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|
/*
* kernel/workqueue.c - generic async execution with shared worker pool
*
* Copyright (C) 2002 Ingo Molnar
*
* Derived from the taskqueue/keventd code by:
* David Woodhouse <dwmw2@infradead.org>
* Andrew Morton
* Kai Petzke <wpp@marie.physik.tu-berlin.de>
* Theodore Ts'o <tytso@mit.edu>
*
* Made to use alloc_percpu by Christoph Lameter.
*
* Copyright (C) 2010 SUSE Linux Products GmbH
* Copyright (C) 2010 Tejun Heo <tj@kernel.org>
*
* This is the generic async execution mechanism. Work items as are
* executed in process context. The worker pool is shared and
* automatically managed. There is one worker pool for each CPU and
* one extra for works which are better served by workers which are
* not bound to any specific CPU.
*
* Please read Documentation/workqueue.txt for details.
*/
#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/signal.h>
#include <linux/completion.h>
#include <linux/workqueue.h>
#include <linux/slab.h>
#include <linux/cpu.h>
#include <linux/notifier.h>
#include <linux/kthread.h>
#include <linux/hardirq.h>
#include <linux/mempolicy.h>
#include <linux/freezer.h>
#include <linux/kallsyms.h>
#include <linux/debug_locks.h>
#include <linux/lockdep.h>
#include <linux/idr.h>
#include <linux/hashtable.h>
#include "workqueue_internal.h"
enum {
/*
* worker_pool flags
*
* A bound pool is either associated or disassociated with its CPU.
* While associated (!DISASSOCIATED), all workers are bound to the
* CPU and none has %WORKER_UNBOUND set and concurrency management
* is in effect.
*
* While DISASSOCIATED, the cpu may be offline and all workers have
* %WORKER_UNBOUND set and concurrency management disabled, and may
* be executing on any CPU. The pool behaves as an unbound one.
*
* Note that DISASSOCIATED can be flipped only while holding
* assoc_mutex to avoid changing binding state while
* create_worker() is in progress.
*/
POOL_MANAGE_WORKERS = 1 << 0, /* need to manage workers */
POOL_MANAGING_WORKERS = 1 << 1, /* managing workers */
POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
POOL_FREEZING = 1 << 3, /* freeze in progress */
/* worker flags */
WORKER_STARTED = 1 << 0, /* started */
WORKER_DIE = 1 << 1, /* die die die */
WORKER_IDLE = 1 << 2, /* is idle */
WORKER_PREP = 1 << 3, /* preparing to run works */
WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
WORKER_UNBOUND = 1 << 7, /* worker is unbound */
WORKER_NOT_RUNNING = WORKER_PREP | WORKER_UNBOUND |
WORKER_CPU_INTENSIVE,
NR_STD_WORKER_POOLS = 2, /* # standard pools per cpu */
BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2,
/* call for help after 10ms
(min two ticks) */
MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
CREATE_COOLDOWN = HZ, /* time to breath after fail */
/*
* Rescue workers are used only on emergencies and shared by
* all cpus. Give -20.
*/
RESCUER_NICE_LEVEL = -20,
HIGHPRI_NICE_LEVEL = -20,
};
/*
* Structure fields follow one of the following exclusion rules.
*
* I: Modifiable by initialization/destruction paths and read-only for
* everyone else.
*
* P: Preemption protected. Disabling preemption is enough and should
* only be modified and accessed from the local cpu.
*
* L: pool->lock protected. Access with pool->lock held.
*
* X: During normal operation, modification requires pool->lock and should
* be done only from local cpu. Either disabling preemption on local
* cpu or grabbing pool->lock is enough for read access. If
* POOL_DISASSOCIATED is set, it's identical to L.
*
* F: wq->flush_mutex protected.
*
* W: workqueue_lock protected.
*/
/* struct worker is defined in workqueue_internal.h */
struct worker_pool {
spinlock_t lock; /* the pool lock */
unsigned int cpu; /* I: the associated cpu */
int id; /* I: pool ID */
unsigned int flags; /* X: flags */
struct list_head worklist; /* L: list of pending works */
int nr_workers; /* L: total number of workers */
/* nr_idle includes the ones off idle_list for rebinding */
int nr_idle; /* L: currently idle ones */
struct list_head idle_list; /* X: list of idle workers */
struct timer_list idle_timer; /* L: worker idle timeout */
struct timer_list mayday_timer; /* L: SOS timer for workers */
/* workers are chained either in busy_hash or idle_list */
DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
/* L: hash of busy workers */
struct mutex assoc_mutex; /* protect POOL_DISASSOCIATED */
struct ida worker_ida; /* L: for worker IDs */
/*
* The current concurrency level. As it's likely to be accessed
* from other CPUs during try_to_wake_up(), put it in a separate
* cacheline.
*/
atomic_t nr_running ____cacheline_aligned_in_smp;
} ____cacheline_aligned_in_smp;
/*
* The per-pool workqueue. While queued, the lower WORK_STRUCT_FLAG_BITS
* of work_struct->data are used for flags and the remaining high bits
* point to the pwq; thus, pwqs need to be aligned at two's power of the
* number of flag bits.
*/
struct pool_workqueue {
struct worker_pool *pool; /* I: the associated pool */
struct workqueue_struct *wq; /* I: the owning workqueue */
int work_color; /* L: current color */
int flush_color; /* L: flushing color */
int nr_in_flight[WORK_NR_COLORS];
/* L: nr of in_flight works */
int nr_active; /* L: nr of active works */
int max_active; /* L: max active works */
struct list_head delayed_works; /* L: delayed works */
} __aligned(1 << WORK_STRUCT_FLAG_BITS);
/*
* Structure used to wait for workqueue flush.
*/
struct wq_flusher {
struct list_head list; /* F: list of flushers */
int flush_color; /* F: flush color waiting for */
struct completion done; /* flush completion */
};
/*
* All cpumasks are assumed to be always set on UP and thus can't be
* used to determine whether there's something to be done.
*/
#ifdef CONFIG_SMP
typedef cpumask_var_t mayday_mask_t;
#define mayday_test_and_set_cpu(cpu, mask) \
cpumask_test_and_set_cpu((cpu), (mask))
#define mayday_clear_cpu(cpu, mask) cpumask_clear_cpu((cpu), (mask))
#define for_each_mayday_cpu(cpu, mask) for_each_cpu((cpu), (mask))
#define alloc_mayday_mask(maskp, gfp) zalloc_cpumask_var((maskp), (gfp))
#define free_mayday_mask(mask) free_cpumask_var((mask))
#else
typedef unsigned long mayday_mask_t;
#define mayday_test_and_set_cpu(cpu, mask) test_and_set_bit(0, &(mask))
#define mayday_clear_cpu(cpu, mask) clear_bit(0, &(mask))
#define for_each_mayday_cpu(cpu, mask) if ((cpu) = 0, (mask))
#define alloc_mayday_mask(maskp, gfp) true
#define free_mayday_mask(mask) do { } while (0)
#endif
/*
* The externally visible workqueue abstraction is an array of
* per-CPU workqueues:
*/
struct workqueue_struct {
unsigned int flags; /* W: WQ_* flags */
union {
struct pool_workqueue __percpu *pcpu;
struct pool_workqueue *single;
unsigned long v;
} pool_wq; /* I: pwq's */
struct list_head list; /* W: list of all workqueues */
struct mutex flush_mutex; /* protects wq flushing */
int work_color; /* F: current work color */
int flush_color; /* F: current flush color */
atomic_t nr_pwqs_to_flush; /* flush in progress */
struct wq_flusher *first_flusher; /* F: first flusher */
struct list_head flusher_queue; /* F: flush waiters */
struct list_head flusher_overflow; /* F: flush overflow list */
mayday_mask_t mayday_mask; /* cpus requesting rescue */
struct worker *rescuer; /* I: rescue worker */
int nr_drainers; /* W: drain in progress */
int saved_max_active; /* W: saved pwq max_active */
#ifdef CONFIG_LOCKDEP
struct lockdep_map lockdep_map;
#endif
char name[]; /* I: workqueue name */
};
static struct kmem_cache *pwq_cache;
struct workqueue_struct *system_wq __read_mostly;
EXPORT_SYMBOL_GPL(system_wq);
struct workqueue_struct *system_highpri_wq __read_mostly;
EXPORT_SYMBOL_GPL(system_highpri_wq);
struct workqueue_struct *system_long_wq __read_mostly;
EXPORT_SYMBOL_GPL(system_long_wq);
struct workqueue_struct *system_unbound_wq __read_mostly;
EXPORT_SYMBOL_GPL(system_unbound_wq);
struct workqueue_struct *system_freezable_wq __read_mostly;
EXPORT_SYMBOL_GPL(system_freezable_wq);
#define CREATE_TRACE_POINTS
#include <trace/events/workqueue.h>
#define for_each_std_worker_pool(pool, cpu) \
for ((pool) = &std_worker_pools(cpu)[0]; \
(pool) < &std_worker_pools(cpu)[NR_STD_WORKER_POOLS]; (pool)++)
#define for_each_busy_worker(worker, i, pool) \
hash_for_each(pool->busy_hash, i, worker, hentry)
static inline int __next_wq_cpu(int cpu, const struct cpumask *mask,
unsigned int sw)
{
if (cpu < nr_cpu_ids) {
if (sw & 1) {
cpu = cpumask_next(cpu, mask);
if (cpu < nr_cpu_ids)
return cpu;
}
if (sw & 2)
return WORK_CPU_UNBOUND;
}
return WORK_CPU_END;
}
static inline int __next_pwq_cpu(int cpu, const struct cpumask *mask,
struct workqueue_struct *wq)
{
return __next_wq_cpu(cpu, mask, !(wq->flags & WQ_UNBOUND) ? 1 : 2);
}
/*
* CPU iterators
*
* An extra cpu number is defined using an invalid cpu number
* (WORK_CPU_UNBOUND) to host workqueues which are not bound to any
* specific CPU. The following iterators are similar to for_each_*_cpu()
* iterators but also considers the unbound CPU.
