/* CPU control. * (C) 2001, 2002, 2003, 2004 Rusty Russell * * This code is licenced under the GPL. */ #include <linux/proc_fs.h> #include <linux/smp.h> #include <linux/init.h> #include <linux/notifier.h> #include <linux/sched.h> #include <linux/unistd.h> #include <linux/cpu.h> #include <linux/oom.h> #include <linux/rcupdate.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/smpboot.h> #include <trace/events/power.h> #define CREATE_TRACE_POINTS #include <trace/events/cpuhp.h> #include "smpboot.h" /** * cpuhp_cpu_state - Per cpu hotplug state storage * @state: The current cpu state * @target: The target state * @thread: Pointer to the hotplug thread * @should_run: Thread should execute * @rollback: Perform a rollback * @cb_stat: The state for a single callback (install/uninstall) * @cb: Single callback function (install/uninstall) * @result: Result of the operation * @done: Signal completion to the issuer of the task */ struct cpuhp_cpu_state { enum cpuhp_state state; enum cpuhp_state target; #ifdef CONFIG_SMP struct task_struct *thread; bool should_run; bool rollback; enum cpuhp_state cb_state; int (*cb)(unsigned int cpu); int result; struct completion done; #endif }; static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state); /** * cpuhp_step - Hotplug state machine step * @name: Name of the step * @startup: Startup function of the step * @teardown: Teardown function of the step * @skip_onerr: Do not invoke the functions on error rollback * Will go away once the notifiers are gone * @cant_stop: Bringup/teardown can't be stopped at this step */ struct cpuhp_step { const char *name; int (*startup)(unsigned int cpu); int (*teardown)(unsigned int cpu); bool skip_onerr; bool cant_stop; }; static DEFINE_MUTEX(cpuhp_state_mutex); static struct cpuhp_step cpuhp_bp_states[]; static struct cpuhp_step cpuhp_ap_states[]; /** * cpuhp_invoke_callback _ Invoke the callbacks for a given state * @cpu: The cpu for which the callback should be invoked * @step: The step in the state machine * @cb: The callback function to invoke * * Called from cpu hotplug and from the state register machinery */ static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state step, int (*cb)(unsigned int)) { struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); int ret = 0; if (cb) { trace_cpuhp_enter(cpu, st->target, step, cb); ret = cb(cpu); trace_cpuhp_exit(cpu, st->state, step, ret); } return ret; } #ifdef CONFIG_SMP /* 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. * The APIs cpu_notifier_register_begin/done() must be used to protect CPU * hotplug callback (un)registration performed using __register_cpu_notifier() * or __unregister_cpu_notifier(). */ void cpu_maps_update_begin(void) { mutex_lock(&cpu_add_remove_lock); } EXPORT_SYMBOL(cpu_notifier_register_begin); void cpu_maps_update_done(void) { mutex_unlock(&cpu_add_remove_lock); } EXPORT_SYMBOL(cpu_notifier_register_done); static RAW_NOTIFIER_HEAD(cpu_chain); /* 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 static struct { struct task_struct *active_writer; /* wait queue to wake up the active_writer */ wait_queue_head_t wq; /* verifies that no writer will get active while readers are active */ struct mutex lock; /* * Also blocks the new readers during * an ongoing cpu hotplug operation. */ atomic_t refcount; #ifdef CONFIG_DEBUG_LOCK_ALLOC struct lockdep_map dep_map; #endif } cpu_hotplug = { .active_writer = NULL, .wq = __WAIT_QUEUE_HEAD_INITIALIZER(cpu_hotplug.wq), .