @target may be modified
+ * underneath us, so we can't reliably determine pwq from @target.
+ *
+ * CONTEXT:
+ * spin_lock_irq(pool->lock).
+ */
+static void insert_wq_barrier(struct pool_workqueue *pwq,
+			      struct wq_barrier *barr,
+			      struct work_struct *target, struct worker *worker)
+{
+	struct list_head *head;
+	unsigned int linked = 0;
+
+	/*
+	 * debugobject calls are safe here even with pool->lock locked
+	 * as we know for sure that this will not trigger any of the
+	 * checks and call back into the fixup functions where we
+	 * might deadlock.
+	 */
+	INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
+	__set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
+
+	init_completion_map(&barr->done, &target->lockdep_map);
+
+	barr->task = current;
+
+	/*
+	 * If @target is currently being executed, schedule the
+	 * barrier to the worker; otherwise, put it after @target.
+	 */
+	if (worker)
+		head = worker->scheduled.next;
+	else {
+		unsigned long *bits = work_data_bits(target);
+
+		head = target->entry.next;
+		/* there can already be other linked works, inherit and set */
+		linked = *bits & WORK_STRUCT_LINKED;
+		__set_bit(WORK_STRUCT_LINKED_BIT, bits);
+	}
+
+	debug_work_activate(&barr->work);
+	insert_work(pwq, &barr->work, head,
+		    work_color_to_flags(WORK_NO_COLOR) | linked);
+}
+
+/**
+ * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
+ * @wq: workqueue being flushed
+ * @flush_color: new flush color, < 0 for no-op
+ * @work_color: new work color, < 0 for no-op
+ *
+ * Prepare pwqs for workqueue flushing.
+ *
+ * If @flush_color is non-negative, flush_color on all pwqs should be
+ * -1.  If no pwq has in-flight commands at the specified color, all
+ * pwq->flush_color's stay at -1 and %false is returned.  If any pwq
+ * has in flight commands, its pwq->flush_color is set to
+ * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
+ * wakeup logic is armed and %true is returned.
+ *
+ * The caller should have initialized @wq->first_flusher prior to
+ * calling this function with non-negative @flush_color.  If
+ * @flush_color is negative, no flush color update is done and %false
+ * is returned.
+ *
+ * If @work_color is non-negative, all pwqs should have the same
+ * work_color which is previous to @work_color and all will be
+ * advanced to @work_color.
+ *
+ * CONTEXT:
+ * mutex_lock(wq->mutex).
+ *
+ * Return:
+ * %true if @flush_color >= 0 and there's something to flush.  %false
+ * otherwise.
+ */
+static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq,
+				      int flush_color, int work_color)
+{
+	bool wait = false;
+	struct pool_workqueue *pwq;
+
+	if (flush_color >= 0) {
+		WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush));
+		atomic_set(&wq->nr_pwqs_to_flush, 1);
+	}
+
+	for_each_pwq(pwq, wq) {
+		struct worker_pool *pool = pwq->pool;
+
+		spin_lock_irq(&pool->lock);
+
+		if (flush_color >= 0) {
+			WARN_ON_ONCE(pwq->flush_color != -1);
+
+			if (pwq->nr_in_flight[flush_color]) {
+				pwq->flush_color = flush_color;
+				atomic_inc(&wq->nr_pwqs_to_flush);
+				wait = true;
+			}
+		}
+
+		if (work_color >= 0) {
+			WARN_ON_ONCE(work_color != work_next_color(pwq->work_color));
+			pwq->work_color = work_color;
+		}
+
+		spin_unlock_irq(&pool->lock);
+	}
+
+	if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush))
+		complete(&wq->first_flusher->done);
+
+	return wait;
+}
+
+/**
+ * flush_workqueue - ensure that any scheduled work has run to completion.
+ * @wq: workqueue to flush
+ *
+ * This function sleeps until all work items which were queued on entry
+ * have finished execution, but it is not livelocked by new incoming ones.
+ */
+void flush_workqueue(struct workqueue_struct *wq)
+{
+	struct wq_flusher this_flusher = {
+		.list = LIST_HEAD_INIT(this_flusher.list),
+		.flush_color = -1,
+		.done = COMPLETION_INITIALIZER_ONSTACK_MAP(this_flusher.done, wq->lockdep_map),
+	};
+	int next_color;
+
+	if (WARN_ON(!wq_online))
+		return;
+
+	lock_map_acquire(&wq->lockdep_map);
+	lock_map_release(&wq->lockdep_map);
+
+	mutex_lock(&wq->mutex);
+
+	/*
+	 * Start-to-wait phase
+	 */
+	next_color = work_next_color(wq->work_color);
+
+	if (next_color != wq->flush_color) {
+		/*
+		 * Color space is not full.  The current work_color
+		 * becomes our flush_color and work_color is advanced
+		 * by one.
+		 */
+		WARN_ON_ONCE(!list_empty(&wq->flusher_overflow));
+		this_flusher.flush_color = wq->work_color;
+		wq->work_color = next_color;
+
+		if (!wq->first_flusher) {
+			/* no flush in progress, become the first flusher */
+			WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
+
+			wq->first_flusher = &this_flusher;
+
+			if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
+						       wq->work_color)) {
+				/* nothing to flush, done */
+				wq->flush_color = next_color;
+				wq->first_flusher = NULL;
+				goto out_unlock;
+			}
+		} else {
+			/* wait in queue */
+			WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color);
+			list_add_tail(&this_flusher.list, &wq->flusher_queue);
+			flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
+		}
+	} else {
+		/*
+		 * Oops, color space is full, wait on overflow queue.
+		 * The next flush completion will assign us
+		 * flush_color and transfer to flusher_queue.
+		 */
+		list_add_tail(&this_flusher.list, &wq->flusher_overflow);
+	}
+
+	check_flush_dependency(wq, NULL);
+
+	mutex_unlock(&wq->mutex);
+
+	wait_for_completion(&this_flusher.done);
+
+	/*
+	 * Wake-up-and-cascade phase
+	 *
+	 * First flushers are responsible for cascading flushes and
+	 * handling overflow.  Non-first flushers can simply return.
+	 */
+	if (wq->first_flusher != &this_flusher)
+		return;
+
+	mutex_lock(&wq->mutex);
+
+	/* we might have raced, check again with mutex held */
+	if (wq->first_flusher != &this_flusher)
+		goto out_unlock;
+
+	wq->first_flusher = NULL;
+
+	WARN_ON_ONCE(!list_empty(&this_flusher.list));
+	WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
+
+	while (true) {
+		struct wq_flusher *next, *tmp;
+
+		/* complete all the flushers sharing the current flush color */
+		list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
+			if (next->flush_color != wq->flush_color)
+				break;
+			list_del_init(&next->list);
+			complete(&next->done);
+		}
+
+		WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) &&
+			     wq->flush_color != work_next_color(wq->work_color));
+
+		/* this flush_color is finished, advance by one */
+		wq->flush_color = work_next_color(wq->flush_color);
+
+		/* one color has been freed, handle overflow queue */
+		if (!list_empty(&wq->flusher_overflow)) {
+			/*
+			 * Assign the same color to all overflowed
+			 * flushers, advance work_color and append to
+			 * flusher_queue.  This is the start-to-wait
+			 * phase for these overflowed flushers.
+			 */
+			list_for_each_entry(tmp, &wq->flusher_overflow, list)
+				tmp->flush_color = wq->work_color;
+
+			wq->work_color = work_next_color(wq->work_color);
+
+			list_splice_tail_init(&wq->flusher_overflow,
+					      &wq->flusher_queue);
+			flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
+		}
+
+		if (list_empty(&wq->flusher_queue)) {
+			WARN_ON_ONCE(wq->flush_color != wq->work_color);
+			break;
+		}
+
+		/*
+		 * Need to flush more colors.  Make the next flusher
+		 * the new first flusher and arm pwqs.
+		 */
+		WARN_ON_ONCE(wq->flush_color == wq->work_color);
+		WARN_ON_ONCE(wq->flush_color != next->flush_color);
+
+		list_del_init(&next->list);
+		wq->first_flusher = next;
+
+		if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))
+			break;
+
+		/*
+		 * Meh... this color is already done, clear first
+		 * flusher and repeat cascading.
+		 */
+		wq->first_flusher = NULL;
+	}
+
+out_unlock:
+	mutex_unlock(&wq->mutex);
+}
+EXPORT_SYMBOL(flush_workqueue);
+
+/**
+ * drain_workqueue - drain a workqueue
+ * @wq: workqueue to drain
+ *
+ * Wait until the workqueue becomes empty.  While draining is in progress,
+ * only chain queueing is allowed.  IOW, only currently pending or running
+ * work items on @wq can queue further work items on it.  @wq is flushed
+ * repeatedly until it becomes empty.  The number of flushing is determined
+ * by the depth of chaining and should be relatively short.  Whine if it
+ * takes too long.
+ */
+void drain_workqueue(struct workqueue_struct *wq)
+{
+	unsigned int flush_cnt = 0;
+	struct pool_workqueue *pwq;
+
+	/*
+	 * __queue_work() needs to test whether there are drainers, is much
+	 * hotter than drain_workqueue() and already looks at @wq->flags.
+	 * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
+	 */
+	mutex_lock(&wq->mutex);
+	if (!wq->nr_drainers++)
+		wq->flags |= __WQ_DRAINING;
+	mutex_unlock(&wq->mutex);
+reflush:
+	flush_workqueue(wq);
+
+	mutex_lock(&wq->mutex);
+
+	for_each_pwq(pwq, wq) {
+		bool drained;
+
+		spin_lock_irq(&pwq->pool->lock);
+		drained = !pwq->nr_active && list_empty(&pwq->delayed_works);
+		spin_unlock_irq(&pwq->pool->lock);
+
+		if (drained)
+			continue;
+
+		if (++flush_cnt == 10 ||
+		    (flush_cnt % 100 == 0 && flush_cnt <= 1000))
+			pr_warn("workqueue %s: drain_workqueue() isn't complete after %u tries\n",
+				wq->name, flush_cnt);
+
+		mutex_unlock(&wq->mutex);
+		goto reflush;
+	}
+
+	if (!--wq->nr_drainers)
+		wq->flags &= ~__WQ_DRAINING;
+	mutex_unlock(&wq->mutex);
+}
+EXPORT_SYMBOL_GPL(drain_workqueue);
+
+static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
+			     bool from_cancel)
+{
+	struct worker *worker = NULL;
+	struct worker_pool *pool;
+	struct pool_workqueue *pwq;
+
+	might_sleep();
+
+	local_irq_disable();
+	pool = get_work_pool(work);
+	if (!pool) {
+		local_irq_enable();
+		return false;
+	}
+
+	spin_lock(&pool->lock);
+	/* see the comment in try_to_grab_pending() with the same code */
+	pwq = get_work_pwq(work);
+	if (pwq) {
+		if (unlikely(pwq->pool != pool))
+			goto already_gone;
+	} else {
+		worker = find_worker_executing_work(pool, work);
+		if (!worker)
+			goto already_gone;
+		pwq = worker->current_pwq;
+	}
+
+	check_flush_dependency(pwq->wq, work);
+
+	insert_wq_barrier(pwq, barr, work, worker);
+	spin_unlock_irq(&pool->lock);
+
+	/*
+	 * Force a lock recursion deadlock when using flush_work() inside a
+	 * single-threaded or rescuer equipped workqueue.
+	 *
+	 * For single threaded workqueues the deadlock happens when the work
+	 * is after the work issuing the flush_work(). For rescuer equipped
+	 * workqueues the deadlock happens when the rescuer stalls, blocking
+	 * forward progress.
+	 */
+	if (!from_cancel &&
+	    (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)) {
+		lock_map_acquire(&pwq->wq->lockdep_map);
+		lock_map_release(&pwq->wq->lockdep_map);
+	}
+
+	return true;
+already_gone:
+	spin_unlock_irq(&pool->lock);
+	return false;
+}
+
+static bool __flush_work(struct work_struct *work, bool from_cancel)
+{
+	struct wq_barrier barr;
+
+	if (WARN_ON(!wq_online))
+		return false;
+
+	if (WARN_ON(!work->func))
+		return false;
+
+	if (!from_cancel) {
+		lock_map_acquire(&work->lockdep_map);
+		lock_map_release(&work->lockdep_map);
+	}
+
+	if (start_flush_work(work, &barr, from_cancel)) {
+		wait_for_completion(&barr.done);
+		destroy_work_on_stack(&barr.work);
+		return true;
+	} else {
+		return false;
+	}
+}
+
+/**
+ * flush_work - wait for a work to finish executing the last queueing instance
+ * @work: the work to flush
+ *
+ * Wait until @work has finished execution.  @work is guaranteed to be idle
+ * on return if it hasn't been requeued since flush started.
+ *
+ * Return:
+ * %true if flush_work() waited for the work to finish execution,
+ * %false if it was already idle.
