Release 4.15 kernel/cpu.c

/* 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/signal.h>
#include <linux/sched/hotplug.h>
#include <linux/sched/task.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/nmi.h>
#include <linux/smpboot.h>
#include <linux/relay.h>
#include <linux/slab.h>
#include <linux/percpu-rwsem.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
 * @single:     Single callback invocation
 * @bringup:    Single callback bringup or teardown selector
 * @cb_state:   The state for a single callback (install/uninstall)
 * @result:     Result of the operation
 * @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;
	
struct completion	done_up;
	
struct completion	done_down;
#endif
};

static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state) = {
	.fail = CPUHP_INVALID,
};

#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);
}

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static inline void cpuhp_lock_release(bool bringup)
{
	lock_map_release(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
}
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#else



static inline void cpuhp_lock_acquire(bool bringup) { }
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static inline void cpuhp_lock_release(bool bringup) { }

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#endif

/**
 * 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;
	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;
	
struct hlist_head	list;
	
bool			skip_onerr;
	
bool			cant_stop;
	
bool			multi_instance;
};

static DEFINE_MUTEX(cpuhp_state_mutex);

static struct cpuhp_step cpuhp_bp_states[];

static struct cpuhp_step cpuhp_ap_states[];



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;
}

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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;
}

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/**
 * 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.
 */


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;

		if (!(bringup ? step->startup.single : step->teardown.single))
			return 0;

		return -EAGAIN;
	}

	if (!step->multi_instance) {
		WARN_ON_ONCE(lastp && *lastp);
		cb = bringup ? step->startup.single : step->teardown.single;
		if (!cb)
			return 0;
		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;
	if (!cbm)
		return 0;

	/* 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;
}

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#ifdef CONFIG_SMP


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);
}

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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);
}

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/*
 * 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;
}

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/* 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);
}

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void cpu_maps_update_done(void)
{
	mutex_unlock(&cpu_add_remove_lock);
}

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/*
 * 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);
}
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EXPORT_SYMBOL_GPL(cpus_read_lock);



void cpus_read_unlock(void)
{
	percpu_up_read(&cpu_hotplug_lock);
}
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EXPORT_SYMBOL_GPL(cpus_read_unlock);



void cpus_write_lock(void)
{
	percpu_down_write(&cpu_hotplug_lock);
}

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void cpus_write_unlock(void)
{
	percpu_up_write(&cpu_hotplug_lock);
}

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void lockdep_assert_cpus_held(void)
{
	percpu_rwsem_assert_held(&cpu_hotplug_lock);
}

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/*
 * 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();
}
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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--;
}

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void cpu_hotplug_enable(void)
{
	cpu_maps_update_begin();
	__cpu_hotplug_enable();
	cpu_maps_update_done();
}
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EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
#endif	/* CONFIG_HOTPLUG_CPU */


static inline enum cpuhp_state

cpuhp_set_state(struct cpuhp_cpu_state *st, enum cpuhp_state target)
{
	enum cpuhp_state prev_state = st->state;

	st->rollback = false;
	st->last = NULL;

	st->target = target;
	st->single = false;
	st->bringup = st->state < target;

	return prev_state;
}

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static inline void

cpuhp_reset_state(struct cpuhp_cpu_state *st, enum cpuhp_state prev_state)
{
	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->target = prev_state;
	st->bringup = !st->bringup;
}

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/* 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);
}

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static int cpuhp_kick_ap(struct cpuhp_cpu_state *st, enum cpuhp_state target)
{
	enum cpuhp_state prev_state;
	int ret;

	prev_state = cpuhp_set_state(st, target);
	__cpuhp_kick_ap(st);
	if ((ret = st->result)) {
		cpuhp_reset_state(st, prev_state);
		__cpuhp_kick_ap(st);
	}

	return ret;
}

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static int bringup_wait_for_ap(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 stopper thread and the hotplug thread of the target cpu */
	stop_machine_unpark(cpu);
	kthread_unpark(st->thread);

	if (st->target <= CPUHP_AP_ONLINE_IDLE)
		return 0;

	return cpuhp_kick_ap(st, st->target);
}

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static int bringup_cpu(unsigned int cpu)
{
	struct task_struct *idle = idle_thread_get(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();

