--- /dev/null
+/* 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 <trace/events/power.h>
+
+#include "smpboot.h"
+
+#ifdef CONFIG_SMP
+/* Serializes the updates to cpu_online_mask, cpu_present_mask */
+static DEFINE_MUTEX(cpu_add_remove_lock);
+
+/*
+ * 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,
+ .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
+ .wq = __WAIT_QUEUE_HEAD_INITIALIZER(cpu_hotplug.wq),
+#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)
+
+/**
+ * hotplug_pcp - per cpu hotplug descriptor
+ * @unplug: set when pin_current_cpu() needs to sync tasks
+ * @sync_tsk: the task that waits for tasks to finish pinned sections
+ * @refcount: counter of tasks in pinned sections
+ * @grab_lock: set when the tasks entering pinned sections should wait
+ * @synced: notifier for @sync_tsk to tell cpu_down it's finished
+ * @mutex: the mutex to make tasks wait (used when @grab_lock is true)
+ * @mutex_init: zero if the mutex hasn't been initialized yet.
+ *
+ * Although @unplug and @sync_tsk may point to the same task, the @unplug
+ * is used as a flag and still exists after @sync_tsk has exited and
+ * @sync_tsk set to NULL.
+ */
+struct hotplug_pcp {
+ struct task_struct *unplug;
+ struct task_struct *sync_tsk;
+ int refcount;
+ int grab_lock;
+ struct completion synced;
+ struct completion unplug_wait;
+#ifdef CONFIG_PREEMPT_RT_FULL
+ /*
+ * Note, on PREEMPT_RT, the hotplug lock must save the state of
+ * the task, otherwise the mutex will cause the task to fail
+ * to sleep when required. (Because it's called from migrate_disable())
+ *
+ * The spinlock_t on PREEMPT_RT is a mutex that saves the task's
+ * state.
+ */
+ spinlock_t lock;
+#else
+ struct mutex mutex;
+#endif
+ int mutex_init;
+};
+
+#ifdef CONFIG_PREEMPT_RT_FULL
+# define hotplug_lock(hp) rt_spin_lock(&(hp)->lock)
+# define hotplug_unlock(hp) rt_spin_unlock(&(hp)->lock)
+#else
+# define hotplug_lock(hp) mutex_lock(&(hp)->mutex)
+# define hotplug_unlock(hp) mutex_unlock(&(hp)->mutex)
+#endif
+
+static DEFINE_PER_CPU(struct hotplug_pcp, hotplug_pcp);
+
+/**
+ * pin_current_cpu - Prevent the current cpu from being unplugged
+ *
+ * Lightweight version of get_online_cpus() to prevent cpu from being
+ * unplugged when code runs in a migration disabled region.
+ *
+ * Must be called with preemption disabled (preempt_count = 1)!
+ */
+void pin_current_cpu(void)
+{
+ struct hotplug_pcp *hp;
+ int force = 0;
+
+retry:
+ hp = this_cpu_ptr(&hotplug_pcp);
+
+ if (!hp->unplug || hp->refcount || force || preempt_count() > 1 ||
+ hp->unplug == current) {
+ hp->refcount++;
+ return;
+ }
+ if (hp->grab_lock) {
+ preempt_enable();
+ hotplug_lock(hp);
+ hotplug_unlock(hp);
+ } else {
+ preempt_enable();
+ /*
+ * Try to push this task off of this CPU.
+ */
+ if (!migrate_me()) {
+ preempt_disable();
+ hp = this_cpu_ptr(&hotplug_pcp);
+ if (!hp->grab_lock) {
+ /*
+ * Just let it continue it's already pinned
+ * or about to sleep.
+ */
+ force = 1;
+ goto retry;
+ }
+ preempt_enable();
+ }
+ }
+ preempt_disable();
+ goto retry;
+}
+
+/**
+ * unpin_current_cpu - Allow unplug of current cpu
+ *
+ * Must be called with preemption or interrupts disabled!