+ */
+bool flush_work(struct work_struct *work)
+{
+	return __flush_work(work, false);
+}
+EXPORT_SYMBOL_GPL(flush_work);
+
+struct cwt_wait {
+	wait_queue_entry_t		wait;
+	struct work_struct	*work;
+};
+
+static int cwt_wakefn(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
+{
+	struct cwt_wait *cwait = container_of(wait, struct cwt_wait, wait);
+
+	if (cwait->work != key)
+		return 0;
+	return autoremove_wake_function(wait, mode, sync, key);
+}
+
+static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
+{
+	static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq);
+	unsigned long flags;
+	int ret;
+
+	do {
+		ret = try_to_grab_pending(work, is_dwork, &flags);
+		/*
+		 * If someone else is already canceling, wait for it to
+		 * finish.  flush_work() doesn't work for PREEMPT_NONE
+		 * because we may get scheduled between @work's completion
+		 * and the other canceling task resuming and clearing
+		 * CANCELING - flush_work() will return false immediately
+		 * as @work is no longer busy, try_to_grab_pending() will
+		 * return -ENOENT as @work is still being canceled and the
+		 * other canceling task won't be able to clear CANCELING as
+		 * we're hogging the CPU.
+		 *
+		 * Let's wait for completion using a waitqueue.  As this
+		 * may lead to the thundering herd problem, use a custom
+		 * wake function which matches @work along with exclusive
+		 * wait and wakeup.
+		 */
+		if (unlikely(ret == -ENOENT)) {
+			struct cwt_wait cwait;
+
+			init_wait(&cwait.wait);
+			cwait.wait.func = cwt_wakefn;
+			cwait.work = work;
+
+			prepare_to_wait_exclusive(&cancel_waitq, &cwait.wait,
+						  TASK_UNINTERRUPTIBLE);
+			if (work_is_canceling(work))
+				schedule();
+			finish_wait(&cancel_waitq, &cwait.wait);
+		}
+	} while (unlikely(ret < 0));
+
+	/* tell other tasks trying to grab @work to back off */
+	mark_work_canceling(work);
+	local_irq_restore(flags);
+
+	/*
+	 * This allows canceling during early boot.  We know that @work
+	 * isn't executing.
+	 */
+	if (wq_online)
+		__flush_work(work, true);
+
+	clear_work_data(work);
+
+	/*
+	 * Paired with prepare_to_wait() above so that either
+	 * waitqueue_active() is visible here or !work_is_canceling() is
+	 * visible there.
+	 */
+	smp_mb();
+	if (waitqueue_active(&cancel_waitq))
+		__wake_up(&cancel_waitq, TASK_NORMAL, 1, work);
+
+	return ret;
+}
+
+/**
+ * cancel_work_sync - cancel a work and wait for it to finish
+ * @work: the work to cancel
+ *
+ * Cancel @work and wait for its execution to finish.  This function
+ * can be used even if the work re-queues itself or migrates to
+ * another workqueue.  On return from this function, @work is
+ * guaranteed to be not pending or executing on any CPU.
+ *
+ * cancel_work_sync(&delayed_work->work) must not be used for
+ * delayed_work's.  Use cancel_delayed_work_sync() instead.
+ *
+ * The caller must ensure that the workqueue on which @work was last
+ * queued can't be destroyed before this function returns.
+ *
+ * Return:
+ * %true if @work was pending, %false otherwise.
+ */
+bool cancel_work_sync(struct work_struct *work)
+{
+	return __cancel_work_timer(work, false);
+}
+EXPORT_SYMBOL_GPL(cancel_work_sync);
+
+/**
+ * flush_delayed_work - wait for a dwork to finish executing the last queueing
+ * @dwork: the delayed work to flush
+ *
+ * Delayed timer is cancelled and the pending work is queued for
+ * immediate execution.  Like flush_work(), this function only
+ * considers the last queueing instance of @dwork.
+ *
+ * Return:
+ * %true if flush_work() waited for the work to finish execution,
+ * %false if it was already idle.
+ */
+bool flush_delayed_work(struct delayed_work *dwork)
+{
+	local_irq_disable();
+	if (del_timer_sync(&dwork->timer))
+		__queue_work(dwork->cpu, dwork->wq, &dwork->work);
+	local_irq_enable();
+	return flush_work(&dwork->work);
+}
+EXPORT_SYMBOL(flush_delayed_work);
+
+/**
+ * flush_rcu_work - wait for a rwork to finish executing the last queueing
+ * @rwork: the rcu work to flush
+ *
+ * Return:
+ * %true if flush_rcu_work() waited for the work to finish execution,
+ * %false if it was already idle.
+ */
+bool flush_rcu_work(struct rcu_work *rwork)
+{
+	if (test_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&rwork->work))) {
+		rcu_barrier();
+		flush_work(&rwork->work);
+		return true;
+	} else {
+		return flush_work(&rwork->work);
+	}
+}
+EXPORT_SYMBOL(flush_rcu_work);
+
+static bool __cancel_work(struct work_struct *work, bool is_dwork)
+{
+	unsigned long flags;
+	int ret;
+
+	do {
+		ret = try_to_grab_pending(work, is_dwork, &flags);
+	} while (unlikely(ret == -EAGAIN));
+
+	if (unlikely(ret < 0))
+		return false;
+
+	set_work_pool_and_clear_pending(work, get_work_pool_id(work));
+	local_irq_restore(flags);
+	return ret;
+}
+
+/**
+ * cancel_delayed_work - cancel a delayed work
+ * @dwork: delayed_work to cancel
+ *
+ * Kill off a pending delayed_work.
+ *
+ * Return: %true if @dwork was pending and canceled; %false if it wasn't
+ * pending.
+ *
+ * Note:
+ * The work callback function may still be running on return, unless
+ * it returns %true and the work doesn't re-arm itself.  Explicitly flush or
+ * use cancel_delayed_work_sync() to wait on it.
+ *
+ * This function is safe to call from any context including IRQ handler.
+ */
+bool cancel_delayed_work(struct delayed_work *dwork)
+{
+	return __cancel_work(&dwork->work, true);
+}
+EXPORT_SYMBOL(cancel_delayed_work);
+
+/**
+ * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
+ * @dwork: the delayed work cancel
+ *
+ * This is cancel_work_sync() for delayed works.
+ *
+ * Return:
+ * %true if @dwork was pending, %false otherwise.
+ */
+bool cancel_delayed_work_sync(struct delayed_work *dwork)
+{
+	return __cancel_work_timer(&dwork->work, true);
+}
+EXPORT_SYMBOL(cancel_delayed_work_sync);
+
+/**
+ * schedule_on_each_cpu - execute a function synchronously on each online CPU
+ * @func: the function to call
+ *
+ * schedule_on_each_cpu() executes @func on each online CPU using the
+ * system workqueue and blocks until all CPUs have completed.
+ * schedule_on_each_cpu() is very slow.
+ *
+ * Return:
+ * 0 on success, -errno on failure.
+ */
+int schedule_on_each_cpu(work_func_t func)
+{
+	int cpu;
+	struct work_struct __percpu *works;
+
+	works = alloc_percpu(struct work_struct);
+	if (!works)
+		return -ENOMEM;
+
+	get_online_cpus();
+
+	for_each_online_cpu(cpu) {
+		struct work_struct *work = per_cpu_ptr(works, cpu);
+
+		INIT_WORK(work, func);
+		schedule_work_on(cpu, work);
+	}
+
+	for_each_online_cpu(cpu)
+		flush_work(per_cpu_ptr(works, cpu));
+
+	put_online_cpus();
+	free_percpu(works);
+	return 0;
+}
+
+/**
+ * execute_in_process_context - reliably execute the routine with user context
+ * @fn:		the function to execute
+ * @ew:		guaranteed storage for the execute work structure (must
+ *		be available when the work executes)
+ *
+ * Executes the function immediately if process context is available,
+ * otherwise schedules the function for delayed execution.
+ *
+ * Return:	0 - function was executed
+ *		1 - function was scheduled for execution
+ */
+int execute_in_process_context(work_func_t fn, struct execute_work *ew)
+{
+	if (!in_interrupt()) {
+		fn(&ew->work);
+		return 0;
+	}
+
+	INIT_WORK(&ew->work, fn);
+	schedule_work(&ew->work);
+
+	return 1;
+}
+EXPORT_SYMBOL_GPL(execute_in_process_context);
+
+/**
+ * free_workqueue_attrs - free a workqueue_attrs
+ * @attrs: workqueue_attrs to free
+ *
+ * Undo alloc_workqueue_attrs().
+ */
+void free_workqueue_attrs(struct workqueue_attrs *attrs)
+{
+	if (attrs) {
+		free_cpumask_var(attrs->cpumask);
+		kfree(attrs);
+	}
+}
+
+/**
+ * alloc_workqueue_attrs - allocate a workqueue_attrs
+ * @gfp_mask: allocation mask to use
+ *
+ * Allocate a new workqueue_attrs, initialize with default settings and
+ * return it.
+ *
+ * Return: The allocated new workqueue_attr on success. %NULL on failure.
+ */
+struct workqueue_attrs *alloc_workqueue_attrs(gfp_t gfp_mask)
+{
+	struct workqueue_attrs *attrs;
+
+	attrs = kzalloc(sizeof(*attrs), gfp_mask);
+	if (!attrs)
+		goto fail;
+	if (!alloc_cpumask_var(&attrs->cpumask, gfp_mask))
+		goto fail;
+
+	cpumask_copy(attrs->cpumask, cpu_possible_mask);
+	return attrs;
+fail:
+	free_workqueue_attrs(attrs);
+	return NULL;
+}
+
+static void copy_workqueue_attrs(struct workqueue_attrs *to,
+				 const struct workqueue_attrs *from)
+{
+	to->nice = from->nice;
+	cpumask_copy(to->cpumask, from->cpumask);
+	/*
+	 * Unlike hash and equality test, this function doesn't ignore
+	 * ->no_numa as it is used for both pool and wq attrs.  Instead,
+	 * get_unbound_pool() explicitly clears ->no_numa after copying.
+	 */
+	to->no_numa = from->no_numa;
+}
+
+/* hash value of the content of @attr */
+static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
+{
+	u32 hash = 0;
+
+	hash = jhash_1word(attrs->nice, hash);
+	hash = jhash(cpumask_bits(attrs->cpumask),
+		     BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
+	return hash;
+}
+
+/* content equality test */
+static bool wqattrs_equal(const struct workqueue_attrs *a,
+			  const struct workqueue_attrs *b)
+{
+	if (a->nice != b->nice)
+		return false;
+	if (!cpumask_equal(a->cpumask, b->cpumask))
+		return false;
+	return true;
+}
+
+/**
+ * init_worker_pool - initialize a newly zalloc'd worker_pool
+ * @pool: worker_pool to initialize
+ *
+ * Initialize a newly zalloc'd @pool.  It also allocates @pool->attrs.
+ *
+ * Return: 0 on success, -errno on failure.  Even on failure, all fields
+ * inside @pool proper are initialized and put_unbound_pool() can be called
+ * on @pool safely to release it.
+ */
+static int init_worker_pool(struct worker_pool *pool)
+{
+	spin_lock_init(&pool->lock);
+	pool->id = -1;
+	pool->cpu = -1;
+	pool->node = NUMA_NO_NODE;
+	pool->flags |= POOL_DISASSOCIATED;
+	pool->watchdog_ts = jiffies;
+	INIT_LIST_HEAD(&pool->worklist);
+	INIT_LIST_HEAD(&pool->idle_list);
+	hash_init(pool->busy_hash);
+
+	timer_setup(&pool->idle_timer, idle_worker_timeout, TIMER_DEFERRABLE);
+
+	timer_setup(&pool->mayday_timer, pool_mayday_timeout, 0);
+
+	INIT_LIST_HEAD(&pool->workers);
+
+	ida_init(&pool->worker_ida);
+	INIT_HLIST_NODE(&pool->hash_node);
+	pool->refcnt = 1;
+
+	/* shouldn't fail above this point */
+	pool->attrs = alloc_workqueue_attrs(GFP_KERNEL);
+	if (!pool->attrs)
+		return -ENOMEM;
+	return 0;
+}
+
+static void rcu_free_wq(struct rcu_head *rcu)
+{
+	struct workqueue_struct *wq =
+		container_of(rcu, struct workqueue_struct, rcu);
+
+	if (!(wq->flags & WQ_UNBOUND))
+		free_percpu(wq->cpu_pwqs);
+	else
+		free_workqueue_attrs(wq->unbound_attrs);
+
+	kfree(wq->rescuer);
+	kfree(wq);
+}
+
+static void rcu_free_pool(struct rcu_head *rcu)
+{
+	struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu);
+
+	ida_destroy(&pool->worker_ida);
+	free_workqueue_attrs(pool->attrs);
+	kfree(pool);
+}
+
+/**
+ * put_unbound_pool - put a worker_pool
+ * @pool: worker_pool to put
+ *
+ * Put @pool.  If its refcnt reaches zero, it gets destroyed in sched-RCU
+ * safe manner.  get_unbound_pool() calls this function on its failure path
+ * and this function should be able to release pools which went through,
+ * successfully or not, init_worker_pool().
+ *
+ * Should be called with wq_pool_mutex held.
+ */
+static void put_unbound_pool(struct worker_pool *pool)
+{
+	DECLARE_COMPLETION_ONSTACK(detach_completion);
+	struct worker *worker;
+
+	lockdep_assert_held(&wq_pool_mutex);
+
+	if (--pool->refcnt)
+		return;
+
+	/* sanity checks */
+	if (WARN_ON(!(pool->cpu < 0)) ||
+	    WARN_ON(!list_empty(&pool->worklist)))
+		return;
+
+	/* release id and unhash */
+	if (pool->id >= 0)
+		idr_remove(&worker_pool_idr, pool->id);
+	hash_del(&pool->hash_node);
+
+	/*
+	 * Become the manager and destroy all workers.  This prevents
+	 * @pool's workers from blocking on attach_mutex.  We're the last
+	 * manager and @pool gets freed with the flag set.