	/* Arch-specific enabling code. */
	ret = __cpu_up(cpu, idle);
	irq_unlock_sparse();
	if (ret)
		return ret;
	return bringup_wait_for_ap(cpu);
}

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/*
 * Hotplug state machine related functions
 */



static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st)
{
	for (st->state--; st->state > st->target; st->state--) {
		struct cpuhp_step *step = cpuhp_get_step(st->state);

		if (!step->skip_onerr)
			cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
	}
}

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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;

	while (st->state < target) {
		st->state++;
		ret = cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
		if (ret) {
			st->target = prev_state;
			undo_cpu_up(cpu, st);
			break;
		}
	}
	return ret;
}

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/*
 * 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_up);
	init_completion(&st->done_down);
}

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static int cpuhp_should_run(unsigned int cpu)
{
	struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);

	return st->should_run;
}

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/*
 * 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;

	/*
         * 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();

	if (WARN_ON_ONCE(!st->should_run))
		return;

	cpuhp_lock_acquire(bringup);

	if (st->single) {
		state = st->cb_state;
		st->should_run = false;
	} else {
		if (bringup) {
			st->state++;
			state = st->state;
			st->should_run = (st->state < st->target);
			WARN_ON_ONCE(st->state > st->target);
		} else {
			state = st->state;
			st->state--;
			st->should_run = (st->state > st->target);
			WARN_ON_ONCE(st->state < st->target);
		}
	}

	WARN_ON_ONCE(!cpuhp_is_ap_state(state));

	if (st->rollback) {
		struct cpuhp_step *step = cpuhp_get_step(state);
		if (step->skip_onerr)
			goto next;
	}

	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;
	}

next:
	cpuhp_lock_release(bringup);

	if (!st->should_run)
		complete_ap_thread(st, bringup);
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Peter Zijlstra
185
60.66%
3
33.33%
Thomas Gleixner
101
33.11%
5
55.56%
Sebastian Andrzej Siewior
19
6.23%
1
11.11%
Total
305
100.00%
9
100.00%

/* 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;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Thomas Gleixner
126
70.00%
8
72.73%
Peter Zijlstra
54
30.00%
3
27.27%
Total
180
100.00%
11
100.00%



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(st, st->target);
	trace_cpuhp_exit(cpu, st->state, prev_state, ret);

	return ret;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Thomas Gleixner
58
61.70%
3
60.00%
Peter Zijlstra
36
38.30%
2
40.00%
Total
94
100.00%
5
100.00%


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));
}

Contributors
Person
Tokens
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Thomas Gleixner
27
100.00%
1
100.00%
Total
27
100.00%
1
100.00%

#ifdef CONFIG_HOTPLUG_CPU
/**
 * 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();
}

Contributors
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Anton Vorontsov
70
100.00%
2
100.00%
Total
70
100.00%
2
100.00%

/* 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();
	int ret;

	/* Ensure this CPU doesn't handle any more interrupts. */
	err = __cpu_disable();
	if (err < 0)
		return err;

	/*
         * We get here while we are in CPUHP_TEARDOWN_CPU state and we must not
         * do this step again.
         */
	WARN_ON(st->state != CPUHP_TEARDOWN_CPU);
	st->state--;
	/* Invoke the former CPU_DYING callbacks */
	for (; st->state > target; st->state--) {
		ret = cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
		/*
                 * DYING must not fail!
                 */
		WARN_ON_ONCE(ret);
	}

	/* Give up timekeeping duties */
	tick_handover_do_timer();
	/* Park the stopper thread */
	stop_machine_park(cpu);
	return 0;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Thomas Gleixner
116
88.55%
4
66.67%
Peter Zijlstra
15
11.45%
2
33.33%
Total
131
100.00%
6
100.00%



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_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(per_cpu_ptr(&cpuhp_state, cpu)->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);

	tick_cleanup_dead_cpu(cpu);
	rcutree_migrate_callbacks(cpu);
	return 0;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Thomas Gleixner
74
51.39%
7
35.00%
Rusty Russell
35
24.31%
4
20.00%
Sebastian Andrzej Siewior
14
9.72%
2
10.00%
Paul E. McKenney
8
5.56%
2
10.00%
Preeti U. Murthy
5
3.47%
1
5.00%
Peter Zijlstra
4
2.78%
2
10.00%
Nicholas Piggin
3
2.08%
1
5.00%
Brendan Jackman
1
0.69%
1
5.00%
Total
144
100.00%
20
100.00%



static void cpuhp_complete_idle_dead(void *arg)
{
	struct cpuhp_cpu_state *st = arg;

	complete_ap_thread(st, false);
}

Contributors
Person
Tokens
Prop
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CommitProp
Thomas Gleixner
21
87.50%
1
50.00%
Peter Zijlstra
3
12.50%
1
50.00%
Total
24
100.00%
2
100.00%