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock), #ifdef CONFIG_DEBUG_LOCK_ALLOC .dep_map = {.name = "cpu_hotplug.lock" }, #endif }; /* Lockdep annotations for get/put_online_cpus() and cpu_hotplug_begin/end() */ #define cpuhp_lock_acquire_read() lock_map_acquire_read(&cpu_hotplug.dep_map) #define cpuhp_lock_acquire_tryread() \ lock_map_acquire_tryread(&cpu_hotplug.dep_map) #define cpuhp_lock_acquire() lock_map_acquire(&cpu_hotplug.dep_map) #define cpuhp_lock_release() lock_map_release(&cpu_hotplug.dep_map) void get_online_cpus(void) { might_sleep(); if (cpu_hotplug.active_writer == current) return; cpuhp_lock_acquire_read(); mutex_lock(&cpu_hotplug.lock); atomic_inc(&cpu_hotplug.refcount); mutex_unlock(&cpu_hotplug.lock); } EXPORT_SYMBOL_GPL(get_online_cpus); void put_online_cpus(void) { int refcount; if (cpu_hotplug.active_writer == current) return; refcount = atomic_dec_return(&cpu_hotplug.refcount); if (WARN_ON(refcount < 0)) /* try to fix things up */ atomic_inc(&cpu_hotplug.refcount); if (refcount <= 0 && waitqueue_active(&cpu_hotplug.wq)) wake_up(&cpu_hotplug.wq); cpuhp_lock_release(); } EXPORT_SYMBOL_GPL(put_online_cpus); /* * This ensures that the hotplug operation can begin only when the * refcount goes to zero. * * Note that during a cpu-hotplug operation, the new readers, if any, * will be blocked by the cpu_hotplug.lock * * Since cpu_hotplug_begin() is always called after invoking * cpu_maps_update_begin(), we can be sure that only one writer is active. * * Note that theoretically, there is a possibility of a livelock: * - Refcount goes to zero, last reader wakes up the sleeping * writer. * - Last reader unlocks the cpu_hotplug.lock. * - A new reader arrives at this moment, bumps up the refcount. * - The writer acquires the cpu_hotplug.lock finds the refcount * non zero and goes to sleep again. * * However, this is very difficult to achieve in practice since * get_online_cpus() not an api which is called all that often. * */ void cpu_hotplug_begin(void) { DEFINE_WAIT(wait); cpu_hotplug.active_writer = current; cpuhp_lock_acquire(); for (;;) { mutex_lock(&cpu_hotplug.lock); prepare_to_wait(&cpu_hotplug.wq, &wait, TASK_UNINTERRUPTIBLE); if (likely(!atomic_read(&cpu_hotplug.refcount))) break; mutex_unlock(&cpu_hotplug.lock); schedule(); } finish_wait(&cpu_hotplug.wq, &wait); } void cpu_hotplug_done(void) { cpu_hotplug.active_writer = NULL; mutex_unlock(&cpu_hotplug.lock); cpuhp_lock_release(); } /* * 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); void cpu_hotplug_enable(void) { cpu_maps_update_begin(); WARN_ON(--cpu_hotplug_disabled < 0); cpu_maps_update_done(); } EXPORT_SYMBOL_GPL(cpu_hotplug_enable); #endif /* CONFIG_HOTPLUG_CPU */ /* Need to know about CPUs going up/down? */ int register_cpu_notifier(struct notifier_block *nb) { int ret; cpu_maps_update_begin(); ret = raw_notifier_chain_register(&cpu_chain, nb); cpu_maps_update_done(); return ret; } int __register_cpu_notifier(struct notifier_block *nb) { return raw_notifier_chain_register(&cpu_chain, nb); } static int __cpu_notify(unsigned long val, unsigned int cpu, int nr_to_call, int *nr_calls) { unsigned long mod = cpuhp_tasks_frozen ? CPU_TASKS_FROZEN : 0; void *hcpu = (void *)(long)cpu; int ret; ret = __raw_notifier_call_chain(&cpu_chain, val | mod, hcpu, nr_to_call, nr_calls); return notifier_to_errno(ret); } static int cpu_notify(unsigned long val, unsigned int cpu) { return __cpu_notify(val, cpu, -1, NULL); } static void cpu_notify_nofail(unsigned long val, unsigned int cpu) { BUG_ON(cpu_notify(val, cpu)); } /* Notifier wrappers for transitioning to state machine */ static int notify_prepare(unsigned int cpu) { int nr_calls = 0; int ret; ret = __cpu_notify(CPU_UP_PREPARE, cpu, -1, &nr_calls); if (ret) { nr_calls--; printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n", __func__, cpu); __cpu_notify(CPU_UP_CANCELED, cpu, nr_calls, NULL); } return ret; } static int notify_online(unsigned int cpu) { cpu_notify(CPU_ONLINE, cpu); return 0; } static int notify_starting(unsigned int cpu) { cpu_notify(CPU_STARTING, cpu); return 0; } static int bringup_wait_for_ap(unsigned int cpu) { struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); wait_for_completion(&st->done); return st->result; } static int bringup_cpu(unsigned int cpu) { struct task_struct *idle = idle_thread_get(cpu); int ret; /* Arch-specific enabling code. */ ret = __cpu_up(cpu, idle); if (ret) { cpu_notify(CPU_UP_CANCELED, cpu); return ret; } ret = bringup_wait_for_ap(cpu); BUG_ON(!cpu_online(cpu)); return ret; } /* * Hotplug state machine related functions */ static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st, struct cpuhp_step *steps) { for (st->state++; st->state < st->target; st->state++) { struct cpuhp_step *step = steps + st->state; if (!step->skip_onerr) cpuhp_invoke_callback(cpu, st->state, step->startup); } } static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st, struct cpuhp_step *steps, enum cpuhp_state target) { enum cpuhp_state prev_state = st->state; int ret = 0; for (; st->state > target; st->state--) { struct cpuhp_step *step = steps + st->state; ret = cpuhp_invoke_callback(cpu, st->state, step->teardown); if (ret) { st->target = prev_state; undo_cpu_down(cpu, st, steps); break; } } return ret; } static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st, struct cpuhp_step *steps) { for (st->state--; st->state > st->target; st->state--) { struct cpuhp_step *step = steps + st->state; if (!step->skip_onerr) cpuhp_invoke_callback(cpu, st->state, step->teardown); } } static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st, struct cpuhp_step *steps, enum cpuhp_state target) { enum cpuhp_state prev_state = st->state; int ret = 0; while (st->state < target) { struct cpuhp_step *step; st->state++; step = steps + st->state; ret = cpuhp_invoke_callback(cpu, st->state, step->startup); if (ret) { st->target = prev_state; undo_cpu_up(cpu, st, steps); break; } } return ret; } /* * The cpu hotplug threads manage the bringup and teardown of the cpus */ static void cpuhp_create(unsigned int cpu) { struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); init_completion(&st->done); } static int cpuhp_should_run(unsigned int cpu) { struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state); return st->should_run; } /* Execute the teardown callbacks. Used to be CPU_DOWN_PREPARE */ static int cpuhp_ap_offline(unsigned int cpu, struct cpuhp_cpu_state *st) { enum cpuhp_state target = max((int)st->target, CPUHP_TEARDOWN_CPU); return cpuhp_down_callbacks(cpu, st, cpuhp_ap_states, target); } /* Execute the online startup callbacks. Used to be CPU_ONLINE */ static int cpuhp_ap_online(unsigned int cpu, struct cpuhp_cpu_state *st) { return cpuhp_up_callbacks(cpu, st, cpuhp_ap_states, st->target); } /* * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke * callbacks when a state gets [un]installed at runtime. */ static void cpuhp_thread_fun(unsigned int cpu) { struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state); int ret = 0; /* * Paired with the mb() in cpuhp_kick_ap_work and * cpuhp_invoke_ap_callback, so the work set is consistent visible. */ smp_mb(); if (!st->should_run) return; st->should_run = false; /* Single callback invocation for [un]install ? */ if (st->cb) { if (st->cb_state < CPUHP_AP_ONLINE) { local_irq_disable(); ret = cpuhp_invoke_callback(cpu, st->cb_state, st->cb); local_irq_enable(); } else { ret = cpuhp_invoke_callback(cpu, st->cb_state, st->cb); } } else if (st->rollback) { BUG_ON(st->state < CPUHP_AP_ONLINE_IDLE); undo_cpu_down(cpu, st, cpuhp_ap_states); /* * This is a momentary workaround to keep the notifier users * happy. Will go away once we got rid of the notifiers. */ cpu_notify_nofail(CPU_DOWN_FAILED, cpu); st->rollback = false; } else { /* Cannot happen .... */ BUG_ON(st->state < CPUHP_AP_ONLINE_IDLE); /* Regular hotplug work */ if (st->state < st->target) ret = cpuhp_ap_online(cpu, st); else if (st->state > st->target) ret = cpuhp_ap_offline(cpu, st); } st->result = ret; complete(&st->done); } /* Invoke a single callback on a remote cpu */ static int cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, int (*cb)(unsigned int)) { struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); if (!cpu_online(cpu)) return 0; /* * 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, cb); st->cb_state = state; st->cb = cb; /* * 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_completion(&st->done); return st->result; } /* Regular hotplug invocation of the AP hotplug thread */ static void __cpuhp_kick_ap_work(struct cpuhp_cpu_state *st) { st->result = 0; st->cb = NULL; /* * 