+	 */
+	spin_lock_irq(&pool->lock);
+	wait_event_lock_irq(wq_manager_wait,
+			    !(pool->flags & POOL_MANAGER_ACTIVE), pool->lock);
+	pool->flags |= POOL_MANAGER_ACTIVE;
+
+	while ((worker = first_idle_worker(pool)))
+		destroy_worker(worker);
+	WARN_ON(pool->nr_workers || pool->nr_idle);
+	spin_unlock_irq(&pool->lock);
+
+	mutex_lock(&wq_pool_attach_mutex);
+	if (!list_empty(&pool->workers))
+		pool->detach_completion = &detach_completion;
+	mutex_unlock(&wq_pool_attach_mutex);
+
+	if (pool->detach_completion)
+		wait_for_completion(pool->detach_completion);
+
+	/* shut down the timers */
+	del_timer_sync(&pool->idle_timer);
+	del_timer_sync(&pool->mayday_timer);
+
+	/* sched-RCU protected to allow dereferences from get_work_pool() */
+	call_rcu_sched(&pool->rcu, rcu_free_pool);
+}
+
+/**
+ * get_unbound_pool - get a worker_pool with the specified attributes
+ * @attrs: the attributes of the worker_pool to get
+ *
+ * Obtain a worker_pool which has the same attributes as @attrs, bump the
+ * reference count and return it.  If there already is a matching
+ * worker_pool, it will be used; otherwise, this function attempts to
+ * create a new one.
+ *
+ * Should be called with wq_pool_mutex held.
+ *
+ * Return: On success, a worker_pool with the same attributes as @attrs.
+ * On failure, %NULL.
+ */
+static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
+{
+	u32 hash = wqattrs_hash(attrs);
+	struct worker_pool *pool;
+	int node;
+	int target_node = NUMA_NO_NODE;
+
+	lockdep_assert_held(&wq_pool_mutex);
+
+	/* do we already have a matching pool? */
+	hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) {
+		if (wqattrs_equal(pool->attrs, attrs)) {
+			pool->refcnt++;
+			return pool;
+		}
+	}
+
+	/* if cpumask is contained inside a NUMA node, we belong to that node */
+	if (wq_numa_enabled) {
+		for_each_node(node) {
+			if (cpumask_subset(attrs->cpumask,
+					   wq_numa_possible_cpumask[node])) {
+				target_node = node;
+				break;
+			}
+		}
+	}
+
+	/* nope, create a new one */
+	pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, target_node);
+	if (!pool || init_worker_pool(pool) < 0)
+		goto fail;
+
+	lockdep_set_subclass(&pool->lock, 1);	/* see put_pwq() */
+	copy_workqueue_attrs(pool->attrs, attrs);
+	pool->node = target_node;
+
+	/*
+	 * no_numa isn't a worker_pool attribute, always clear it.  See
+	 * 'struct workqueue_attrs' comments for detail.
+	 */
+	pool->attrs->no_numa = false;
+
+	if (worker_pool_assign_id(pool) < 0)
+		goto fail;
+
+	/* create and start the initial worker */
+	if (wq_online && !create_worker(pool))
+		goto fail;
+
+	/* install */
+	hash_add(unbound_pool_hash, &pool->hash_node, hash);
+
+	return pool;
+fail:
+	if (pool)
+		put_unbound_pool(pool);
+	return NULL;
+}
+
+static void rcu_free_pwq(struct rcu_head *rcu)
+{
+	kmem_cache_free(pwq_cache,
+			container_of(rcu, struct pool_workqueue, rcu));
+}
+
+/*
+ * Scheduled on system_wq by put_pwq() when an unbound pwq hits zero refcnt
+ * and needs to be destroyed.
+ */
+static void pwq_unbound_release_workfn(struct work_struct *work)
+{
+	struct pool_workqueue *pwq = container_of(work, struct pool_workqueue,
+						  unbound_release_work);
+	struct workqueue_struct *wq = pwq->wq;
+	struct worker_pool *pool = pwq->pool;
+	bool is_last = false;
+
+	/*
+	 * when @pwq is not linked, it doesn't hold any reference to the
+	 * @wq, and @wq is invalid to access.
+	 */
+	if (!list_empty(&pwq->pwqs_node)) {
+		if (WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND)))
+			return;
+
+		mutex_lock(&wq->mutex);
+		list_del_rcu(&pwq->pwqs_node);
+		is_last = list_empty(&wq->pwqs);
+		mutex_unlock(&wq->mutex);
+	}
+
+	mutex_lock(&wq_pool_mutex);
+	put_unbound_pool(pool);
+	mutex_unlock(&wq_pool_mutex);
+
+	call_rcu_sched(&pwq->rcu, rcu_free_pwq);
+
+	/*
+	 * If we're the last pwq going away, @wq is already dead and no one
+	 * is gonna access it anymore.  Schedule RCU free.
+	 */
+	if (is_last)
+		call_rcu_sched(&wq->rcu, rcu_free_wq);
+}
+
+/**
+ * pwq_adjust_max_active - update a pwq's max_active to the current setting
+ * @pwq: target pool_workqueue
+ *
+ * If @pwq isn't freezing, set @pwq->max_active to the associated
+ * workqueue's saved_max_active and activate delayed work items
+ * accordingly.  If @pwq is freezing, clear @pwq->max_active to zero.
+ */
+static void pwq_adjust_max_active(struct pool_workqueue *pwq)
+{
+	struct workqueue_struct *wq = pwq->wq;
+	bool freezable = wq->flags & WQ_FREEZABLE;
+	unsigned long flags;
+
+	/* for @wq->saved_max_active */
+	lockdep_assert_held(&wq->mutex);
+
+	/* fast exit for non-freezable wqs */
+	if (!freezable && pwq->max_active == wq->saved_max_active)
+		return;
+
+	/* this function can be called during early boot w/ irq disabled */
+	spin_lock_irqsave(&pwq->pool->lock, flags);
+
+	/*
+	 * During [un]freezing, the caller is responsible for ensuring that
+	 * this function is called at least once after @workqueue_freezing
+	 * is updated and visible.
+	 */
+	if (!freezable || !workqueue_freezing) {
+		bool kick = false;
+
+		pwq->max_active = wq->saved_max_active;
+
+		while (!list_empty(&pwq->delayed_works) &&
+		       pwq->nr_active < pwq->max_active) {
+			pwq_activate_first_delayed(pwq);
+			kick = true;
+		}
+
+		/*
+		 * Need to kick a worker after thawed or an unbound wq's
+		 * max_active is bumped. In realtime scenarios, always kicking a
+		 * worker will cause interference on the isolated cpu cores, so
+		 * let's kick iff work items were activated.
+		 */
+		if (kick)
+			wake_up_worker(pwq->pool);
+	} else {
+		pwq->max_active = 0;
+	}
+
+	spin_unlock_irqrestore(&pwq->pool->lock, flags);
+}
+
+/* initialize newly alloced @pwq which is associated with @wq and @pool */
+static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
+		     struct worker_pool *pool)
+{
+	BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);
+
+	memset(pwq, 0, sizeof(*pwq));
+
+	pwq->pool = pool;
+	pwq->wq = wq;
+	pwq->flush_color = -1;
+	pwq->refcnt = 1;
+	INIT_LIST_HEAD(&pwq->delayed_works);
+	INIT_LIST_HEAD(&pwq->pwqs_node);
+	INIT_LIST_HEAD(&pwq->mayday_node);
+	INIT_WORK(&pwq->unbound_release_work, pwq_unbound_release_workfn);
+}
+
+/* sync @pwq with the current state of its associated wq and link it */
+static void link_pwq(struct pool_workqueue *pwq)
+{
+	struct workqueue_struct *wq = pwq->wq;
+
+	lockdep_assert_held(&wq->mutex);
+
+	/* may be called multiple times, ignore if already linked */
+	if (!list_empty(&pwq->pwqs_node))
+		return;
+
+	/* set the matching work_color */
+	pwq->work_color = wq->work_color;
+
+	/* sync max_active to the current setting */
+	pwq_adjust_max_active(pwq);
+
+	/* link in @pwq */
+	list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
+}
+
+/* obtain a pool matching @attr and create a pwq associating the pool and @wq */
+static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
+					const struct workqueue_attrs *attrs)
+{
+	struct worker_pool *pool;
+	struct pool_workqueue *pwq;
+
+	lockdep_assert_held(&wq_pool_mutex);
+
+	pool = get_unbound_pool(attrs);
+	if (!pool)
+		return NULL;
+
+	pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
+	if (!pwq) {
+		put_unbound_pool(pool);
+		return NULL;
+	}
+
+	init_pwq(pwq, wq, pool);
+	return pwq;
+}
+
+/**
+ * wq_calc_node_cpumask - calculate a wq_attrs' cpumask for the specified node
+ * @attrs: the wq_attrs of the default pwq of the target workqueue
+ * @node: the target NUMA node
+ * @cpu_going_down: if >= 0, the CPU to consider as offline
+ * @cpumask: outarg, the resulting cpumask
+ *
+ * Calculate the cpumask a workqueue with @attrs should use on @node.  If
+ * @cpu_going_down is >= 0, that cpu is considered offline during
+ * calculation.  The result is stored in @cpumask.
+ *
+ * If NUMA affinity is not enabled, @attrs->cpumask is always used.  If
+ * enabled and @node has online CPUs requested by @attrs, the returned
+ * cpumask is the intersection of the possible CPUs of @node and
+ * @attrs->cpumask.
+ *
+ * The caller is responsible for ensuring that the cpumask of @node stays
+ * stable.
+ *
+ * Return: %true if the resulting @cpumask is different from @attrs->cpumask,
+ * %false if equal.
+ */
+static bool wq_calc_node_cpumask(const struct workqueue_attrs *attrs, int node,
+				 int cpu_going_down, cpumask_t *cpumask)
+{
+	if (!wq_numa_enabled || attrs->no_numa)
+		goto use_dfl;
+
+	/* does @node have any online CPUs @attrs wants? */
+	cpumask_and(cpumask, cpumask_of_node(node), attrs->cpumask);
+	if (cpu_going_down >= 0)
+		cpumask_clear_cpu(cpu_going_down, cpumask);
+
+	if (cpumask_empty(cpumask))
+		goto use_dfl;
+
+	/* yeap, return possible CPUs in @node that @attrs wants */
+	cpumask_and(cpumask, attrs->cpumask, wq_numa_possible_cpumask[node]);
+
+	if (cpumask_empty(cpumask)) {
+		pr_warn_once("WARNING: workqueue cpumask: online intersect > "
+				"possible intersect\n");
+		return false;
+	}
+
+	return !cpumask_equal(cpumask, attrs->cpumask);
+
+use_dfl:
+	cpumask_copy(cpumask, attrs->cpumask);
+	return false;
+}
+
+/* install @pwq into @wq's numa_pwq_tbl[] for @node and return the old pwq */
+static struct pool_workqueue *numa_pwq_tbl_install(struct workqueue_struct *wq,
+						   int node,
+						   struct pool_workqueue *pwq)
+{
+	struct pool_workqueue *old_pwq;
+
+	lockdep_assert_held(&wq_pool_mutex);
+	lockdep_assert_held(&wq->mutex);
+
+	/* link_pwq() can handle duplicate calls */
+	link_pwq(pwq);
+
+	old_pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
+	rcu_assign_pointer(wq->numa_pwq_tbl[node], pwq);
+	return old_pwq;
+}
+
+/* context to store the prepared attrs & pwqs before applying */
+struct apply_wqattrs_ctx {
+	struct workqueue_struct	*wq;		/* target workqueue */
+	struct workqueue_attrs	*attrs;		/* attrs to apply */
+	struct list_head	list;		/* queued for batching commit */
+	struct pool_workqueue	*dfl_pwq;
+	struct pool_workqueue	*pwq_tbl[];
+};
+
+/* free the resources after success or abort */
+static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
+{
+	if (ctx) {
+		int node;
+
+		for_each_node(node)
+			put_pwq_unlocked(ctx->pwq_tbl[node]);
+		put_pwq_unlocked(ctx->dfl_pwq);
+
+		free_workqueue_attrs(ctx->attrs);
+
+		kfree(ctx);
+	}
+}
+
+/* allocate the attrs and pwqs for later installation */
+static struct apply_wqattrs_ctx *
+apply_wqattrs_prepare(struct workqueue_struct *wq,
+		      const struct workqueue_attrs *attrs)
+{
+	struct apply_wqattrs_ctx *ctx;
+	struct workqueue_attrs *new_attrs, *tmp_attrs;
+	int node;
+
+	lockdep_assert_held(&wq_pool_mutex);
+
+	ctx = kzalloc(struct_size(ctx, pwq_tbl, nr_node_ids), GFP_KERNEL);
+
+	new_attrs = alloc_workqueue_attrs(GFP_KERNEL);
+	tmp_attrs = alloc_workqueue_attrs(GFP_KERNEL);
+	if (!ctx || !new_attrs || !tmp_attrs)
+		goto out_free;
+
+	/*
+	 * Calculate the attrs of the default pwq.
+	 * If the user configured cpumask doesn't overlap with the
+	 * wq_unbound_cpumask, we fallback to the wq_unbound_cpumask.
+	 */
+	copy_workqueue_attrs(new_attrs, attrs);
+	cpumask_and(new_attrs->cpumask, new_attrs->cpumask, wq_unbound_cpumask);
+	if (unlikely(cpumask_empty(new_attrs->cpumask)))
+		cpumask_copy(new_attrs->cpumask, wq_unbound_cpumask);
+
+	/*
+	 * We may create multiple pwqs with differing cpumasks.  Make a
+	 * copy of @new_attrs which will be modified and used to obtain
+	 * pools.