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);
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Thomas Gleixner
54
100.00%
3
100.00%
Total
54
100.00%
3
100.00%



static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st)
{
	for (st->state++; st->state < st->target; st->state++) {
		struct cpuhp_step *step = cpuhp_get_step(st->state);

		if (!step->skip_onerr)
			cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
	}
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Peter Zijlstra
71
100.00%
1
100.00%
Total
71
100.00%
1
100.00%



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;

	for (; st->state > target; st->state--) {
		ret = cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
		if (ret) {
			st->target = prev_state;
			undo_cpu_down(cpu, st);
			break;
		}
	}
	return ret;
}

Contributors
Person
Tokens
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Commits
CommitProp
Peter Zijlstra
88
100.00%
1
100.00%
Total
88
100.00%
1
100.00%

/* 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(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 > CPUHP_TEARDOWN_CPU && st->state < prev_state) {
		cpuhp_reset_state(st, prev_state);
		__cpuhp_kick_ap(st);
	}

out:
	cpus_write_unlock();
	/*
         * Do post unplug cleanup. This is still protected against
         * concurrent CPU hotplug via cpu_add_remove_lock.
         */
	lockup_detector_cleanup();
	return ret;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Thomas Gleixner
130
68.78%
9
69.23%
Peter Zijlstra
30
15.87%
1
7.69%
Sebastian Andrzej Siewior
24
12.70%
1
7.69%
Rafael J. Wysocki
3
1.59%
1
7.69%
Gautham R. Shenoy
2
1.06%
1
7.69%
Total
189
100.00%
13
100.00%



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;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Rafael J. Wysocki
29
54.72%
2
33.33%
Thomas Gleixner
8
15.09%
1
16.67%
Maksim Krasnyanskiy
7
13.21%
1
16.67%
Rusty Russell
5
9.43%
1
16.67%
Gautham R. Shenoy
4
7.55%
1
16.67%
Total
53
100.00%
6
100.00%



int cpu_down(unsigned int cpu)
{
	return do_cpu_down(cpu, CPUHP_OFFLINE);
}
Contributors
Person
Tokens
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CommitProp
Thomas Gleixner
17
100.00%
1
100.00%
Total
17
100.00%
1
100.00%


EXPORT_SYMBOL(cpu_down);

#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);
	int ret;

	rcu_cpu_starting(cpu);	/* Enables RCU usage on this CPU. */
	while (st->state < target) {
		st->state++;
		ret = cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
		/*
                 * STARTING must not fail!
                 */
		WARN_ON_ONCE(ret);
	}
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Thomas Gleixner
66
77.65%
3
42.86%
Peter Zijlstra
13
15.29%
2
28.57%
Paul E. McKenney
5
5.88%
1
14.29%
Sebastian Andrzej Siewior
1
1.18%
1
14.29%
Total
85
100.00%
7
100.00%

/*
 * Called from the idle task. Wake up the controlling task which brings the
 * stopper and 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;

	st->state = CPUHP_AP_ONLINE_IDLE;
	complete_ap_thread(st, true);
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Thomas Gleixner
38
92.68%
3
75.00%
Peter Zijlstra
3
7.32%
1
25.00%
Total
41
100.00%
4
100.00%

/* 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 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;

	cpuhp_set_state(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();
	return ret;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Thomas Gleixner
111
62.01%
10
50.00%
Rusty Russell
19
10.61%
1
5.00%
Suresh B. Siddha
15
8.38%
1
5.00%
Rafael J. Wysocki
9
5.03%
2
10.00%
Yasuaki Ishimatsu
9
5.03%
1
5.00%
Andrew Morton
7
3.91%
2
10.00%
Gautham R. Shenoy
5
2.79%
2
10.00%
Peter Zijlstra
4
2.23%
1
5.00%
Total
179
100.00%
20
100.00%