*
* for_each_wq_cpu() : possible CPUs + WORK_CPU_UNBOUND
* for_each_online_wq_cpu() : online CPUs + WORK_CPU_UNBOUND
* for_each_pwq_cpu() : possible CPUs for bound workqueues,
* WORK_CPU_UNBOUND for unbound workqueues
*/
#define for_each_wq_cpu(cpu) \
for ((cpu) = __next_wq_cpu(-1, cpu_possible_mask, 3); \
(cpu) < WORK_CPU_END; \
(cpu) = __next_wq_cpu((cpu), cpu_possible_mask, 3))
#define for_each_online_wq_cpu(cpu) \
for ((cpu) = __next_wq_cpu(-1, cpu_online_mask, 3); \
(cpu) < WORK_CPU_END; \
(cpu) = __next_wq_cpu((cpu), cpu_online_mask, 3))
#define for_each_pwq_cpu(cpu, wq) \
for ((cpu) = __next_pwq_cpu(-1, cpu_possible_mask, (wq)); \
(cpu) < WORK_CPU_END; \
(cpu) = __next_pwq_cpu((cpu), cpu_possible_mask, (wq)))
#ifdef CONFIG_DEBUG_OBJECTS_WORK
static struct debug_obj_descr work_debug_descr;
static void *work_debug_hint(void *addr)
{
return ((struct work_struct *) addr)->func;
}
/*
* fixup_init is called when:
* - an active object is initialized
*/
static int work_fixup_init(void *addr, enum debug_obj_state state)
{
struct work_struct *work = addr;
switch (state) {
case ODEBUG_STATE_ACTIVE:
cancel_work_sync(work);
debug_object_init(work, &work_debug_descr);
return 1;
default:
return 0;
}
}
/*
* fixup_activate is called when:
* - an active object is activated
* - an unknown object is activated (might be a statically initialized object)
*/
static int work_fixup_activate(void *addr, enum debug_obj_state state)
{
struct work_struct *work = addr;
switch (state) {
case ODEBUG_STATE_NOTAVAILABLE:
/*
* This is not really a fixup. The work struct was
* statically initialized. We just make sure that it
* is tracked in the object tracker.
*/
if (test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work))) {
debug_object_init(work, &work_debug_descr);
debug_object_activate(work, &work_debug_descr);
return 0;
}
WARN_ON_ONCE(1);
return 0;
case ODEBUG_STATE_ACTIVE:
WARN_ON(1);
default:
return 0;
}
}
/*
* fixup_free is called when:
* - an active object is freed
*/
static int work_fixup_free(void *addr, enum debug_obj_state state)
{
struct work_struct *work = addr;
switch (state) {
case ODEBUG_STATE_ACTIVE:
cancel_work_sync(work);
debug_object_free(work, &work_debug_descr);
return 1;
default:
return 0;
}
}
static struct debug_obj_descr work_debug_descr = {
.name = "work_struct",
.debug_hint = work_debug_hint,
.fixup_init = work_fixup_init,
.fixup_activate = work_fixup_activate,
.fixup_free = work_fixup_free,
};
static inline void debug_work_activate(struct work_struct *work)
{
debug_object_activate(work, &work_debug_descr);
}
static inline void debug_work_deactivate(struct work_struct *work)
{
debug_object_deactivate(work, &work_debug_descr);
}
void __init_work(struct work_struct *work, int onstack)
{
if (onstack)
debug_object_init_on_stack(work, &work_debug_descr);
else
debug_object_init(work, &work_debug_descr);
}
EXPORT_SYMBOL_GPL(__init_work);
void destroy_work_on_stack(struct work_struct *work)
{
debug_object_free(work, &work_debug_descr);
}
EXPORT_SYMBOL_GPL(destroy_work_on_stack);
#else
static inline void debug_work_activate(struct work_struct *work) { }
static inline void debug_work_deactivate(struct work_struct *work) { }
#endif
/* Serializes the accesses to the list of workqueues. */
static DEFINE_SPINLOCK(workqueue_lock);
static LIST_HEAD(workqueues);
static bool workqueue_freezing; /* W: have wqs started freezing? */
/*
* The CPU and unbound standard worker pools. The unbound ones have
* POOL_DISASSOCIATED set, and their workers have WORKER_UNBOUND set.
*/
static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS],
cpu_std_worker_pools);
static struct worker_pool unbound_std_worker_pools[NR_STD_WORKER_POOLS];
/* idr of all pools */
static DEFINE_MUTEX(worker_pool_idr_mutex);
static DEFINE_IDR(worker_pool_idr);
static int worker_thread(void *__worker);
static struct worker_pool *std_worker_pools(int cpu)
{
if (cpu != WORK_CPU_UNBOUND)
return per_cpu(cpu_std_worker_pools, cpu);
else
return unbound_std_worker_pools;
}
static int std_worker_pool_pri(struct worker_pool *pool)
{
return pool - std_worker_pools(pool->cpu);
}
/* allocate ID and assign it to @pool */
static int worker_pool_assign_id(struct worker_pool *pool)
{
int ret;
mutex_lock(&worker_pool_idr_mutex);
idr_pre_get(&worker_pool_idr, GFP_KERNEL);
ret = idr_get_new(&worker_pool_idr, pool, &pool->id);
mutex_unlock(&worker_pool_idr_mutex);
return ret;
}
/*
* Lookup worker_pool by id. The idr currently is built during boot and
* never modified. Don't worry about locking for now.
*/
static struct worker_pool *worker_pool_by_id(int pool_id)
{
return idr_find(&worker_pool_idr, pool_id);
}
static struct worker_pool *get_std_worker_pool(int cpu, bool highpri)
{
struct worker_pool *pools = std_worker_pools(cpu);
return &pools[highpri];
}
static struct pool_workqueue *get_pwq(unsigned int cpu,
struct workqueue_struct *wq)
{
if (!(wq->flags & WQ_UNBOUND)) {
if (likely(cpu < nr_cpu_ids))
return per_cpu_ptr(wq->pool_wq.pcpu, cpu);
} else if (likely(cpu == WORK_CPU_UNBOUND))
return wq->pool_wq.single;
return NULL;
}
static unsigned int work_color_to_flags(int color)
{
return color << WORK_STRUCT_COLOR_SHIFT;
}
static int get_work_color(struct work_struct *work)
{
return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) &
((1 << WORK_STRUCT_COLOR_BITS) - 1);
}
static int work_next_color(int color)
{
return (color + 1) % WORK_NR_COLORS;
}
/*
* While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
* contain the pointer to the queued pwq. Once execution starts, the flag
* is cleared and the high bits contain OFFQ flags and pool ID.
*
* set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
* and clear_work_data() can be used to set the pwq, pool or clear
* work->data. These functions should only be called while the work is
* owned - ie. while the PENDING bit is set.
*
* get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
* corresponding to a work. Pool is available once the work has been
* queued anywhere after initialization until it is sync canceled. pwq is
* available only while the work item is queued.
*
* %WORK_OFFQ_CANCELING is used to mark a work item which is being
* canceled. While being canceled, a work item may have its PENDING set
* but stay off timer and worklist for arbitrarily long and nobody should
* try to steal the PENDING bit.
*/
static inline void set_work_data(struct work_struct *work, unsigned long data,
unsigned long flags)
{
WARN_ON_ONCE(!work_pending(work));
atomic_long_set(&work->data, data | flags | work_static(work));
}
static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq,
unsigned long extra_flags)
{
set_work_data(work, (unsigned long)pwq,
WORK_STRUCT_PENDING | WORK_STRUCT_PWQ | extra_flags);
}
static void set_work_pool_and_keep_pending(struct work_struct *work,
int pool_id)
{
set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT,
WORK_STRUCT_PENDING);
}
static void set_work_pool_and_clear_pending(struct work_struct *work,
int pool_id)
{
/*
* The following wmb is paired with the implied mb in
* test_and_set_bit(PENDING) and ensures all updates to @work made
* here are visible to and precede any updates by the next PENDING
* owner.
*/
smp_wmb();
set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0);
}
static void clear_work_data(struct work_struct *work)
{
smp_wmb(); /* see set_work_pool_and_clear_pending() */
set_work_data(work, WORK_STRUCT_NO_POOL, 0);
}
static struct pool_workqueue *get_work_pwq(struct work_struct *work)
{
unsigned long data = atomic_long_read(&work->data);
if (data & WORK_STRUCT_PWQ)
return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
else
return NULL;
}
/**
* get_work_pool - return the worker_pool a given work was associated with
* @work: the work item of interest
*
* Return the worker_pool @work was last associated with. %NULL if none.
*/
static struct worker_pool *get_work_pool(struct work_struct *work)
{
unsigned long data = atomic_long_read(&work->data);
struct worker_pool *pool;
int pool_id;
if (data & WORK_STRUCT_PWQ)
return ((struct pool_workqueue *)
(data & WORK_STRUCT_WQ_DATA_MASK))->pool;
pool_id = data >> WORK_OFFQ_POOL_SHIFT;
if (pool_id == WORK_OFFQ_POOL_NONE)
return NULL;
pool = worker_pool_by_id(pool_id);
WARN_ON_ONCE(!pool);
return pool;
}
/**
* get_work_pool_id - return the worker pool ID a given work is associated with
* @work: the work item of interest
*
* Return the worker_pool ID @work was last associated with.
* %WORK_OFFQ_POOL_NONE if none.
*/
static int get_work_pool_id(struct work_struct *work)
{
unsigned long data = atomic_long_read(&work->data);
if (data & WORK_STRUCT_PWQ)
return ((struct pool_workqueue *)
(data & WORK_STRUCT_WQ_DATA_MASK))->pool->id;
return data >> WORK_OFFQ_POOL_SHIFT;
}
static void mark_work_canceling(struct work_struct *work)
{
unsigned long pool_id = get_work_pool_id(work);
pool_id <<= WORK_OFFQ_POOL_SHIFT;
set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING);
}
static bool work_is_canceling(struct work_struct *work)
{
unsigned long data = atomic_long_read(&work->data);
return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING);
}
/*
* Policy functions. These define the policies on how the global worker
* pools are managed. Unless noted otherwise, these functions assume that
* they're being called with pool->lock held.
*/
static bool __need_more_worker(struct worker_pool *pool)
{
return !atomic_read(&pool->nr_running);
}
/*
* Need to wake up a worker? Called from anything but currently
* running workers.
*
* Note that, because unbound workers never contribute to nr_running, this
* function will always return %true for unbound pools as long as the
* worklist isn't empty.
*/
static bool need_more_worker(struct worker_pool *pool)
{
return !list_empty(&pool->worklist) && __need_more_worker(pool);
}
/* Can I start working? Called from busy but !running workers. */
static bool may_start_working(struct worker_pool *pool)
{
return pool->nr_idle;
}
/* Do I need to keep working? Called from currently running workers. */
static bool keep_working(struct worker_pool *pool)
{
return !list_empty(&pool->worklist) &&
atomic_read(&pool->nr_running) <= 1;
}
/* Do we need a new worker? Called from manager. */
static bool need_to_create_worker(struct worker_pool *pool)
{
return need_more_worker(pool) && !may_start_working(pool);
}
/* Do I need to be the manager? */
static bool need_to_manage_workers(struct worker_pool *pool)
{
return need_to_create_worker(pool) ||
(pool->flags & POOL_MANAGE_WORKERS);
}
/* Do we have too many workers and should some go away? */
static bool too_many_workers(struct worker_pool *pool)
{
bool managing = pool->flags & POOL_MANAGING_WORKERS;
int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
int nr_busy = pool->nr_workers - nr_idle;
/*
* nr_idle and idle_list may disagree if idle rebinding is in
* progress. Never return %true if idle_list is empty.