+	 */
+	copy_workqueue_attrs(tmp_attrs, new_attrs);
+
+	/*
+	 * If something goes wrong during CPU up/down, we'll fall back to
+	 * the default pwq covering whole @attrs->cpumask.  Always create
+	 * it even if we don't use it immediately.
+	 */
+	ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
+	if (!ctx->dfl_pwq)
+		goto out_free;
+
+	for_each_node(node) {
+		if (wq_calc_node_cpumask(new_attrs, node, -1, tmp_attrs->cpumask)) {
+			ctx->pwq_tbl[node] = alloc_unbound_pwq(wq, tmp_attrs);
+			if (!ctx->pwq_tbl[node])
+				goto out_free;
+		} else {
+			ctx->dfl_pwq->refcnt++;
+			ctx->pwq_tbl[node] = ctx->dfl_pwq;
+		}
+	}
+
+	/* save the user configured attrs and sanitize it. */
+	copy_workqueue_attrs(new_attrs, attrs);
+	cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
+	ctx->attrs = new_attrs;
+
+	ctx->wq = wq;
+	free_workqueue_attrs(tmp_attrs);
+	return ctx;
+
+out_free:
+	free_workqueue_attrs(tmp_attrs);
+	free_workqueue_attrs(new_attrs);
+	apply_wqattrs_cleanup(ctx);
+	return NULL;
+}
+
+/* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
+static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
+{
+	int node;
+
+	/* all pwqs have been created successfully, let's install'em */
+	mutex_lock(&ctx->wq->mutex);
+
+	copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);
+
+	/* save the previous pwq and install the new one */
+	for_each_node(node)
+		ctx->pwq_tbl[node] = numa_pwq_tbl_install(ctx->wq, node,
+							  ctx->pwq_tbl[node]);
+
+	/* @dfl_pwq might not have been used, ensure it's linked */
+	link_pwq(ctx->dfl_pwq);
+	swap(ctx->wq->dfl_pwq, ctx->dfl_pwq);
+
+	mutex_unlock(&ctx->wq->mutex);
+}
+
+static void apply_wqattrs_lock(void)
+{
+	/* CPUs should stay stable across pwq creations and installations */
+	get_online_cpus();
+	mutex_lock(&wq_pool_mutex);
+}
+
+static void apply_wqattrs_unlock(void)
+{
+	mutex_unlock(&wq_pool_mutex);
+	put_online_cpus();
+}
+
+static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
+					const struct workqueue_attrs *attrs)
+{
+	struct apply_wqattrs_ctx *ctx;
+
+	/* only unbound workqueues can change attributes */
+	if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
+		return -EINVAL;
+
+	/* creating multiple pwqs breaks ordering guarantee */
+	if (!list_empty(&wq->pwqs)) {
+		if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
+			return -EINVAL;
+
+		wq->flags &= ~__WQ_ORDERED;
+	}
+
+	ctx = apply_wqattrs_prepare(wq, attrs);
+	if (!ctx)
+		return -ENOMEM;
+
+	/* the ctx has been prepared successfully, let's commit it */
+	apply_wqattrs_commit(ctx);
+	apply_wqattrs_cleanup(ctx);
+
+	return 0;
+}
+
+/**
+ * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
+ * @wq: the target workqueue
+ * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
+ *
+ * Apply @attrs to an unbound workqueue @wq.  Unless disabled, on NUMA
+ * machines, this function maps a separate pwq to each NUMA node with
+ * possibles CPUs in @attrs->cpumask so that work items are affine to the
+ * NUMA node it was issued on.  Older pwqs are released as in-flight work
+ * items finish.  Note that a work item which repeatedly requeues itself
+ * back-to-back will stay on its current pwq.
+ *
+ * Performs GFP_KERNEL allocations.
+ *
+ * Return: 0 on success and -errno on failure.
+ */
+int apply_workqueue_attrs(struct workqueue_struct *wq,
+			  const struct workqueue_attrs *attrs)
+{
+	int ret;
+
+	apply_wqattrs_lock();
+	ret = apply_workqueue_attrs_locked(wq, attrs);
+	apply_wqattrs_unlock();
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(apply_workqueue_attrs);
+
+/**
+ * wq_update_unbound_numa - update NUMA affinity of a wq for CPU hot[un]plug
+ * @wq: the target workqueue
+ * @cpu: the CPU coming up or going down
+ * @online: whether @cpu is coming up or going down
+ *
+ * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
+ * %CPU_DOWN_FAILED.  @cpu is being hot[un]plugged, update NUMA affinity of
+ * @wq accordingly.
+ *
+ * If NUMA affinity can't be adjusted due to memory allocation failure, it
+ * falls back to @wq->dfl_pwq which may not be optimal but is always
+ * correct.
+ *
+ * Note that when the last allowed CPU of a NUMA node goes offline for a
+ * workqueue with a cpumask spanning multiple nodes, the workers which were
+ * already executing the work items for the workqueue will lose their CPU
+ * affinity and may execute on any CPU.  This is similar to how per-cpu
+ * workqueues behave on CPU_DOWN.  If a workqueue user wants strict
+ * affinity, it's the user's responsibility to flush the work item from
+ * CPU_DOWN_PREPARE.
+ */
+static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,
+				   bool online)
+{
+	int node = cpu_to_node(cpu);
+	int cpu_off = online ? -1 : cpu;
+	struct pool_workqueue *old_pwq = NULL, *pwq;
+	struct workqueue_attrs *target_attrs;
+	cpumask_t *cpumask;
+
+	lockdep_assert_held(&wq_pool_mutex);
+
+	if (!wq_numa_enabled || !(wq->flags & WQ_UNBOUND) ||
+	    wq->unbound_attrs->no_numa)
+		return;
+
+	/*
+	 * We don't wanna alloc/free wq_attrs for each wq for each CPU.
+	 * Let's use a preallocated one.  The following buf is protected by
+	 * CPU hotplug exclusion.
+	 */
+	target_attrs = wq_update_unbound_numa_attrs_buf;
+	cpumask = target_attrs->cpumask;
+
+	copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
+	pwq = unbound_pwq_by_node(wq, node);
+
+	/*
+	 * Let's determine what needs to be done.  If the target cpumask is
+	 * different from the default pwq's, we need to compare it to @pwq's
+	 * and create a new one if they don't match.  If the target cpumask
+	 * equals the default pwq's, the default pwq should be used.
+	 */
+	if (wq_calc_node_cpumask(wq->dfl_pwq->pool->attrs, node, cpu_off, cpumask)) {
+		if (cpumask_equal(cpumask, pwq->pool->attrs->cpumask))
+			return;
+	} else {
+		goto use_dfl_pwq;
+	}
+
+	/* create a new pwq */
+	pwq = alloc_unbound_pwq(wq, target_attrs);
+	if (!pwq) {
+		pr_warn("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n",
+			wq->name);
+		goto use_dfl_pwq;
+	}
+
+	/* Install the new pwq. */
+	mutex_lock(&wq->mutex);
+	old_pwq = numa_pwq_tbl_install(wq, node, pwq);
+	goto out_unlock;
+
+use_dfl_pwq:
+	mutex_lock(&wq->mutex);
+	spin_lock_irq(&wq->dfl_pwq->pool->lock);
+	get_pwq(wq->dfl_pwq);
+	spin_unlock_irq(&wq->dfl_pwq->pool->lock);
+	old_pwq = numa_pwq_tbl_install(wq, node, wq->dfl_pwq);
+out_unlock:
+	mutex_unlock(&wq->mutex);
+	put_pwq_unlocked(old_pwq);
+}
+
+static int alloc_and_link_pwqs(struct workqueue_struct *wq)
+{
+	bool highpri = wq->flags & WQ_HIGHPRI;
+	int cpu, ret;
+
+	if (!(wq->flags & WQ_UNBOUND)) {
+		wq->cpu_pwqs = alloc_percpu(struct pool_workqueue);
+		if (!wq->cpu_pwqs)
+			return -ENOMEM;
+
+		for_each_possible_cpu(cpu) {
+			struct pool_workqueue *pwq =
+				per_cpu_ptr(wq->cpu_pwqs, cpu);
+			struct worker_pool *cpu_pools =
+				per_cpu(cpu_worker_pools, cpu);
+
+			init_pwq(pwq, wq, &cpu_pools[highpri]);
+
+			mutex_lock(&wq->mutex);
+			link_pwq(pwq);
+			mutex_unlock(&wq->mutex);
+		}
+		return 0;
+	} else if (wq->flags & __WQ_ORDERED) {
+		ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]);
+		/* there should only be single pwq for ordering guarantee */
+		WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node ||
+			      wq->pwqs.prev != &wq->dfl_pwq->pwqs_node),
+		     "ordering guarantee broken for workqueue %s\n", wq->name);
+		return ret;
+	} else {
+		return apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);
+	}
+}
+
+static int wq_clamp_max_active(int max_active, unsigned int flags,
+			       const char *name)
+{
+	int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
+
+	if (max_active < 1 || max_active > lim)
+		pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
+			max_active, name, 1, lim);
+
+	return clamp_val(max_active, 1, lim);
+}
+
+/*
+ * Workqueues which may be used during memory reclaim should have a rescuer
+ * to guarantee forward progress.
+ */
+static int init_rescuer(struct workqueue_struct *wq)
+{
+	struct worker *rescuer;
+	int ret;
+
+	if (!(wq->flags & WQ_MEM_RECLAIM))
+		return 0;
+
+	rescuer = alloc_worker(NUMA_NO_NODE);
+	if (!rescuer)
+		return -ENOMEM;
+
+	rescuer->rescue_wq = wq;
+	rescuer->task = kthread_create(rescuer_thread, rescuer, "%s", wq->name);
+	ret = PTR_ERR_OR_ZERO(rescuer->task);
+	if (ret) {
+		kfree(rescuer);
+		return ret;
+	}
+
+	wq->rescuer = rescuer;
+	kthread_bind_mask(rescuer->task, cpu_possible_mask);
+	wake_up_process(rescuer->task);
+
+	return 0;
+}
+
+struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
+					       unsigned int flags,
+					       int max_active,
+					       struct lock_class_key *key,
+					       const char *lock_name, ...)
+{
+	size_t tbl_size = 0;
+	va_list args;
+	struct workqueue_struct *wq;
+	struct pool_workqueue *pwq;
+
+	/*
+	 * Unbound && max_active == 1 used to imply ordered, which is no
+	 * longer the case on NUMA machines due to per-node pools.  While
+	 * alloc_ordered_workqueue() is the right way to create an ordered
+	 * workqueue, keep the previous behavior to avoid subtle breakages
+	 * on NUMA.
+	 */
+	if ((flags & WQ_UNBOUND) && max_active == 1)
+		flags |= __WQ_ORDERED;
+
+	/* see the comment above the definition of WQ_POWER_EFFICIENT */
+	if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
+		flags |= WQ_UNBOUND;
+
+	/* allocate wq and format name */
+	if (flags & WQ_UNBOUND)
+		tbl_size = nr_node_ids * sizeof(wq->numa_pwq_tbl[0]);
+
+	wq = kzalloc(sizeof(*wq) + tbl_size, GFP_KERNEL);
+	if (!wq)
+		return NULL;
+
+	if (flags & WQ_UNBOUND) {
+		wq->unbound_attrs = alloc_workqueue_attrs(GFP_KERNEL);
+		if (!wq->unbound_attrs)
+			goto err_free_wq;
+	}
+
+	va_start(args, lock_name);
+	vsnprintf(wq->name, sizeof(wq->name), fmt, args);
+	va_end(args);
+
+	max_active = max_active ?: WQ_DFL_ACTIVE;
+	max_active = wq_clamp_max_active(max_active, flags, wq->name);
+
+	/* init wq */
+	wq->flags = flags;
+	wq->saved_max_active = max_active;
+	mutex_init(&wq->mutex);
+	atomic_set(&wq->nr_pwqs_to_flush, 0);
+	INIT_LIST_HEAD(&wq->pwqs);
+	INIT_LIST_HEAD(&wq->flusher_queue);
+	INIT_LIST_HEAD(&wq->flusher_overflow);
+	INIT_LIST_HEAD(&wq->maydays);
+
+	lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
+	INIT_LIST_HEAD(&wq->list);
+
+	if (alloc_and_link_pwqs(wq) < 0)
+		goto err_free_wq;
+
+	if (wq_online && init_rescuer(wq) < 0)
+		goto err_destroy;
+
+	if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq))
+		goto err_destroy;
+
+	/*
+	 * wq_pool_mutex protects global freeze state and workqueues list.
+	 * Grab it, adjust max_active and add the new @wq to workqueues
+	 * list.
+	 */
+	mutex_lock(&wq_pool_mutex);
+
+	mutex_lock(&wq->mutex);
+	for_each_pwq(pwq, wq)
+		pwq_adjust_max_active(pwq);
+	mutex_unlock(&wq->mutex);
+
+	list_add_tail_rcu(&wq->list, &workqueues);
+
+	mutex_unlock(&wq_pool_mutex);
+
+	return wq;
+
+err_free_wq:
+	free_workqueue_attrs(wq->unbound_attrs);
+	kfree(wq);
+	return NULL;
+err_destroy:
+	destroy_workqueue(wq);
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(__alloc_workqueue_key);
+
+/**
+ * destroy_workqueue - safely terminate a workqueue
+ * @wq: target workqueue
+ *
+ * Safely destroy a workqueue. All work currently pending will be done first.
