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-rw-r--r--kernel/cpu.c3241
1 files changed, 3241 insertions, 0 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c
new file mode 100644
index 0000000000..72e0f5380b
--- /dev/null
+++ b/kernel/cpu.c
@@ -0,0 +1,3241 @@
+/* CPU control.
+ * (C) 2001, 2002, 2003, 2004 Rusty Russell
+ *
+ * This code is licenced under the GPL.
+ */
+#include <linux/sched/mm.h>
+#include <linux/proc_fs.h>
+#include <linux/smp.h>
+#include <linux/init.h>
+#include <linux/notifier.h>
+#include <linux/sched/signal.h>
+#include <linux/sched/hotplug.h>
+#include <linux/sched/isolation.h>
+#include <linux/sched/task.h>
+#include <linux/sched/smt.h>
+#include <linux/unistd.h>
+#include <linux/cpu.h>
+#include <linux/oom.h>
+#include <linux/rcupdate.h>
+#include <linux/delay.h>
+#include <linux/export.h>
+#include <linux/bug.h>
+#include <linux/kthread.h>
+#include <linux/stop_machine.h>
+#include <linux/mutex.h>
+#include <linux/gfp.h>
+#include <linux/suspend.h>
+#include <linux/lockdep.h>
+#include <linux/tick.h>
+#include <linux/irq.h>
+#include <linux/nmi.h>
+#include <linux/smpboot.h>
+#include <linux/relay.h>
+#include <linux/slab.h>
+#include <linux/scs.h>
+#include <linux/percpu-rwsem.h>
+#include <linux/cpuset.h>
+#include <linux/random.h>
+#include <linux/cc_platform.h>
+
+#include <trace/events/power.h>
+#define CREATE_TRACE_POINTS
+#include <trace/events/cpuhp.h>
+
+#include "smpboot.h"
+
+/**
+ * struct cpuhp_cpu_state - Per cpu hotplug state storage
+ * @state: The current cpu state
+ * @target: The target state
+ * @fail: Current CPU hotplug callback state
+ * @thread: Pointer to the hotplug thread
+ * @should_run: Thread should execute
+ * @rollback: Perform a rollback
+ * @single: Single callback invocation
+ * @bringup: Single callback bringup or teardown selector
+ * @cpu: CPU number
+ * @node: Remote CPU node; for multi-instance, do a
+ * single entry callback for install/remove
+ * @last: For multi-instance rollback, remember how far we got
+ * @cb_state: The state for a single callback (install/uninstall)
+ * @result: Result of the operation
+ * @ap_sync_state: State for AP synchronization
+ * @done_up: Signal completion to the issuer of the task for cpu-up
+ * @done_down: Signal completion to the issuer of the task for cpu-down
+ */
+struct cpuhp_cpu_state {
+ enum cpuhp_state state;
+ enum cpuhp_state target;
+ enum cpuhp_state fail;
+#ifdef CONFIG_SMP
+ struct task_struct *thread;
+ bool should_run;
+ bool rollback;
+ bool single;
+ bool bringup;
+ struct hlist_node *node;
+ struct hlist_node *last;
+ enum cpuhp_state cb_state;
+ int result;
+ atomic_t ap_sync_state;
+ struct completion done_up;
+ struct completion done_down;
+#endif
+};
+
+static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state) = {
+ .fail = CPUHP_INVALID,
+};
+
+#ifdef CONFIG_SMP
+cpumask_t cpus_booted_once_mask;
+#endif
+
+#if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
+static struct lockdep_map cpuhp_state_up_map =
+ STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_map);
+static struct lockdep_map cpuhp_state_down_map =
+ STATIC_LOCKDEP_MAP_INIT("cpuhp_state-down", &cpuhp_state_down_map);
+
+
+static inline void cpuhp_lock_acquire(bool bringup)
+{
+ lock_map_acquire(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
+}
+
+static inline void cpuhp_lock_release(bool bringup)
+{
+ lock_map_release(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
+}
+#else
+
+static inline void cpuhp_lock_acquire(bool bringup) { }
+static inline void cpuhp_lock_release(bool bringup) { }
+
+#endif
+
+/**
+ * struct cpuhp_step - Hotplug state machine step
+ * @name: Name of the step
+ * @startup: Startup function of the step
+ * @teardown: Teardown function of the step
+ * @cant_stop: Bringup/teardown can't be stopped at this step
+ * @multi_instance: State has multiple instances which get added afterwards
+ */
+struct cpuhp_step {
+ const char *name;
+ union {
+ int (*single)(unsigned int cpu);
+ int (*multi)(unsigned int cpu,
+ struct hlist_node *node);
+ } startup;
+ union {
+ int (*single)(unsigned int cpu);
+ int (*multi)(unsigned int cpu,
+ struct hlist_node *node);
+ } teardown;
+ /* private: */
+ struct hlist_head list;
+ /* public: */
+ bool cant_stop;
+ bool multi_instance;
+};
+
+static DEFINE_MUTEX(cpuhp_state_mutex);
+static struct cpuhp_step cpuhp_hp_states[];
+
+static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
+{
+ return cpuhp_hp_states + state;
+}
+
+static bool cpuhp_step_empty(bool bringup, struct cpuhp_step *step)
+{
+ return bringup ? !step->startup.single : !step->teardown.single;
+}
+
+/**
+ * cpuhp_invoke_callback - Invoke the callbacks for a given state
+ * @cpu: The cpu for which the callback should be invoked
+ * @state: The state to do callbacks for
+ * @bringup: True if the bringup callback should be invoked
+ * @node: For multi-instance, do a single entry callback for install/remove
+ * @lastp: For multi-instance rollback, remember how far we got
+ *
+ * Called from cpu hotplug and from the state register machinery.
+ *
+ * Return: %0 on success or a negative errno code
+ */
+static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
+ bool bringup, struct hlist_node *node,
+ struct hlist_node **lastp)
+{
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+ struct cpuhp_step *step = cpuhp_get_step(state);
+ int (*cbm)(unsigned int cpu, struct hlist_node *node);
+ int (*cb)(unsigned int cpu);
+ int ret, cnt;
+
+ if (st->fail == state) {
+ st->fail = CPUHP_INVALID;
+ return -EAGAIN;
+ }
+
+ if (cpuhp_step_empty(bringup, step)) {
+ WARN_ON_ONCE(1);
+ return 0;
+ }
+
+ if (!step->multi_instance) {
+ WARN_ON_ONCE(lastp && *lastp);
+ cb = bringup ? step->startup.single : step->teardown.single;
+
+ trace_cpuhp_enter(cpu, st->target, state, cb);
+ ret = cb(cpu);
+ trace_cpuhp_exit(cpu, st->state, state, ret);
+ return ret;
+ }
+ cbm = bringup ? step->startup.multi : step->teardown.multi;
+
+ /* Single invocation for instance add/remove */
+ if (node) {
+ WARN_ON_ONCE(lastp && *lastp);
+ trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
+ ret = cbm(cpu, node);
+ trace_cpuhp_exit(cpu, st->state, state, ret);
+ return ret;
+ }
+
+ /* State transition. Invoke on all instances */
+ cnt = 0;
+ hlist_for_each(node, &step->list) {
+ if (lastp && node == *lastp)
+ break;
+
+ trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
+ ret = cbm(cpu, node);
+ trace_cpuhp_exit(cpu, st->state, state, ret);
+ if (ret) {
+ if (!lastp)
+ goto err;
+
+ *lastp = node;
+ return ret;
+ }
+ cnt++;
+ }
+ if (lastp)
+ *lastp = NULL;
+ return 0;
+err:
+ /* Rollback the instances if one failed */
+ cbm = !bringup ? step->startup.multi : step->teardown.multi;
+ if (!cbm)
+ return ret;
+
+ hlist_for_each(node, &step->list) {
+ if (!cnt--)
+ break;
+
+ trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
+ ret = cbm(cpu, node);
+ trace_cpuhp_exit(cpu, st->state, state, ret);
+ /*
+ * Rollback must not fail,
+ */
+ WARN_ON_ONCE(ret);
+ }
+ return ret;
+}
+
+#ifdef CONFIG_SMP
+static bool cpuhp_is_ap_state(enum cpuhp_state state)
+{
+ /*
+ * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
+ * purposes as that state is handled explicitly in cpu_down.
+ */
+ return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
+}
+
+static inline void wait_for_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
+{
+ struct completion *done = bringup ? &st->done_up : &st->done_down;
+ wait_for_completion(done);
+}
+
+static inline void complete_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
+{
+ struct completion *done = bringup ? &st->done_up : &st->done_down;
+ complete(done);
+}
+
+/*
+ * The former STARTING/DYING states, ran with IRQs disabled and must not fail.
+ */
+static bool cpuhp_is_atomic_state(enum cpuhp_state state)
+{
+ return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE;
+}
+
+/* Synchronization state management */
+enum cpuhp_sync_state {
+ SYNC_STATE_DEAD,
+ SYNC_STATE_KICKED,
+ SYNC_STATE_SHOULD_DIE,
+ SYNC_STATE_ALIVE,
+ SYNC_STATE_SHOULD_ONLINE,
+ SYNC_STATE_ONLINE,
+};
+
+#ifdef CONFIG_HOTPLUG_CORE_SYNC
+/**
+ * cpuhp_ap_update_sync_state - Update synchronization state during bringup/teardown
+ * @state: The synchronization state to set
+ *
+ * No synchronization point. Just update of the synchronization state, but implies
+ * a full barrier so that the AP changes are visible before the control CPU proceeds.
+ */
+static inline void cpuhp_ap_update_sync_state(enum cpuhp_sync_state state)
+{
+ atomic_t *st = this_cpu_ptr(&cpuhp_state.ap_sync_state);
+
+ (void)atomic_xchg(st, state);
+}
+
+void __weak arch_cpuhp_sync_state_poll(void) { cpu_relax(); }
+
+static bool cpuhp_wait_for_sync_state(unsigned int cpu, enum cpuhp_sync_state state,
+ enum cpuhp_sync_state next_state)
+{
+ atomic_t *st = per_cpu_ptr(&cpuhp_state.ap_sync_state, cpu);
+ ktime_t now, end, start = ktime_get();
+ int sync;
+
+ end = start + 10ULL * NSEC_PER_SEC;
+
+ sync = atomic_read(st);
+ while (1) {
+ if (sync == state) {
+ if (!atomic_try_cmpxchg(st, &sync, next_state))
+ continue;
+ return true;
+ }
+
+ now = ktime_get();
+ if (now > end) {
+ /* Timeout. Leave the state unchanged */
+ return false;
+ } else if (now - start < NSEC_PER_MSEC) {
+ /* Poll for one millisecond */
+ arch_cpuhp_sync_state_poll();
+ } else {
+ usleep_range_state(USEC_PER_MSEC, 2 * USEC_PER_MSEC, TASK_UNINTERRUPTIBLE);
+ }
+ sync = atomic_read(st);
+ }
+ return true;
+}
+#else /* CONFIG_HOTPLUG_CORE_SYNC */
+static inline void cpuhp_ap_update_sync_state(enum cpuhp_sync_state state) { }
+#endif /* !CONFIG_HOTPLUG_CORE_SYNC */
+
+#ifdef CONFIG_HOTPLUG_CORE_SYNC_DEAD
+/**
+ * cpuhp_ap_report_dead - Update synchronization state to DEAD
+ *
+ * No synchronization point. Just update of the synchronization state.
+ */
+void cpuhp_ap_report_dead(void)
+{
+ cpuhp_ap_update_sync_state(SYNC_STATE_DEAD);
+}
+
+void __weak arch_cpuhp_cleanup_dead_cpu(unsigned int cpu) { }
+
+/*
+ * Late CPU shutdown synchronization point. Cannot use cpuhp_state::done_down
+ * because the AP cannot issue complete() at this stage.
+ */
+static void cpuhp_bp_sync_dead(unsigned int cpu)
+{
+ atomic_t *st = per_cpu_ptr(&cpuhp_state.ap_sync_state, cpu);
+ int sync = atomic_read(st);
+
+ do {
+ /* CPU can have reported dead already. Don't overwrite that! */
+ if (sync == SYNC_STATE_DEAD)
+ break;
+ } while (!atomic_try_cmpxchg(st, &sync, SYNC_STATE_SHOULD_DIE));
+
+ if (cpuhp_wait_for_sync_state(cpu, SYNC_STATE_DEAD, SYNC_STATE_DEAD)) {
+ /* CPU reached dead state. Invoke the cleanup function */
+ arch_cpuhp_cleanup_dead_cpu(cpu);
+ return;
+ }
+
+ /* No further action possible. Emit message and give up. */
+ pr_err("CPU%u failed to report dead state\n", cpu);
+}
+#else /* CONFIG_HOTPLUG_CORE_SYNC_DEAD */
+static inline void cpuhp_bp_sync_dead(unsigned int cpu) { }
+#endif /* !CONFIG_HOTPLUG_CORE_SYNC_DEAD */
+
+#ifdef CONFIG_HOTPLUG_CORE_SYNC_FULL
+/**
+ * cpuhp_ap_sync_alive - Synchronize AP with the control CPU once it is alive
+ *
+ * Updates the AP synchronization state to SYNC_STATE_ALIVE and waits
+ * for the BP to release it.