*/
if (list_empty(&pool->idle_list))
return false;
return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
}
/*
* Wake up functions.
*/
/* Return the first worker. Safe with preemption disabled */
static struct worker *first_worker(struct worker_pool *pool)
{
if (unlikely(list_empty(&pool->idle_list)))
return NULL;
return list_first_entry(&pool->idle_list, struct worker, entry);
}
/**
* wake_up_worker - wake up an idle worker
* @pool: worker pool to wake worker from
*
* Wake up the first idle worker of @pool.
*
* CONTEXT:
* spin_lock_irq(pool->lock).
*/
static void wake_up_worker(struct worker_pool *pool)
{
struct worker *worker = first_worker(pool);
if (likely(worker))
wake_up_process(worker->task);
}
/**
* wq_worker_waking_up - a worker is waking up
* @task: task waking up
* @cpu: CPU @task is waking up to
*
* This function is called during try_to_wake_up() when a worker is
* being awoken.
*
* CONTEXT:
* spin_lock_irq(rq->lock)
*/
void wq_worker_waking_up(struct task_struct *task, unsigned int cpu)
{
struct worker *worker = kthread_data(task);
if (!(worker->flags & WORKER_NOT_RUNNING)) {
WARN_ON_ONCE(worker->pool->cpu != cpu);
atomic_inc(&worker->pool->nr_running);
}
}
/**
* wq_worker_sleeping - a worker is going to sleep
* @task: task going to sleep
* @cpu: CPU in question, must be the current CPU number
*
* This function is called during schedule() when a busy worker is
* going to sleep. Worker on the same cpu can be woken up by
* returning pointer to its task.
*
* CONTEXT:
* spin_lock_irq(rq->lock)
*
* RETURNS:
* Worker task on @cpu to wake up, %NULL if none.
*/
struct task_struct *wq_worker_sleeping(struct task_struct *task,
unsigned int cpu)
{
struct worker *worker = kthread_data(task), *to_wakeup = NULL;
struct worker_pool *pool;
/*
* Rescuers, which may not have all the fields set up like normal
* workers, also reach here, let's not access anything before
* checking NOT_RUNNING.
*/
if (worker->flags & WORKER_NOT_RUNNING)
return NULL;
pool = worker->pool;
/* this can only happen on the local cpu */
if (WARN_ON_ONCE(cpu != raw_smp_processor_id()))
return NULL;
/*
* The counterpart of the following dec_and_test, implied mb,
* worklist not empty test sequence is in insert_work().
* Please read comment there.
*
* NOT_RUNNING is clear. This means that we're bound to and
* running on the local cpu w/ rq lock held and preemption
* disabled, which in turn means that none else could be
* manipulating idle_list, so dereferencing idle_list without pool
* lock is safe.
*/
if (atomic_dec_and_test(&pool->nr_running) &&
!list_empty(&pool->worklist))
to_wakeup = first_worker(pool);
return to_wakeup ? to_wakeup->task : NULL;
}
/**
* worker_set_flags - set worker flags and adjust nr_running accordingly
* @worker: self
* @flags: flags to set
* @wakeup: wakeup an idle worker if necessary
*
* Set @flags in @worker->flags and adjust nr_running accordingly. If
* nr_running becomes zero and @wakeup is %true, an idle worker is
* woken up.
*
* CONTEXT:
* spin_lock_irq(pool->lock)
*/
static inline void worker_set_flags(struct worker *worker, unsigned int flags,
bool wakeup)
{
struct worker_pool *pool = worker->pool;
WARN_ON_ONCE(worker->task != current);
/*
* If transitioning into NOT_RUNNING, adjust nr_running and
* wake up an idle worker as necessary if requested by
* @wakeup.
*/
if ((flags & WORKER_NOT_RUNNING) &&
!(worker->flags & WORKER_NOT_RUNNING)) {
if (wakeup) {
if (atomic_dec_and_test(&pool->nr_running) &&
!list_empty(&pool->worklist))
wake_up_worker(pool);
} else
atomic_dec(&pool->nr_running);
}
worker->flags |= flags;
}
/**
* worker_clr_flags - clear worker flags and adjust nr_running accordingly
* @worker: self
* @flags: flags to clear
*
* Clear @flags in @worker->flags and adjust nr_running accordingly.
*
* CONTEXT:
* spin_lock_irq(pool->lock)
*/
static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
{
struct worker_pool *pool = worker->pool;
unsigned int oflags = worker->flags;
WARN_ON_ONCE(worker->task != current);
worker->flags &= ~flags;
/*
* If transitioning out of NOT_RUNNING, increment nr_running. Note
* that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
* of multiple flags, not a single flag.
*/
if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
if (!(worker->flags & WORKER_NOT_RUNNING))
atomic_inc(&pool->nr_running);
}
/**
* find_worker_executing_work - find worker which is executing a work
* @pool: pool of interest
* @work: work to find worker for
*
* Find a worker which is executing @work on @pool by searching
* @pool->busy_hash which is keyed by the address of @work. For a worker
* to match, its current execution should match the address of @work and
* its work function. This is to avoid unwanted dependency between
* unrelated work executions through a work item being recycled while still
* being executed.
*
* This is a bit tricky. A work item may be freed once its execution
* starts and nothing prevents the freed area from being recycled for
* another work item. If the same work item address ends up being reused
* before the original execution finishes, workqueue will identify the
* recycled work item as currently executing and make it wait until the
* current execution finishes, introducing an unwanted dependency.
*
* This function checks the work item address, work function and workqueue
* to avoid false positives. Note that this isn't complete as one may
* construct a work function which can introduce dependency onto itself
* through a recycled work item. Well, if somebody wants to shoot oneself
* in the foot that badly, there's only so much we can do, and if such
* deadlock actually occurs, it should be easy to locate the culprit work
* function.
*
* CONTEXT:
* spin_lock_irq(pool->lock).
*
* RETURNS:
* Pointer to worker which is executing @work if found, NULL
* otherwise.
*/
static struct worker *find_worker_executing_work(struct worker_pool *pool,
struct work_struct *work)
{
struct worker *worker;
hash_for_each_possible(pool->busy_hash, worker, hentry,
(unsigned long)work)
if (worker->current_work == work &&
worker->current_func == work->func)
return worker;
return NULL;
}
/**
* move_linked_works - move linked works to a list
* @work: start of series of works to be scheduled
* @head: target list to append @work to
* @nextp: out paramter for nested worklist walking
*
* Schedule linked works starting from @work to @head. Work series to
* be scheduled starts at @work and includes any consecutive work with
* WORK_STRUCT_LINKED set in its predecessor.
*
* If @nextp is not NULL, it's updated to point to the next work of
* the last scheduled work. This allows move_linked_works() to be
* nested inside outer list_for_each_entry_safe().
*
* CONTEXT:
* spin_lock_irq(pool->lock).
*/
static void move_linked_works(struct work_struct *work, struct list_head *head,
struct work_struct **nextp)
{
struct work_struct *n;
/*
* Linked worklist will always end before the end of the list,
* use NULL for list head.
*/
list_for_each_entry_safe_from(work, n, NULL, entry) {
list_move_tail(&work->entry, head);
if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
break;
}
/*
* If we're already inside safe list traversal and have moved
* multiple works to the scheduled queue, the next position
* needs to be updated.
*/
if (nextp)
*nextp = n;
}
static void pwq_activate_delayed_work(struct work_struct *work)
{
struct pool_workqueue *pwq = get_work_pwq(work);
trace_workqueue_activate_work(work);
move_linked_works(work, &pwq->pool->worklist, NULL);
__clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
pwq->nr_active++;
}
static void pwq_activate_first_delayed(struct pool_workqueue *pwq)
{
struct work_struct *work = list_first_entry(&pwq->delayed_works,
struct work_struct, entry);
pwq_activate_delayed_work(work);
}
/**
* pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
* @pwq: pwq of interest
* @color: color of work which left the queue
*
* A work either has completed or is removed from pending queue,
* decrement nr_in_flight of its pwq and handle workqueue flushing.
*
* CONTEXT:
* spin_lock_irq(pool->lock).
*/
static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, int color)
{
/* ignore uncolored works */
if (color == WORK_NO_COLOR)
return;
pwq->nr_in_flight[color]--;
pwq->nr_active--;
if (!list_empty(&pwq->delayed_works)) {
/* one down, submit a delayed one */
if (pwq->nr_active < pwq->max_active)
pwq_activate_first_delayed(pwq);
}
/* is flush in progress and are we at the flushing tip? */
if (likely(pwq->flush_color != color))
return;
/* are there still in-flight works? */
if (pwq->nr_in_flight[color])
return;
/* this pwq is done, clear flush_color */
pwq->flush_color = -1;
/*
* If this was the last pwq, wake up the first flusher. It
* will handle the rest.
*/
if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
complete(&pwq->wq->first_flusher->done);
}
/**
* try_to_grab_pending - steal work item from worklist and disable irq
* @work: work item to steal
* @is_dwork: @work is a delayed_work
* @flags: place to store irq state
*
* Try to grab PENDING bit of @work. This function can handle @work in any
* stable state - idle, on timer or on worklist. Return values are
*
* 1 if @work was pending and we successfully stole PENDING
* 0 if @work was idle and we claimed PENDING
* -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry
* -ENOENT if someone else is canceling @work, this state may persist
* for arbitrarily long
*
* On >= 0 return, the caller owns @work's PENDING bit. To avoid getting
* interrupted while holding PENDING and @work off queue, irq must be
* disabled on entry. This, combined with delayed_work->timer being
* irqsafe, ensures that we return -EAGAIN for finite short period of time.
*
* On successful return, >= 0, irq is disabled and the caller is
* responsible for releasing it using local_irq_restore(*@flags).
*
* This function is safe to call from any context including IRQ handler.
*/
static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
unsigned long *flags)
{
struct worker_pool *pool;
struct pool_workqueue *pwq;
local_irq_save(*flags);
/* try to steal the timer if it exists */
if (is_dwork) {
struct delayed_work *dwork = to_delayed_work(work);
/*
* dwork->timer is irqsafe. If del_timer() fails, it's
* guaranteed that the timer is not queued anywhere and not
* running on the local CPU.