+ */
+void destroy_workqueue(struct workqueue_struct *wq)
+{
+	struct pool_workqueue *pwq;
+	int node;
+
+	/*
+	 * Remove it from sysfs first so that sanity check failure doesn't
+	 * lead to sysfs name conflicts.
+	 */
+	workqueue_sysfs_unregister(wq);
+
+	/* drain it before proceeding with destruction */
+	drain_workqueue(wq);
+
+	/* kill rescuer, if sanity checks fail, leave it w/o rescuer */
+	if (wq->rescuer) {
+		struct worker *rescuer = wq->rescuer;
+
+		/* this prevents new queueing */
+		spin_lock_irq(&wq_mayday_lock);
+		wq->rescuer = NULL;
+		spin_unlock_irq(&wq_mayday_lock);
+
+		/* rescuer will empty maydays list before exiting */
+		kthread_stop(rescuer->task);
+		kfree(rescuer);
+	}
+
+	/* sanity checks */
+	mutex_lock(&wq->mutex);
+	for_each_pwq(pwq, wq) {
+		int i;
+
+		for (i = 0; i < WORK_NR_COLORS; i++) {
+			if (WARN_ON(pwq->nr_in_flight[i])) {
+				mutex_unlock(&wq->mutex);
+				show_workqueue_state();
+				return;
+			}
+		}
+
+		if (WARN_ON((pwq != wq->dfl_pwq) && (pwq->refcnt > 1)) ||
+		    WARN_ON(pwq->nr_active) ||
+		    WARN_ON(!list_empty(&pwq->delayed_works))) {
+			mutex_unlock(&wq->mutex);
+			show_workqueue_state();
+			return;
+		}
+	}
+	mutex_unlock(&wq->mutex);
+
+	/*
+	 * wq list is used to freeze wq, remove from list after
+	 * flushing is complete in case freeze races us.
+	 */
+	mutex_lock(&wq_pool_mutex);
+	list_del_rcu(&wq->list);
+	mutex_unlock(&wq_pool_mutex);
+
+	if (!(wq->flags & WQ_UNBOUND)) {
+		/*
+		 * The base ref is never dropped on per-cpu pwqs.  Directly
+		 * schedule RCU free.
+		 */
+		call_rcu_sched(&wq->rcu, rcu_free_wq);
+	} else {
+		/*
+		 * We're the sole accessor of @wq at this point.  Directly
+		 * access numa_pwq_tbl[] and dfl_pwq to put the base refs.
+		 * @wq will be freed when the last pwq is released.
+		 */
+		for_each_node(node) {
+			pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
+			RCU_INIT_POINTER(wq->numa_pwq_tbl[node], NULL);
+			put_pwq_unlocked(pwq);
+		}
+
+		/*
+		 * Put dfl_pwq.  @wq may be freed any time after dfl_pwq is
+		 * put.  Don't access it afterwards.
+		 */
+		pwq = wq->dfl_pwq;
+		wq->dfl_pwq = NULL;
+		put_pwq_unlocked(pwq);
+	}
+}
+EXPORT_SYMBOL_GPL(destroy_workqueue);
+
+/**
+ * workqueue_set_max_active - adjust max_active of a workqueue
+ * @wq: target workqueue
+ * @max_active: new max_active value.
+ *
+ * Set max_active of @wq to @max_active.
+ *
+ * CONTEXT:
+ * Don't call from IRQ context.
+ */
+void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
+{
+	struct pool_workqueue *pwq;
+
+	/* disallow meddling with max_active for ordered workqueues */
+	if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
+		return;
+
+	max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
+
+	mutex_lock(&wq->mutex);
+
+	wq->flags &= ~__WQ_ORDERED;
+	wq->saved_max_active = max_active;
+
+	for_each_pwq(pwq, wq)
+		pwq_adjust_max_active(pwq);
+
+	mutex_unlock(&wq->mutex);
+}
+EXPORT_SYMBOL_GPL(workqueue_set_max_active);
+
+/**
+ * current_work - retrieve %current task's work struct
+ *
+ * Determine if %current task is a workqueue worker and what it's working on.
+ * Useful to find out the context that the %current task is running in.
+ *
+ * Return: work struct if %current task is a workqueue worker, %NULL otherwise.
+ */
+struct work_struct *current_work(void)
+{
+	struct worker *worker = current_wq_worker();
+
+	return worker ? worker->current_work : NULL;
+}
+EXPORT_SYMBOL(current_work);
+
+/**
+ * current_is_workqueue_rescuer - is %current workqueue rescuer?
+ *
+ * Determine whether %current is a workqueue rescuer.  Can be used from
+ * work functions to determine whether it's being run off the rescuer task.
+ *
+ * Return: %true if %current is a workqueue rescuer. %false otherwise.
+ */
+bool current_is_workqueue_rescuer(void)
+{
+	struct worker *worker = current_wq_worker();
+
+	return worker && worker->rescue_wq;
+}
+
+/**
+ * workqueue_congested - test whether a workqueue is congested
+ * @cpu: CPU in question
+ * @wq: target workqueue
+ *
+ * Test whether @wq's cpu workqueue for @cpu is congested.  There is
+ * no synchronization around this function and the test result is
+ * unreliable and only useful as advisory hints or for debugging.
+ *
+ * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
+ * Note that both per-cpu and unbound workqueues may be associated with
+ * multiple pool_workqueues which have separate congested states.  A
+ * workqueue being congested on one CPU doesn't mean the workqueue is also
+ * contested on other CPUs / NUMA nodes.
+ *
+ * Return:
+ * %true if congested, %false otherwise.
+ */
+bool workqueue_congested(int cpu, struct workqueue_struct *wq)
+{
+	struct pool_workqueue *pwq;
+	bool ret;
+
+	rcu_read_lock_sched();
+
+	if (cpu == WORK_CPU_UNBOUND)
+		cpu = smp_processor_id();
+
+	if (!(wq->flags & WQ_UNBOUND))
+		pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
+	else
+		pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
+
+	ret = !list_empty(&pwq->delayed_works);
+	rcu_read_unlock_sched();
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(workqueue_congested);
+
+/**
+ * work_busy - test whether a work is currently pending or running
+ * @work: the work to be tested
+ *
+ * Test whether @work is currently pending or running.  There is no
+ * synchronization around this function and the test result is
+ * unreliable and only useful as advisory hints or for debugging.
+ *
+ * Return:
+ * OR'd bitmask of WORK_BUSY_* bits.
+ */
+unsigned int work_busy(struct work_struct *work)
+{
+	struct worker_pool *pool;
+	unsigned long flags;
+	unsigned int ret = 0;
+
+	if (work_pending(work))
+		ret |= WORK_BUSY_PENDING;
+
+	local_irq_save(flags);
+	pool = get_work_pool(work);
+	if (pool) {
+		spin_lock(&pool->lock);
+		if (find_worker_executing_work(pool, work))
+			ret |= WORK_BUSY_RUNNING;
+		spin_unlock(&pool->lock);
+	}
+	local_irq_restore(flags);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(work_busy);
+
+/**
+ * set_worker_desc - set description for the current work item
+ * @fmt: printf-style format string
+ * @...: arguments for the format string
+ *
+ * This function can be called by a running work function to describe what
+ * the work item is about.  If the worker task gets dumped, this
+ * information will be printed out together to help debugging.  The
+ * description can be at most WORKER_DESC_LEN including the trailing '\0'.
+ */
+void set_worker_desc(const char *fmt, ...)
+{
+	struct worker *worker = current_wq_worker();
+	va_list args;
+
+	if (worker) {
+		va_start(args, fmt);
+		vsnprintf(worker->desc, sizeof(worker->desc), fmt, args);
+		va_end(args);
+	}
+}
+EXPORT_SYMBOL_GPL(set_worker_desc);
+
+/**
+ * print_worker_info - print out worker information and description
+ * @log_lvl: the log level to use when printing
+ * @task: target task
+ *
+ * If @task is a worker and currently executing a work item, print out the
+ * name of the workqueue being serviced and worker description set with
+ * set_worker_desc() by the currently executing work item.
+ *
+ * This function can be safely called on any task as long as the
+ * task_struct itself is accessible.  While safe, this function isn't
+ * synchronized and may print out mixups or garbages of limited length.
+ */
+void print_worker_info(const char *log_lvl, struct task_struct *task)
+{
+	work_func_t *fn = NULL;
+	char name[WQ_NAME_LEN] = { };
+	char desc[WORKER_DESC_LEN] = { };
+	struct pool_workqueue *pwq = NULL;
+	struct workqueue_struct *wq = NULL;
+	struct worker *worker;
+
+	if (!(task->flags & PF_WQ_WORKER))
+		return;
+
+	/*
+	 * This function is called without any synchronization and @task
+	 * could be in any state.  Be careful with dereferences.
+	 */
+	worker = kthread_probe_data(task);
+
+	/*
+	 * Carefully copy the associated workqueue's workfn, name and desc.
+	 * Keep the original last '\0' in case the original is garbage.
+	 */
+	probe_kernel_read(&fn, &worker->current_func, sizeof(fn));
+	probe_kernel_read(&pwq, &worker->current_pwq, sizeof(pwq));
+	probe_kernel_read(&wq, &pwq->wq, sizeof(wq));
+	probe_kernel_read(name, wq->name, sizeof(name) - 1);
+	probe_kernel_read(desc, worker->desc, sizeof(desc) - 1);
+
+	if (fn || name[0] || desc[0]) {
+		printk("%sWorkqueue: %s %pf", log_lvl, name, fn);
+		if (strcmp(name, desc))
+			pr_cont(" (%s)", desc);
+		pr_cont("\n");
+	}
+}
+
+static void pr_cont_pool_info(struct worker_pool *pool)
+{
+	pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask);
+	if (pool->node != NUMA_NO_NODE)
+		pr_cont(" node=%d", pool->node);
+	pr_cont(" flags=0x%x nice=%d", pool->flags, pool->attrs->nice);
+}
+
+static void pr_cont_work(bool comma, struct work_struct *work)
+{
+	if (work->func == wq_barrier_func) {
+		struct wq_barrier *barr;
+
+		barr = container_of(work, struct wq_barrier, work);
+
+		pr_cont("%s BAR(%d)", comma ? "," : "",
+			task_pid_nr(barr->task));
+	} else {
+		pr_cont("%s %pf", comma ? "," : "", work->func);
+	}
+}
+
+static void show_pwq(struct pool_workqueue *pwq)
+{
+	struct worker_pool *pool = pwq->pool;
+	struct work_struct *work;
+	struct worker *worker;
+	bool has_in_flight = false, has_pending = false;
+	int bkt;
+
+	pr_info("  pwq %d:", pool->id);
+	pr_cont_pool_info(pool);
+
+	pr_cont(" active=%d/%d refcnt=%d%s\n",
+		pwq->nr_active, pwq->max_active, pwq->refcnt,
+		!list_empty(&pwq->mayday_node) ? " MAYDAY" : "");
+
+	hash_for_each(pool->busy_hash, bkt, worker, hentry) {
+		if (worker->current_pwq == pwq) {
+			has_in_flight = true;
+			break;
+		}
+	}
+	if (has_in_flight) {
+		bool comma = false;
+
+		pr_info("    in-flight:");
+		hash_for_each(pool->busy_hash, bkt, worker, hentry) {
+			if (worker->current_pwq != pwq)
+				continue;
+
+			pr_cont("%s %d%s:%pf", comma ? "," : "",
+				task_pid_nr(worker->task),
+				worker == pwq->wq->rescuer ? "(RESCUER)" : "",
+				worker->current_func);
+			list_for_each_entry(work, &worker->scheduled, entry)
+				pr_cont_work(false, work);
+			comma = true;
+		}
+		pr_cont("\n");
+	}
+
+	list_for_each_entry(work, &pool->worklist, entry) {
+		if (get_work_pwq(work) == pwq) {
+			has_pending = true;
+			break;
+		}
+	}
+	if (has_pending) {
+		bool comma = false;
+
+		pr_info("    pending:");
+		list_for_each_entry(work, &pool->worklist, entry) {
+			if (get_work_pwq(work) != pwq)
+				continue;
+
+			pr_cont_work(comma, work);
+			comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
+		}
+		pr_cont("\n");
+	}
+
+	if (!list_empty(&pwq->delayed_works)) {
+		bool comma = false;
+
+		pr_info("    delayed:");
+		list_for_each_entry(work, &pwq->delayed_works, entry) {
+			pr_cont_work(comma, work);
+			comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
+		}
+		pr_cont("\n");
+	}
+}
+
+/**
+ * show_workqueue_state - dump workqueue state
+ *
+ * Called from a sysrq handler or try_to_freeze_tasks() and prints out
+ * all busy workqueues and pools.
+ */
+void show_workqueue_state(void)
+{
+	struct workqueue_struct *wq;
+	struct worker_pool *pool;
+	unsigned long flags;
+	int pi;
+
+	rcu_read_lock_sched();
+
+	pr_info("Showing busy workqueues and worker pools:\n");
+
+	list_for_each_entry_rcu(wq, &workqueues, list) {
+		struct pool_workqueue *pwq;
+		bool idle = true;
+
+		for_each_pwq(pwq, wq) {
+			if (pwq->nr_active || !list_empty(&pwq->delayed_works)) {
+				idle = false;
+				break;
+			}
+		}
+		if (idle)
+			continue;
+
+		pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags);
+
+		for_each_pwq(pwq, wq) {
+			spin_lock_irqsave(&pwq->pool->lock, flags);
+			if (pwq->nr_active || !list_empty(&pwq->delayed_works))
+				show_pwq(pwq);
+			spin_unlock_irqrestore(&pwq->pool->lock, flags);
+			/*
+			 * We could be printing a lot from atomic context, e.g.