+ */
+void cpuhp_ap_sync_alive(void)
+{
+ atomic_t *st = this_cpu_ptr(&cpuhp_state.ap_sync_state);
+
+ cpuhp_ap_update_sync_state(SYNC_STATE_ALIVE);
+
+ /* Wait for the control CPU to release it. */
+ while (atomic_read(st) != SYNC_STATE_SHOULD_ONLINE)
+ cpu_relax();
+}
+
+static bool cpuhp_can_boot_ap(unsigned int cpu)
+{
+ atomic_t *st = per_cpu_ptr(&cpuhp_state.ap_sync_state, cpu);
+ int sync = atomic_read(st);
+
+again:
+ switch (sync) {
+ case SYNC_STATE_DEAD:
+ /* CPU is properly dead */
+ break;
+ case SYNC_STATE_KICKED:
+ /* CPU did not come up in previous attempt */
+ break;
+ case SYNC_STATE_ALIVE:
+ /* CPU is stuck cpuhp_ap_sync_alive(). */
+ break;
+ default:
+ /* CPU failed to report online or dead and is in limbo state. */
+ return false;
+ }
+
+ /* Prepare for booting */
+ if (!atomic_try_cmpxchg(st, &sync, SYNC_STATE_KICKED))
+ goto again;
+
+ return true;
+}
+
+void __weak arch_cpuhp_cleanup_kick_cpu(unsigned int cpu) { }
+
+/*
+ * Early CPU bringup synchronization point. Cannot use cpuhp_state::done_up
+ * because the AP cannot issue complete() so early in the bringup.
+ */
+static int cpuhp_bp_sync_alive(unsigned int cpu)
+{
+ int ret = 0;
+
+ if (!IS_ENABLED(CONFIG_HOTPLUG_CORE_SYNC_FULL))
+ return 0;
+
+ if (!cpuhp_wait_for_sync_state(cpu, SYNC_STATE_ALIVE, SYNC_STATE_SHOULD_ONLINE)) {
+ pr_err("CPU%u failed to report alive state\n", cpu);
+ ret = -EIO;
+ }
+
+ /* Let the architecture cleanup the kick alive mechanics. */
+ arch_cpuhp_cleanup_kick_cpu(cpu);
+ return ret;
+}
+#else /* CONFIG_HOTPLUG_CORE_SYNC_FULL */
+static inline int cpuhp_bp_sync_alive(unsigned int cpu) { return 0; }
+static inline bool cpuhp_can_boot_ap(unsigned int cpu) { return true; }
+#endif /* !CONFIG_HOTPLUG_CORE_SYNC_FULL */
+
+/* Serializes the updates to cpu_online_mask, cpu_present_mask */
+static DEFINE_MUTEX(cpu_add_remove_lock);
+bool cpuhp_tasks_frozen;
+EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
+
+/*
+ * The following two APIs (cpu_maps_update_begin/done) must be used when
+ * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
+ */
+void cpu_maps_update_begin(void)
+{
+ mutex_lock(&cpu_add_remove_lock);
+}
+
+void cpu_maps_update_done(void)
+{
+ mutex_unlock(&cpu_add_remove_lock);
+}
+
+/*
+ * If set, cpu_up and cpu_down will return -EBUSY and do nothing.
+ * Should always be manipulated under cpu_add_remove_lock
+ */
+static int cpu_hotplug_disabled;
+
+#ifdef CONFIG_HOTPLUG_CPU
+
+DEFINE_STATIC_PERCPU_RWSEM(cpu_hotplug_lock);
+
+void cpus_read_lock(void)
+{
+ percpu_down_read(&cpu_hotplug_lock);
+}
+EXPORT_SYMBOL_GPL(cpus_read_lock);
+
+int cpus_read_trylock(void)
+{
+ return percpu_down_read_trylock(&cpu_hotplug_lock);
+}
+EXPORT_SYMBOL_GPL(cpus_read_trylock);
+
+void cpus_read_unlock(void)
+{
+ percpu_up_read(&cpu_hotplug_lock);
+}
+EXPORT_SYMBOL_GPL(cpus_read_unlock);
+
+void cpus_write_lock(void)
+{
+ percpu_down_write(&cpu_hotplug_lock);
+}
+
+void cpus_write_unlock(void)
+{
+ percpu_up_write(&cpu_hotplug_lock);
+}
+
+void lockdep_assert_cpus_held(void)
+{
+ /*
+ * We can't have hotplug operations before userspace starts running,
+ * and some init codepaths will knowingly not take the hotplug lock.
+ * This is all valid, so mute lockdep until it makes sense to report
+ * unheld locks.
+ */
+ if (system_state < SYSTEM_RUNNING)
+ return;
+
+ percpu_rwsem_assert_held(&cpu_hotplug_lock);
+}
+
+#ifdef CONFIG_LOCKDEP
+int lockdep_is_cpus_held(void)
+{
+ return percpu_rwsem_is_held(&cpu_hotplug_lock);
+}
+#endif
+
+static void lockdep_acquire_cpus_lock(void)
+{
+ rwsem_acquire(&cpu_hotplug_lock.dep_map, 0, 0, _THIS_IP_);
+}
+
+static void lockdep_release_cpus_lock(void)
+{
+ rwsem_release(&cpu_hotplug_lock.dep_map, _THIS_IP_);
+}
+
+/*
+ * Wait for currently running CPU hotplug operations to complete (if any) and
+ * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
+ * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
+ * hotplug path before performing hotplug operations. So acquiring that lock
+ * guarantees mutual exclusion from any currently running hotplug operations.
+ */
+void cpu_hotplug_disable(void)
+{
+ cpu_maps_update_begin();
+ cpu_hotplug_disabled++;
+ cpu_maps_update_done();
+}
+EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
+
+static void __cpu_hotplug_enable(void)
+{
+ if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
+ return;
+ cpu_hotplug_disabled--;
+}
+
+void cpu_hotplug_enable(void)
+{
+ cpu_maps_update_begin();
+ __cpu_hotplug_enable();
+ cpu_maps_update_done();
+}
+EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
+
+#else
+
+static void lockdep_acquire_cpus_lock(void)
+{
+}
+
+static void lockdep_release_cpus_lock(void)
+{
+}
+
+#endif /* CONFIG_HOTPLUG_CPU */
+
+/*
+ * Architectures that need SMT-specific errata handling during SMT hotplug
+ * should override this.
+ */
+void __weak arch_smt_update(void) { }
+
+#ifdef CONFIG_HOTPLUG_SMT
+
+enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
+static unsigned int cpu_smt_max_threads __ro_after_init;
+unsigned int cpu_smt_num_threads __read_mostly = UINT_MAX;
+
+void __init cpu_smt_disable(bool force)
+{
+ if (!cpu_smt_possible())
+ return;
+
+ if (force) {
+ pr_info("SMT: Force disabled\n");
+ cpu_smt_control = CPU_SMT_FORCE_DISABLED;
+ } else {
+ pr_info("SMT: disabled\n");
+ cpu_smt_control = CPU_SMT_DISABLED;
+ }
+ cpu_smt_num_threads = 1;
+}
+
+/*
+ * The decision whether SMT is supported can only be done after the full
+ * CPU identification. Called from architecture code.
+ */
+void __init cpu_smt_set_num_threads(unsigned int num_threads,
+ unsigned int max_threads)
+{
+ WARN_ON(!num_threads || (num_threads > max_threads));
+
+ if (max_threads == 1)
+ cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
+
+ cpu_smt_max_threads = max_threads;
+
+ /*
+ * If SMT has been disabled via the kernel command line or SMT is
+ * not supported, set cpu_smt_num_threads to 1 for consistency.
+ * If enabled, take the architecture requested number of threads
+ * to bring up into account.
+ */
+ if (cpu_smt_control != CPU_SMT_ENABLED)
+ cpu_smt_num_threads = 1;
+ else if (num_threads < cpu_smt_num_threads)
+ cpu_smt_num_threads = num_threads;
+}
+
+static int __init smt_cmdline_disable(char *str)
+{
+ cpu_smt_disable(str && !strcmp(str, "force"));
+ return 0;
+}
+early_param("nosmt", smt_cmdline_disable);
+
+/*
+ * For Archicture supporting partial SMT states check if the thread is allowed.
+ * Otherwise this has already been checked through cpu_smt_max_threads when
+ * setting the SMT level.
+ */
+static inline bool cpu_smt_thread_allowed(unsigned int cpu)
+{
+#ifdef CONFIG_SMT_NUM_THREADS_DYNAMIC
+ return topology_smt_thread_allowed(cpu);
+#else
+ return true;
+#endif
+}
+
+static inline bool cpu_bootable(unsigned int cpu)
+{
+ if (cpu_smt_control == CPU_SMT_ENABLED && cpu_smt_thread_allowed(cpu))
+ return true;
+
+ /* All CPUs are bootable if controls are not configured */
+ if (cpu_smt_control == CPU_SMT_NOT_IMPLEMENTED)
+ return true;
+
+ /* All CPUs are bootable if CPU is not SMT capable */
+ if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
+ return true;
+
+ if (topology_is_primary_thread(cpu))
+ return true;
+
+ /*
+ * On x86 it's required to boot all logical CPUs at least once so
+ * that the init code can get a chance to set CR4.MCE on each
+ * CPU. Otherwise, a broadcasted MCE observing CR4.MCE=0b on any
+ * core will shutdown the machine.
+ */
+ return !cpumask_test_cpu(cpu, &cpus_booted_once_mask);
+}
+
+/* Returns true if SMT is supported and not forcefully (irreversibly) disabled */
+bool cpu_smt_possible(void)
+{
+ return cpu_smt_control != CPU_SMT_FORCE_DISABLED &&
+ cpu_smt_control != CPU_SMT_NOT_SUPPORTED;
+}
+EXPORT_SYMBOL_GPL(cpu_smt_possible);
+
+#else
+static inline bool cpu_bootable(unsigned int cpu) { return true; }
+#endif
+
+static inline enum cpuhp_state
+cpuhp_set_state(int cpu, struct cpuhp_cpu_state *st, enum cpuhp_state target)
+{
+ enum cpuhp_state prev_state = st->state;
+ bool bringup = st->state < target;
+
+ st->rollback = false;
+ st->last = NULL;
+
+ st->target = target;
+ st->single = false;
+ st->bringup = bringup;
+ if (cpu_dying(cpu) != !bringup)
+ set_cpu_dying(cpu, !bringup);
+
+ return prev_state;
+}
+
+static inline void
+cpuhp_reset_state(int cpu, struct cpuhp_cpu_state *st,
+ enum cpuhp_state prev_state)
+{
+ bool bringup = !st->bringup;
+
+ st->target = prev_state;
+
+ /*
+ * Already rolling back. No need invert the bringup value or to change
+ * the current state.
+ */
+ if (st->rollback)
+ return;
+
+ st->rollback = true;
+
+ /*
+ * If we have st->last we need to undo partial multi_instance of this
+ * state first. Otherwise start undo at the previous state.