*/
if (likely(del_timer(&dwork->timer)))
return 1;
}
/* try to claim PENDING the normal way */
if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
return 0;
/*
* The queueing is in progress, or it is already queued. Try to
* steal it from ->worklist without clearing WORK_STRUCT_PENDING.
*/
pool = get_work_pool(work);
if (!pool)
goto fail;
spin_lock(&pool->lock);
/*
* work->data is guaranteed to point to pwq only while the work
* item is queued on pwq->wq, and both updating work->data to point
* to pwq on queueing and to pool on dequeueing are done under
* pwq->pool->lock. This in turn guarantees that, if work->data
* points to pwq which is associated with a locked pool, the work
* item is currently queued on that pool.
*/
pwq = get_work_pwq(work);
if (pwq && pwq->pool == pool) {
debug_work_deactivate(work);
/*
* A delayed work item cannot be grabbed directly because
* it might have linked NO_COLOR work items which, if left
* on the delayed_list, will confuse pwq->nr_active
* management later on and cause stall. Make sure the work
* item is activated before grabbing.
*/
if (*work_data_bits(work) & WORK_STRUCT_DELAYED)
pwq_activate_delayed_work(work);
list_del_init(&work->entry);
pwq_dec_nr_in_flight(get_work_pwq(work), get_work_color(work));
/* work->data points to pwq iff queued, point to pool */
set_work_pool_and_keep_pending(work, pool->id);
spin_unlock(&pool->lock);
return 1;
}
spin_unlock(&pool->lock);
fail:
local_irq_restore(*flags);
if (work_is_canceling(work))
return -ENOENT;
cpu_relax();
return -EAGAIN;
}
/**
* insert_work - insert a work into a pool
* @pwq: pwq @work belongs to
* @work: work to insert
* @head: insertion point
* @extra_flags: extra WORK_STRUCT_* flags to set
*
* Insert @work which belongs to @pwq after @head. @extra_flags is or'd to
* work_struct flags.
*
* CONTEXT:
* spin_lock_irq(pool->lock).
*/
static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
struct list_head *head, unsigned int extra_flags)
{
struct worker_pool *pool = pwq->pool;
/* we own @work, set data and link */
set_work_pwq(work, pwq, extra_flags);
list_add_tail(&work->entry, head);
/*
* Ensure either worker_sched_deactivated() sees the above
* list_add_tail() or we see zero nr_running to avoid workers
* lying around lazily while there are works to be processed.
*/
smp_mb();
if (__need_more_worker(pool))
wake_up_worker(pool);
}
/*
* Test whether @work is being queued from another work executing on the
* same workqueue.
*/
static bool is_chained_work(struct workqueue_struct *wq)
{
struct worker *worker;
worker = current_wq_worker();
/*
* Return %true iff I'm a worker execuing a work item on @wq. If
* I'm @worker, it's safe to dereference it without locking.
*/
return worker && worker->current_pwq->wq == wq;
}
static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
struct work_struct *work)
{
struct pool_workqueue *pwq;
struct list_head *worklist;
unsigned int work_flags;
unsigned int req_cpu = cpu;
/*
* While a work item is PENDING && off queue, a task trying to
* steal the PENDING will busy-loop waiting for it to either get
* queued or lose PENDING. Grabbing PENDING and queueing should
* happen with IRQ disabled.
*/
WARN_ON_ONCE(!irqs_disabled());
debug_work_activate(work);
/* if dying, only works from the same workqueue are allowed */
if (unlikely(wq->flags & WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq)))
return;
/* determine the pwq to use */
if (!(wq->flags & WQ_UNBOUND)) {
struct worker_pool *last_pool;
if (cpu == WORK_CPU_UNBOUND)
cpu = raw_smp_processor_id();
/*
* It's multi cpu. If @work was previously on a different
* cpu, it might still be running there, in which case the
* work needs to be queued on that cpu to guarantee
* non-reentrancy.
*/
pwq = get_pwq(cpu, wq);
last_pool = get_work_pool(work);
if (last_pool && last_pool != pwq->pool) {
struct worker *worker;
spin_lock(&last_pool->lock);
worker = find_worker_executing_work(last_pool, work);
if (worker && worker->current_pwq->wq == wq) {
pwq = get_pwq(last_pool->cpu, wq);
} else {
/* meh... not running there, queue here */
spin_unlock(&last_pool->lock);
spin_lock(&pwq->pool->lock);
}
} else {
spin_lock(&pwq->pool->lock);
}
} else {
pwq = get_pwq(WORK_CPU_UNBOUND, wq);
spin_lock(&pwq->pool->lock);
}
/* pwq determined, queue */
trace_workqueue_queue_work(req_cpu, pwq, work);
if (WARN_ON(!list_empty(&work->entry))) {
spin_unlock(&pwq->pool->lock);
return;
}
pwq->nr_in_flight[pwq->work_color]++;
work_flags = work_color_to_flags(pwq->work_color);
if (likely(pwq->nr_active < pwq->max_active)) {
trace_workqueue_activate_work(work);
pwq->nr_active++;
worklist = &pwq->pool->worklist;
} else {
work_flags |= WORK_STRUCT_DELAYED;
worklist = &pwq->delayed_works;
}
insert_work(pwq, work, worklist, work_flags);
spin_unlock(&pwq->pool->lock);
}
/**
* queue_work_on - queue work on specific cpu
* @cpu: CPU number to execute work on
* @wq: workqueue to use
* @work: work to queue
*
* Returns %false if @work was already on a queue, %true otherwise.
*
* We queue the work to a specific CPU, the caller must ensure it
* can't go away.
*/
bool queue_work_on(int cpu, struct workqueue_struct *wq,
struct work_struct *work)
{
bool ret = false;
unsigned long flags;
local_irq_save(flags);
if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
__queue_work(cpu, wq, work);
ret = true;
}
local_irq_restore(flags);
return ret;
}
EXPORT_SYMBOL_GPL(queue_work_on);
/**
* queue_work - queue work on a workqueue
* @wq: workqueue to use
* @work: work to queue
*
* Returns %false if @work was already on a queue, %true otherwise.
*
* We queue the work to the CPU on which it was submitted, but if the CPU dies
* it can be processed by another CPU.
*/
bool queue_work(struct workqueue_struct *wq, struct work_struct *work)
{
return queue_work_on(WORK_CPU_UNBOUND, wq, work);
}
EXPORT_SYMBOL_GPL(queue_work);
void delayed_work_timer_fn(unsigned long __data)
{
struct delayed_work *dwork = (struct delayed_work *)__data;
/* should have been called from irqsafe timer with irq already off */
__queue_work(dwork->cpu, dwork->wq, &dwork->work);
}
EXPORT_SYMBOL(delayed_work_timer_fn);
static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
struct delayed_work *dwork, unsigned long delay)
{
struct timer_list *timer = &dwork->timer;
struct work_struct *work = &dwork->work;
WARN_ON_ONCE(timer->function != delayed_work_timer_fn ||
timer->data != (unsigned long)dwork);
WARN_ON_ONCE(timer_pending(timer));
WARN_ON_ONCE(!list_empty(&work->entry));
/*
* If @delay is 0, queue @dwork->work immediately. This is for
* both optimization and correctness. The earliest @timer can
* expire is on the closest next tick and delayed_work users depend
* on that there's no such delay when @delay is 0.
*/
if (!delay) {
__queue_work(cpu, wq, &dwork->work);
return;
}
timer_stats_timer_set_start_info(&dwork->timer);
dwork->wq = wq;
dwork->cpu = cpu;
timer->expires = jiffies + delay;
if (unlikely(cpu != WORK_CPU_UNBOUND))
add_timer_on(timer, cpu);
else
add_timer(timer);
}
/**
* queue_delayed_work_on - queue work on specific CPU after delay
* @cpu: CPU number to execute work on
* @wq: workqueue to use
* @dwork: work to queue
* @delay: number of jiffies to wait before queueing
*
* Returns %false if @work was already on a queue, %true otherwise. If
* @delay is zero and @dwork is idle, it will be scheduled for immediate
* execution.
*/
bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
struct delayed_work *dwork, unsigned long delay)
{
struct work_struct *work = &dwork->work;
bool ret = false;
unsigned long flags;
/* read the comment in __queue_work() */
local_irq_save(flags);
if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
__queue_delayed_work(cpu, wq, dwork, delay);
ret = true;
}
local_irq_restore(flags);
return ret;
}
EXPORT_SYMBOL_GPL(queue_delayed_work_on);
/**
* queue_delayed_work - queue work on a workqueue after delay
* @wq: workqueue to use
* @dwork: delayable work to queue
* @delay: number of jiffies to wait before queueing
*
* Equivalent to queue_delayed_work_on() but tries to use the local CPU.
*/
bool queue_delayed_work(struct workqueue_struct *wq,
struct delayed_work *dwork, unsigned long delay)
{
return queue_delayed_work_on(WORK_CPU_UNBOUND, wq, dwork, delay);
}
EXPORT_SYMBOL_GPL(queue_delayed_work);
/**
* mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
* @cpu: CPU number to execute work on
* @wq: workqueue to use
* @dwork: work to queue
* @delay: number of jiffies to wait before queueing
*
* If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
* modify @dwork's timer so that it expires after @delay. If @delay is
* zero, @work is guaranteed to be scheduled immediately regardless of its
* current state.
*
* Returns %false if @dwork was idle and queued, %true if @dwork was
* pending and its timer was modified.
*
* This function is safe to call from any context including IRQ handler.
* See try_to_grab_pending() for details.
*/
bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
struct delayed_work *dwork, unsigned long delay)
{
unsigned long flags;
int ret;
do {
ret = try_to_grab_pending(&dwork->work, true, &flags);
} while (unlikely(ret == -EAGAIN));
if (likely(ret >= 0)) {
__queue_delayed_work(cpu, wq, dwork, delay);
local_irq_restore(flags);
}
/* -ENOENT from try_to_grab_pending() becomes %true */
return ret;
}
EXPORT_SYMBOL_GPL(mod_delayed_work_on);
/**
* mod_delayed_work - modify delay of or queue a delayed work
* @wq: workqueue to use
* @dwork: work to queue
* @delay: number of jiffies to wait before queueing
*
* mod_delayed_work_on() on local CPU.
*/
bool mod_delayed_work(struct workqueue_struct *wq, struct delayed_work *dwork,
unsigned long delay)
{
return mod_delayed_work_on(WORK_CPU_UNBOUND, wq, dwork, delay);
}
EXPORT_SYMBOL_GPL(mod_delayed_work);
/**
* worker_enter_idle - enter idle state
* @worker: worker which is entering idle state
*
* @worker is entering idle state. Update stats and idle timer if
* necessary.