+			 * sysrq-t -> show_workqueue_state(). Avoid triggering
+			 * hard lockup.
+			 */
+			touch_nmi_watchdog();
+		}
+	}
+
+	for_each_pool(pool, pi) {
+		struct worker *worker;
+		bool first = true;
+
+		spin_lock_irqsave(&pool->lock, flags);
+		if (pool->nr_workers == pool->nr_idle)
+			goto next_pool;
+
+		pr_info("pool %d:", pool->id);
+		pr_cont_pool_info(pool);
+		pr_cont(" hung=%us workers=%d",
+			jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000,
+			pool->nr_workers);
+		if (pool->manager)
+			pr_cont(" manager: %d",
+				task_pid_nr(pool->manager->task));
+		list_for_each_entry(worker, &pool->idle_list, entry) {
+			pr_cont(" %s%d", first ? "idle: " : "",
+				task_pid_nr(worker->task));
+			first = false;
+		}
+		pr_cont("\n");
+	next_pool:
+		spin_unlock_irqrestore(&pool->lock, flags);
+		/*
+		 * We could be printing a lot from atomic context, e.g.
+		 * sysrq-t -> show_workqueue_state(). Avoid triggering
+		 * hard lockup.
+		 */
+		touch_nmi_watchdog();
+	}
+
+	rcu_read_unlock_sched();
+}
+
+/* used to show worker information through /proc/PID/{comm,stat,status} */
+void wq_worker_comm(char *buf, size_t size, struct task_struct *task)
+{
+	int off;
+
+	/* always show the actual comm */
+	off = strscpy(buf, task->comm, size);
+	if (off < 0)
+		return;
+
+	/* stabilize PF_WQ_WORKER and worker pool association */
+	mutex_lock(&wq_pool_attach_mutex);
+
+	if (task->flags & PF_WQ_WORKER) {
+		struct worker *worker = kthread_data(task);
+		struct worker_pool *pool = worker->pool;
+
+		if (pool) {
+			spin_lock_irq(&pool->lock);
+			/*
+			 * ->desc tracks information (wq name or
+			 * set_worker_desc()) for the latest execution.  If
+			 * current, prepend '+', otherwise '-'.
+			 */
+			if (worker->desc[0] != '\0') {
+				if (worker->current_work)
+					scnprintf(buf + off, size - off, "+%s",
+						  worker->desc);
+				else
+					scnprintf(buf + off, size - off, "-%s",
+						  worker->desc);
+			}
+			spin_unlock_irq(&pool->lock);
+		}
+	}
+
+	mutex_unlock(&wq_pool_attach_mutex);
+}
+
+#ifdef CONFIG_SMP
+
+/*
+ * CPU hotplug.
+ *
+ * There are two challenges in supporting CPU hotplug.  Firstly, there
+ * are a lot of assumptions on strong associations among work, pwq and
+ * pool which make migrating pending and scheduled works very
+ * difficult to implement without impacting hot paths.  Secondly,
+ * worker pools serve mix of short, long and very long running works making
+ * blocked draining impractical.
+ *
+ * This is solved by allowing the pools to be disassociated from the CPU
+ * running as an unbound one and allowing it to be reattached later if the
+ * cpu comes back online.
+ */
+
+static void unbind_workers(int cpu)
+{
+	struct worker_pool *pool;
+	struct worker *worker;
+
+	for_each_cpu_worker_pool(pool, cpu) {
+		mutex_lock(&wq_pool_attach_mutex);
+		spin_lock_irq(&pool->lock);
+
+		/*
+		 * We've blocked all attach/detach operations. Make all workers
+		 * unbound and set DISASSOCIATED.  Before this, all workers
+		 * except for the ones which are still executing works from
+		 * before the last CPU down must be on the cpu.  After
+		 * this, they may become diasporas.
+		 */
+		for_each_pool_worker(worker, pool)
+			worker->flags |= WORKER_UNBOUND;
+
+		pool->flags |= POOL_DISASSOCIATED;
+
+		spin_unlock_irq(&pool->lock);
+		mutex_unlock(&wq_pool_attach_mutex);
+
+		/*
+		 * Call schedule() so that we cross rq->lock and thus can
+		 * guarantee sched callbacks see the %WORKER_UNBOUND flag.
+		 * This is necessary as scheduler callbacks may be invoked
+		 * from other cpus.
+		 */
+		schedule();
+
+		/*
+		 * Sched callbacks are disabled now.  Zap nr_running.
+		 * After this, nr_running stays zero and need_more_worker()
+		 * and keep_working() are always true as long as the
+		 * worklist is not empty.  This pool now behaves as an
+		 * unbound (in terms of concurrency management) pool which
+		 * are served by workers tied to the pool.
+		 */
+		atomic_set(&pool->nr_running, 0);
+
+		/*
+		 * With concurrency management just turned off, a busy
+		 * worker blocking could lead to lengthy stalls.  Kick off
+		 * unbound chain execution of currently pending work items.
+		 */
+		spin_lock_irq(&pool->lock);
+		wake_up_worker(pool);
+		spin_unlock_irq(&pool->lock);
+	}
+}
+
+/**
+ * rebind_workers - rebind all workers of a pool to the associated CPU
+ * @pool: pool of interest
+ *
+ * @pool->cpu is coming online.  Rebind all workers to the CPU.
+ */
+static void rebind_workers(struct worker_pool *pool)
+{
+	struct worker *worker;
+
+	lockdep_assert_held(&wq_pool_attach_mutex);
+
+	/*
+	 * Restore CPU affinity of all workers.  As all idle workers should
+	 * be on the run-queue of the associated CPU before any local
+	 * wake-ups for concurrency management happen, restore CPU affinity
+	 * of all workers first and then clear UNBOUND.  As we're called
+	 * from CPU_ONLINE, the following shouldn't fail.
+	 */
+	for_each_pool_worker(worker, pool)
+		WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
+						  pool->attrs->cpumask) < 0);
+
+	spin_lock_irq(&pool->lock);
+
+	pool->flags &= ~POOL_DISASSOCIATED;
+
+	for_each_pool_worker(worker, pool) {
+		unsigned int worker_flags = worker->flags;
+
+		/*
+		 * A bound idle worker should actually be on the runqueue
+		 * of the associated CPU for local wake-ups targeting it to
+		 * work.  Kick all idle workers so that they migrate to the
+		 * associated CPU.  Doing this in the same loop as
+		 * replacing UNBOUND with REBOUND is safe as no worker will
+		 * be bound before @pool->lock is released.
+		 */
+		if (worker_flags & WORKER_IDLE)
+			wake_up_process(worker->task);
+
+		/*
+		 * We want to clear UNBOUND but can't directly call
+		 * worker_clr_flags() or adjust nr_running.  Atomically
+		 * replace UNBOUND with another NOT_RUNNING flag REBOUND.
+		 * @worker will clear REBOUND using worker_clr_flags() when
+		 * it initiates the next execution cycle thus restoring
+		 * concurrency management.  Note that when or whether
+		 * @worker clears REBOUND doesn't affect correctness.
+		 *
+		 * WRITE_ONCE() is necessary because @worker->flags may be
+		 * tested without holding any lock in
+		 * wq_worker_waking_up().  Without it, NOT_RUNNING test may
+		 * fail incorrectly leading to premature concurrency
+		 * management operations.
+		 */
+		WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND));
+		worker_flags |= WORKER_REBOUND;
+		worker_flags &= ~WORKER_UNBOUND;
+		WRITE_ONCE(worker->flags, worker_flags);
+	}
+
+	spin_unlock_irq(&pool->lock);
+}
+
+/**
+ * restore_unbound_workers_cpumask - restore cpumask of unbound workers
+ * @pool: unbound pool of interest
+ * @cpu: the CPU which is coming up
+ *
+ * An unbound pool may end up with a cpumask which doesn't have any online
+ * CPUs.  When a worker of such pool get scheduled, the scheduler resets
+ * its cpus_allowed.  If @cpu is in @pool's cpumask which didn't have any
+ * online CPU before, cpus_allowed of all its workers should be restored.
+ */
+static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
+{
+	static cpumask_t cpumask;
+	struct worker *worker;
+
+	lockdep_assert_held(&wq_pool_attach_mutex);
+
+	/* is @cpu allowed for @pool? */
+	if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
+		return;
+
+	cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask);
+
+	/* as we're called from CPU_ONLINE, the following shouldn't fail */
+	for_each_pool_worker(worker, pool)
+		WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, &cpumask) < 0);
+}
+
+int workqueue_prepare_cpu(unsigned int cpu)
+{
+	struct worker_pool *pool;
+
+	for_each_cpu_worker_pool(pool, cpu) {
+		if (pool->nr_workers)
+			continue;
+		if (!create_worker(pool))
+			return -ENOMEM;
+	}
+	return 0;
+}
+
+int workqueue_online_cpu(unsigned int cpu)
+{
+	struct worker_pool *pool;
+	struct workqueue_struct *wq;
+	int pi;
+
+	mutex_lock(&wq_pool_mutex);
+
+	for_each_pool(pool, pi) {
+		mutex_lock(&wq_pool_attach_mutex);
+
+		if (pool->cpu == cpu)
+			rebind_workers(pool);
+		else if (pool->cpu < 0)
+			restore_unbound_workers_cpumask(pool, cpu);
+
+		mutex_unlock(&wq_pool_attach_mutex);
+	}
+
+	/* update NUMA affinity of unbound workqueues */
+	list_for_each_entry(wq, &workqueues, list)
+		wq_update_unbound_numa(wq, cpu, true);
+
+	mutex_unlock(&wq_pool_mutex);
+	return 0;
+}
+
+int workqueue_offline_cpu(unsigned int cpu)
+{
+	struct workqueue_struct *wq;
+
+	/* unbinding per-cpu workers should happen on the local CPU */
+	if (WARN_ON(cpu != smp_processor_id()))
+		return -1;
+
+	unbind_workers(cpu);
+
+	/* update NUMA affinity of unbound workqueues */
+	mutex_lock(&wq_pool_mutex);
+	list_for_each_entry(wq, &workqueues, list)
+		wq_update_unbound_numa(wq, cpu, false);
+	mutex_unlock(&wq_pool_mutex);
+
+	return 0;
+}
+
+struct work_for_cpu {
+	struct work_struct work;
+	long (*fn)(void *);
+	void *arg;
+	long ret;
+};
+
+static void work_for_cpu_fn(struct work_struct *work)
+{
+	struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
+
+	wfc->ret = wfc->fn(wfc->arg);
+}
+
+/**
+ * work_on_cpu - run a function in thread context on a particular cpu
+ * @cpu: the cpu to run on
+ * @fn: the function to run
+ * @arg: the function arg
+ *
+ * It is up to the caller to ensure that the cpu doesn't go offline.
+ * The caller must not hold any locks which would prevent @fn from completing.
+ *
+ * Return: The value @fn returns.
+ */
+long work_on_cpu(int cpu, long (*fn)(void *), void *arg)
+{
+	struct work_for_cpu wfc = { .fn = fn, .arg = arg };
+
+	INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn);
+	schedule_work_on(cpu, &wfc.work);
+	flush_work(&wfc.work);
+	destroy_work_on_stack(&wfc.work);
+	return wfc.ret;
+}
+EXPORT_SYMBOL_GPL(work_on_cpu);
+
+/**
+ * work_on_cpu_safe - run a function in thread context on a particular cpu
+ * @cpu: the cpu to run on
+ * @fn:  the function to run
+ * @arg: the function argument
+ *
+ * Disables CPU hotplug and calls work_on_cpu(). The caller must not hold
+ * any locks which would prevent @fn from completing.
+ *
+ * Return: The value @fn returns.
+ */
+long work_on_cpu_safe(int cpu, long (*fn)(void *), void *arg)
+{
+	long ret = -ENODEV;
+
+	get_online_cpus();
+	if (cpu_online(cpu))
+		ret = work_on_cpu(cpu, fn, arg);
+	put_online_cpus();
+	return ret;
+}
+EXPORT_SYMBOL_GPL(work_on_cpu_safe);
+#endif /* CONFIG_SMP */
+
+#ifdef CONFIG_FREEZER
+
+/**
+ * freeze_workqueues_begin - begin freezing workqueues
+ *
+ * Start freezing workqueues.  After this function returns, all freezable
+ * workqueues will queue new works to their delayed_works list instead of
+ * pool->worklist.
+ *
+ * CONTEXT:
+ * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
+ */
+void freeze_workqueues_begin(void)
+{
+	struct workqueue_struct *wq;
+	struct pool_workqueue *pwq;
+
+	mutex_lock(&wq_pool_mutex);
+
+	WARN_ON_ONCE(workqueue_freezing);
+	workqueue_freezing = true;
+
+	list_for_each_entry(wq, &workqueues, list) {
+		mutex_lock(&wq->mutex);
+		for_each_pwq(pwq, wq)
+			pwq_adjust_max_active(pwq);
+		mutex_unlock(&wq->mutex);
+	}
+
+	mutex_unlock(&wq_pool_mutex);
+}
+
+/**
+ * freeze_workqueues_busy - are freezable workqueues still busy?