+ */
+void unpin_current_cpu(void)
+{
+ struct hotplug_pcp *hp = this_cpu_ptr(&hotplug_pcp);
+
+ WARN_ON(hp->refcount <= 0);
+
+ /* This is safe. sync_unplug_thread is pinned to this cpu */
+ if (!--hp->refcount && hp->unplug && hp->unplug != current)
+ wake_up_process(hp->unplug);
+}
+
+static void wait_for_pinned_cpus(struct hotplug_pcp *hp)
+{
+ set_current_state(TASK_UNINTERRUPTIBLE);
+ while (hp->refcount) {
+ schedule_preempt_disabled();
+ set_current_state(TASK_UNINTERRUPTIBLE);
+ }
+}
+
+static int sync_unplug_thread(void *data)
+{
+ struct hotplug_pcp *hp = data;
+
+ wait_for_completion(&hp->unplug_wait);
+ preempt_disable();
+ hp->unplug = current;
+ wait_for_pinned_cpus(hp);
+
+ /*
+ * This thread will synchronize the cpu_down() with threads
+ * that have pinned the CPU. When the pinned CPU count reaches
+ * zero, we inform the cpu_down code to continue to the next step.
+ */
+ set_current_state(TASK_UNINTERRUPTIBLE);
+ preempt_enable();
+ complete(&hp->synced);
+
+ /*
+ * If all succeeds, the next step will need tasks to wait till
+ * the CPU is offline before continuing. To do this, the grab_lock
+ * is set and tasks going into pin_current_cpu() will block on the
+ * mutex. But we still need to wait for those that are already in
+ * pinned CPU sections. If the cpu_down() failed, the kthread_should_stop()
+ * will kick this thread out.
+ */
+ while (!hp->grab_lock && !kthread_should_stop()) {
+ schedule();
+ set_current_state(TASK_UNINTERRUPTIBLE);
+ }
+
+ /* Make sure grab_lock is seen before we see a stale completion */
+ smp_mb();
+
+ /*
+ * Now just before cpu_down() enters stop machine, we need to make
+ * sure all tasks that are in pinned CPU sections are out, and new
+ * tasks will now grab the lock, keeping them from entering pinned
+ * CPU sections.
+ */
+ if (!kthread_should_stop()) {
+ preempt_disable();
+ wait_for_pinned_cpus(hp);
+ preempt_enable();
+ complete(&hp->synced);
+ }
+
+ set_current_state(TASK_UNINTERRUPTIBLE);
+ while (!kthread_should_stop()) {
+ schedule();
+ set_current_state(TASK_UNINTERRUPTIBLE);
+ }
+ set_current_state(TASK_RUNNING);
+
+ /*
+ * Force this thread off this CPU as it's going down and
+ * we don't want any more work on this CPU.
+ */
+ current->flags &= ~PF_NO_SETAFFINITY;
+ set_cpus_allowed_ptr(current, cpu_present_mask);
+ migrate_me();
+ return 0;
+}
+
+static void __cpu_unplug_sync(struct hotplug_pcp *hp)
+{
+ wake_up_process(hp->sync_tsk);
+ wait_for_completion(&hp->synced);
+}
+
+static void __cpu_unplug_wait(unsigned int cpu)
+{
+ struct hotplug_pcp *hp = &per_cpu(hotplug_pcp, cpu);
+
+ complete(&hp->unplug_wait);
+ wait_for_completion(&hp->synced);
+}
+
+/*
+ * Start the sync_unplug_thread on the target cpu and wait for it to
+ * complete.
+ */
+static int cpu_unplug_begin(unsigned int cpu)
+{
+ struct hotplug_pcp *hp = &per_cpu(hotplug_pcp, cpu);
+ int err;
+
+ /* Protected by cpu_hotplug.lock */
+ if (!hp->mutex_init) {
+#ifdef CONFIG_PREEMPT_RT_FULL
+ spin_lock_init(&hp->lock);
+#else
+ mutex_init(&hp->mutex);
+#endif
+ hp->mutex_init = 1;
+ }
+
+ /* Inform the scheduler to migrate tasks off this CPU */
+ tell_sched_cpu_down_begin(cpu);
+
+ init_completion(&hp->synced);
+ init_completion(&hp->unplug_wait);
+
+ hp->sync_tsk = kthread_create(sync_unplug_thread, hp, "sync_unplug/%d", cpu);
+ if (IS_ERR(hp->sync_tsk)) {
+ err = PTR_ERR(hp->sync_tsk);
+ hp->sync_tsk = NULL;
+ return err;
+ }
+ kthread_bind(hp->sync_tsk, cpu);
+
+ /*
+ * Wait for tasks to get out of the pinned sections,
+ * it's still OK if new tasks enter. Some CPU notifiers will
+ * wait for tasks that are going to enter these sections and
+ * we must not have them block.