*
* LOCKING:
* spin_lock_irq(pool->lock).
*/
static void worker_enter_idle(struct worker *worker)
{
struct worker_pool *pool = worker->pool;
if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
WARN_ON_ONCE(!list_empty(&worker->entry) &&
(worker->hentry.next || worker->hentry.pprev)))
return;
/* can't use worker_set_flags(), also called from start_worker() */
worker->flags |= WORKER_IDLE;
pool->nr_idle++;
worker->last_active = jiffies;
/* idle_list is LIFO */
list_add(&worker->entry, &pool->idle_list);
if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
/*
* Sanity check nr_running. Because wq_unbind_fn() releases
* pool->lock between setting %WORKER_UNBOUND and zapping
* nr_running, the warning may trigger spuriously. Check iff
* unbind is not in progress.
*/
WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
pool->nr_workers == pool->nr_idle &&
atomic_read(&pool->nr_running));
}
/**
* worker_leave_idle - leave idle state
* @worker: worker which is leaving idle state
*
* @worker is leaving idle state. Update stats.
*
* LOCKING:
* spin_lock_irq(pool->lock).
*/
static void worker_leave_idle(struct worker *worker)
{
struct worker_pool *pool = worker->pool;
if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
return;
worker_clr_flags(worker, WORKER_IDLE);
pool->nr_idle--;
list_del_init(&worker->entry);
}
/**
* worker_maybe_bind_and_lock - try to bind %current to worker_pool and lock it
* @pool: target worker_pool
*
* Bind %current to the cpu of @pool if it is associated and lock @pool.
*
* Works which are scheduled while the cpu is online must at least be
* scheduled to a worker which is bound to the cpu so that if they are
* flushed from cpu callbacks while cpu is going down, they are
* guaranteed to execute on the cpu.
*
* This function is to be used by unbound workers and rescuers to bind
* themselves to the target cpu and may race with cpu going down or
* coming online. kthread_bind() can't be used because it may put the
* worker to already dead cpu and set_cpus_allowed_ptr() can't be used
* verbatim as it's best effort and blocking and pool may be
* [dis]associated in the meantime.
*
* This function tries set_cpus_allowed() and locks pool and verifies the
* binding against %POOL_DISASSOCIATED which is set during
* %CPU_DOWN_PREPARE and cleared during %CPU_ONLINE, so if the worker
* enters idle state or fetches works without dropping lock, it can
* guarantee the scheduling requirement described in the first paragraph.
*
* CONTEXT:
* Might sleep. Called without any lock but returns with pool->lock
* held.
*
* RETURNS:
* %true if the associated pool is online (@worker is successfully
* bound), %false if offline.
*/
static bool worker_maybe_bind_and_lock(struct worker_pool *pool)
__acquires(&pool->lock)
{
while (true) {
/*
* The following call may fail, succeed or succeed
* without actually migrating the task to the cpu if
* it races with cpu hotunplug operation. Verify
* against POOL_DISASSOCIATED.
*/
if (!(pool->flags & POOL_DISASSOCIATED))
set_cpus_allowed_ptr(current, get_cpu_mask(pool->cpu));
spin_lock_irq(&pool->lock);
if (pool->flags & POOL_DISASSOCIATED)
return false;
if (task_cpu(current) == pool->cpu &&
cpumask_equal(¤t->cpus_allowed,
get_cpu_mask(pool->cpu)))
return true;
spin_unlock_irq(&pool->lock);
/*
* We've raced with CPU hot[un]plug. Give it a breather
* and retry migration. cond_resched() is required here;
* otherwise, we might deadlock against cpu_stop trying to
* bring down the CPU on non-preemptive kernel.
*/
cpu_relax();
cond_resched();
}
}
/*
* Rebind an idle @worker to its CPU. worker_thread() will test
* list_empty(@worker->entry) before leaving idle and call this function.
*/
static void idle_worker_rebind(struct worker *worker)
{
/* CPU may go down again inbetween, clear UNBOUND only on success */
if (worker_maybe_bind_and_lock(worker->pool))
worker_clr_flags(worker, WORKER_UNBOUND);
/* rebind complete, become available again */
list_add(&worker->entry, &worker->pool->idle_list);
spin_unlock_irq(&worker->pool->lock);
}
/*
* Function for @worker->rebind.work used to rebind unbound busy workers to
* the associated cpu which is coming back online. This is scheduled by
* cpu up but can race with other cpu hotplug operations and may be
* executed twice without intervening cpu down.
*/
static void busy_worker_rebind_fn(struct work_struct *work)
{
struct worker *worker = container_of(work, struct worker, rebind_work);
if (worker_maybe_bind_and_lock(worker->pool))
worker_clr_flags(worker, WORKER_UNBOUND);
spin_unlock_irq(&worker->pool->lock);
}
/**
* rebind_workers - rebind all workers of a pool to the associated CPU
* @pool: pool of interest
*
* @pool->cpu is coming online. Rebind all workers to the CPU. Rebinding
* is different for idle and busy ones.
*
* Idle ones will be removed from the idle_list and woken up. They will
* add themselves back after completing rebind. This ensures that the
* idle_list doesn't contain any unbound workers when re-bound busy workers
* try to perform local wake-ups for concurrency management.
*
* Busy workers can rebind after they finish their current work items.
* Queueing the rebind work item at the head of the scheduled list is
* enough. Note that nr_running will be properly bumped as busy workers
* rebind.
*
* On return, all non-manager workers are scheduled for rebind - see
* manage_workers() for the manager special case. Any idle worker
* including the manager will not appear on @idle_list until rebind is
* complete, making local wake-ups safe.
*/
static void rebind_workers(struct worker_pool *pool)
{
struct worker *worker, *n;
int i;
lockdep_assert_held(&pool->assoc_mutex);
lockdep_assert_held(&pool->lock);
/* dequeue and kick idle ones */
list_for_each_entry_safe(worker, n, &pool->idle_list, entry) {
/*
* idle workers should be off @pool->idle_list until rebind
* is complete to avoid receiving premature local wake-ups.
*/
list_del_init(&worker->entry);
/*
* worker_thread() will see the above dequeuing and call
* idle_worker_rebind().
*/
wake_up_process(worker->task);
}
/* rebind busy workers */
for_each_busy_worker(worker, i, pool) {
struct work_struct *rebind_work = &worker->rebind_work;
struct workqueue_struct *wq;
if (test_and_set_bit(WORK_STRUCT_PENDING_BIT,
work_data_bits(rebind_work)))
continue;
debug_work_activate(rebind_work);
/*
* wq doesn't really matter but let's keep @worker->pool
* and @pwq->pool consistent for sanity.
*/
if (std_worker_pool_pri(worker->pool))
wq = system_highpri_wq;
else
wq = system_wq;
insert_work(get_pwq(pool->cpu, wq), rebind_work,
worker->scheduled.next,
work_color_to_flags(WORK_NO_COLOR));
}
}
static struct worker *alloc_worker(void)
{
struct worker *worker;
worker = kzalloc(sizeof(*worker), GFP_KERNEL);
if (worker) {
INIT_LIST_HEAD(&worker->entry);
INIT_LIST_HEAD(&worker->scheduled);
INIT_WORK(&worker->rebind_work, busy_worker_rebind_fn);
/* on creation a worker is in !idle && prep state */
worker->flags = WORKER_PREP;
}
return worker;
}
/**
* create_worker - create a new workqueue worker
* @pool: pool the new worker will belong to
*
* Create a new worker which is bound to @pool. The returned worker
* can be started by calling start_worker() or destroyed using
* destroy_worker().
*
* CONTEXT:
* Might sleep. Does GFP_KERNEL allocations.
*
* RETURNS:
* Pointer to the newly created worker.
*/
static struct worker *create_worker(struct worker_pool *pool)
{
const char *pri = std_worker_pool_pri(pool) ? "H" : "";
struct worker *worker = NULL;
int id = -1;
spin_lock_irq(&pool->lock);
while (ida_get_new(&pool->worker_ida, &id)) {
spin_unlock_irq(&pool->lock);
if (!ida_pre_get(&pool->worker_ida, GFP_KERNEL))
goto fail;
spin_lock_irq(&pool->lock);
}
spin_unlock_irq(&pool->lock);
worker = alloc_worker();
if (!worker)
goto fail;
worker->pool = pool;
worker->id = id;
if (pool->cpu != WORK_CPU_UNBOUND)
worker->task = kthread_create_on_node(worker_thread,
worker, cpu_to_node(pool->cpu),
"kworker/%u:%d%s", pool->cpu, id, pri);
else
worker->task = kthread_create(worker_thread, worker,
"kworker/u:%d%s", id, pri);
if (IS_ERR(worker->task))
goto fail;
if (std_worker_pool_pri(pool))
set_user_nice(worker->task, HIGHPRI_NICE_LEVEL);
/*
* Determine CPU binding of the new worker depending on
* %POOL_DISASSOCIATED. The caller is responsible for ensuring the
* flag remains stable across this function. See the comments
* above the flag definition for details.
*
* As an unbound worker may later become a regular one if CPU comes
* online, make sure every worker has %PF_THREAD_BOUND set.
*/
if (!(pool->flags & POOL_DISASSOCIATED)) {
kthread_bind(worker->task, pool->cpu);
} else {
worker->task->flags |= PF_THREAD_BOUND;
worker->flags |= WORKER_UNBOUND;
}
return worker;
fail:
if (id >= 0) {
spin_lock_irq(&pool->lock);
ida_remove(&pool->worker_ida, id);
spin_unlock_irq(&pool->lock);
}
kfree(worker);
return NULL;
}
/**
* start_worker - start a newly created worker
* @worker: worker to start
*
* Make the pool aware of @worker and start it.
*
* CONTEXT:
* spin_lock_irq(pool->lock).
*/
static void start_worker(struct worker *worker)
{
worker->flags |= WORKER_STARTED;
worker->pool->nr_workers++;
worker_enter_idle(worker);
wake_up_process(worker->task);
}
/**
* destroy_worker - destroy a workqueue worker
* @worker: worker to be destroyed
*
* Destroy @worker and adjust @pool stats accordingly.
*
* CONTEXT:
* spin_lock_irq(pool->lock) which is released and regrabbed.