+ *
+ * Check whether freezing is complete.  This function must be called
+ * between freeze_workqueues_begin() and thaw_workqueues().
+ *
+ * CONTEXT:
+ * Grabs and releases wq_pool_mutex.
+ *
+ * Return:
+ * %true if some freezable workqueues are still busy.  %false if freezing
+ * is complete.
+ */
+bool freeze_workqueues_busy(void)
+{
+	bool busy = false;
+	struct workqueue_struct *wq;
+	struct pool_workqueue *pwq;
+
+	mutex_lock(&wq_pool_mutex);
+
+	WARN_ON_ONCE(!workqueue_freezing);
+
+	list_for_each_entry(wq, &workqueues, list) {
+		if (!(wq->flags & WQ_FREEZABLE))
+			continue;
+		/*
+		 * nr_active is monotonically decreasing.  It's safe
+		 * to peek without lock.
+		 */
+		rcu_read_lock_sched();
+		for_each_pwq(pwq, wq) {
+			WARN_ON_ONCE(pwq->nr_active < 0);
+			if (pwq->nr_active) {
+				busy = true;
+				rcu_read_unlock_sched();
+				goto out_unlock;
+			}
+		}
+		rcu_read_unlock_sched();
+	}
+out_unlock:
+	mutex_unlock(&wq_pool_mutex);
+	return busy;
+}
+
+/**
+ * thaw_workqueues - thaw workqueues
+ *
+ * Thaw workqueues.  Normal queueing is restored and all collected
+ * frozen works are transferred to their respective pool worklists.
+ *
+ * CONTEXT:
+ * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
+ */
+void thaw_workqueues(void)
+{
+	struct workqueue_struct *wq;
+	struct pool_workqueue *pwq;
+
+	mutex_lock(&wq_pool_mutex);
+
+	if (!workqueue_freezing)
+		goto out_unlock;
+
+	workqueue_freezing = false;
+
+	/* restore max_active and repopulate worklist */
+	list_for_each_entry(wq, &workqueues, list) {
+		mutex_lock(&wq->mutex);
+		for_each_pwq(pwq, wq)
+			pwq_adjust_max_active(pwq);
+		mutex_unlock(&wq->mutex);
+	}
+
+out_unlock:
+	mutex_unlock(&wq_pool_mutex);
+}
+#endif /* CONFIG_FREEZER */
+
+static int workqueue_apply_unbound_cpumask(void)
+{
+	LIST_HEAD(ctxs);
+	int ret = 0;
+	struct workqueue_struct *wq;
+	struct apply_wqattrs_ctx *ctx, *n;
+
+	lockdep_assert_held(&wq_pool_mutex);
+
+	list_for_each_entry(wq, &workqueues, list) {
+		if (!(wq->flags & WQ_UNBOUND))
+			continue;
+		/* creating multiple pwqs breaks ordering guarantee */
+		if (wq->flags & __WQ_ORDERED)
+			continue;
+
+		ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs);
+		if (!ctx) {
+			ret = -ENOMEM;
+			break;
+		}
+
+		list_add_tail(&ctx->list, &ctxs);
+	}
+
+	list_for_each_entry_safe(ctx, n, &ctxs, list) {
+		if (!ret)
+			apply_wqattrs_commit(ctx);
+		apply_wqattrs_cleanup(ctx);
+	}
+
+	return ret;
+}
+
+/**
+ *  workqueue_set_unbound_cpumask - Set the low-level unbound cpumask
+ *  @cpumask: the cpumask to set
+ *
+ *  The low-level workqueues cpumask is a global cpumask that limits
+ *  the affinity of all unbound workqueues.  This function check the @cpumask
+ *  and apply it to all unbound workqueues and updates all pwqs of them.
+ *
+ *  Retun:	0	- Success
+ *  		-EINVAL	- Invalid @cpumask
+ *  		-ENOMEM	- Failed to allocate memory for attrs or pwqs.
+ */
+int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
+{
+	int ret = -EINVAL;
+	cpumask_var_t saved_cpumask;
+
+	/*
+	 * Not excluding isolated cpus on purpose.
+	 * If the user wishes to include them, we allow that.
+	 */
+	cpumask_and(cpumask, cpumask, cpu_possible_mask);
+	if (!cpumask_empty(cpumask)) {
+		apply_wqattrs_lock();
+		if (cpumask_equal(cpumask, wq_unbound_cpumask)) {
+			ret = 0;
+			goto out_unlock;
+		}
+
+		if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL)) {
+			ret = -ENOMEM;
+			goto out_unlock;
+		}
+
+		/* save the old wq_unbound_cpumask. */
+		cpumask_copy(saved_cpumask, wq_unbound_cpumask);
+
+		/* update wq_unbound_cpumask at first and apply it to wqs. */
+		cpumask_copy(wq_unbound_cpumask, cpumask);
+		ret = workqueue_apply_unbound_cpumask();
+
+		/* restore the wq_unbound_cpumask when failed. */
+		if (ret < 0)
+			cpumask_copy(wq_unbound_cpumask, saved_cpumask);
+
+		free_cpumask_var(saved_cpumask);
+out_unlock:
+		apply_wqattrs_unlock();
+	}
+
+	return ret;
+}
+
+#ifdef CONFIG_SYSFS
+/*
+ * Workqueues with WQ_SYSFS flag set is visible to userland via
+ * /sys/bus/workqueue/devices/WQ_NAME.  All visible workqueues have the
+ * following attributes.
+ *
+ *  per_cpu	RO bool	: whether the workqueue is per-cpu or unbound
+ *  max_active	RW int	: maximum number of in-flight work items
+ *
+ * Unbound workqueues have the following extra attributes.
+ *
+ *  pool_ids	RO int	: the associated pool IDs for each node
+ *  nice	RW int	: nice value of the workers
+ *  cpumask	RW mask	: bitmask of allowed CPUs for the workers
+ *  numa	RW bool	: whether enable NUMA affinity
+ */
+struct wq_device {
+	struct workqueue_struct		*wq;
+	struct device			dev;
+};
+
+static struct workqueue_struct *dev_to_wq(struct device *dev)
+{
+	struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
+
+	return wq_dev->wq;
+}
+
+static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr,
+			    char *buf)
+{
+	struct workqueue_struct *wq = dev_to_wq(dev);
+
+	return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND));
+}
+static DEVICE_ATTR_RO(per_cpu);
+
+static ssize_t max_active_show(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	struct workqueue_struct *wq = dev_to_wq(dev);
+
+	return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active);
+}
+
+static ssize_t max_active_store(struct device *dev,
+				struct device_attribute *attr, const char *buf,
+				size_t count)
+{
+	struct workqueue_struct *wq = dev_to_wq(dev);
+	int val;
+
+	if (sscanf(buf, "%d", &val) != 1 || val <= 0)
+		return -EINVAL;
+
+	workqueue_set_max_active(wq, val);
+	return count;
+}
+static DEVICE_ATTR_RW(max_active);
+
+static struct attribute *wq_sysfs_attrs[] = {
+	&dev_attr_per_cpu.attr,
+	&dev_attr_max_active.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(wq_sysfs);
+
+static ssize_t wq_pool_ids_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct workqueue_struct *wq = dev_to_wq(dev);
+	const char *delim = "";
+	int node, written = 0;
+
+	rcu_read_lock_sched();
+	for_each_node(node) {
+		written += scnprintf(buf + written, PAGE_SIZE - written,
+				     "%s%d:%d", delim, node,
+				     unbound_pwq_by_node(wq, node)->pool->id);
+		delim = " ";
+	}
+	written += scnprintf(buf + written, PAGE_SIZE - written, "\n");
+	rcu_read_unlock_sched();
+
+	return written;
+}
+
+static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr,
+			    char *buf)
+{
+	struct workqueue_struct *wq = dev_to_wq(dev);
+	int written;
+
+	mutex_lock(&wq->mutex);
+	written = scnprintf(buf, PAGE_SIZE, "%d\n", wq->unbound_attrs->nice);
+	mutex_unlock(&wq->mutex);
+
+	return written;
+}
+
+/* prepare workqueue_attrs for sysfs store operations */
+static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq)
+{
+	struct workqueue_attrs *attrs;
+
+	lockdep_assert_held(&wq_pool_mutex);
+
+	attrs = alloc_workqueue_attrs(GFP_KERNEL);
+	if (!attrs)
+		return NULL;
+
+	copy_workqueue_attrs(attrs, wq->unbound_attrs);
+	return attrs;
+}
+
+static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr,
+			     const char *buf, size_t count)
+{
+	struct workqueue_struct *wq = dev_to_wq(dev);
+	struct workqueue_attrs *attrs;
+	int ret = -ENOMEM;
+
+	apply_wqattrs_lock();
+
+	attrs = wq_sysfs_prep_attrs(wq);
+	if (!attrs)
+		goto out_unlock;
+
+	if (sscanf(buf, "%d", &attrs->nice) == 1 &&
+	    attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE)
+		ret = apply_workqueue_attrs_locked(wq, attrs);
+	else
+		ret = -EINVAL;
+
+out_unlock:
+	apply_wqattrs_unlock();
+	free_workqueue_attrs(attrs);
+	return ret ?: count;
+}
+
+static ssize_t wq_cpumask_show(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	struct workqueue_struct *wq = dev_to_wq(dev);
+	int written;
+
+	mutex_lock(&wq->mutex);
+	written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
+			    cpumask_pr_args(wq->unbound_attrs->cpumask));
+	mutex_unlock(&wq->mutex);
+	return written;
+}
+
+static ssize_t wq_cpumask_store(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf, size_t count)
+{
+	struct workqueue_struct *wq = dev_to_wq(dev);
+	struct workqueue_attrs *attrs;
+	int ret = -ENOMEM;
+
+	apply_wqattrs_lock();
+
+	attrs = wq_sysfs_prep_attrs(wq);
+	if (!attrs)
+		goto out_unlock;
+
+	ret = cpumask_parse(buf, attrs->cpumask);
+	if (!ret)
+		ret = apply_workqueue_attrs_locked(wq, attrs);
+
+out_unlock:
+	apply_wqattrs_unlock();
+	free_workqueue_attrs(attrs);
+	return ret ?: count;
+}
+
+static ssize_t wq_numa_show(struct device *dev, struct device_attribute *attr,
+			    char *buf)
+{
+	struct workqueue_struct *wq = dev_to_wq(dev);
+	int written;
+
+	mutex_lock(&wq->mutex);
+	written = scnprintf(buf, PAGE_SIZE, "%d\n",
+			    !wq->unbound_attrs->no_numa);
+	mutex_unlock(&wq->mutex);
+
+	return written;
+}
+
+static ssize_t wq_numa_store(struct device *dev, struct device_attribute *attr,
+			     const char *buf, size_t count)
+{
+	struct workqueue_struct *wq = dev_to_wq(dev);
+	struct workqueue_attrs *attrs;
+	int v, ret = -ENOMEM;
+
+	apply_wqattrs_lock();
+
+	attrs = wq_sysfs_prep_attrs(wq);
+	if (!attrs)
+		goto out_unlock;
+
+	ret = -EINVAL;
+	if (sscanf(buf, "%d", &v) == 1) {
+		attrs->no_numa = !v;
+		ret = apply_workqueue_attrs_locked(wq, attrs);
+	}
+
+out_unlock:
+	apply_wqattrs_unlock();
+	free_workqueue_attrs(attrs);
+	return ret ?: count;
+}
+
+static struct device_attribute wq_sysfs_unbound_attrs[] = {
+	__ATTR(pool_ids, 0444, wq_pool_ids_show, NULL),
+	__ATTR(nice, 0644, wq_nice_show, wq_nice_store),
+	__ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store),
+	__ATTR(numa, 0644, wq_numa_show, wq_numa_store),
+	__ATTR_NULL,
+};
+
+static struct bus_type wq_subsys = {
+	.name				= "workqueue",
+	.dev_groups			= wq_sysfs_groups,
+};
+
+static ssize_t wq_unbound_cpumask_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	int written;
+
+	mutex_lock(&wq_pool_mutex);
+	written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
+			    cpumask_pr_args(wq_unbound_cpumask));
+	mutex_unlock(&wq_pool_mutex);
+
+	return written;
+}
+
+static ssize_t wq_unbound_cpumask_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t count)
+{
+	cpumask_var_t cpumask;
+	int ret;
+
+	if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
+		return -ENOMEM;
+
+	ret = cpumask_parse(buf, cpumask);
+	if (!ret)
+		ret = workqueue_set_unbound_cpumask(cpumask);
+
+	free_cpumask_var(cpumask);
+	return ret ? ret : count;
+}
+
+static struct device_attribute wq_sysfs_cpumask_attr =
+	__ATTR(cpumask, 0644, wq_unbound_cpumask_show,
+	       wq_unbound_cpumask_store);
+
+static int __init wq_sysfs_init(void)
+{
+	int err;
+
+	err = subsys_virtual_register(&wq_subsys, NULL);
+	if (err)
+		return err;
+
+	return device_create_file(wq_subsys.dev_root, &wq_sysfs_cpumask_attr);
+}
+core_initcall(wq_sysfs_init);
+
+static void wq_device_release(struct device *dev)
+{
+	struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
+
+	kfree(wq_dev);
+}
+
+/**
+ * workqueue_sysfs_register - make a workqueue visible in sysfs
+ * @wq: the workqueue to register
+ *
+ * Expose @wq in sysfs under /sys/bus/workqueue/devices.
+ * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
+ * which is the preferred method.