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;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Rafael J. Wysocki
36
33.96%
2
20.00%
Kamezawa Hiroyuki
29
27.36%
1
10.00%
Minskey Guo
14
13.21%
1
10.00%
Thomas Gleixner
8
7.55%
1
10.00%
Maksim Krasnyanskiy
7
6.60%
1
10.00%
Gautham R. Shenoy
4
3.77%
1
10.00%
Fabian Frederick
4
3.77%
1
10.00%
Toshi Kani
3
2.83%
1
10.00%
Rusty Russell
1
0.94%
1
10.00%
Total
106
100.00%
10
100.00%



int cpu_up(unsigned int cpu)
{
	return do_cpu_up(cpu, CPUHP_ONLINE);
}
Contributors
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Thomas Gleixner
17
100.00%
1
100.00%
Total
17
100.00%
1
100.00%


EXPORT_SYMBOL_GPL(cpu_up);

#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 (!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;
		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;
}

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86
58.90%
3
23.08%
Todd E Brandt
24
16.44%
1
7.69%
James Morse
13
8.90%
1
7.69%
Rusty Russell
8
5.48%
2
15.38%
Gautham R. Shenoy
4
2.74%
1
7.69%
Vitaly Kuznetsov
4
2.74%
1
7.69%
Fabian Frederick
3
2.05%
1
7.69%
Thomas Gleixner
2
1.37%
1
7.69%
Xiaotian Feng
1
0.68%
1
7.69%
Ingo Molnar
1
0.68%
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void __weak arch_enable_nonboot_cpus_begin(void)
{
}

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void __weak arch_enable_nonboot_cpus_end(void)
{
}

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void enable_nonboot_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_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();
}

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Rafael J. Wysocki
73
62.39%
4
36.36%
Todd E Brandt
24
20.51%
1
9.09%
Suresh B. Siddha
6
5.13%
1
9.09%
Gautham R. Shenoy
4
3.42%
1
9.09%
Fabian Frederick
3
2.56%
1
9.09%
Rusty Russell
3
2.56%
1
9.09%
Lianwei Wang
2
1.71%
1
9.09%
Thomas Gleixner
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static int __init alloc_frozen_cpus(void)
{
	if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
		return -ENOMEM;
	return 0;
}
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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;
}


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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;
}
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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_bp_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_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	= hrtimers_dead_cpu,
        },
	[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:dead",
		.startup.single		= timers_prepare_cpu,
		.teardown.single	= timers_dead_cpu,
        },
	/* Kicks the plugged cpu into life */
	[CPUHP_BRINGUP_CPU] = {
		.name			= "cpu:bringup",
		.startup.single		= bringup_cpu,
		.teardown.single	= NULL,
		.cant_stop		= true,
        },
	/*
         * Handled on controll processor until the plugged processor manages
         * this itself.
         */
	[CPUHP_TEARDOWN_CPU] = {
		.name			= "cpu:teardown",
		.startup.single		= NULL,
		.teardown.single	= 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.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,
        },
	/* 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:online",
		.startup.single		= smpboot_unpark_threads,
		.teardown.single	= NULL,
        },
	[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_WORKQUEUE_ONLINE] = {
		.name			= "workqueue:online",
		.startup.single		= workqueue_online_cpu,
		.teardown.single	= workqueue_offline_cpu,
        },
	[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;
}

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/*
 * 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_ap_states + CPUHP_AP_ONLINE_DYN;
		end = CPUHP_AP_ONLINE_DYN_END;
		break;
	case CPUHP_BP_PREPARE_DYN:
		step = cpuhp_bp_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;
}

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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;
}

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5
3.42%
1
14.29%
Sebastian Andrzej Siewior
5
3.42%
1
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146
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7
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static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
{
	return cpuhp_get_step(state)->teardown.single;
}

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/*
 * 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 ((bringup && !sp->startup.single) ||
	    (!bringup && !sp->teardown.single))
		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;
}

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/*
 * 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);
	}
}

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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;
}

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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;
}
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EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);

/**
 * __cpuhp_setup_state_cpuslocked - 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
 * @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.
 * Returns:
 *   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;
}
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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;
}
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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;
}
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2
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Sebastian Andrzej Siewior
6
4.44%
1
33.33%
Total
135
100.00%
3
100.00%