+ */
+ wake_up_process(hp->sync_tsk);
+ return 0;
+}
+
+static void cpu_unplug_sync(unsigned int cpu)
+{
+ struct hotplug_pcp *hp = &per_cpu(hotplug_pcp, cpu);
+
+ init_completion(&hp->synced);
+ /* The completion needs to be initialzied before setting grab_lock */
+ smp_wmb();
+
+ /* Grab the mutex before setting grab_lock */
+ hotplug_lock(hp);
+ hp->grab_lock = 1;
+
+ /*
+ * The CPU notifiers have been completed.
+ * Wait for tasks to get out of pinned CPU sections and have new
+ * tasks block until the CPU is completely down.
+ */
+ __cpu_unplug_sync(hp);
+
+ /* All done with the sync thread */
+ kthread_stop(hp->sync_tsk);
+ hp->sync_tsk = NULL;
+}
+
+static void cpu_unplug_done(unsigned int cpu)
+{
+ struct hotplug_pcp *hp = &per_cpu(hotplug_pcp, cpu);
+
+ hp->unplug = NULL;
+ /* Let all tasks know cpu unplug is finished before cleaning up */
+ smp_wmb();
+
+ if (hp->sync_tsk)
+ kthread_stop(hp->sync_tsk);
+
+ if (hp->grab_lock) {
+ hotplug_unlock(hp);
+ /* protected by cpu_hotplug.lock */
+ hp->grab_lock = 0;
+ }
+ tell_sched_cpu_down_done(cpu);
+}
+
+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);
+
+bool try_get_online_cpus(void)
+{
+ if (cpu_hotplug.active_writer == current)
+ return true;
+ if (!mutex_trylock(&cpu_hotplug.lock))
+ return false;
+ cpuhp_lock_acquire_tryread();
+ atomic_inc(&cpu_hotplug.refcount);
+ mutex_unlock(&cpu_hotplug.lock);
+ return true;
+}
+EXPORT_SYMBOL_GPL(try_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 = 1;
+ cpu_maps_update_done();
+}
+
+void cpu_hotplug_enable(void)
+{
+ cpu_maps_update_begin();
+ cpu_hotplug_disabled = 0;
+ cpu_maps_update_done();
+}
+
+#endif /* CONFIG_HOTPLUG_CPU */
+
+/* Need to know about CPUs going up/down? */
+int __ref 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 __ref __register_cpu_notifier(struct notifier_block *nb)
+{
+ return raw_notifier_chain_register(&cpu_chain, nb);
+}
+
+static int __cpu_notify(unsigned long val, void *v, int nr_to_call,
+ int *nr_calls)
+{
+ int ret;
+
+ ret = __raw_notifier_call_chain(&cpu_chain, val, v, nr_to_call,
+ nr_calls);
+
+ return notifier_to_errno(ret);
+}
+
+static int cpu_notify(unsigned long val, void *v)
+{
+ return __cpu_notify(val, v, -1, NULL);
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+
+static void cpu_notify_nofail(unsigned long val, void *v)
+{
+ BUG_ON(cpu_notify(val, v));
+}
+EXPORT_SYMBOL(register_cpu_notifier);
+EXPORT_SYMBOL(__register_cpu_notifier);
+
+void __ref 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 __ref __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_irq(&tasklist_lock);
+ do_each_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);
+ } while_each_thread(g, p);
+ read_unlock_irq(&tasklist_lock);
+}
+
+struct take_cpu_down_param {
+ unsigned long mod;
+ void *hcpu;
+};
+
+/* Take this CPU down. */
+static int __ref take_cpu_down(void *_param)
+{
+ struct take_cpu_down_param *param = _param;
+ int err;
+
+ /* Ensure this CPU doesn't handle any more interrupts. */
+ err = __cpu_disable();
+ if (err < 0)
+ return err;
+
+ cpu_notify(CPU_DYING | param->mod, param->hcpu);
+ /* Give up timekeeping duties */
+ tick_handover_do_timer();
+ /* Park the stopper thread */
+ kthread_park(current);
+ return 0;
+}
+
+/* Requires cpu_add_remove_lock to be held */
+static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