+ *
+ * Workqueue user should use this function directly iff it wants to apply
+ * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
+ * apply_workqueue_attrs() may race against userland updating the
+ * attributes.
+ *
+ * Return: 0 on success, -errno on failure.
+ */
+int workqueue_sysfs_register(struct workqueue_struct *wq)
+{
+	struct wq_device *wq_dev;
+	int ret;
+
+	/*
+	 * Adjusting max_active or creating new pwqs by applying
+	 * attributes breaks ordering guarantee.  Disallow exposing ordered
+	 * workqueues.
+	 */
+	if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
+		return -EINVAL;
+
+	wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);
+	if (!wq_dev)
+		return -ENOMEM;
+
+	wq_dev->wq = wq;
+	wq_dev->dev.bus = &wq_subsys;
+	wq_dev->dev.release = wq_device_release;
+	dev_set_name(&wq_dev->dev, "%s", wq->name);
+
+	/*
+	 * unbound_attrs are created separately.  Suppress uevent until
+	 * everything is ready.
+	 */
+	dev_set_uevent_suppress(&wq_dev->dev, true);
+
+	ret = device_register(&wq_dev->dev);
+	if (ret) {
+		put_device(&wq_dev->dev);
+		wq->wq_dev = NULL;
+		return ret;
+	}
+
+	if (wq->flags & WQ_UNBOUND) {
+		struct device_attribute *attr;
+
+		for (attr = wq_sysfs_unbound_attrs; attr->attr.name; attr++) {
+			ret = device_create_file(&wq_dev->dev, attr);
+			if (ret) {
+				device_unregister(&wq_dev->dev);
+				wq->wq_dev = NULL;
+				return ret;
+			}
+		}
+	}
+
+	dev_set_uevent_suppress(&wq_dev->dev, false);
+	kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD);
+	return 0;
+}
+
+/**
+ * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
+ * @wq: the workqueue to unregister
+ *
+ * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
+ */
+static void workqueue_sysfs_unregister(struct workqueue_struct *wq)
+{
+	struct wq_device *wq_dev = wq->wq_dev;
+
+	if (!wq->wq_dev)
+		return;
+
+	wq->wq_dev = NULL;
+	device_unregister(&wq_dev->dev);
+}
+#else	/* CONFIG_SYSFS */
+static void workqueue_sysfs_unregister(struct workqueue_struct *wq)	{ }
+#endif	/* CONFIG_SYSFS */
+
+/*
+ * Workqueue watchdog.
+ *
+ * Stall may be caused by various bugs - missing WQ_MEM_RECLAIM, illegal
+ * flush dependency, a concurrency managed work item which stays RUNNING
+ * indefinitely.  Workqueue stalls can be very difficult to debug as the
+ * usual warning mechanisms don't trigger and internal workqueue state is
+ * largely opaque.
+ *
+ * Workqueue watchdog monitors all worker pools periodically and dumps
+ * state if some pools failed to make forward progress for a while where
+ * forward progress is defined as the first item on ->worklist changing.
+ *
+ * This mechanism is controlled through the kernel parameter
+ * "workqueue.watchdog_thresh" which can be updated at runtime through the
+ * corresponding sysfs parameter file.
+ */
+#ifdef CONFIG_WQ_WATCHDOG
+
+static unsigned long wq_watchdog_thresh = 30;
+static struct timer_list wq_watchdog_timer;
+
+static unsigned long wq_watchdog_touched = INITIAL_JIFFIES;
+static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES;
+
+static void wq_watchdog_reset_touched(void)
+{
+	int cpu;
+
+	wq_watchdog_touched = jiffies;
+	for_each_possible_cpu(cpu)
+		per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
+}
+
+static void wq_watchdog_timer_fn(struct timer_list *unused)
+{
+	unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
+	bool lockup_detected = false;
+	unsigned long now = jiffies;
+	struct worker_pool *pool;
+	int pi;
+
+	if (!thresh)
+		return;
+
+	rcu_read_lock();
+
+	for_each_pool(pool, pi) {
+		unsigned long pool_ts, touched, ts;
+
+		if (list_empty(&pool->worklist))
+			continue;
+
+		/*
+		 * If a virtual machine is stopped by the host it can look to
+		 * the watchdog like a stall.
+		 */
+		kvm_check_and_clear_guest_paused();
+
+		/* get the latest of pool and touched timestamps */
+		pool_ts = READ_ONCE(pool->watchdog_ts);
+		touched = READ_ONCE(wq_watchdog_touched);
+
+		if (time_after(pool_ts, touched))
+			ts = pool_ts;
+		else
+			ts = touched;
+
+		if (pool->cpu >= 0) {
+			unsigned long cpu_touched =
+				READ_ONCE(per_cpu(wq_watchdog_touched_cpu,
+						  pool->cpu));
+			if (time_after(cpu_touched, ts))
+				ts = cpu_touched;
+		}
+
+		/* did we stall? */
+		if (time_after(now, ts + thresh)) {
+			lockup_detected = true;
+			pr_emerg("BUG: workqueue lockup - pool");
+			pr_cont_pool_info(pool);
+			pr_cont(" stuck for %us!\n",
+				jiffies_to_msecs(now - pool_ts) / 1000);
+		}
+	}
+
+	rcu_read_unlock();
+
+	if (lockup_detected)
+		show_workqueue_state();
+
+	wq_watchdog_reset_touched();
+	mod_timer(&wq_watchdog_timer, jiffies + thresh);
+}
+
+notrace void wq_watchdog_touch(int cpu)
+{
+	if (cpu >= 0)
+		per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
+	else
+		wq_watchdog_touched = jiffies;
+}
+
+static void wq_watchdog_set_thresh(unsigned long thresh)
+{
+	wq_watchdog_thresh = 0;
+	del_timer_sync(&wq_watchdog_timer);
+
+	if (thresh) {
+		wq_watchdog_thresh = thresh;
+		wq_watchdog_reset_touched();
+		mod_timer(&wq_watchdog_timer, jiffies + thresh * HZ);
+	}
+}
+
+static int wq_watchdog_param_set_thresh(const char *val,
+					const struct kernel_param *kp)
+{
+	unsigned long thresh;
+	int ret;
+
+	ret = kstrtoul(val, 0, &thresh);
+	if (ret)
+		return ret;
+
+	if (system_wq)
+		wq_watchdog_set_thresh(thresh);
+	else
+		wq_watchdog_thresh = thresh;
+
+	return 0;
+}
+
+static const struct kernel_param_ops wq_watchdog_thresh_ops = {
+	.set	= wq_watchdog_param_set_thresh,
+	.get	= param_get_ulong,
+};
+
+module_param_cb(watchdog_thresh, &wq_watchdog_thresh_ops, &wq_watchdog_thresh,
+		0644);
+
+static void wq_watchdog_init(void)
+{
+	timer_setup(&wq_watchdog_timer, wq_watchdog_timer_fn, TIMER_DEFERRABLE);
+	wq_watchdog_set_thresh(wq_watchdog_thresh);
+}
+
+#else	/* CONFIG_WQ_WATCHDOG */
+
+static inline void wq_watchdog_init(void) { }
+
+#endif	/* CONFIG_WQ_WATCHDOG */
+
+static void __init wq_numa_init(void)
+{
+	cpumask_var_t *tbl;
+	int node, cpu;
+
+	if (num_possible_nodes() <= 1)
+		return;
+
+	if (wq_disable_numa) {
+		pr_info("workqueue: NUMA affinity support disabled\n");
+		return;
+	}
+
+	wq_update_unbound_numa_attrs_buf = alloc_workqueue_attrs(GFP_KERNEL);
+	BUG_ON(!wq_update_unbound_numa_attrs_buf);
+
+	/*
+	 * We want masks of possible CPUs of each node which isn't readily
+	 * available.  Build one from cpu_to_node() which should have been
+	 * fully initialized by now.
+	 */
+	tbl = kcalloc(nr_node_ids, sizeof(tbl[0]), GFP_KERNEL);
+	BUG_ON(!tbl);
+
+	for_each_node(node)
+		BUG_ON(!zalloc_cpumask_var_node(&tbl[node], GFP_KERNEL,
+				node_online(node) ? node : NUMA_NO_NODE));
+
+	for_each_possible_cpu(cpu) {
+		node = cpu_to_node(cpu);
+		if (WARN_ON(node == NUMA_NO_NODE)) {
+			pr_warn("workqueue: NUMA node mapping not available for cpu%d, disabling NUMA support\n", cpu);
+			/* happens iff arch is bonkers, let's just proceed */
+			return;
+		}
+		cpumask_set_cpu(cpu, tbl[node]);
+	}
+
+	wq_numa_possible_cpumask = tbl;
+	wq_numa_enabled = true;
+}
+
+/**
+ * workqueue_init_early - early init for workqueue subsystem
+ *
+ * This is the first half of two-staged workqueue subsystem initialization
+ * and invoked as soon as the bare basics - memory allocation, cpumasks and
+ * idr are up.  It sets up all the data structures and system workqueues
+ * and allows early boot code to create workqueues and queue/cancel work
+ * items.  Actual work item execution starts only after kthreads can be
+ * created and scheduled right before early initcalls.
+ */
+int __init workqueue_init_early(void)
+{
+	int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
+	int hk_flags = HK_FLAG_DOMAIN | HK_FLAG_WQ;
+	int i, cpu;
+
+	WARN_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
+
+	BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
+	cpumask_copy(wq_unbound_cpumask, housekeeping_cpumask(hk_flags));
+
+	pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
+
+	/* initialize CPU pools */
+	for_each_possible_cpu(cpu) {
+		struct worker_pool *pool;
+
+		i = 0;
+		for_each_cpu_worker_pool(pool, cpu) {
+			BUG_ON(init_worker_pool(pool));
+			pool->cpu = cpu;
+			cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));
+			pool->attrs->nice = std_nice[i++];
+			pool->node = cpu_to_node(cpu);
+
+			/* alloc pool ID */
+			mutex_lock(&wq_pool_mutex);
+			BUG_ON(worker_pool_assign_id(pool));
+			mutex_unlock(&wq_pool_mutex);
+		}
+	}
+
+	/* create default unbound and ordered wq attrs */
+	for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
+		struct workqueue_attrs *attrs;
+
+		BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL)));
+		attrs->nice = std_nice[i];
+		unbound_std_wq_attrs[i] = attrs;
+
+		/*
+		 * An ordered wq should have only one pwq as ordering is
+		 * guaranteed by max_active which is enforced by pwqs.
+		 * Turn off NUMA so that dfl_pwq is used for all nodes.
+		 */
+		BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL)));
+		attrs->nice = std_nice[i];
+		attrs->no_numa = true;
+		ordered_wq_attrs[i] = attrs;
+	}
+
+	system_wq = alloc_workqueue("events", 0, 0);
+	system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);
+	system_long_wq = alloc_workqueue("events_long", 0, 0);
+	system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
+					    WQ_UNBOUND_MAX_ACTIVE);
+	system_freezable_wq = alloc_workqueue("events_freezable",
+					      WQ_FREEZABLE, 0);
+	system_power_efficient_wq = alloc_workqueue("events_power_efficient",
+					      WQ_POWER_EFFICIENT, 0);
+	system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_power_efficient",
+					      WQ_FREEZABLE | WQ_POWER_EFFICIENT,
+					      0);
+	BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||
+	       !system_unbound_wq || !system_freezable_wq ||
+	       !system_power_efficient_wq ||
+	       !system_freezable_power_efficient_wq);
+
+	return 0;
+}
+
+/**
+ * workqueue_init - bring workqueue subsystem fully online
+ *
+ * This is the latter half of two-staged workqueue subsystem initialization
+ * and invoked as soon as kthreads can be created and scheduled.
+ * Workqueues have been created and work items queued on them, but there
+ * are no kworkers executing the work items yet.  Populate the worker pools
+ * with the initial workers and enable future kworker creations.
+ */
+int __init workqueue_init(void)
+{
+	struct workqueue_struct *wq;
+	struct worker_pool *pool;
+	int cpu, bkt;
+
+	/*
+	 * It'd be simpler to initialize NUMA in workqueue_init_early() but
+	 * CPU to node mapping may not be available that early on some
+	 * archs such as power and arm64.  As per-cpu pools created
+	 * previously could be missing node hint and unbound pools NUMA
+	 * affinity, fix them up.
+	 *
+	 * Also, while iterating workqueues, create rescuers if requested.
+	 */
+	wq_numa_init();
+
+	mutex_lock(&wq_pool_mutex);
+
+	for_each_possible_cpu(cpu) {
+		for_each_cpu_worker_pool(pool, cpu) {
+			pool->node = cpu_to_node(cpu);
+		}
+	}
+
+	list_for_each_entry(wq, &workqueues, list) {
+		wq_update_unbound_numa(wq, smp_processor_id(), true);
+		WARN(init_rescuer(wq),
+		     "workqueue: failed to create early rescuer for %s",
+		     wq->name);
+	}
+
+	mutex_unlock(&wq_pool_mutex);
+
+	/* create the initial workers */
+	for_each_online_cpu(cpu) {
+		for_each_cpu_worker_pool(pool, cpu) {
+			pool->flags &= ~POOL_DISASSOCIATED;
+			BUG_ON(!create_worker(pool));
+		}
+	}
+
+	hash_for_each(unbound_pool_hash, bkt, pool, hash_node)
+		BUG_ON(!create_worker(pool));
+
+	wq_online = true;
+	wq_watchdog_init();
+
+	return 0;
+}