+ */
+ if (!st->last) {
+ if (st->bringup)
+ st->state--;
+ else
+ st->state++;
+ }
+
+ st->bringup = bringup;
+ if (cpu_dying(cpu) != !bringup)
+ set_cpu_dying(cpu, !bringup);
+}
+
+/* Regular hotplug invocation of the AP hotplug thread */
+static void __cpuhp_kick_ap(struct cpuhp_cpu_state *st)
+{
+ if (!st->single && st->state == st->target)
+ return;
+
+ st->result = 0;
+ /*
+ * Make sure the above stores are visible before should_run becomes
+ * true. Paired with the mb() above in cpuhp_thread_fun()
+ */
+ smp_mb();
+ st->should_run = true;
+ wake_up_process(st->thread);
+ wait_for_ap_thread(st, st->bringup);
+}
+
+static int cpuhp_kick_ap(int cpu, struct cpuhp_cpu_state *st,
+ enum cpuhp_state target)
+{
+ enum cpuhp_state prev_state;
+ int ret;
+
+ prev_state = cpuhp_set_state(cpu, st, target);
+ __cpuhp_kick_ap(st);
+ if ((ret = st->result)) {
+ cpuhp_reset_state(cpu, st, prev_state);
+ __cpuhp_kick_ap(st);
+ }
+
+ return ret;
+}
+
+static int bringup_wait_for_ap_online(unsigned int cpu)
+{
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+
+ /* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */
+ wait_for_ap_thread(st, true);
+ if (WARN_ON_ONCE((!cpu_online(cpu))))
+ return -ECANCELED;
+
+ /* Unpark the hotplug thread of the target cpu */
+ kthread_unpark(st->thread);
+
+ /*
+ * SMT soft disabling on X86 requires to bring the CPU out of the
+ * BIOS 'wait for SIPI' state in order to set the CR4.MCE bit. The
+ * CPU marked itself as booted_once in notify_cpu_starting() so the
+ * cpu_bootable() check will now return false if this is not the
+ * primary sibling.
+ */
+ if (!cpu_bootable(cpu))
+ return -ECANCELED;
+ return 0;
+}
+
+#ifdef CONFIG_HOTPLUG_SPLIT_STARTUP
+static int cpuhp_kick_ap_alive(unsigned int cpu)
+{
+ if (!cpuhp_can_boot_ap(cpu))
+ return -EAGAIN;
+
+ return arch_cpuhp_kick_ap_alive(cpu, idle_thread_get(cpu));
+}
+
+static int cpuhp_bringup_ap(unsigned int cpu)
+{
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+ int ret;
+
+ /*
+ * Some architectures have to walk the irq descriptors to
+ * setup the vector space for the cpu which comes online.
+ * Prevent irq alloc/free across the bringup.
+ */
+ irq_lock_sparse();
+
+ ret = cpuhp_bp_sync_alive(cpu);
+ if (ret)
+ goto out_unlock;
+
+ ret = bringup_wait_for_ap_online(cpu);
+ if (ret)
+ goto out_unlock;
+
+ irq_unlock_sparse();
+
+ if (st->target <= CPUHP_AP_ONLINE_IDLE)
+ return 0;
+
+ return cpuhp_kick_ap(cpu, st, st->target);
+
+out_unlock:
+ irq_unlock_sparse();
+ return ret;
+}
+#else
+static int bringup_cpu(unsigned int cpu)
+{
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+ struct task_struct *idle = idle_thread_get(cpu);
+ int ret;
+
+ if (!cpuhp_can_boot_ap(cpu))
+ return -EAGAIN;
+
+ /*
+ * Some architectures have to walk the irq descriptors to
+ * setup the vector space for the cpu which comes online.
+ *
+ * Prevent irq alloc/free across the bringup by acquiring the
+ * sparse irq lock. Hold it until the upcoming CPU completes the
+ * startup in cpuhp_online_idle() which allows to avoid
+ * intermediate synchronization points in the architecture code.
+ */
+ irq_lock_sparse();
+
+ ret = __cpu_up(cpu, idle);
+ if (ret)
+ goto out_unlock;
+
+ ret = cpuhp_bp_sync_alive(cpu);
+ if (ret)
+ goto out_unlock;
+
+ ret = bringup_wait_for_ap_online(cpu);
+ if (ret)
+ goto out_unlock;
+
+ irq_unlock_sparse();
+
+ if (st->target <= CPUHP_AP_ONLINE_IDLE)
+ return 0;
+
+ return cpuhp_kick_ap(cpu, st, st->target);
+
+out_unlock:
+ irq_unlock_sparse();
+ return ret;
+}
+#endif
+
+static int finish_cpu(unsigned int cpu)
+{
+ struct task_struct *idle = idle_thread_get(cpu);
+ struct mm_struct *mm = idle->active_mm;
+
+ /*
+ * idle_task_exit() will have switched to &init_mm, now
+ * clean up any remaining active_mm state.
+ */
+ if (mm != &init_mm)
+ idle->active_mm = &init_mm;
+ mmdrop_lazy_tlb(mm);
+ return 0;
+}
+
+/*
+ * Hotplug state machine related functions
+ */
+
+/*
+ * Get the next state to run. Empty ones will be skipped. Returns true if a
+ * state must be run.
+ *
+ * st->state will be modified ahead of time, to match state_to_run, as if it
+ * has already ran.
+ */
+static bool cpuhp_next_state(bool bringup,
+ enum cpuhp_state *state_to_run,
+ struct cpuhp_cpu_state *st,
+ enum cpuhp_state target)
+{
+ do {
+ if (bringup) {
+ if (st->state >= target)
+ return false;
+
+ *state_to_run = ++st->state;
+ } else {
+ if (st->state <= target)
+ return false;
+
+ *state_to_run = st->state--;
+ }
+
+ if (!cpuhp_step_empty(bringup, cpuhp_get_step(*state_to_run)))
+ break;
+ } while (true);
+
+ return true;
+}
+
+static int __cpuhp_invoke_callback_range(bool bringup,
+ unsigned int cpu,
+ struct cpuhp_cpu_state *st,
+ enum cpuhp_state target,
+ bool nofail)
+{
+ enum cpuhp_state state;
+ int ret = 0;
+
+ while (cpuhp_next_state(bringup, &state, st, target)) {
+ int err;
+
+ err = cpuhp_invoke_callback(cpu, state, bringup, NULL, NULL);
+ if (!err)
+ continue;
+
+ if (nofail) {
+ pr_warn("CPU %u %s state %s (%d) failed (%d)\n",
+ cpu, bringup ? "UP" : "DOWN",
+ cpuhp_get_step(st->state)->name,
+ st->state, err);
+ ret = -1;
+ } else {
+ ret = err;
+ break;
+ }
+ }
+
+ return ret;
+}
+
+static inline int cpuhp_invoke_callback_range(bool bringup,
+ unsigned int cpu,
+ struct cpuhp_cpu_state *st,
+ enum cpuhp_state target)
+{
+ return __cpuhp_invoke_callback_range(bringup, cpu, st, target, false);
+}
+
+static inline void cpuhp_invoke_callback_range_nofail(bool bringup,
+ unsigned int cpu,
+ struct cpuhp_cpu_state *st,
+ enum cpuhp_state target)
+{
+ __cpuhp_invoke_callback_range(bringup, cpu, st, target, true);
+}
+
+static inline bool can_rollback_cpu(struct cpuhp_cpu_state *st)
+{
+ if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
+ return true;
+ /*
+ * When CPU hotplug is disabled, then taking the CPU down is not
+ * possible because takedown_cpu() and the architecture and
+ * subsystem specific mechanisms are not available. So the CPU
+ * which would be completely unplugged again needs to stay around
+ * in the current state.
+ */
+ return st->state <= CPUHP_BRINGUP_CPU;
+}
+
+static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
+ enum cpuhp_state target)
+{
+ enum cpuhp_state prev_state = st->state;
+ int ret = 0;
+
+ ret = cpuhp_invoke_callback_range(true, cpu, st, target);
+ if (ret) {
+ pr_debug("CPU UP failed (%d) CPU %u state %s (%d)\n",
+ ret, cpu, cpuhp_get_step(st->state)->name,
+ st->state);
+
+ cpuhp_reset_state(cpu, st, prev_state);
+ if (can_rollback_cpu(st))
+ WARN_ON(cpuhp_invoke_callback_range(false, cpu, st,
+ prev_state));
+ }
+ return ret;
+}
+
+/*
+ * The cpu hotplug threads manage the bringup and teardown of the cpus
+ */
+static int cpuhp_should_run(unsigned int cpu)
+{
+ struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
+
+ return st->should_run;
+}
+
+/*
+ * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
+ * callbacks when a state gets [un]installed at runtime.
+ *
+ * Each invocation of this function by the smpboot thread does a single AP
+ * state callback.
+ *
+ * It has 3 modes of operation:
+ * - single: runs st->cb_state
+ * - up: runs ++st->state, while st->state < st->target
+ * - down: runs st->state--, while st->state > st->target
+ *
+ * When complete or on error, should_run is cleared and the completion is fired.
+ */
+static void cpuhp_thread_fun(unsigned int cpu)
+{
+ struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
+ bool bringup = st->bringup;
+ enum cpuhp_state state;
+
+ if (WARN_ON_ONCE(!st->should_run))
+ return;
+
+ /*
+ * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
+ * that if we see ->should_run we also see the rest of the state.
+ */
+ smp_mb();
+
+ /*
+ * The BP holds the hotplug lock, but we're now running on the AP,
+ * ensure that anybody asserting the lock is held, will actually find
+ * it so.
+ */
+ lockdep_acquire_cpus_lock();
+ cpuhp_lock_acquire(bringup);
+
+ if (st->single) {
+ state = st->cb_state;
+ st->should_run = false;
+ } else {
+ st->should_run = cpuhp_next_state(bringup, &state, st, st->target);
+ if (!st->should_run)
+ goto end;
+ }
+
+ WARN_ON_ONCE(!cpuhp_is_ap_state(state));
+
+ if (cpuhp_is_atomic_state(state)) {
+ local_irq_disable();
+ st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
+ local_irq_enable();
+
+ /*
+ * STARTING/DYING must not fail!
+ */
+ WARN_ON_ONCE(st->result);
+ } else {
+ st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
+ }
+
+ if (st->result) {
+ /*
+ * If we fail on a rollback, we're up a creek without no
+ * paddle, no way forward, no way back. We loose, thanks for
+ * playing.
+ */
+ WARN_ON_ONCE(st->rollback);
+ st->should_run = false;
+ }
+
+end:
+ cpuhp_lock_release(bringup);
+ lockdep_release_cpus_lock();
+
+ if (!st->should_run)
+ complete_ap_thread(st, bringup);
+}
+
+/* Invoke a single callback on a remote cpu */
+static int
+cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
+ struct hlist_node *node)
+{
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+ int ret;
+
+ if (!cpu_online(cpu))
+ return 0;
+
+ cpuhp_lock_acquire(false);
+ cpuhp_lock_release(false);
+
+ cpuhp_lock_acquire(true);
+ cpuhp_lock_release(true);
+
+ /*
+ * If we are up and running, use the hotplug thread. For early calls
+ * we invoke the thread function directly.
+ */
+ if (!st->thread)
+ return cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
+
+ st->rollback = false;
+ st->last = NULL;
+
+ st->node = node;
+ st->bringup = bringup;
+ st->cb_state = state;
+ st->single = true;
+
+ __cpuhp_kick_ap(st);
+
+ /*
+ * If we failed and did a partial, do a rollback.
+ */
+ if ((ret = st->result) && st->last) {
+ st->rollback = true;
+ st->bringup = !bringup;
+
+ __cpuhp_kick_ap(st);
+ }
+
+ /*
+ * Clean up the leftovers so the next hotplug operation wont use stale
+ * data.
+ */
+ st->node = st->last = NULL;
+ return ret;
+}
+
+static int cpuhp_kick_ap_work(unsigned int cpu)
+{
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+ enum cpuhp_state prev_state = st->state;
+ int ret;
+
+ cpuhp_lock_acquire(false);
+ cpuhp_lock_release(false);
+
+ cpuhp_lock_acquire(true);
+ cpuhp_lock_release(true);
+
+ trace_cpuhp_enter(cpu, st->target, prev_state, cpuhp_kick_ap_work);
+ ret = cpuhp_kick_ap(cpu, st, st->target);
+ trace_cpuhp_exit(cpu, st->state, prev_state, ret);
+
+ return ret;
+}
+
+static struct smp_hotplug_thread cpuhp_threads = {
+ .store = &cpuhp_state.thread,
+ .thread_should_run = cpuhp_should_run,
+ .thread_fn = cpuhp_thread_fun,
+ .thread_comm = "cpuhp/%u",
+ .selfparking = true,
+};
+
+static __init void cpuhp_init_state(void)
+{
+ struct cpuhp_cpu_state *st;
+ int cpu;
+
+ for_each_possible_cpu(cpu) {
+ st = per_cpu_ptr(&cpuhp_state, cpu);
+ init_completion(&st->done_up);
+ init_completion(&st->done_down);
+ }
+}
+
+void __init cpuhp_threads_init(void)
+{
+ cpuhp_init_state();
+ BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
+ kthread_unpark(this_cpu_read(cpuhp_state.thread));
+}
+
+/*
+ *
+ * Serialize hotplug trainwrecks outside of the cpu_hotplug_lock
+ * protected region.