*/
static void destroy_worker(struct worker *worker)
{
struct worker_pool *pool = worker->pool;
int id = worker->id;
/* sanity check frenzy */
if (WARN_ON(worker->current_work) ||
WARN_ON(!list_empty(&worker->scheduled)))
return;
if (worker->flags & WORKER_STARTED)
pool->nr_workers--;
if (worker->flags & WORKER_IDLE)
pool->nr_idle--;
list_del_init(&worker->entry);
worker->flags |= WORKER_DIE;
spin_unlock_irq(&pool->lock);
kthread_stop(worker->task);
kfree(worker);
spin_lock_irq(&pool->lock);
ida_remove(&pool->worker_ida, id);
}
static void idle_worker_timeout(unsigned long __pool)
{
struct worker_pool *pool = (void *)__pool;
spin_lock_irq(&pool->lock);
if (too_many_workers(pool)) {
struct worker *worker;
unsigned long expires;
/* idle_list is kept in LIFO order, check the last one */
worker = list_entry(pool->idle_list.prev, struct worker, entry);
expires = worker->last_active + IDLE_WORKER_TIMEOUT;
if (time_before(jiffies, expires))
mod_timer(&pool->idle_timer, expires);
else {
/* it's been idle for too long, wake up manager */
pool->flags |= POOL_MANAGE_WORKERS;
wake_up_worker(pool);
}
}
spin_unlock_irq(&pool->lock);
}
static bool send_mayday(struct work_struct *work)
{
struct pool_workqueue *pwq = get_work_pwq(work);
struct workqueue_struct *wq = pwq->wq;
unsigned int cpu;
if (!(wq->flags & WQ_RESCUER))
return false;
/* mayday mayday mayday */
cpu = pwq->pool->cpu;
/* WORK_CPU_UNBOUND can't be set in cpumask, use cpu 0 instead */
if (cpu == WORK_CPU_UNBOUND)
cpu = 0;
if (!mayday_test_and_set_cpu(cpu, wq->mayday_mask))
wake_up_process(wq->rescuer->task);
return true;
}
static void pool_mayday_timeout(unsigned long __pool)
{
struct worker_pool *pool = (void *)__pool;
struct work_struct *work;
spin_lock_irq(&pool->lock);
if (need_to_create_worker(pool)) {
/*
* We've been trying to create a new worker but
* haven't been successful. We might be hitting an
* allocation deadlock. Send distress signals to
* rescuers.
*/
list_for_each_entry(work, &pool->worklist, entry)
send_mayday(work);
}
spin_unlock_irq(&pool->lock);
mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
}
/**
* maybe_create_worker - create a new worker if necessary
* @pool: pool to create a new worker for
*
* Create a new worker for @pool if necessary. @pool is guaranteed to
* have at least one idle worker on return from this function. If
* creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
* sent to all rescuers with works scheduled on @pool to resolve
* possible allocation deadlock.
*
* On return, need_to_create_worker() is guaranteed to be false and
* may_start_working() true.
*
* LOCKING:
* spin_lock_irq(pool->lock) which may be released and regrabbed
* multiple times. Does GFP_KERNEL allocations. Called only from
* manager.
*
* RETURNS:
* false if no action was taken and pool->lock stayed locked, true
* otherwise.
*/
static bool maybe_create_worker(struct worker_pool *pool)
__releases(&pool->lock)
__acquires(&pool->lock)
{
if (!need_to_create_worker(pool))
return false;
restart:
spin_unlock_irq(&pool->lock);
/* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
while (true) {
struct worker *worker;
worker = create_worker(pool);
if (worker) {
del_timer_sync(&pool->mayday_timer);
spin_lock_irq(&pool->lock);
start_worker(worker);
if (WARN_ON_ONCE(need_to_create_worker(pool)))
goto restart;
return true;
}
if (!need_to_create_worker(pool))
break;
__set_current_state(TASK_INTERRUPTIBLE);
schedule_timeout(CREATE_COOLDOWN);
if (!need_to_create_worker(pool))
break;
}
del_timer_sync(&pool->mayday_timer);
spin_lock_irq(&pool->lock);
if (need_to_create_worker(pool))
goto restart;
return true;
}
/**
* maybe_destroy_worker - destroy workers which have been idle for a while
* @pool: pool to destroy workers for
*
* Destroy @pool workers which have been idle for longer than
* IDLE_WORKER_TIMEOUT.
*
* LOCKING:
* spin_lock_irq(pool->lock) which may be released and regrabbed
* multiple times. Called only from manager.
*
* RETURNS:
* false if no action was taken and pool->lock stayed locked, true
* otherwise.
*/
static bool maybe_destroy_workers(struct worker_pool *pool)
{
bool ret = false;
while (too_many_workers(pool)) {
struct worker *worker;
unsigned long expires;
worker = list_entry(pool->idle_list.prev, struct worker, entry);
expires = worker->last_active + IDLE_WORKER_TIMEOUT;
if (time_before(jiffies, expires)) {
mod_timer(&pool->idle_timer, expires);
break;
}
destroy_worker(worker);
ret = true;
}
return ret;
}
/**
* manage_workers - manage worker pool
* @worker: self
*
* Assume the manager role and manage the worker pool @worker belongs
* to. At any given time, there can be only zero or one manager per
* pool. The exclusion is handled automatically by this function.
*
* The caller can safely start processing works on false return. On
* true return, it's guaranteed that need_to_create_worker() is false
* and may_start_working() is true.
*
* CONTEXT:
* spin_lock_irq(pool->lock) which may be released and regrabbed
* multiple times. Does GFP_KERNEL allocations.
*
* RETURNS:
* spin_lock_irq(pool->lock) which may be released and regrabbed
* multiple times. Does GFP_KERNEL allocations.
*/
static bool manage_workers(struct worker *worker)
{
struct worker_pool *pool = worker->pool;
bool ret = false;
if (pool->flags & POOL_MANAGING_WORKERS)
return ret;
pool->flags |= POOL_MANAGING_WORKERS;
/*
* To simplify both worker management and CPU hotplug, hold off
* management while hotplug is in progress. CPU hotplug path can't
* grab %POOL_MANAGING_WORKERS to achieve this because that can
* lead to idle worker depletion (all become busy thinking someone
* else is managing) which in turn can result in deadlock under
* extreme circumstances. Use @pool->assoc_mutex to synchronize
* manager against CPU hotplug.
*
* assoc_mutex would always be free unless CPU hotplug is in
* progress. trylock first without dropping @pool->lock.
*/
if (unlikely(!mutex_trylock(&pool->assoc_mutex))) {
spin_unlock_irq(&pool->lock);
mutex_lock(&pool->assoc_mutex);
/*
* CPU hotplug could have happened while we were waiting
* for assoc_mutex. Hotplug itself can't handle us
* because manager isn't either on idle or busy list, and
* @pool's state and ours could have deviated.
*
* As hotplug is now excluded via assoc_mutex, we can
* simply try to bind. It will succeed or fail depending
* on @pool's current state. Try it and adjust
* %WORKER_UNBOUND accordingly.
*/
if (worker_maybe_bind_and_lock(pool))
worker->flags &= ~WORKER_UNBOUND;
else
worker->flags |= WORKER_UNBOUND;
ret = true;
}
pool->flags &= ~POOL_MANAGE_WORKERS;
/*
* Destroy and then create so that may_start_working() is true
* on return.
*/
ret |= maybe_destroy_workers(pool);
ret |= maybe_create_worker(pool);
pool->flags &= ~POOL_MANAGING_WORKERS;
mutex_unlock(&pool->assoc_mutex);
return ret;
}
/**
* process_one_work - process single work
* @worker: self
* @work: work to process
*
* Process @work. This function contains all the logics necessary to
* process a single work including synchronization against and
* interaction with other workers on the same cpu, queueing and
* flushing. As long as context requirement is met, any worker can
* call this function to process a work.
*
* CONTEXT:
* spin_lock_irq(pool->lock) which is released and regrabbed.
*/
static void process_one_work(struct worker *worker, struct work_struct *work)
__releases(&pool->lock)
__acquires(&pool->lock)
{
struct pool_workqueue *pwq = get_work_pwq(work);
struct worker_pool *pool = worker->pool;
bool cpu_intensive = pwq->wq->flags & WQ_CPU_INTENSIVE;
int work_color;
struct worker *collision;
#ifdef CONFIG_LOCKDEP
/*
* It is permissible to free the struct work_struct from
* inside the function that is called from it, this we need to
* take into account for lockdep too. To avoid bogus "held
* lock freed" warnings as well as problems when looking into
* work->lockdep_map, make a copy and use that here.
*/
struct lockdep_map lockdep_map;
lockdep_copy_map(&lockdep_map, &work->lockdep_map);
#endif
/*
* Ensure we're on the correct CPU. DISASSOCIATED test is
* necessary to avoid spurious warnings from rescuers servicing the
* unbound or a disassociated pool.
*/
WARN_ON_ONCE(!(worker->flags & WORKER_UNBOUND) &&
!(pool->flags & POOL_DISASSOCIATED) &&
raw_smp_processor_id() != pool->cpu);
/*
* A single work shouldn't be executed concurrently by
* multiple workers on a single cpu. Check whether anyone is
* already processing the work. If so, defer the work to the
* currently executing one.
*/
collision = find_worker_executing_work(pool, work);
if (unlikely(collision)) {
move_linked_works(work, &collision->scheduled, NULL);
return;
}
/* claim and dequeue */
debug_work_deactivate(work);
hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
worker->current_work = work;
worker->current_func = work->func;
worker->current_pwq = pwq;
work_color = get_work_color(work);
list_del_init(&work->entry);
/*
* CPU intensive works don't participate in concurrency
* management. They're the scheduler's responsibility.
*/
if (unlikely(cpu_intensive))
worker_set_flags(worker, WORKER_CPU_INTENSIVE, true);
/*
* Unbound pool isn't concurrency managed and work items should be
* executed ASAP. Wake up another worker if necessary.
*/
if ((worker->flags & WORKER_UNBOUND) && need_more_worker(pool))
wake_up_worker(pool);
/*
* Record the last pool and clear PENDING which should be the last
* update to @work. Also, do this inside @pool->lock so that
* PENDING and queued state changes happen together while IRQ is
* disabled.
*/
set_work_pool_and_clear_pending(work, pool->id);
spin_unlock_irq(&pool->lock);
lock_map_acquire_read(&pwq->wq->lockdep_map);
lock_map_acquire(&lockdep_map);
trace_workqueue_execute_start(work);
worker->current_func(work);
/*
* While we must be careful to not use "work" after this, the trace
* point will only record its address.