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); } static int cpuhp_kick_ap_work(unsigned int cpu) { struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); enum cpuhp_state state = st->state; trace_cpuhp_enter(cpu, st->target, state, cpuhp_kick_ap_work); __cpuhp_kick_ap_work(st); wait_for_completion(&st->done); trace_cpuhp_exit(cpu, st->state, state, st->result); return st->result; } static struct smp_hotplug_thread cpuhp_threads = { .store = &cpuhp_state.thread, .create = &cpuhp_create, .thread_should_run = cpuhp_should_run, .thread_fn = cpuhp_thread_fun, .thread_comm = "cpuhp/%u", .selfparking = true, }; void __init cpuhp_threads_init(void) { BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads)); kthread_unpark(this_cpu_read(cpuhp_state.thread)); } #ifdef CONFIG_HOTPLUG_CPU EXPORT_SYMBOL(register_cpu_notifier); EXPORT_SYMBOL(__register_cpu_notifier); void unregister_cpu_notifier(struct notifier_block *nb) { cpu_maps_update_begin(); raw_notifier_chain_unregister(&cpu_chain, nb); cpu_maps_update_done(); } EXPORT_SYMBOL(unregister_cpu_notifier); void __unregister_cpu_notifier(struct notifier_block *nb) { raw_notifier_chain_unregister(&cpu_chain, nb); } EXPORT_SYMBOL(__unregister_cpu_notifier); /** * 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; cpumask_clear_cpu(cpu, mm_cpumask(t->mm)); task_unlock(t); } rcu_read_unlock(); } static inline void check_for_tasks(int dead_cpu) { struct task_struct *g, *p; read_lock(&tasklist_lock); for_each_process_thread(g, p) { if (!p->on_rq) continue; /* * We do the check with unlocked task_rq(p)->lock. * Order the reading to do not warn about a task, * which was running on this cpu in the past, and * it's just been woken on another cpu. */ rmb(); if (task_cpu(p) != dead_cpu) continue; pr_warn("Task %s (pid=%d) is on cpu %d (state=%ld, flags=%x)\n", p->comm, task_pid_nr(p), dead_cpu, p->state, p->flags); } read_unlock(&tasklist_lock); } static int notify_down_prepare(unsigned int cpu) { int err, nr_calls = 0; err = __cpu_notify(CPU_DOWN_PREPARE, cpu, -1, &nr_calls); if (err) { nr_calls--; __cpu_notify(CPU_DOWN_FAILED, cpu, nr_calls, NULL); pr_warn("%s: attempt to take down CPU %u failed\n", __func__, cpu); } return err; } static int notify_dying(unsigned int cpu) { cpu_notify(CPU_DYING, cpu); return 0; } /* 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; /* Invoke the former CPU_DYING callbacks */ for (; st->state > target; st->state--) { struct cpuhp_step *step = cpuhp_ap_states + st->state; cpuhp_invoke_callback(cpu, st->state, step->teardown); } /* Give up timekeeping duties */ tick_handover_do_timer(); /* 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(per_cpu_ptr(&cpuhp_state, cpu)->thread); smpboot_park_threads(cpu); /* * 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(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(per_cpu_ptr(&cpuhp_state, cpu)->thread); return err; } BUG_ON(cpu_online(cpu)); /* * The migration_call() CPU_DYING callback 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_completion(&st->done); 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); tick_cleanup_dead_cpu(cpu); return 0; } static int notify_dead(unsigned int cpu) { cpu_notify_nofail(CPU_DEAD, cpu); check_for_tasks(cpu); return 0; } static void cpuhp_complete_idle_dead(void *arg) { struct cpuhp_cpu_state *st = arg; complete(&st->done); } 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); } #else #define notify_down_prepare NULL #define takedown_cpu NULL #define notify_dead NULL #define notify_dying NULL #endif #ifdef CONFIG_HOTPLUG_CPU /* 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; bool hasdied = false; if (num_online_cpus() == 1) return -EBUSY; if (!cpu_present(cpu)) return -EINVAL; cpu_hotplug_begin(); cpuhp_tasks_frozen = tasks_frozen; prev_state = st->state; st->target = 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) { 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; } /* * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need * to do the further cleanups. */ ret = cpuhp_down_callbacks(cpu, st, cpuhp_bp_states, target); if (ret && st->state > CPUHP_TEARDOWN_CPU && st->state < prev_state) { st->target = prev_state; st->rollback = true; cpuhp_kick_ap_work(cpu); } hasdied = prev_state != st->state && st->state == CPUHP_OFFLINE; out: cpu_hotplug_done(); /* This post dead nonsense must die */ if (!ret && hasdied) cpu_notify_nofail(CPU_POST_DEAD, cpu); return ret; } static int do_cpu_down(unsigned int cpu, enum cpuhp_state target) { int err; cpu_maps_update_begin(); if (cpu_hotplug_disabled) { err = -EBUSY; goto out; } err = _cpu_down(cpu, 0, target); out: cpu_maps_update_done(); return err; } int cpu_down(unsigned int cpu) { return do_cpu_down(cpu, CPUHP_OFFLINE); } EXPORT_SYMBOL(cpu_down); #endif /*CONFIG_HOTPLUG_CPU*/ /** * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers * @cpu: cpu that just started * * This function calls the cpu_chain notifiers with CPU_STARTING. * 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); while (st->state < target) { struct cpuhp_step *step; st->state++; step = cpuhp_ap_states + st->state; cpuhp_invoke_callback(cpu, st->state, step->startup); } } /* * Called from the idle task. We need to set active here, so we can kick off * the stopper thread and unpark the smpboot threads. If the target state is * beyond CPUHP_AP_ONLINE_IDLE we kick cpuhp thread and let it bring up the * cpu further. */ void cpuhp_online_idle(enum cpuhp_state state) { struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state); unsigned int cpu = smp_processor_id(); /* Happens for the boot cpu */ if (state != CPUHP_AP_ONLINE_IDLE) return; st->state = CPUHP_AP_ONLINE_IDLE; /* Unpark the stopper thread and the hotplug thread of this cpu */ stop_machine_unpark(cpu); kthread_unpark(st->thread); /* Should we go further up ? */ if (st->target > CPUHP_AP_ONLINE_IDLE) __cpuhp_kick_ap_work(st); else complete(&st->done); } /* 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; cpu_hotplug_begin(); if (!cpu_present(cpu)) { ret = -EINVAL; goto out; } /* * The caller of do_cpu_up might have raced with another * caller. Ignore it for now. */ 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; } } cpuhp_tasks_frozen = tasks_frozen; st->target = 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, cpuhp_bp_states, target); out: cpu_hotplug_done(); return ret; } static int do_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; } err = _cpu_up(cpu, 0, target); out: cpu_maps_update_done(); return err; } int cpu_up(unsigned int cpu) { return do_cpu_up(cpu, CPUHP_ONLINE); } EXPORT_SYMBOL_GPL(cpu_up); #ifdef CONFIG_PM_SLEEP_SMP static cpumask_var_t frozen_cpus; int disable_nonboot_cpus(void) { int cpu, first_cpu, error = 0; cpu_maps_update_begin(); first_cpu = 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 == first_cpu) continue; 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 disable_nonboot_cpus() users are * supposed to do enable_nonboot_cpus() on the failure path. */ cpu_hotplug_disabled++; cpu_maps_update_done(); return error; } void __weak arch_enable_nonboot_cpus_begin(void) { } void __weak arch_enable_nonboot_cpus_end(void) { } void enable_nonboot_cpus(void) { int cpu, error; /* Allow everyone to use the CPU hotplug again */ cpu_maps_update_begin(); WARN_ON(--cpu_hotplug_disabled < 0); if (cpumask_empty(frozen_cpus)) goto out; pr_info("Enabling non-boot CPUs ...\n"); arch_enable_nonboot_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_enable_nonboot_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 */ #endif /* CONFIG_SMP */ /* Boot processor state steps */ static struct cpuhp_step cpuhp_bp_states[] = { [CPUHP_OFFLINE] = { .name = "offline", .startup = NULL, .teardown = NULL, }, #ifdef CONFIG_SMP [CPUHP_CREATE_THREADS]= { .name = "threads:create", .startup = smpboot_create_threads, .teardown = NULL, .cant_stop = true, }, [CPUHP_PERF_PREPARE] = { .name = "perf prepare", .startup = perf_event_init_cpu, .teardown = perf_event_exit_cpu, }, [CPUHP_WORKQUEUE_PREP] = { .name = "workqueue prepare", .startup = workqueue_prepare_cpu, .teardown = NULL, }, [CPUHP_HRTIMERS_PREPARE] = { .name = "hrtimers prepare", .startup = hrtimers_prepare_cpu, .teardown = hrtimers_dead_cpu, }, [CPUHP_SMPCFD_PREPARE] = { .name = "SMPCFD prepare", .startup = smpcfd_prepare_cpu, .teardown = smpcfd_dead_cpu, }, [CPUHP_RCUTREE_PREP] = { .name = "RCU-tree prepare", .startup = rcutree_prepare_cpu, .teardown = rcutree_dead_cpu, }, /* * Preparatory and dead notifiers. Will be replaced once the notifiers * are converted to states. */ [CPUHP_NOTIFY_PREPARE] = { .name = "notify:prepare", .startup = notify_prepare, .teardown = notify_dead, .skip_onerr = true, .cant_stop = true, }, /* * 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_DEAD] = { .name = "timers dead", .startup = NULL, .teardown = timers_dead_cpu, }, /* Kicks the plugged cpu into life */ [CPUHP_BRINGUP_CPU] = { .name = "cpu:bringup", .startup = bringup_cpu, .teardown = NULL, .cant_stop = true, }, [CPUHP_AP_SMPCFD_DYING] = { .startup = NULL, .teardown = smpcfd_dying_cpu, }, /* * Handled on controll processor until the plugged processor manages * this itself. */ [CPUHP_TEARDOWN_CPU] = { .name = "cpu:teardown", .startup = NULL, .teardown = takedown_cpu, .cant_stop = true, }, #else [CPUHP_BRINGUP_CPU] = { }, #endif }; /* Application processor state steps */ static struct cpuhp_step cpuhp_ap_states[] = { #ifdef CONFIG_SMP /* 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 = sched_cpu_starting, .teardown = sched_cpu_dying, }, [CPUHP_AP_RCUTREE_DYING] = { .startup = NULL, .teardown = rcutree_dying_cpu, }, /* * Low level startup/teardown notifiers. Run with interrupts * disabled. Will be removed once the notifiers are converted to * states. */ [CPUHP_AP_NOTIFY_STARTING] = { .name = "notify:starting", .startup = notify_starting, .teardown = notify_dying, .skip_onerr = true, .cant_stop = true, }, /* Entry state on starting. Interrupts enabled from here on. Transient * state for synchronsization */ [CPUHP_AP_ONLINE] = { .name = "ap:online", }, /* Handle smpboot threads park/unpark */ [CPUHP_AP_SMPBOOT_THREADS] = { .name = "smpboot:threads", .startup = smpboot_unpark_threads, .teardown = NULL, }, [CPUHP_AP_PERF_ONLINE] = { .name = "perf online", .startup = perf_event_init_cpu, .teardown = perf_event_exit_cpu, }, [CPUHP_AP_WORKQUEUE_ONLINE] = { .name = "workqueue online", .startup = workqueue_online_cpu, .teardown = workqueue_offline_cpu, }, [CPUHP_AP_RCUTREE_ONLINE] = { .name = "RCU-tree online", .startup = rcutree_online_cpu, .teardown = rcutree_offline_cpu, }, /* * Online/down_prepare notifiers. Will be removed once the notifiers * are converted to states. */ [CPUHP_AP_NOTIFY_ONLINE] = { .name = "notify:online", .startup = notify_online, .teardown = notify_down_prepare, .skip_onerr = true, }, #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 = sched_cpu_activate, .teardown = sched_cpu_deactivate, }, #endif /* CPU is fully up and running. */ [CPUHP_ONLINE] = { .name = "online", .startup = NULL, .teardown = 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; } 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 explicitely in cpu_down. */ return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU; } static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state) { struct cpuhp_step *sp; sp = cpuhp_is_ap_state(state) ? cpuhp_ap_states : cpuhp_bp_states; return sp + state; } static void cpuhp_store_callbacks(enum cpuhp_state state, const char *name, int (*startup)(unsigned int cpu), int (*teardown)(unsigned int cpu)) { /* (Un)Install the callbacks for further cpu hotplug operations */ struct cpuhp_step *sp; mutex_lock(&cpuhp_state_mutex); sp = cpuhp_get_step(state); sp->startup = startup; sp->teardown = teardown; sp->name = name; mutex_unlock(&cpuhp_state_mutex); } static void *cpuhp_get_teardown_cb(enum cpuhp_state state) { return cpuhp_get_step(state)->teardown; } /* * 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, int (*cb)(unsigned int), bool bringup) { int ret; if (!cb) 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, cb); else ret = cpuhp_invoke_callback(cpu, state, cb); #else ret = cpuhp_invoke_callback(cpu, state, cb); #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, int (*teardown)(unsigned int cpu)) { int cpu; if (!teardown) return; /* 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, teardown, false); } } /* * 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; mutex_lock(&cpuhp_state_mutex); for (i = CPUHP_AP_ONLINE_DYN; i <= CPUHP_AP_ONLINE_DYN_END; i++) { if (cpuhp_ap_states[i].name) continue; cpuhp_ap_states[i].name = "Reserved"; mutex_unlock(&cpuhp_state_mutex); return i; } mutex_unlock(&cpuhp_state_mutex); WARN(1, "No more dynamic states available for CPU hotplug\n"); return -ENOSPC; } /** * __cpuhp_setup_state - Setup the callbacks for an hotplug machine state * @state: The state to setup * @invoke: If true, the startup function is invoked for cpus where * cpu state >= @state * @startup: startup callback function * @teardown: teardown callback function * * Returns 0 if successful, otherwise a proper error code */ int __cpuhp_setup_state(enum cpuhp_state state, const char *name, bool invoke, int (*startup)(unsigned int cpu), int (*teardown)(unsigned int cpu)) { int cpu, ret = 0; int dyn_state = 0; if (cpuhp_cb_check(state) || !name) return -EINVAL; get_online_cpus(); /* currently assignments for the ONLINE state are possible */ if (state == CPUHP_AP_ONLINE_DYN) { dyn_state = 1; ret = cpuhp_reserve_state(state); if (ret < 0) goto out; state = ret; } cpuhp_store_callbacks(state, name, startup, teardown); if (!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, startup, true); if (ret) { cpuhp_rollback_install(cpu, state, teardown); cpuhp_store_callbacks(state, NULL, NULL, NULL); goto out; } } out: put_online_cpus(); if (!ret && dyn_state) return state; return ret; } EXPORT_SYMBOL(__cpuhp_setup_state); /** * __cpuhp_remove_state - 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 teardown callback is currently not allowed to fail. Think * about module removal! */ void __cpuhp_remove_state(enum cpuhp_state state, bool invoke) { int (*teardown)(unsigned int cpu) = cpuhp_get_teardown_cb(state); int cpu; BUG_ON(cpuhp_cb_check(state)); get_online_cpus(); if (!invoke || !teardown) 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, teardown, false); } remove: cpuhp_store_callbacks(state, NULL, NULL, NULL); put_online_cpus(); } EXPORT_SYMBOL(__cpuhp_remove_state); #if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU) static ssize_t show_cpuhp_state(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(state, 0444, show_cpuhp_state, NULL); static ssize_t write_cpuhp_target(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) return ret; if (st->state < target) ret = do_cpu_up(dev->id, target); else ret = do_cpu_down(dev->id, target); unlock_device_hotplug(); return ret ? ret : count; } static ssize_t show_cpuhp_target(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(target, 0644, show_cpuhp_target, write_cpuhp_target); static struct attribute *cpuhp_cpu_attrs[] = { &dev_attr_state.attr, &dev_attr_target.attr, NULL }; static struct attribute_group cpuhp_cpu_attr_group = { .attrs = cpuhp_cpu_attrs, .name = "hotplug", NULL }; static ssize_t show_cpuhp_states(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(states, 0444, show_cpuhp_states, NULL); static struct attribute *cpuhp_cpu_root_attrs[] = { &dev_attr_states.attr, NULL }; static struct attribute_group cpuhp_cpu_root_attr_group = { .attrs = cpuhp_cpu_root_attrs, .name = "hotplug", NULL }; static int __init cpuhp_sysfs_init(void) { int cpu, ret; ret = sysfs_create_group(&cpu_subsys.dev_root->kobj, &cpuhp_cpu_root_attr_group); 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 /* * 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); 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); } /* * 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); } /* * Must be called _AFTER_ setting up the per_cpu areas */ void __init boot_cpu_state_init(void) { per_cpu_ptr(&cpuhp_state, smp_processor_id())->state = CPUHP_ONLINE; }