+ *
+ * The operation is still serialized against concurrent CPU hotplug via
+ * cpu_add_remove_lock, i.e. CPU map protection. But it is _not_
+ * serialized against other hotplug related activity like adding or
+ * removing of state callbacks and state instances, which invoke either the
+ * startup or the teardown callback of the affected state.
+ *
+ * This is required for subsystems which are unfixable vs. CPU hotplug and
+ * evade lock inversion problems by scheduling work which has to be
+ * completed _before_ cpu_up()/_cpu_down() returns.
+ *
+ * Don't even think about adding anything to this for any new code or even
+ * drivers. It's only purpose is to keep existing lock order trainwrecks
+ * working.
+ *
+ * For cpu_down() there might be valid reasons to finish cleanups which are
+ * not required to be done under cpu_hotplug_lock, but that's a different
+ * story and would be not invoked via this.
+ */
+static void cpu_up_down_serialize_trainwrecks(bool tasks_frozen)
+{
+ /*
+ * cpusets delegate hotplug operations to a worker to "solve" the
+ * lock order problems. Wait for the worker, but only if tasks are
+ * _not_ frozen (suspend, hibernate) as that would wait forever.
+ *
+ * The wait is required because otherwise the hotplug operation
+ * returns with inconsistent state, which could even be observed in
+ * user space when a new CPU is brought up. The CPU plug uevent
+ * would be delivered and user space reacting on it would fail to
+ * move tasks to the newly plugged CPU up to the point where the
+ * work has finished because up to that point the newly plugged CPU
+ * is not assignable in cpusets/cgroups. On unplug that's not
+ * necessarily a visible issue, but it is still inconsistent state,
+ * which is the real problem which needs to be "fixed". This can't
+ * prevent the transient state between scheduling the work and
+ * returning from waiting for it.
+ */
+ if (!tasks_frozen)
+ cpuset_wait_for_hotplug();
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+#ifndef arch_clear_mm_cpumask_cpu
+#define arch_clear_mm_cpumask_cpu(cpu, mm) cpumask_clear_cpu(cpu, mm_cpumask(mm))
+#endif
+
+/**
+ * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
+ * @cpu: a CPU id
+ *
+ * This function walks all processes, finds a valid mm struct for each one and
+ * then clears a corresponding bit in mm's cpumask. While this all sounds
+ * trivial, there are various non-obvious corner cases, which this function
+ * tries to solve in a safe manner.
+ *
+ * Also note that the function uses a somewhat relaxed locking scheme, so it may
+ * be called only for an already offlined CPU.
+ */
+void clear_tasks_mm_cpumask(int cpu)
+{
+ struct task_struct *p;
+
+ /*
+ * This function is called after the cpu is taken down and marked
+ * offline, so its not like new tasks will ever get this cpu set in
+ * their mm mask. -- Peter Zijlstra
+ * Thus, we may use rcu_read_lock() here, instead of grabbing
+ * full-fledged tasklist_lock.
+ */
+ WARN_ON(cpu_online(cpu));
+ rcu_read_lock();
+ for_each_process(p) {
+ struct task_struct *t;
+
+ /*
+ * Main thread might exit, but other threads may still have
+ * a valid mm. Find one.
+ */
+ t = find_lock_task_mm(p);
+ if (!t)
+ continue;
+ arch_clear_mm_cpumask_cpu(cpu, t->mm);
+ task_unlock(t);
+ }
+ rcu_read_unlock();
+}
+
+/* Take this CPU down. */
+static int take_cpu_down(void *_param)
+{
+ struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
+ enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
+ int err, cpu = smp_processor_id();
+
+ /* Ensure this CPU doesn't handle any more interrupts. */
+ err = __cpu_disable();
+ if (err < 0)
+ return err;
+
+ /*
+ * Must be called from CPUHP_TEARDOWN_CPU, which means, as we are going
+ * down, that the current state is CPUHP_TEARDOWN_CPU - 1.
+ */
+ WARN_ON(st->state != (CPUHP_TEARDOWN_CPU - 1));
+
+ /*
+ * Invoke the former CPU_DYING callbacks. DYING must not fail!
+ */
+ cpuhp_invoke_callback_range_nofail(false, cpu, st, target);
+
+ /* Give up timekeeping duties */
+ tick_handover_do_timer();
+ /* Remove CPU from timer broadcasting */
+ tick_offline_cpu(cpu);
+ /* Park the stopper thread */
+ stop_machine_park(cpu);
+ return 0;
+}
+
+static int takedown_cpu(unsigned int cpu)
+{
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+ int err;
+
+ /* Park the smpboot threads */
+ kthread_park(st->thread);
+
+ /*
+ * Prevent irq alloc/free while the dying cpu reorganizes the
+ * interrupt affinities.
+ */
+ irq_lock_sparse();
+
+ /*
+ * So now all preempt/rcu users must observe !cpu_active().
+ */
+ err = stop_machine_cpuslocked(take_cpu_down, NULL, cpumask_of(cpu));
+ if (err) {
+ /* CPU refused to die */
+ irq_unlock_sparse();
+ /* Unpark the hotplug thread so we can rollback there */
+ kthread_unpark(st->thread);
+ return err;
+ }
+ BUG_ON(cpu_online(cpu));
+
+ /*
+ * The teardown callback for CPUHP_AP_SCHED_STARTING will have removed
+ * all runnable tasks from the CPU, there's only the idle task left now
+ * that the migration thread is done doing the stop_machine thing.
+ *
+ * Wait for the stop thread to go away.
+ */
+ wait_for_ap_thread(st, false);
+ BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
+
+ /* Interrupts are moved away from the dying cpu, reenable alloc/free */
+ irq_unlock_sparse();
+
+ hotplug_cpu__broadcast_tick_pull(cpu);
+ /* This actually kills the CPU. */
+ __cpu_die(cpu);
+
+ cpuhp_bp_sync_dead(cpu);
+
+ tick_cleanup_dead_cpu(cpu);
+ rcutree_migrate_callbacks(cpu);
+ return 0;
+}
+
+static void cpuhp_complete_idle_dead(void *arg)
+{
+ struct cpuhp_cpu_state *st = arg;
+
+ complete_ap_thread(st, false);
+}
+
+void cpuhp_report_idle_dead(void)
+{
+ struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
+
+ BUG_ON(st->state != CPUHP_AP_OFFLINE);
+ rcu_report_dead(smp_processor_id());
+ st->state = CPUHP_AP_IDLE_DEAD;
+ /*
+ * We cannot call complete after rcu_report_dead() so we delegate it
+ * to an online cpu.
+ */
+ smp_call_function_single(cpumask_first(cpu_online_mask),
+ cpuhp_complete_idle_dead, st, 0);
+}
+
+static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
+ enum cpuhp_state target)
+{
+ enum cpuhp_state prev_state = st->state;
+ int ret = 0;
+
+ ret = cpuhp_invoke_callback_range(false, cpu, st, target);
+ if (ret) {
+ pr_debug("CPU DOWN failed (%d) CPU %u state %s (%d)\n",
+ ret, cpu, cpuhp_get_step(st->state)->name,
+ st->state);
+
+ cpuhp_reset_state(cpu, st, prev_state);
+
+ if (st->state < prev_state)
+ WARN_ON(cpuhp_invoke_callback_range(true, cpu, st,
+ prev_state));
+ }
+
+ return ret;
+}
+
+/* Requires cpu_add_remove_lock to be held */
+static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
+ enum cpuhp_state target)
+{
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+ int prev_state, ret = 0;
+
+ if (num_online_cpus() == 1)
+ return -EBUSY;
+
+ if (!cpu_present(cpu))
+ return -EINVAL;
+
+ cpus_write_lock();
+
+ cpuhp_tasks_frozen = tasks_frozen;
+
+ prev_state = cpuhp_set_state(cpu, st, target);
+ /*
+ * If the current CPU state is in the range of the AP hotplug thread,
+ * then we need to kick the thread.
+ */
+ if (st->state > CPUHP_TEARDOWN_CPU) {
+ st->target = max((int)target, CPUHP_TEARDOWN_CPU);
+ ret = cpuhp_kick_ap_work(cpu);
+ /*
+ * The AP side has done the error rollback already. Just
+ * return the error code..
+ */
+ if (ret)
+ goto out;
+
+ /*
+ * We might have stopped still in the range of the AP hotplug
+ * thread. Nothing to do anymore.
+ */
+ if (st->state > CPUHP_TEARDOWN_CPU)
+ goto out;
+
+ st->target = target;
+ }
+ /*
+ * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
+ * to do the further cleanups.
+ */
+ ret = cpuhp_down_callbacks(cpu, st, target);
+ if (ret && st->state < prev_state) {
+ if (st->state == CPUHP_TEARDOWN_CPU) {
+ cpuhp_reset_state(cpu, st, prev_state);
+ __cpuhp_kick_ap(st);
+ } else {
+ WARN(1, "DEAD callback error for CPU%d", cpu);
+ }
+ }
+
+out:
+ cpus_write_unlock();
+ /*
+ * Do post unplug cleanup. This is still protected against
+ * concurrent CPU hotplug via cpu_add_remove_lock.
+ */
+ lockup_detector_cleanup();
+ arch_smt_update();
+ cpu_up_down_serialize_trainwrecks(tasks_frozen);
+ return ret;
+}
+
+struct cpu_down_work {
+ unsigned int cpu;
+ enum cpuhp_state target;
+};
+
+static long __cpu_down_maps_locked(void *arg)
+{
+ struct cpu_down_work *work = arg;
+
+ return _cpu_down(work->cpu, 0, work->target);
+}
+
+static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
+{
+ struct cpu_down_work work = { .cpu = cpu, .target = target, };
+
+ /*
+ * If the platform does not support hotplug, report it explicitly to
+ * differentiate it from a transient offlining failure.
+ */
+ if (cc_platform_has(CC_ATTR_HOTPLUG_DISABLED))
+ return -EOPNOTSUPP;
+ if (cpu_hotplug_disabled)
+ return -EBUSY;
+
+ /*
+ * Ensure that the control task does not run on the to be offlined
+ * CPU to prevent a deadlock against cfs_b->period_timer.
+ * Also keep at least one housekeeping cpu onlined to avoid generating
+ * an empty sched_domain span.
+ */
+ for_each_cpu_and(cpu, cpu_online_mask, housekeeping_cpumask(HK_TYPE_DOMAIN)) {
+ if (cpu != work.cpu)
+ return work_on_cpu(cpu, __cpu_down_maps_locked, &work);
+ }
+ return -EBUSY;
+}
+
+static int cpu_down(unsigned int cpu, enum cpuhp_state target)
+{
+ int err;
+
+ cpu_maps_update_begin();
+ err = cpu_down_maps_locked(cpu, target);
+ cpu_maps_update_done();
+ return err;
+}
+
+/**
+ * cpu_device_down - Bring down a cpu device
+ * @dev: Pointer to the cpu device to offline
+ *
+ * This function is meant to be used by device core cpu subsystem only.
+ *
+ * Other subsystems should use remove_cpu() instead.
+ *
+ * Return: %0 on success or a negative errno code
+ */
+int cpu_device_down(struct device *dev)
+{
+ return cpu_down(dev->id, CPUHP_OFFLINE);
+}
+
+int remove_cpu(unsigned int cpu)
+{
+ int ret;
+
+ lock_device_hotplug();
+ ret = device_offline(get_cpu_device(cpu));
+ unlock_device_hotplug();
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(remove_cpu);
+
+void smp_shutdown_nonboot_cpus(unsigned int primary_cpu)
+{
+ unsigned int cpu;
+ int error;
+
+ cpu_maps_update_begin();
+
+ /*
+ * Make certain the cpu I'm about to reboot on is online.
+ *
+ * This is inline to what migrate_to_reboot_cpu() already do.
+ */
+ if (!cpu_online(primary_cpu))
+ primary_cpu = cpumask_first(cpu_online_mask);
+
+ for_each_online_cpu(cpu) {
+ if (cpu == primary_cpu)
+ continue;
+
+ error = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
+ if (error) {
+ pr_err("Failed to offline CPU%d - error=%d",
+ cpu, error);
+ break;
+ }
+ }
+
+ /*
+ * Ensure all but the reboot CPU are offline.
+ */
+ BUG_ON(num_online_cpus() > 1);
+
+ /*
+ * Make sure the CPUs won't be enabled by someone else after this
+ * point. Kexec will reboot to a new kernel shortly resetting
+ * everything along the way.