+{
+ int mycpu, err, nr_calls = 0;
+ void *hcpu = (void *)(long)cpu;
+ unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
+ struct take_cpu_down_param tcd_param = {
+ .mod = mod,
+ .hcpu = hcpu,
+ };
+ cpumask_var_t cpumask;
+ cpumask_var_t cpumask_org;
+
+ if (num_online_cpus() == 1)
+ return -EBUSY;
+
+ if (!cpu_online(cpu))
+ return -EINVAL;
+
+ /* Move the downtaker off the unplug cpu */
+ if (!alloc_cpumask_var(&cpumask, GFP_KERNEL))
+ return -ENOMEM;
+ if (!alloc_cpumask_var(&cpumask_org, GFP_KERNEL)) {
+ free_cpumask_var(cpumask);
+ return -ENOMEM;
+ }
+
+ cpumask_copy(cpumask_org, tsk_cpus_allowed(current));
+ cpumask_andnot(cpumask, cpu_online_mask, cpumask_of(cpu));
+ set_cpus_allowed_ptr(current, cpumask);
+ free_cpumask_var(cpumask);
+ migrate_disable();
+ mycpu = smp_processor_id();
+ if (mycpu == cpu) {
+ printk(KERN_ERR "Yuck! Still on unplug CPU\n!");
+ migrate_enable();
+ err = -EBUSY;
+ goto restore_cpus;
+ }
+ migrate_enable();
+
+ cpu_hotplug_begin();
+ err = cpu_unplug_begin(cpu);
+ if (err) {
+ printk("cpu_unplug_begin(%d) failed\n", cpu);
+ goto out_cancel;
+ }
+
+ err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls);
+ if (err) {
+ nr_calls--;
+ __cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL);
+ pr_warn("%s: attempt to take down CPU %u failed\n",
+ __func__, cpu);
+ goto out_release;
+ }
+
+ /*
+ * By now we've cleared cpu_active_mask, wait for all preempt-disabled
+ * and RCU users of this state to go away such that all new such users
+ * will observe it.
+ *
+ * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might
+ * not imply sync_sched(), so explicitly call both.
+ *
+ * Do sync before park smpboot threads to take care the rcu boost case.
+ */
+#ifdef CONFIG_PREEMPT
+ synchronize_sched();
+#endif
+ synchronize_rcu();
+
+ __cpu_unplug_wait(cpu);
+ smpboot_park_threads(cpu);
+
+ /* Notifiers are done. Don't let any more tasks pin this CPU. */
+ cpu_unplug_sync(cpu);
+
+ /*
+ * So now all preempt/rcu users must observe !cpu_active().
+ */
+
+ err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
+ if (err) {
+ /* CPU didn't die: tell everyone. Can't complain. */
+ smpboot_unpark_threads(cpu);
+ cpu_notify_nofail(CPU_DOWN_FAILED | mod, hcpu);
+ goto out_release;
+ }
+ 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.
+ */
+ while (!per_cpu(cpu_dead_idle, cpu))
+ cpu_relax();
+ smp_mb(); /* Read from cpu_dead_idle before __cpu_die(). */
+ per_cpu(cpu_dead_idle, cpu) = false;
+
+ hotplug_cpu__broadcast_tick_pull(cpu);
+ /* This actually kills the CPU. */
+ __cpu_die(cpu);
+
+ /* CPU is completely dead: tell everyone. Too late to complain. */
+ tick_cleanup_dead_cpu(cpu);
+ cpu_notify_nofail(CPU_DEAD | mod, hcpu);
+
+ check_for_tasks(cpu);
+
+out_release:
+ cpu_unplug_done(cpu);
+out_cancel:
+ cpu_hotplug_done();
+ if (!err)
+ cpu_notify_nofail(CPU_POST_DEAD | mod, hcpu);
+restore_cpus:
+ set_cpus_allowed_ptr(current, cpumask_org);
+ free_cpumask_var(cpumask_org);
+ return err;
+}
+
+int __ref cpu_down(unsigned int cpu)
+{
+ int err;
+
+ cpu_maps_update_begin();
+
+ if (cpu_hotplug_disabled) {
+ err = -EBUSY;
+ goto out;
+ }
+
+ err = _cpu_down(cpu, 0);
+
+out:
+ cpu_maps_update_done();
+ return err;
+}
+EXPORT_SYMBOL(cpu_down);
+#endif /*CONFIG_HOTPLUG_CPU*/
+
+/*
+ * Unpark per-CPU smpboot kthreads at CPU-online time.