*/
trace_workqueue_execute_end(work);
lock_map_release(&lockdep_map);
lock_map_release(&pwq->wq->lockdep_map);
if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
" last function: %pf\n",
current->comm, preempt_count(), task_pid_nr(current),
worker->current_func);
debug_show_held_locks(current);
dump_stack();
}
spin_lock_irq(&pool->lock);
/* clear cpu intensive status */
if (unlikely(cpu_intensive))
worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
/* we're done with it, release */
hash_del(&worker->hentry);
worker->current_work = NULL;
worker->current_func = NULL;
worker->current_pwq = NULL;
pwq_dec_nr_in_flight(pwq, work_color);
}
/**
* process_scheduled_works - process scheduled works
* @worker: self
*
* Process all scheduled works. Please note that the scheduled list
* may change while processing a work, so this function repeatedly
* fetches a work from the top and executes it.
*
* CONTEXT:
* spin_lock_irq(pool->lock) which may be released and regrabbed
* multiple times.
*/
static void process_scheduled_works(struct worker *worker)
{
while (!list_empty(&worker->scheduled)) {
struct work_struct *work = list_first_entry(&worker->scheduled,
struct work_struct, entry);
process_one_work(worker, work);
}
}
/**
* worker_thread - the worker thread function
* @__worker: self
*
* The worker thread function. There are NR_CPU_WORKER_POOLS dynamic pools
* of these per each cpu. These workers process all works regardless of
* their specific target workqueue. The only exception is works which
* belong to workqueues with a rescuer which will be explained in
* rescuer_thread().
*/
static int worker_thread(void *__worker)
{
struct worker *worker = __worker;
struct worker_pool *pool = worker->pool;
/* tell the scheduler that this is a workqueue worker */
worker->task->flags |= PF_WQ_WORKER;
woke_up:
spin_lock_irq(&pool->lock);
/* we are off idle list if destruction or rebind is requested */
if (unlikely(list_empty(&worker->entry))) {
spin_unlock_irq(&pool->lock);
/* if DIE is set, destruction is requested */
if (worker->flags & WORKER_DIE) {
worker->task->flags &= ~PF_WQ_WORKER;
return 0;
}
/* otherwise, rebind */
idle_worker_rebind(worker);
goto woke_up;
}
worker_leave_idle(worker);
recheck:
/* no more worker necessary? */
if (!need_more_worker(pool))
goto sleep;
/* do we need to manage? */
if (unlikely(!may_start_working(pool)) && manage_workers(worker))
goto recheck;
/*
* ->scheduled list can only be filled while a worker is
* preparing to process a work or actually processing it.
* Make sure nobody diddled with it while I was sleeping.
*/
WARN_ON_ONCE(!list_empty(&worker->scheduled));
/*
* When control reaches this point, we're guaranteed to have
* at least one idle worker or that someone else has already
* assumed the manager role.
*/
worker_clr_flags(worker, WORKER_PREP);
do {
struct work_struct *work =
list_first_entry(&pool->worklist,
struct work_struct, entry);
if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
/* optimization path, not strictly necessary */
process_one_work(worker, work);
if (unlikely(!list_empty(&worker->scheduled)))
process_scheduled_works(worker);
} else {
move_linked_works(work, &worker->scheduled, NULL);
process_scheduled_works(worker);
}
} while (keep_working(pool));
worker_set_flags(worker, WORKER_PREP, false);
sleep:
if (unlikely(need_to_manage_workers(pool)) && manage_workers(worker))
goto recheck;
/*
* pool->lock is held and there's no work to process and no need to
* manage, sleep. Workers are woken up only while holding
* pool->lock or from local cpu, so setting the current state
* before releasing pool->lock is enough to prevent losing any
* event.
*/
worker_enter_idle(worker);
__set_current_state(TASK_INTERRUPTIBLE);
spin_unlock_irq(&pool->lock);
schedule();
goto woke_up;
}
/**
* rescuer_thread - the rescuer thread function
* @__rescuer: self
*
* Workqueue rescuer thread function. There's one rescuer for each
* workqueue which has WQ_RESCUER set.
*
* Regular work processing on a pool may block trying to create a new
* worker which uses GFP_KERNEL allocation which has slight chance of
* developing into deadlock if some works currently on the same queue
* need to be processed to satisfy the GFP_KERNEL allocation. This is
* the problem rescuer solves.
*
* When such condition is possible, the pool summons rescuers of all
* workqueues which have works queued on the pool and let them process
* those works so that forward progress can be guaranteed.
*
* This should happen rarely.
*/
static int rescuer_thread(void *__rescuer)
{
struct worker *rescuer = __rescuer;
struct workqueue_struct *wq = rescuer->rescue_wq;
struct list_head *scheduled = &rescuer->scheduled;
bool is_unbound = wq->flags & WQ_UNBOUND;
unsigned int cpu;
set_user_nice(current, RESCUER_NICE_LEVEL);
/*
* Mark rescuer as worker too. As WORKER_PREP is never cleared, it
* doesn't participate in concurrency management.
*/
rescuer->task->flags |= PF_WQ_WORKER;
repeat:
set_current_state(TASK_INTERRUPTIBLE);
if (kthread_should_stop()) {
__set_current_state(TASK_RUNNING);
rescuer->task->flags &= ~PF_WQ_WORKER;
return 0;
}
/*
* See whether any cpu is asking for help. Unbounded
* workqueues use cpu 0 in mayday_mask for CPU_UNBOUND.
*/
for_each_mayday_cpu(cpu, wq->mayday_mask) {
unsigned int tcpu = is_unbound ? WORK_CPU_UNBOUND : cpu;
struct pool_workqueue *pwq = get_pwq(tcpu, wq);
struct worker_pool *pool = pwq->pool;
struct work_struct *work, *n;
__set_current_state(TASK_RUNNING);
mayday_clear_cpu(cpu, wq->mayday_mask);
/* migrate to the target cpu if possible */
worker_maybe_bind_and_lock(pool);
rescuer->pool = pool;
/*
* Slurp in all works issued via this workqueue and
* process'em.
*/
WARN_ON_ONCE(!list_empty(&rescuer->scheduled));
list_for_each_entry_safe(work, n, &pool->worklist, entry)
if (get_work_pwq(work) == pwq)
move_linked_works(work, scheduled, &n);
process_scheduled_works(rescuer);
/*
* Leave this pool. If keep_working() is %true, notify a
* regular worker; otherwise, we end up with 0 concurrency
* and stalling the execution.
*/
if (keep_working(pool))
wake_up_worker(pool);
rescuer->pool = NULL;
spin_unlock_irq(&pool->lock);
}
/* rescuers should never participate in concurrency management */
WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
schedule();
goto repeat;
}
struct wq_barrier {
struct work_struct work;
struct completion done;
};
static void wq_barrier_func(struct work_struct *work)
{
struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
complete(&barr->done);
}
/**
* insert_wq_barrier - insert a barrier work
* @pwq: pwq to insert barrier into
* @barr: wq_barrier to insert
* @target: target work to attach @barr to
* @worker: worker currently executing @target, NULL if @target is not executing
*
* @barr is linked to @target such that @barr is completed only after
* @target finishes execution. Please note that the ordering
* guarantee is observed only with respect to @target and on the local
* cpu.
*
* Currently, a queued barrier can't be canceled. This is because
* try_to_grab_pending() can't determine whether the work to be
* grabbed is at the head of the queue and thus can't clear LINKED
* flag of the previous work while there must be a valid next work
* after a work with LINKED flag set.
*
* Note that when @worker is non-NULL, @target may be modified
* underneath us, so we can't reliably determine pwq from @target.
*
* CONTEXT:
* spin_lock_irq(pool->lock).
*/
static void insert_wq_barrier(struct pool_workqueue *pwq,
struct wq_barrier *barr,
struct work_struct *target, struct worker *worker)
{
struct list_head *head;
unsigned int linked = 0;
/*
* debugobject calls are safe here even with pool->lock locked
* as we know for sure that this will not trigger any of the
* checks and call back into the fixup functions where we
* might deadlock.
*/
INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
__set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
init_completion(&barr->done);
/*
* If @target is currently being executed, schedule the
* barrier to the worker; otherwise, put it after @target.
*/
if (worker)
head = worker->scheduled.next;
else {
unsigned long *bits = work_data_bits(target);
head = target->entry.next;
/* there can already be other linked works, inherit and set */
linked = *bits & WORK_STRUCT_LINKED;
__set_bit(WORK_STRUCT_LINKED_BIT, bits);
}
debug_work_activate(&barr->work);
insert_work(pwq, &barr->work, head,
work_color_to_flags(WORK_NO_COLOR) | linked);
}
/**
* flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
* @wq: workqueue being flushed
* @flush_color: new flush color, < 0 for no-op
* @work_color: new work color, < 0 for no-op
*
* Prepare pwqs for workqueue flushing.
*
* If @flush_color is non-negative, flush_color on all pwqs should be
* -1. If no pwq has in-flight commands at the specified color, all
* pwq->flush_color's stay at -1 and %false is returned. If any pwq
* has in flight commands, its pwq->flush_color is set to
* @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
* wakeup logic is armed and %true is returned.
*
* The caller should have initialized @wq->first_flusher prior to
* calling this function with non-negative @flush_color. If
* @flush_color is negative, no flush color update is done and %false
* is returned.
*
* If @work_color is non-negative, all pwqs should have the same
* work_color which is previous to @work_color and all will be
* advanced to @work_color.
*
* CONTEXT:
* mutex_lock(wq->flush_mutex).
*
* RETURNS:
* %true if @flush_color >= 0 and there's something to flush. %false
* otherwise.
*/
static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq,
int flush_color, int work_color)
{
bool wait = false;
unsigned int cpu;
if (flush_color >= 0) {
WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush));
atomic_set(&wq->nr_pwqs_to_flush, 1);
}
for_each_pwq_cpu(cpu, wq) {
struct pool_workqueue *pwq = get_pwq(cpu, wq);
struct worker_pool *pool = pwq->pool;
spin_lock_irq(&pool->lock);
if (flush_color >= 0) {
WARN_ON_ONCE(pwq->flush_color != -1);
if (pwq->nr_in_flight[flush_color]) {
pwq->flush_color = flush_color;
atomic_inc(&wq->nr_pwqs_to_flush);
wait = true;
}
}
if (work_color >= 0) {
WARN_ON_ONCE(work_color != work_next_color(pwq->work_color));
pwq->work_color = work_color;
}
spin_unlock_irq(&pool->lock);
}
if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush))
complete(&wq->first_flusher->done);
return wait;
}
/**
* flush_workqueue - ensure that any scheduled work has run to completion.
* @wq: workqueue to flush
*
* Forces execution of the workqueue and blocks until its completion.
* This is typically used in driver shutdown handlers.
*
* We sleep until all works which were queued on entry have been handled,
* but we are not livelocked by new incoming ones.