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);
}
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3
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15
10.14%
2
40.00%
Total
148
100.00%
5
100.00%


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();
}
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16.00%
2
66.67%
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25
100.00%
3
100.00%


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);
}
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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)
		goto out;

	if (st->state < target)
		ret = do_cpu_up(dev->id, target);
	else
		ret = do_cpu_down(dev->id, target);
out:
	unlock_device_hotplug();
	return ret ? ret : count;
}

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5
2.50%
1
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200
100.00%
2
100.00%



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);
}
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static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target);




static ssize_t write_cpuhp_fail(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;

	/*
         * Cannot fail STARTING/DYING callbacks.
         */
	if (cpuhp_is_atomic_state(fail))
		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;
}

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static ssize_t show_cpuhp_fail(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);
}

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static DEVICE_ATTR(fail, 0644, show_cpuhp_fail, write_cpuhp_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 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;
}
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static DEVICE_ATTR(states, 0444, show_cpuhp_states, NULL);


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
};



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;
}
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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);
}

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19
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2
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void init_cpu_possible(const struct cpumask *src)
{
	cpumask_copy(&__cpu_possible_mask, src);
}

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2
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19
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2
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void init_cpu_online(const struct cpumask *src)
{
	cpumask_copy(&__cpu_online_mask, src);
}

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19
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2
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/*
 * 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
}

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43
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Peter Zijlstra
9
17.31%
1
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52
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2
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/*
 * 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;
}
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21
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1
100.00%

Overall Contributors
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Thomas Gleixner
4375
60.10%
51
34.23%
Peter Zijlstra
1336
18.35%
8
5.37%
Rafael J. Wysocki
250
3.43%
6
4.03%
Sebastian Andrzej Siewior
249
3.42%
7
4.70%
Rusty Russell
222
3.05%
10
6.71%
Srivatsa S. Bhat
108
1.48%
2
1.34%
Anton Vorontsov
80
1.10%
2
1.34%
Mike Travis
58
0.80%
1
0.67%
Lai Jiangshan
56
0.77%
2
1.34%
Todd E Brandt
51
0.70%
1
0.67%
Gautham R. Shenoy
49
0.67%
3
2.01%
Rasmus Villemoes
49
0.67%
2
1.34%
Richard Weinberger
48
0.66%
2
1.34%
Linus Torvalds
43
0.59%
3
2.01%
Suresh B. Siddha
35
0.48%
2
1.34%
Kamezawa Hiroyuki
29
0.40%
1
0.67%
Lianwei Wang
26
0.36%
1
0.67%
Paul E. McKenney
21
0.29%
6
4.03%
Ashok Raj
20
0.27%
2
1.34%
Richard Cochran
20
0.27%
2
1.34%
Maksim Krasnyanskiy
17
0.23%
2
1.34%
Vitaly Kuznetsov
15
0.21%
2
1.34%
Ingo Molnar
14
0.19%
6
4.03%
Minskey Guo
14
0.19%
1
0.67%
James Morse
13
0.18%
1
0.67%
Fabian Frederick
10
0.14%
1
0.67%
Yasuaki Ishimatsu
9
0.12%
1
0.67%
Preeti U. Murthy
8
0.11%
1
0.67%
Andrew Morton
7
0.10%
2
1.34%
David Hildenbrand
7
0.10%
1
0.67%
Rui Zhang
5
0.07%
1
0.67%
Ethan Barnes
5
0.07%
1
0.67%
Fenghua Yu
4
0.05%
2
1.34%
Mathieu Malaterre
4
0.05%
1
0.67%
Toshi Kani
4
0.05%
2
1.34%
Nicholas Piggin
3
0.04%
1
0.67%
Michal Hocko
3
0.04%
1
0.67%
Tejun Heo
3
0.04%
1
0.67%
Joonas Lahtinen
2
0.03%
1
0.67%
Arvind Yadav
2
0.03%
1
0.67%
Michael Rodriguez
1
0.01%
1
0.67%
Brendan Jackman
1
0.01%
1
0.67%
Boris Ostrovsky
1
0.01%
1
0.67%
Paul Gortmaker
1
0.01%
1
0.67%
Xiaotian Feng
1
0.01%
1
0.67%
Total
7279
100.00%
149
100.00%
Directory: kernel

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