+ */
+ cpu_hotplug_disabled++;
+
+ cpu_maps_update_done();
+}
+
+#else
+#define takedown_cpu NULL
+#endif /*CONFIG_HOTPLUG_CPU*/
+
+/**
+ * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
+ * @cpu: cpu that just started
+ *
+ * It must be called by the arch code on the new cpu, before the new cpu
+ * enables interrupts and before the "boot" cpu returns from __cpu_up().
+ */
+void notify_cpu_starting(unsigned int cpu)
+{
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+ enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
+
+ rcu_cpu_starting(cpu); /* Enables RCU usage on this CPU. */
+ cpumask_set_cpu(cpu, &cpus_booted_once_mask);
+
+ /*
+ * STARTING must not fail!
+ */
+ cpuhp_invoke_callback_range_nofail(true, cpu, st, target);
+}
+
+/*
+ * Called from the idle task. Wake up the controlling task which brings the
+ * hotplug thread of the upcoming CPU up and then delegates the rest of the
+ * online bringup to the hotplug thread.
+ */
+void cpuhp_online_idle(enum cpuhp_state state)
+{
+ struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
+
+ /* Happens for the boot cpu */
+ if (state != CPUHP_AP_ONLINE_IDLE)
+ return;
+
+ cpuhp_ap_update_sync_state(SYNC_STATE_ONLINE);
+
+ /*
+ * Unpark the stopper thread before we start the idle loop (and start
+ * scheduling); this ensures the stopper task is always available.
+ */
+ stop_machine_unpark(smp_processor_id());
+
+ st->state = CPUHP_AP_ONLINE_IDLE;
+ complete_ap_thread(st, true);
+}
+
+/* Requires cpu_add_remove_lock to be held */
+static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
+{
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+ struct task_struct *idle;
+ int ret = 0;
+
+ cpus_write_lock();
+
+ if (!cpu_present(cpu)) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ /*
+ * The caller of cpu_up() might have raced with another
+ * caller. Nothing to do.
+ */
+ if (st->state >= target)
+ goto out;
+
+ if (st->state == CPUHP_OFFLINE) {
+ /* Let it fail before we try to bring the cpu up */
+ idle = idle_thread_get(cpu);
+ if (IS_ERR(idle)) {
+ ret = PTR_ERR(idle);
+ goto out;
+ }
+
+ /*
+ * Reset stale stack state from the last time this CPU was online.
+ */
+ scs_task_reset(idle);
+ kasan_unpoison_task_stack(idle);
+ }
+
+ cpuhp_tasks_frozen = tasks_frozen;
+
+ cpuhp_set_state(cpu, st, target);
+ /*
+ * If the current CPU state is in the range of the AP hotplug thread,
+ * then we need to kick the thread once more.
+ */
+ if (st->state > CPUHP_BRINGUP_CPU) {
+ ret = cpuhp_kick_ap_work(cpu);
+ /*
+ * The AP side has done the error rollback already. Just
+ * return the error code..
+ */
+ if (ret)
+ goto out;
+ }
+
+ /*
+ * Try to reach the target state. We max out on the BP at
+ * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
+ * responsible for bringing it up to the target state.
+ */
+ target = min((int)target, CPUHP_BRINGUP_CPU);
+ ret = cpuhp_up_callbacks(cpu, st, target);
+out:
+ cpus_write_unlock();
+ arch_smt_update();
+ cpu_up_down_serialize_trainwrecks(tasks_frozen);
+ return ret;
+}
+
+static int cpu_up(unsigned int cpu, enum cpuhp_state target)
+{
+ int err = 0;
+
+ if (!cpu_possible(cpu)) {
+ pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
+ cpu);
+#if defined(CONFIG_IA64)
+ pr_err("please check additional_cpus= boot parameter\n");
+#endif
+ return -EINVAL;
+ }
+
+ err = try_online_node(cpu_to_node(cpu));
+ if (err)
+ return err;
+
+ cpu_maps_update_begin();
+
+ if (cpu_hotplug_disabled) {
+ err = -EBUSY;
+ goto out;
+ }
+ if (!cpu_bootable(cpu)) {
+ err = -EPERM;
+ goto out;
+ }
+
+ err = _cpu_up(cpu, 0, target);
+out:
+ cpu_maps_update_done();
+ return err;
+}
+
+/**
+ * cpu_device_up - Bring up a cpu device
+ * @dev: Pointer to the cpu device to online
+ *
+ * This function is meant to be used by device core cpu subsystem only.
+ *
+ * Other subsystems should use add_cpu() instead.
+ *
+ * Return: %0 on success or a negative errno code
+ */
+int cpu_device_up(struct device *dev)
+{
+ return cpu_up(dev->id, CPUHP_ONLINE);
+}
+
+int add_cpu(unsigned int cpu)
+{
+ int ret;
+
+ lock_device_hotplug();
+ ret = device_online(get_cpu_device(cpu));
+ unlock_device_hotplug();
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(add_cpu);
+
+/**
+ * bringup_hibernate_cpu - Bring up the CPU that we hibernated on
+ * @sleep_cpu: The cpu we hibernated on and should be brought up.
+ *
+ * On some architectures like arm64, we can hibernate on any CPU, but on
+ * wake up the CPU we hibernated on might be offline as a side effect of
+ * using maxcpus= for example.
+ *
+ * Return: %0 on success or a negative errno code
+ */
+int bringup_hibernate_cpu(unsigned int sleep_cpu)
+{
+ int ret;
+
+ if (!cpu_online(sleep_cpu)) {
+ pr_info("Hibernated on a CPU that is offline! Bringing CPU up.\n");
+ ret = cpu_up(sleep_cpu, CPUHP_ONLINE);
+ if (ret) {
+ pr_err("Failed to bring hibernate-CPU up!\n");
+ return ret;
+ }
+ }
+ return 0;
+}
+
+static void __init cpuhp_bringup_mask(const struct cpumask *mask, unsigned int ncpus,
+ enum cpuhp_state target)
+{
+ unsigned int cpu;
+
+ for_each_cpu(cpu, mask) {
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+
+ if (cpu_up(cpu, target) && can_rollback_cpu(st)) {
+ /*
+ * If this failed then cpu_up() might have only
+ * rolled back to CPUHP_BP_KICK_AP for the final
+ * online. Clean it up. NOOP if already rolled back.
+ */
+ WARN_ON(cpuhp_invoke_callback_range(false, cpu, st, CPUHP_OFFLINE));
+ }
+
+ if (!--ncpus)
+ break;
+ }
+}
+
+#ifdef CONFIG_HOTPLUG_PARALLEL
+static bool __cpuhp_parallel_bringup __ro_after_init = true;
+
+static int __init parallel_bringup_parse_param(char *arg)
+{
+ return kstrtobool(arg, &__cpuhp_parallel_bringup);
+}
+early_param("cpuhp.parallel", parallel_bringup_parse_param);
+
+static inline bool cpuhp_smt_aware(void)
+{
+ return cpu_smt_max_threads > 1;
+}
+
+static inline const struct cpumask *cpuhp_get_primary_thread_mask(void)
+{
+ return cpu_primary_thread_mask;
+}
+
+/*
+ * On architectures which have enabled parallel bringup this invokes all BP
+ * prepare states for each of the to be onlined APs first. The last state
+ * sends the startup IPI to the APs. The APs proceed through the low level
+ * bringup code in parallel and then wait for the control CPU to release
+ * them one by one for the final onlining procedure.
+ *
+ * This avoids waiting for each AP to respond to the startup IPI in
+ * CPUHP_BRINGUP_CPU.
+ */
+static bool __init cpuhp_bringup_cpus_parallel(unsigned int ncpus)
+{
+ const struct cpumask *mask = cpu_present_mask;
+
+ if (__cpuhp_parallel_bringup)
+ __cpuhp_parallel_bringup = arch_cpuhp_init_parallel_bringup();
+ if (!__cpuhp_parallel_bringup)
+ return false;
+
+ if (cpuhp_smt_aware()) {
+ const struct cpumask *pmask = cpuhp_get_primary_thread_mask();
+ static struct cpumask tmp_mask __initdata;
+
+ /*
+ * X86 requires to prevent that SMT siblings stopped while
+ * the primary thread does a microcode update for various
+ * reasons. Bring the primary threads up first.
+ */
+ cpumask_and(&tmp_mask, mask, pmask);
+ cpuhp_bringup_mask(&tmp_mask, ncpus, CPUHP_BP_KICK_AP);
+ cpuhp_bringup_mask(&tmp_mask, ncpus, CPUHP_ONLINE);
+ /* Account for the online CPUs */
+ ncpus -= num_online_cpus();
+ if (!ncpus)
+ return true;
+ /* Create the mask for secondary CPUs */
+ cpumask_andnot(&tmp_mask, mask, pmask);
+ mask = &tmp_mask;
+ }
+
+ /* Bring the not-yet started CPUs up */
+ cpuhp_bringup_mask(mask, ncpus, CPUHP_BP_KICK_AP);
+ cpuhp_bringup_mask(mask, ncpus, CPUHP_ONLINE);
+ return true;
+}
+#else
+static inline bool cpuhp_bringup_cpus_parallel(unsigned int ncpus) { return false; }
+#endif /* CONFIG_HOTPLUG_PARALLEL */
+
+void __init bringup_nonboot_cpus(unsigned int setup_max_cpus)
+{
+ /* Try parallel bringup optimization if enabled */
+ if (cpuhp_bringup_cpus_parallel(setup_max_cpus))
+ return;
+
+ /* Full per CPU serialized bringup */
+ cpuhp_bringup_mask(cpu_present_mask, setup_max_cpus, CPUHP_ONLINE);
+}
+
+#ifdef CONFIG_PM_SLEEP_SMP
+static cpumask_var_t frozen_cpus;
+
+int freeze_secondary_cpus(int primary)
+{
+ int cpu, error = 0;
+
+ cpu_maps_update_begin();
+ if (primary == -1) {
+ primary = cpumask_first(cpu_online_mask);
+ if (!housekeeping_cpu(primary, HK_TYPE_TIMER))
+ primary = housekeeping_any_cpu(HK_TYPE_TIMER);
+ } else {
+ if (!cpu_online(primary))
+ primary = cpumask_first(cpu_online_mask);
+ }
+
+ /*
+ * We take down all of the non-boot CPUs in one shot to avoid races
+ * with the userspace trying to use the CPU hotplug at the same time
+ */
+ cpumask_clear(frozen_cpus);
+
+ pr_info("Disabling non-boot CPUs ...\n");
+ for_each_online_cpu(cpu) {
+ if (cpu == primary)
+ continue;
+
+ if (pm_wakeup_pending()) {
+ pr_info("Wakeup pending. Abort CPU freeze\n");
+ error = -EBUSY;
+ break;
+ }
+
+ trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
+ error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
+ trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
+ if (!error)
+ cpumask_set_cpu(cpu, frozen_cpus);
+ else {
+ pr_err("Error taking CPU%d down: %d\n", cpu, error);
+ break;
+ }
+ }
+
+ if (!error)
+ BUG_ON(num_online_cpus() > 1);
+ else
+ pr_err("Non-boot CPUs are not disabled\n");
+
+ /*
+ * Make sure the CPUs won't be enabled by someone else. We need to do
+ * this even in case of failure as all freeze_secondary_cpus() users are
+ * supposed to do thaw_secondary_cpus() on the failure path.
+ */
+ cpu_hotplug_disabled++;
+
+ cpu_maps_update_done();
+ return error;
+}
+
+void __weak arch_thaw_secondary_cpus_begin(void)
+{
+}
+
+void __weak arch_thaw_secondary_cpus_end(void)
+{
+}
+
+void thaw_secondary_cpus(void)
+{
+ int cpu, error;
+
+ /* Allow everyone to use the CPU hotplug again */
+ cpu_maps_update_begin();
+ __cpu_hotplug_enable();
+ if (cpumask_empty(frozen_cpus))
+ goto out;
+
+ pr_info("Enabling non-boot CPUs ...\n");
+
+ arch_thaw_secondary_cpus_begin();
+
+ for_each_cpu(cpu, frozen_cpus) {
+ trace_suspend_resume(TPS("CPU_ON"), cpu, true);
+ error = _cpu_up(cpu, 1, CPUHP_ONLINE);
+ trace_suspend_resume(TPS("CPU_ON"), cpu, false);
+ if (!error) {
+ pr_info("CPU%d is up\n", cpu);
+ continue;
+ }
+ pr_warn("Error taking CPU%d up: %d\n", cpu, error);
+ }
+
+ arch_thaw_secondary_cpus_end();
+
+ cpumask_clear(frozen_cpus);
+out:
+ cpu_maps_update_done();
+}
+
+static int __init alloc_frozen_cpus(void)
+{
+ if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
+ return -ENOMEM;
+ return 0;
+}
+core_initcall(alloc_frozen_cpus);
+
+/*
+ * When callbacks for CPU hotplug notifications are being executed, we must
+ * ensure that the state of the system with respect to the tasks being frozen
+ * or not, as reported by the notification, remains unchanged *throughout the
+ * duration* of the execution of the callbacks.