+ */
+static int smpboot_thread_call(struct notifier_block *nfb,
+ unsigned long action, void *hcpu)
+{
+ int cpu = (long)hcpu;
+
+ switch (action & ~CPU_TASKS_FROZEN) {
+
+ case CPU_ONLINE:
+ smpboot_unpark_threads(cpu);
+ break;
+
+ default:
+ break;
+ }
+
+ return NOTIFY_OK;
+}
+
+static struct notifier_block smpboot_thread_notifier = {
+ .notifier_call = smpboot_thread_call,
+ .priority = CPU_PRI_SMPBOOT,
+};
+
+void __cpuinit smpboot_thread_init(void)
+{
+ register_cpu_notifier(&smpboot_thread_notifier);
+}
+
+/* Requires cpu_add_remove_lock to be held */
+static int _cpu_up(unsigned int cpu, int tasks_frozen)
+{
+ int ret, nr_calls = 0;
+ void *hcpu = (void *)(long)cpu;
+ unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
+ struct task_struct *idle;
+
+ cpu_hotplug_begin();
+
+ if (cpu_online(cpu) || !cpu_present(cpu)) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ idle = idle_thread_get(cpu);
+ if (IS_ERR(idle)) {
+ ret = PTR_ERR(idle);
+ goto out;
+ }
+
+ ret = smpboot_create_threads(cpu);
+ if (ret)
+ goto out;
+
+ ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls);
+ if (ret) {
+ nr_calls--;
+ pr_warn("%s: attempt to bring up CPU %u failed\n",
+ __func__, cpu);
+ goto out_notify;
+ }
+
+ /* Arch-specific enabling code. */
+ ret = __cpu_up(cpu, idle);
+ if (ret != 0)
+ goto out_notify;
+ BUG_ON(!cpu_online(cpu));
+
+ /* Now call notifier in preparation. */
+ cpu_notify(CPU_ONLINE | mod, hcpu);
+
+out_notify:
+ if (ret != 0)
+ __cpu_notify(CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
+out:
+ cpu_hotplug_done();
+
+ return ret;
+}
+
+int cpu_up(unsigned int cpu)
+{
+ 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);
+
+out:
+ cpu_maps_update_done();
+ return err;
+}
+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);
+ 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);
+ /* Make sure the CPUs won't be enabled by someone else */
+ cpu_hotplug_disabled = 1;
+ } else {
+ pr_err("Non-boot CPUs are not disabled\n");
+ }
+ cpu_maps_update_done();
+ return error;
+}
+
+void __weak arch_enable_nonboot_cpus_begin(void)
+{
+}
+
+void __weak arch_enable_nonboot_cpus_end(void)
+{
+}
+
+void __ref enable_nonboot_cpus(void)
+{
+ int cpu, error;
+
+ /* Allow everyone to use the CPU hotplug again */
+ cpu_maps_update_begin();
+ 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);
+ 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 */
+
+/**
+ * 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)
+{
+ unsigned long val = CPU_STARTING;
+
+#ifdef CONFIG_PM_SLEEP_SMP
+ if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus))
+ val = CPU_STARTING_FROZEN;
+#endif /* CONFIG_PM_SLEEP_SMP */
+ cpu_notify(val, (void *)(long)cpu);
+}
+
+#endif /* CONFIG_SMP */
+
+/*
+ * 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
+static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
+ = CPU_BITS_ALL;
+#else
+static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
+#endif
+const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits);
+EXPORT_SYMBOL(cpu_possible_mask);
+
+static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
+const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits);
+EXPORT_SYMBOL(cpu_online_mask);
+
+static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
+const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits);
+EXPORT_SYMBOL(cpu_present_mask);
+
+static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
+const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
+EXPORT_SYMBOL(cpu_active_mask);
+
+void set_cpu_possible(unsigned int cpu, bool possible)
+{
+ if (possible)
+ cpumask_set_cpu(cpu, to_cpumask(cpu_possible_bits));
+ else
+ cpumask_clear_cpu(cpu, to_cpumask(cpu_possible_bits));
+}
+
+void set_cpu_present(unsigned int cpu, bool present)
+{
+ if (present)
+ cpumask_set_cpu(cpu, to_cpumask(cpu_present_bits));
+ else
+ cpumask_clear_cpu(cpu, to_cpumask(cpu_present_bits));
+}
+
+void set_cpu_online(unsigned int cpu, bool online)
+{
+ if (online) {
+ cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
+ cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
+ } else {
+ cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
+ }
+}
+
+void set_cpu_active(unsigned int cpu, bool active)
+{
+ if (active)
+ cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
+ else
+ cpumask_clear_cpu(cpu, to_cpumask(cpu_active_bits));
+}
+
+void init_cpu_present(const struct cpumask *src)
+{
+ cpumask_copy(to_cpumask(cpu_present_bits), src);
+}
+
+void init_cpu_possible(const struct cpumask *src)
+{
+ cpumask_copy(to_cpumask(cpu_possible_bits), src);
+}
+
+void init_cpu_online(const struct cpumask *src)
+{
+ cpumask_copy(to_cpumask(cpu_online_bits), src);
+}
Code Review / kvmfornfv.git / blobdiff