+ * Hence we need to prevent the freezer from racing with regular CPU hotplug.
+ *
+ * This synchronization is implemented by mutually excluding regular CPU
+ * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
+ * Hibernate notifications.
+ */
+static int
+cpu_hotplug_pm_callback(struct notifier_block *nb,
+ unsigned long action, void *ptr)
+{
+ switch (action) {
+
+ case PM_SUSPEND_PREPARE:
+ case PM_HIBERNATION_PREPARE:
+ cpu_hotplug_disable();
+ break;
+
+ case PM_POST_SUSPEND:
+ case PM_POST_HIBERNATION:
+ cpu_hotplug_enable();
+ break;
+
+ default:
+ return NOTIFY_DONE;
+ }
+
+ return NOTIFY_OK;
+}
+
+
+static int __init cpu_hotplug_pm_sync_init(void)
+{
+ /*
+ * cpu_hotplug_pm_callback has higher priority than x86
+ * bsp_pm_callback which depends on cpu_hotplug_pm_callback
+ * to disable cpu hotplug to avoid cpu hotplug race.
+ */
+ pm_notifier(cpu_hotplug_pm_callback, 0);
+ return 0;
+}
+core_initcall(cpu_hotplug_pm_sync_init);
+
+#endif /* CONFIG_PM_SLEEP_SMP */
+
+int __boot_cpu_id;
+
+#endif /* CONFIG_SMP */
+
+/* Boot processor state steps */
+static struct cpuhp_step cpuhp_hp_states[] = {
+ [CPUHP_OFFLINE] = {
+ .name = "offline",
+ .startup.single = NULL,
+ .teardown.single = NULL,
+ },
+#ifdef CONFIG_SMP
+ [CPUHP_CREATE_THREADS]= {
+ .name = "threads:prepare",
+ .startup.single = smpboot_create_threads,
+ .teardown.single = NULL,
+ .cant_stop = true,
+ },
+ [CPUHP_PERF_PREPARE] = {
+ .name = "perf:prepare",
+ .startup.single = perf_event_init_cpu,
+ .teardown.single = perf_event_exit_cpu,
+ },
+ [CPUHP_RANDOM_PREPARE] = {
+ .name = "random:prepare",
+ .startup.single = random_prepare_cpu,
+ .teardown.single = NULL,
+ },
+ [CPUHP_WORKQUEUE_PREP] = {
+ .name = "workqueue:prepare",
+ .startup.single = workqueue_prepare_cpu,
+ .teardown.single = NULL,
+ },
+ [CPUHP_HRTIMERS_PREPARE] = {
+ .name = "hrtimers:prepare",
+ .startup.single = hrtimers_prepare_cpu,
+ .teardown.single = NULL,
+ },
+ [CPUHP_SMPCFD_PREPARE] = {
+ .name = "smpcfd:prepare",
+ .startup.single = smpcfd_prepare_cpu,
+ .teardown.single = smpcfd_dead_cpu,
+ },
+ [CPUHP_RELAY_PREPARE] = {
+ .name = "relay:prepare",
+ .startup.single = relay_prepare_cpu,
+ .teardown.single = NULL,
+ },
+ [CPUHP_SLAB_PREPARE] = {
+ .name = "slab:prepare",
+ .startup.single = slab_prepare_cpu,
+ .teardown.single = slab_dead_cpu,
+ },
+ [CPUHP_RCUTREE_PREP] = {
+ .name = "RCU/tree:prepare",
+ .startup.single = rcutree_prepare_cpu,
+ .teardown.single = rcutree_dead_cpu,
+ },
+ /*
+ * On the tear-down path, timers_dead_cpu() must be invoked
+ * before blk_mq_queue_reinit_notify() from notify_dead(),
+ * otherwise a RCU stall occurs.
+ */
+ [CPUHP_TIMERS_PREPARE] = {
+ .name = "timers:prepare",
+ .startup.single = timers_prepare_cpu,
+ .teardown.single = timers_dead_cpu,
+ },
+
+#ifdef CONFIG_HOTPLUG_SPLIT_STARTUP
+ /*
+ * Kicks the AP alive. AP will wait in cpuhp_ap_sync_alive() until
+ * the next step will release it.
+ */
+ [CPUHP_BP_KICK_AP] = {
+ .name = "cpu:kick_ap",
+ .startup.single = cpuhp_kick_ap_alive,
+ },
+
+ /*
+ * Waits for the AP to reach cpuhp_ap_sync_alive() and then
+ * releases it for the complete bringup.
+ */
+ [CPUHP_BRINGUP_CPU] = {
+ .name = "cpu:bringup",
+ .startup.single = cpuhp_bringup_ap,
+ .teardown.single = finish_cpu,
+ .cant_stop = true,
+ },
+#else
+ /*
+ * All-in-one CPU bringup state which includes the kick alive.
+ */
+ [CPUHP_BRINGUP_CPU] = {
+ .name = "cpu:bringup",
+ .startup.single = bringup_cpu,
+ .teardown.single = finish_cpu,
+ .cant_stop = true,
+ },
+#endif
+ /* Final state before CPU kills itself */
+ [CPUHP_AP_IDLE_DEAD] = {
+ .name = "idle:dead",
+ },
+ /*
+ * Last state before CPU enters the idle loop to die. Transient state
+ * for synchronization.
+ */
+ [CPUHP_AP_OFFLINE] = {
+ .name = "ap:offline",
+ .cant_stop = true,
+ },
+ /* First state is scheduler control. Interrupts are disabled */
+ [CPUHP_AP_SCHED_STARTING] = {
+ .name = "sched:starting",
+ .startup.single = sched_cpu_starting,
+ .teardown.single = sched_cpu_dying,
+ },
+ [CPUHP_AP_RCUTREE_DYING] = {
+ .name = "RCU/tree:dying",
+ .startup.single = NULL,
+ .teardown.single = rcutree_dying_cpu,
+ },
+ [CPUHP_AP_SMPCFD_DYING] = {
+ .name = "smpcfd:dying",
+ .startup.single = NULL,
+ .teardown.single = smpcfd_dying_cpu,
+ },
+ [CPUHP_AP_HRTIMERS_DYING] = {
+ .name = "hrtimers:dying",
+ .startup.single = NULL,
+ .teardown.single = hrtimers_cpu_dying,
+ },
+
+ /* Entry state on starting. Interrupts enabled from here on. Transient
+ * state for synchronsization */
+ [CPUHP_AP_ONLINE] = {
+ .name = "ap:online",
+ },
+ /*
+ * Handled on control processor until the plugged processor manages
+ * this itself.
+ */
+ [CPUHP_TEARDOWN_CPU] = {
+ .name = "cpu:teardown",
+ .startup.single = NULL,
+ .teardown.single = takedown_cpu,
+ .cant_stop = true,
+ },
+
+ [CPUHP_AP_SCHED_WAIT_EMPTY] = {
+ .name = "sched:waitempty",
+ .startup.single = NULL,
+ .teardown.single = sched_cpu_wait_empty,
+ },
+
+ /* Handle smpboot threads park/unpark */
+ [CPUHP_AP_SMPBOOT_THREADS] = {
+ .name = "smpboot/threads:online",
+ .startup.single = smpboot_unpark_threads,
+ .teardown.single = smpboot_park_threads,
+ },
+ [CPUHP_AP_IRQ_AFFINITY_ONLINE] = {
+ .name = "irq/affinity:online",
+ .startup.single = irq_affinity_online_cpu,
+ .teardown.single = NULL,
+ },
+ [CPUHP_AP_PERF_ONLINE] = {
+ .name = "perf:online",
+ .startup.single = perf_event_init_cpu,
+ .teardown.single = perf_event_exit_cpu,
+ },
+ [CPUHP_AP_WATCHDOG_ONLINE] = {
+ .name = "lockup_detector:online",
+ .startup.single = lockup_detector_online_cpu,
+ .teardown.single = lockup_detector_offline_cpu,
+ },
+ [CPUHP_AP_WORKQUEUE_ONLINE] = {
+ .name = "workqueue:online",
+ .startup.single = workqueue_online_cpu,
+ .teardown.single = workqueue_offline_cpu,
+ },
+ [CPUHP_AP_RANDOM_ONLINE] = {
+ .name = "random:online",
+ .startup.single = random_online_cpu,
+ .teardown.single = NULL,
+ },
+ [CPUHP_AP_RCUTREE_ONLINE] = {
+ .name = "RCU/tree:online",
+ .startup.single = rcutree_online_cpu,
+ .teardown.single = rcutree_offline_cpu,
+ },
+#endif
+ /*
+ * The dynamically registered state space is here
+ */
+
+#ifdef CONFIG_SMP
+ /* Last state is scheduler control setting the cpu active */
+ [CPUHP_AP_ACTIVE] = {
+ .name = "sched:active",
+ .startup.single = sched_cpu_activate,
+ .teardown.single = sched_cpu_deactivate,
+ },
+#endif
+
+ /* CPU is fully up and running. */
+ [CPUHP_ONLINE] = {
+ .name = "online",
+ .startup.single = NULL,
+ .teardown.single = NULL,
+ },
+};
+
+/* Sanity check for callbacks */
+static int cpuhp_cb_check(enum cpuhp_state state)
+{
+ if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
+ return -EINVAL;
+ return 0;
+}
+
+/*
+ * Returns a free for dynamic slot assignment of the Online state. The states
+ * are protected by the cpuhp_slot_states mutex and an empty slot is identified
+ * by having no name assigned.
+ */
+static int cpuhp_reserve_state(enum cpuhp_state state)
+{
+ enum cpuhp_state i, end;
+ struct cpuhp_step *step;
+
+ switch (state) {
+ case CPUHP_AP_ONLINE_DYN:
+ step = cpuhp_hp_states + CPUHP_AP_ONLINE_DYN;
+ end = CPUHP_AP_ONLINE_DYN_END;
+ break;
+ case CPUHP_BP_PREPARE_DYN:
+ step = cpuhp_hp_states + CPUHP_BP_PREPARE_DYN;
+ end = CPUHP_BP_PREPARE_DYN_END;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ for (i = state; i <= end; i++, step++) {
+ if (!step->name)
+ return i;
+ }
+ WARN(1, "No more dynamic states available for CPU hotplug\n");
+ return -ENOSPC;
+}
+
+static int cpuhp_store_callbacks(enum cpuhp_state state, const char *name,
+ int (*startup)(unsigned int cpu),
+ int (*teardown)(unsigned int cpu),
+ bool multi_instance)
+{
+ /* (Un)Install the callbacks for further cpu hotplug operations */
+ struct cpuhp_step *sp;
+ int ret = 0;
+
+ /*
+ * If name is NULL, then the state gets removed.
+ *
+ * CPUHP_AP_ONLINE_DYN and CPUHP_BP_PREPARE_DYN are handed out on
+ * the first allocation from these dynamic ranges, so the removal
+ * would trigger a new allocation and clear the wrong (already
+ * empty) state, leaving the callbacks of the to be cleared state
+ * dangling, which causes wreckage on the next hotplug operation.
+ */
+ if (name && (state == CPUHP_AP_ONLINE_DYN ||
+ state == CPUHP_BP_PREPARE_DYN)) {
+ ret = cpuhp_reserve_state(state);
+ if (ret < 0)
+ return ret;
+ state = ret;
+ }
+ sp = cpuhp_get_step(state);
+ if (name && sp->name)
+ return -EBUSY;
+
+ sp->startup.single = startup;
+ sp->teardown.single = teardown;
+ sp->name = name;
+ sp->multi_instance = multi_instance;
+ INIT_HLIST_HEAD(&sp->list);
+ return ret;
+}
+
+static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
+{
+ return cpuhp_get_step(state)->teardown.single;
+}
+
+/*
+ * Call the startup/teardown function for a step either on the AP or
+ * on the current CPU.
+ */
+static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
+ struct hlist_node *node)
+{
+ struct cpuhp_step *sp = cpuhp_get_step(state);
+ int ret;
+
+ /*
+ * If there's nothing to do, we done.
+ * Relies on the union for multi_instance.
+ */
+ if (cpuhp_step_empty(bringup, sp))
+ return 0;
+ /*
+ * The non AP bound callbacks can fail on bringup. On teardown
+ * e.g. module removal we crash for now.
+ */
+#ifdef CONFIG_SMP
+ if (cpuhp_is_ap_state(state))
+ ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
+ else
+ ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
+#else
+ ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
+#endif
+ BUG_ON(ret && !bringup);
+ return ret;
+}
+
+/*
+ * Called from __cpuhp_setup_state on a recoverable failure.
+ *
+ * Note: The teardown callbacks for rollback are not allowed to fail!
+ */
+static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
+ struct hlist_node *node)
+{
+ int cpu;
+
+ /* Roll back the already executed steps on the other cpus */
+ for_each_present_cpu(cpu) {
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+ int cpustate = st->state;
+
+ if (cpu >= failedcpu)
+ break;
+
+ /* Did we invoke the startup call on that cpu ? */
+ if (cpustate >= state)
+ cpuhp_issue_call(cpu, state, false, node);
+ }
+}
+
+int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state,
+ struct hlist_node *node,
+ bool invoke)
+{
+ struct cpuhp_step *sp;
+ int cpu;
+ int ret;
+
+ lockdep_assert_cpus_held();
+
+ sp = cpuhp_get_step(state);
+ if (sp->multi_instance == false)
+ return -EINVAL;
+
+ mutex_lock(&cpuhp_state_mutex);
+
+ if (!invoke || !sp->startup.multi)
+ goto add_node;
+
+ /*
+ * Try to call the startup callback for each present cpu
+ * depending on the hotplug state of the cpu.
+ */
+ for_each_present_cpu(cpu) {
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+ int cpustate = st->state;
+
+ if (cpustate < state)
+ continue;
+
+ ret = cpuhp_issue_call(cpu, state, true, node);
+ if (ret) {
+ if (sp->teardown.multi)
+ cpuhp_rollback_install(cpu, state, node);
+ goto unlock;
+ }
+ }
+add_node:
+ ret = 0;
+ hlist_add_head(node, &sp->list);
+unlock:
+ mutex_unlock(&cpuhp_state_mutex);
+ return ret;
+}
+
+int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
+ bool invoke)
+{
+ int ret;
+
+ cpus_read_lock();
+ ret = __cpuhp_state_add_instance_cpuslocked(state, node, invoke);
+ cpus_read_unlock();
+ return ret;
+}
+EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
+
+/**
+ * __cpuhp_setup_state_cpuslocked - Setup the callbacks for an hotplug machine state
+ * @state: The state to setup
+ * @name: Name of the step
+ * @invoke: If true, the startup function is invoked for cpus where
+ * cpu state >= @state
+ * @startup: startup callback function
+ * @teardown: teardown callback function
+ * @multi_instance: State is set up for multiple instances which get
+ * added afterwards.
+ *
+ * The caller needs to hold cpus read locked while calling this function.
+ * Return:
+ * On success:
+ * Positive state number if @state is CPUHP_AP_ONLINE_DYN;
+ * 0 for all other states
+ * On failure: proper (negative) error code
+ */
+int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
+ const char *name, bool invoke,
+ int (*startup)(unsigned int cpu),
+ int (*teardown)(unsigned int cpu),
+ bool multi_instance)
+{
+ int cpu, ret = 0;
+ bool dynstate;
+
+ lockdep_assert_cpus_held();
+
+ if (cpuhp_cb_check(state) || !name)
+ return -EINVAL;
+
+ mutex_lock(&cpuhp_state_mutex);
+
+ ret = cpuhp_store_callbacks(state, name, startup, teardown,
+ multi_instance);
+
+ dynstate = state == CPUHP_AP_ONLINE_DYN;
+ if (ret > 0 && dynstate) {
+ state = ret;
+ ret = 0;
+ }
+
+ if (ret || !invoke || !startup)
+ goto out;
+
+ /*
+ * Try to call the startup callback for each present cpu
+ * depending on the hotplug state of the cpu.
+ */
+ for_each_present_cpu(cpu) {
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+ int cpustate = st->state;
+
+ if (cpustate < state)
+ continue;
+
+ ret = cpuhp_issue_call(cpu, state, true, NULL);
+ if (ret) {
+ if (teardown)
+ cpuhp_rollback_install(cpu, state, NULL);
+ cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
+ goto out;
+ }
+ }
+out:
+ mutex_unlock(&cpuhp_state_mutex);
+ /*
+ * If the requested state is CPUHP_AP_ONLINE_DYN, return the
+ * dynamically allocated state in case of success.
+ */
+ if (!ret && dynstate)
+ return state;
+ return ret;
+}
+EXPORT_SYMBOL(__cpuhp_setup_state_cpuslocked);
+
+int __cpuhp_setup_state(enum cpuhp_state state,
+ const char *name, bool invoke,
+ int (*startup)(unsigned int cpu),
+ int (*teardown)(unsigned int cpu),
+ bool multi_instance)
+{
+ int ret;
+
+ cpus_read_lock();
+ ret = __cpuhp_setup_state_cpuslocked(state, name, invoke, startup,
+ teardown, multi_instance);
+ cpus_read_unlock();
+ return ret;
+}
+EXPORT_SYMBOL(__cpuhp_setup_state);
+
+int __cpuhp_state_remove_instance(enum cpuhp_state state,
+ struct hlist_node *node, bool invoke)
+{
+ struct cpuhp_step *sp = cpuhp_get_step(state);
+ int cpu;
+
+ BUG_ON(cpuhp_cb_check(state));
+
+ if (!sp->multi_instance)
+ return -EINVAL;
+
+ cpus_read_lock();
+ mutex_lock(&cpuhp_state_mutex);
+
+ if (!invoke || !cpuhp_get_teardown_cb(state))
+ goto remove;
+ /*
+ * Call the teardown callback for each present cpu depending
+ * on the hotplug state of the cpu. This function is not
+ * allowed to fail currently!
+ */
+ for_each_present_cpu(cpu) {
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+ int cpustate = st->state;
+
+ if (cpustate >= state)
+ cpuhp_issue_call(cpu, state, false, node);
+ }
+
+remove:
+ hlist_del(node);
+ mutex_unlock(&cpuhp_state_mutex);
+ cpus_read_unlock();
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
+
+/**
+ * __cpuhp_remove_state_cpuslocked - Remove the callbacks for an hotplug machine state
+ * @state: The state to remove
+ * @invoke: If true, the teardown function is invoked for cpus where
+ * cpu state >= @state
+ *
+ * The caller needs to hold cpus read locked while calling this function.
+ * The teardown callback is currently not allowed to fail. Think
+ * about module removal!
+ */
+void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke)
+{
+ struct cpuhp_step *sp = cpuhp_get_step(state);
+ int cpu;
+
+ BUG_ON(cpuhp_cb_check(state));
+
+ lockdep_assert_cpus_held();
+
+ mutex_lock(&cpuhp_state_mutex);
+ if (sp->multi_instance) {
+ WARN(!hlist_empty(&sp->list),
+ "Error: Removing state %d which has instances left.\n",
+ state);
+ goto remove;
+ }
+
+ if (!invoke || !cpuhp_get_teardown_cb(state))
+ goto remove;
+
+ /*
+ * Call the teardown callback for each present cpu depending
+ * on the hotplug state of the cpu. This function is not
+ * allowed to fail currently!
+ */
+ for_each_present_cpu(cpu) {
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+ int cpustate = st->state;
+
+ if (cpustate >= state)
+ cpuhp_issue_call(cpu, state, false, NULL);
+ }
+remove:
+ cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
+ mutex_unlock(&cpuhp_state_mutex);
+}
+EXPORT_SYMBOL(__cpuhp_remove_state_cpuslocked);
+
+void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
+{
+ cpus_read_lock();
+ __cpuhp_remove_state_cpuslocked(state, invoke);
+ cpus_read_unlock();
+}
+EXPORT_SYMBOL(__cpuhp_remove_state);
+
+#ifdef CONFIG_HOTPLUG_SMT
+static void cpuhp_offline_cpu_device(unsigned int cpu)
+{
+ struct device *dev = get_cpu_device(cpu);
+
+ dev->offline = true;
+ /* Tell user space about the state change */
+ kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
+}
+
+static void cpuhp_online_cpu_device(unsigned int cpu)
+{
+ struct device *dev = get_cpu_device(cpu);
+
+ dev->offline = false;
+ /* Tell user space about the state change */
+ kobject_uevent(&dev->kobj, KOBJ_ONLINE);
+}
+
+int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
+{
+ int cpu, ret = 0;
+
+ cpu_maps_update_begin();
+ for_each_online_cpu(cpu) {
+ if (topology_is_primary_thread(cpu))
+ continue;
+ /*
+ * Disable can be called with CPU_SMT_ENABLED when changing
+ * from a higher to lower number of SMT threads per core.
+ */
+ if (ctrlval == CPU_SMT_ENABLED && cpu_smt_thread_allowed(cpu))
+ continue;
+ ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
+ if (ret)
+ break;
+ /*
+ * As this needs to hold the cpu maps lock it's impossible
+ * to call device_offline() because that ends up calling
+ * cpu_down() which takes cpu maps lock. cpu maps lock
+ * needs to be held as this might race against in kernel
+ * abusers of the hotplug machinery (thermal management).
+ *
+ * So nothing would update device:offline state. That would
+ * leave the sysfs entry stale and prevent onlining after
+ * smt control has been changed to 'off' again. This is
+ * called under the sysfs hotplug lock, so it is properly
+ * serialized against the regular offline usage.
+ */
+ cpuhp_offline_cpu_device(cpu);
+ }
+ if (!ret)
+ cpu_smt_control = ctrlval;
+ cpu_maps_update_done();
+ return ret;
+}
+
+int cpuhp_smt_enable(void)
+{
+ int cpu, ret = 0;
+
+ cpu_maps_update_begin();
+ cpu_smt_control = CPU_SMT_ENABLED;
+ for_each_present_cpu(cpu) {
+ /* Skip online CPUs and CPUs on offline nodes */
+ if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))
+ continue;
+ if (!cpu_smt_thread_allowed(cpu))
+ continue;
+ ret = _cpu_up(cpu, 0, CPUHP_ONLINE);
+ if (ret)
+ break;
+ /* See comment in cpuhp_smt_disable() */
+ cpuhp_online_cpu_device(cpu);
+ }
+ cpu_maps_update_done();
+ return ret;
+}
+#endif
+
+#if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
+static ssize_t state_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
+
+ return sprintf(buf, "%d\n", st->state);
+}
+static DEVICE_ATTR_RO(state);
+
+static ssize_t target_store(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
+ struct cpuhp_step *sp;
+ int target, ret;
+
+ ret = kstrtoint(buf, 10, &target);
+ if (ret)
+ return ret;
+
+#ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
+ if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
+ return -EINVAL;
+#else
+ if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
+ return -EINVAL;
+#endif
+
+ ret = lock_device_hotplug_sysfs();
+ if (ret)
+ return ret;
+
+ mutex_lock(&cpuhp_state_mutex);
+ sp = cpuhp_get_step(target);
+ ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
+ mutex_unlock(&cpuhp_state_mutex);
+ if (ret)
+ goto out;
+
+ if (st->state < target)
+ ret = cpu_up(dev->id, target);
+ else if (st->state > target)
+ ret = cpu_down(dev->id, target);
+ else if (WARN_ON(st->target != target))
+ st->target = target;
+out:
+ unlock_device_hotplug();
+ return ret ? ret : count;
+}
+
+static ssize_t target_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
+
+ return sprintf(buf, "%d\n", st->target);
+}
+static DEVICE_ATTR_RW(target);
+
+static ssize_t fail_store(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
+ struct cpuhp_step *sp;
+ int fail, ret;
+
+ ret = kstrtoint(buf, 10, &fail);
+ if (ret)
+ return ret;
+
+ if (fail == CPUHP_INVALID) {
+ st->fail = fail;
+ return count;
+ }
+
+ if (fail < CPUHP_OFFLINE || fail > CPUHP_ONLINE)
+ return -EINVAL;
+
+ /*
+ * Cannot fail STARTING/DYING callbacks.
+ */
+ if (cpuhp_is_atomic_state(fail))
+ return -EINVAL;
+
+ /*
+ * DEAD callbacks cannot fail...
+ * ... neither can CPUHP_BRINGUP_CPU during hotunplug. The latter
+ * triggering STARTING callbacks, a failure in this state would
+ * hinder rollback.
+ */
+ if (fail <= CPUHP_BRINGUP_CPU && st->state > CPUHP_BRINGUP_CPU)
+ return -EINVAL;
+
+ /*
+ * Cannot fail anything that doesn't have callbacks.
+ */
+ mutex_lock(&cpuhp_state_mutex);
+ sp = cpuhp_get_step(fail);
+ if (!sp->startup.single && !sp->teardown.single)
+ ret = -EINVAL;
+ mutex_unlock(&cpuhp_state_mutex);
+ if (ret)
+ return ret;
+
+ st->fail = fail;
+
+ return count;
+}
+
+static ssize_t fail_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
+
+ return sprintf(buf, "%d\n", st->fail);
+}
+
+static DEVICE_ATTR_RW(fail);
+
+static struct attribute *cpuhp_cpu_attrs[] = {
+ &dev_attr_state.attr,
+ &dev_attr_target.attr,
+ &dev_attr_fail.attr,
+ NULL
+};
+
+static const struct attribute_group cpuhp_cpu_attr_group = {
+ .attrs = cpuhp_cpu_attrs,
+ .name = "hotplug",
+ NULL
+};
+
+static ssize_t states_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ ssize_t cur, res = 0;
+ int i;
+
+ mutex_lock(&cpuhp_state_mutex);
+ for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
+ struct cpuhp_step *sp = cpuhp_get_step(i);
+
+ if (sp->name) {
+ cur = sprintf(buf, "%3d: %s\n", i, sp->name);
+ buf += cur;
+ res += cur;
+ }
+ }
+ mutex_unlock(&cpuhp_state_mutex);
+ return res;
+}
+static DEVICE_ATTR_RO(states);
+
+static struct attribute *cpuhp_cpu_root_attrs[] = {
+ &dev_attr_states.attr,
+ NULL
+};
+
+static const struct attribute_group cpuhp_cpu_root_attr_group = {
+ .attrs = cpuhp_cpu_root_attrs,
+ .name = "hotplug",
+ NULL
+};
+
+#ifdef CONFIG_HOTPLUG_SMT
+
+static bool cpu_smt_num_threads_valid(unsigned int threads)
+{
+ if (IS_ENABLED(CONFIG_SMT_NUM_THREADS_DYNAMIC))
+ return threads >= 1 && threads <= cpu_smt_max_threads;
+ return threads == 1 || threads == cpu_smt_max_threads;
+}
+
+static ssize_t
+__store_smt_control(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ int ctrlval, ret, num_threads, orig_threads;
+ bool force_off;
+
+ if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
+ return -EPERM;
+
+ if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
+ return -ENODEV;
+
+ if (sysfs_streq(buf, "on")) {
+ ctrlval = CPU_SMT_ENABLED;
+ num_threads = cpu_smt_max_threads;
+ } else if (sysfs_streq(buf, "off")) {
+ ctrlval = CPU_SMT_DISABLED;
+ num_threads = 1;
+ } else if (sysfs_streq(buf, "forceoff")) {
+ ctrlval = CPU_SMT_FORCE_DISABLED;
+ num_threads = 1;
+ } else if (kstrtoint(buf, 10, &num_threads) == 0) {
+ if (num_threads == 1)
+ ctrlval = CPU_SMT_DISABLED;
+ else if (cpu_smt_num_threads_valid(num_threads))
+ ctrlval = CPU_SMT_ENABLED;
+ else
+ return -EINVAL;
+ } else {
+ return -EINVAL;
+ }
+
+ ret = lock_device_hotplug_sysfs();
+ if (ret)
+ return ret;
+
+ orig_threads = cpu_smt_num_threads;
+ cpu_smt_num_threads = num_threads;
+
+ force_off = ctrlval != cpu_smt_control && ctrlval == CPU_SMT_FORCE_DISABLED;
+
+ if (num_threads > orig_threads)
+ ret = cpuhp_smt_enable();
+ else if (num_threads < orig_threads || force_off)
+ ret = cpuhp_smt_disable(ctrlval);
+
+ unlock_device_hotplug();
+ return ret ? ret : count;
+}
+
+#else /* !CONFIG_HOTPLUG_SMT */
+static ssize_t
+__store_smt_control(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ return -ENODEV;
+}
+#endif /* CONFIG_HOTPLUG_SMT */
+
+static const char *smt_states[] = {
+ [CPU_SMT_ENABLED] = "on",
+ [CPU_SMT_DISABLED] = "off",
+ [CPU_SMT_FORCE_DISABLED] = "forceoff",
+ [CPU_SMT_NOT_SUPPORTED] = "notsupported",
+ [CPU_SMT_NOT_IMPLEMENTED] = "notimplemented",
+};
+
+static ssize_t control_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ const char *state = smt_states[cpu_smt_control];
+
+#ifdef CONFIG_HOTPLUG_SMT
+ /*
+ * If SMT is enabled but not all threads are enabled then show the
+ * number of threads. If all threads are enabled show "on". Otherwise
+ * show the state name.
+ */
+ if (cpu_smt_control == CPU_SMT_ENABLED &&
+ cpu_smt_num_threads != cpu_smt_max_threads)
+ return sysfs_emit(buf, "%d\n", cpu_smt_num_threads);
+#endif
+
+ return snprintf(buf, PAGE_SIZE - 2, "%s\n", state);
+}
+
+static ssize_t control_store(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ return __store_smt_control(dev, attr, buf, count);
+}
+static DEVICE_ATTR_RW(control);
+
+static ssize_t active_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ return snprintf(buf, PAGE_SIZE - 2, "%d\n", sched_smt_active());
+}
+static DEVICE_ATTR_RO(active);
+
+static struct attribute *cpuhp_smt_attrs[] = {
+ &dev_attr_control.attr,
+ &dev_attr_active.attr,
+ NULL
+};
+
+static const struct attribute_group cpuhp_smt_attr_group = {
+ .attrs = cpuhp_smt_attrs,
+ .name = "smt",
+ NULL
+};
+
+static int __init cpu_smt_sysfs_init(void)
+{
+ struct device *dev_root;
+ int ret = -ENODEV;
+
+ dev_root = bus_get_dev_root(&cpu_subsys);
+ if (dev_root) {
+ ret = sysfs_create_group(&dev_root->kobj, &cpuhp_smt_attr_group);
+ put_device(dev_root);
+ }
+ return ret;
+}
+
+static int __init cpuhp_sysfs_init(void)
+{
+ struct device *dev_root;
+ int cpu, ret;
+
+ ret = cpu_smt_sysfs_init();
+ if (ret)
+ return ret;
+
+ dev_root = bus_get_dev_root(&cpu_subsys);
+ if (dev_root) {
+ ret = sysfs_create_group(&dev_root->kobj, &cpuhp_cpu_root_attr_group);
+ put_device(dev_root);
+ if (ret)
+ return ret;
+ }
+
+ for_each_possible_cpu(cpu) {
+ struct device *dev = get_cpu_device(cpu);
+
+ if (!dev)
+ continue;
+ ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
+ if (ret)
+ return ret;
+ }
+ return 0;
+}
+device_initcall(cpuhp_sysfs_init);
+#endif /* CONFIG_SYSFS && CONFIG_HOTPLUG_CPU */
+
+/*
+ * cpu_bit_bitmap[] is a special, "compressed" data structure that
+ * represents all NR_CPUS bits binary values of 1<<nr.
+ *
+ * It is used by cpumask_of() to get a constant address to a CPU
+ * mask value that has a single bit set only.
+ */
+
+/* cpu_bit_bitmap[0] is empty - so we can back into it */
+#define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
+#define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
+#define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
+#define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
+
+const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
+
+ MASK_DECLARE_8(0), MASK_DECLARE_8(8),
+ MASK_DECLARE_8(16), MASK_DECLARE_8(24),
+#if BITS_PER_LONG > 32
+ MASK_DECLARE_8(32), MASK_DECLARE_8(40),
+ MASK_DECLARE_8(48), MASK_DECLARE_8(56),
+#endif
+};
+EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
+
+const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
+EXPORT_SYMBOL(cpu_all_bits);
+
+#ifdef CONFIG_INIT_ALL_POSSIBLE
+struct cpumask __cpu_possible_mask __read_mostly
+ = {CPU_BITS_ALL};
+#else
+struct cpumask __cpu_possible_mask __read_mostly;
+#endif
+EXPORT_SYMBOL(__cpu_possible_mask);
+
+struct cpumask __cpu_online_mask __read_mostly;
+EXPORT_SYMBOL(__cpu_online_mask);
+
+struct cpumask __cpu_present_mask __read_mostly;
+EXPORT_SYMBOL(__cpu_present_mask);
+
+struct cpumask __cpu_active_mask __read_mostly;
+EXPORT_SYMBOL(__cpu_active_mask);
+
+struct cpumask __cpu_dying_mask __read_mostly;
+EXPORT_SYMBOL(__cpu_dying_mask);
+
+atomic_t __num_online_cpus __read_mostly;
+EXPORT_SYMBOL(__num_online_cpus);
+
+void init_cpu_present(const struct cpumask *src)
+{
+ cpumask_copy(&__cpu_present_mask, src);
+}
+
+void init_cpu_possible(const struct cpumask *src)
+{
+ cpumask_copy(&__cpu_possible_mask, src);
+}
+
+void init_cpu_online(const struct cpumask *src)
+{
+ cpumask_copy(&__cpu_online_mask, src);
+}
+
+void set_cpu_online(unsigned int cpu, bool online)
+{
+ /*
+ * atomic_inc/dec() is required to handle the horrid abuse of this
+ * function by the reboot and kexec code which invoke it from
+ * IPI/NMI broadcasts when shutting down CPUs. Invocation from
+ * regular CPU hotplug is properly serialized.
+ *
+ * Note, that the fact that __num_online_cpus is of type atomic_t
+ * does not protect readers which are not serialized against
+ * concurrent hotplug operations.
+ */
+ if (online) {
+ if (!cpumask_test_and_set_cpu(cpu, &__cpu_online_mask))
+ atomic_inc(&__num_online_cpus);
+ } else {
+ if (cpumask_test_and_clear_cpu(cpu, &__cpu_online_mask))
+ atomic_dec(&__num_online_cpus);
+ }
+}
+
+/*
+ * Activate the first processor.
+ */
+void __init boot_cpu_init(void)
+{
+ int cpu = smp_processor_id();
+
+ /* Mark the boot cpu "present", "online" etc for SMP and UP case */
+ set_cpu_online(cpu, true);
+ set_cpu_active(cpu, true);
+ set_cpu_present(cpu, true);
+ set_cpu_possible(cpu, true);
+
+#ifdef CONFIG_SMP
+ __boot_cpu_id = cpu;
+#endif
+}
+
+/*
+ * Must be called _AFTER_ setting up the per_cpu areas
+ */
+void __init boot_cpu_hotplug_init(void)
+{
+#ifdef CONFIG_SMP
+ cpumask_set_cpu(smp_processor_id(), &cpus_booted_once_mask);
+ atomic_set(this_cpu_ptr(&cpuhp_state.ap_sync_state), SYNC_STATE_ONLINE);
+#endif
+ this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);
+ this_cpu_write(cpuhp_state.target, CPUHP_ONLINE);
+}
+
+/*
+ * These are used for a global "mitigations=" cmdline option for toggling
+ * optional CPU mitigations.
+ */
+enum cpu_mitigations {
+ CPU_MITIGATIONS_OFF,
+ CPU_MITIGATIONS_AUTO,
+ CPU_MITIGATIONS_AUTO_NOSMT,
+};
+
+static enum cpu_mitigations cpu_mitigations __ro_after_init =
+ CPU_MITIGATIONS_AUTO;
+
+static int __init mitigations_parse_cmdline(char *arg)
+{
+ if (!strcmp(arg, "off"))
+ cpu_mitigations = CPU_MITIGATIONS_OFF;
+ else if (!strcmp(arg, "auto"))
+ cpu_mitigations = CPU_MITIGATIONS_AUTO;
+ else if (!strcmp(arg, "auto,nosmt"))
+ cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT;
+ else
+ pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n",
+ arg);
+
+ return 0;
+}
+early_param("mitigations", mitigations_parse_cmdline);
+
+/* mitigations=off */
+bool cpu_mitigations_off(void)
+{
+ return cpu_mitigations == CPU_MITIGATIONS_OFF;
+}
+EXPORT_SYMBOL_GPL(cpu_mitigations_off);
+
+/* mitigations=auto,nosmt */
+bool cpu_mitigations_auto_nosmt(void)
+{
+ return cpu_mitigations == CPU_MITIGATIONS_AUTO_NOSMT;
+}
+EXPORT_SYMBOL_GPL(cpu_mitigations_auto_nosmt);