*/
void flush_workqueue(struct workqueue_struct *wq)
{
struct wq_flusher this_flusher = {
.list = LIST_HEAD_INIT(this_flusher.list),
.flush_color = -1,
.done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done),
};
int next_color;
lock_map_acquire(&wq->lockdep_map);
lock_map_release(&wq->lockdep_map);
mutex_lock(&wq->flush_mutex);
/*
* Start-to-wait phase
*/
next_color = work_next_color(wq->work_color);
if (next_color != wq->flush_color) {
/*
* Color space is not full. The current work_color
* becomes our flush_color and work_color is advanced
* by one.
*/
WARN_ON_ONCE(!list_empty(&wq->flusher_overflow));
this_flusher.flush_color = wq->work_color;
wq->work_color = next_color;
if (!wq->first_flusher) {
/* no flush in progress, become the first flusher */
WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
wq->first_flusher = &this_flusher;
if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
wq->work_color)) {
/* nothing to flush, done */
wq->flush_color = next_color;
wq->first_flusher = NULL;
goto out_unlock;
}
} else {
/* wait in queue */
WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color);
list_add_tail(&this_flusher.list, &wq->flusher_queue);
flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
}
} else {
/*
* Oops, color space is full, wait on overflow queue.
* The next flush completion will assign us
* flush_color and transfer to flusher_queue.
*/
list_add_tail(&this_flusher.list, &wq->flusher_overflow);
}
mutex_unlock(&wq->flush_mutex);
wait_for_completion(&this_flusher.done);
/*
* Wake-up-and-cascade phase
*
* First flushers are responsible for cascading flushes and
* handling overflow. Non-first flushers can simply return.
*/
if (wq->first_flusher != &this_flusher)
return;
mutex_lock(&wq->flush_mutex);
/* we might have raced, check again with mutex held */
if (wq->first_flusher != &this_flusher)
goto out_unlock;
wq->first_flusher = NULL;
WARN_ON_ONCE(!list_empty(&this_flusher.list));
WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
while (true) {
struct wq_flusher *next, *tmp;
/* complete all the flushers sharing the current flush color */
list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
if (next->flush_color != wq->flush_color)
break;
list_del_init(&next->list);
complete(&next->done);
}
WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) &&
wq->flush_color != work_next_color(wq->work_color));
/* this flush_color is finished, advance by one */
wq->flush_color = work_next_color(wq->flush_color);
/* one color has been freed, handle overflow queue */
if (!list_empty(&wq->flusher_overflow)) {
/*
* Assign the same color to all overflowed
* flushers, advance work_color and append to
* flusher_queue. This is the start-to-wait
* phase for these overflowed flushers.
*/
list_for_each_entry(tmp, &wq->flusher_overflow, list)
tmp->flush_color = wq->work_color;
wq->work_color = work_next_color(wq->work_color);
list_splice_tail_init(&wq->flusher_overflow,
&wq->flusher_queue);
flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
}
if (list_empty(&wq->flusher_queue)) {
WARN_ON_ONCE(wq->flush_color != wq->work_color);
break;
}
/*
* Need to flush more colors. Make the next flusher
* the new first flusher and arm pwqs.
*/
WARN_ON_ONCE(wq->flush_color == wq->work_color);
WARN_ON_ONCE(wq->flush_color != next->flush_color);
list_del_init(&next->list);
wq->first_flusher = next;
if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))
break;
/*
* Meh... this color is already done, clear first
* flusher and repeat cascading.
*/
wq->first_flusher = NULL;
}
out_unlock:
mutex_unlock(&wq->flush_mutex);
}
EXPORT_SYMBOL_GPL(flush_workqueue);
/**
* drain_workqueue - drain a workqueue
* @wq: workqueue to drain
*
* Wait until the workqueue becomes empty. While draining is in progress,
* only chain queueing is allowed. IOW, only currently pending or running
* work items on @wq can queue further work items on it. @wq is flushed
* repeatedly until it becomes empty. The number of flushing is detemined
* by the depth of chaining and should be relatively short. Whine if it
* takes too long.
*/
void drain_workqueue(struct workqueue_struct *wq)
{
unsigned int flush_cnt = 0;
unsigned int cpu;
/*
* __queue_work() needs to test whether there are drainers, is much
* hotter than drain_workqueue() and already looks at @wq->flags.
* Use WQ_DRAINING so that queue doesn't have to check nr_drainers.
*/
spin_lock_irq(&workqueue_lock);
if (!wq->nr_drainers++)
wq->flags |= WQ_DRAINING;
spin_unlock_irq(&workqueue_lock);
reflush:
flush_workqueue(wq);
for_each_pwq_cpu(cpu, wq) {
struct pool_workqueue *pwq = get_pwq(cpu, wq);
bool drained;
spin_lock_irq(&pwq->pool->lock);
drained = !pwq->nr_active && list_empty(&pwq->delayed_works);
spin_unlock_irq(&pwq->pool->lock);
if (drained)
continue;
if (++flush_cnt == 10 ||
(flush_cnt % 100 == 0 && flush_cnt <= 1000))
pr_warn("workqueue %s: flush on destruction isn't complete after %u tries\n",
wq->name, flush_cnt);
goto reflush;
}
spin_lock_irq(&workqueue_lock);
if (!--wq->nr_drainers)
wq->flags &= ~WQ_DRAINING;
spin_unlock_irq(&workqueue_lock);
}
EXPORT_SYMBOL_GPL(drain_workqueue);
static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
{
struct worker *worker = NULL;
struct worker_pool *pool;
struct pool_workqueue *pwq;
might_sleep();
pool = get_work_pool(work);
if (!pool)
return false;
spin_lock_irq(&pool->lock);
/* see the comment in try_to_grab_pending() with the same code */
pwq = get_work_pwq(work);
if (pwq) {
if (unlikely(pwq->pool != pool))
goto already_gone;
} else {
worker = find_worker_executing_work(pool, work);
if (!worker)
goto already_gone;
pwq = worker->current_pwq;
}
insert_wq_barrier(pwq, barr, work, worker);
spin_unlock_irq(&pool->lock);
/*
* If @max_active is 1 or rescuer is in use, flushing another work
* item on the same workqueue may lead to deadlock. Make sure the
* flusher is not running on the same workqueue by verifying write
* access.
*/
if (pwq->wq->saved_max_active == 1 || pwq->wq->flags & WQ_RESCUER)
lock_map_acquire(&pwq->wq->lockdep_map);
else
lock_map_acquire_read(&pwq->wq->lockdep_map);
lock_map_release(&pwq->wq->lockdep_map);
return true;
already_gone:
spin_unlock_irq(&pool->lock);
return false;
}
/**
* flush_work - wait for a work to finish executing the last queueing instance
* @work: the work to flush
*
* Wait until @work has finished execution. @work is guaranteed to be idle
* on return if it hasn't been requeued since flush started.
*
* RETURNS:
* %true if flush_work() waited for the work to finish execution,
* %false if it was already idle.
*/
bool flush_work(struct work_struct *work)
{
struct wq_barrier barr;
lock_map_acquire(&work->lockdep_map);
lock_map_release(&work->lockdep_map);
if (start_flush_work(work, &barr)) {
wait_for_completion(&barr.done);
destroy_work_on_stack(&barr.work);
return true;
} else {
return false;
}
}
EXPORT_SYMBOL_GPL(flush_work);
static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
{
unsigned long flags;
int ret;
do {
ret = try_to_grab_pending(work, is_dwork, &flags);
/*
* If someone else is canceling, wait for the same event it
* would be waiting for before retrying.
*/
if (unlikely(ret == -ENOENT))
flush_work(work);
} while (unlikely(ret < 0));
/* tell other tasks trying to grab @work to back off */
mark_work_canceling(work);
local_irq_restore(flags);
flush_work(work);
clear_work_data(work);
return ret;
}
/**
* cancel_work_sync - cancel a work and wait for it to finish
* @work: the work to cancel
*
* Cancel @work and wait for its execution to finish. This function
* can be used even if the work re-queues itself or migrates to
* another workqueue. On return from this function, @work is
* guaranteed to be not pending or executing on any CPU.
*
* cancel_work_sync(&delayed_work->work) must not be used for
* delayed_work's. Use cancel_delayed_work_sync() instead.
*
* The caller must ensure that the workqueue on which @work was last
* queued can't be destroyed before this function returns.
*
* RETURNS:
* %true if @work was pending, %false otherwise.
*/
bool cancel_work_sync(struct work_struct *work)
{
return __cancel_work_timer(work, false);
}
EXPORT_SYMBOL_GPL(cancel_work_sync);
/**
* flush_delayed_work - wait for a dwork to finish executing the last queueing
* @dwork: the delayed work to flush
*
* Delayed timer is cancelled and the pending work is queued for
* immediate execution. Like flush_work(), this function only
* considers the last queueing instance of @dwork.
*
* RETURNS:
* %true if flush_work() waited for the work to finish execution,
* %false if it was already idle.
*/
bool flush_delayed_work(struct delayed_work *dwork)
{
local_irq_disable();
if (del_timer_sync(&dwork->timer))
__queue_work(dwork->cpu, dwork->wq, &dwork->work);
local_irq_enable();
return flush_work(&dwork->work);
}
EXPORT_SYMBOL(flush_delayed_work);
/**
* cancel_delayed_work - cancel a delayed work
* @dwork: delayed_work to cancel
*
* Kill off a pending delayed_work. Returns %true if @dwork was pending
* and canceled; %false if wasn't pending. Note that the work callback
* function may still be running on return, unless it returns %true and the
* work doesn't re-arm itself. Explicitly flush or use
* cancel_delayed_work_sync() to wait on it.
*
* This function is safe to call from any context including IRQ handler.
*/
bool cancel_delayed_work(struct delayed_work *dwork)
{
unsigned long flags;
int ret;
do {
ret = try_to_grab_pending(&dwork->work, true, &flags);
} while (unlikely(ret == -EAGAIN));
if (unlikely(ret < 0))
return false;
set_work_pool_and_clear_pending(&dwork->work,
get_work_pool_id(&dwork->work));
local_irq_restore(flags);
return ret;
}
EXPORT_SYMBOL(cancel_delayed_work);
/**
* cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
* @dwork: the delayed work cancel
*
* This is cancel_work_sync() for delayed works.
*
* RETURNS:
* %true if @dwork was pending, %false otherwise.
*/
bool cancel_delayed_work_sync(struct delayed_work *dwork)
{
return __cancel_work_timer(&dwork->work, true);
}
EXPORT_SYMBOL(cancel_delayed_work_sync);
/**
* schedule_work_on - put work task on a specific cpu
* @cpu: cpu to put the work task on
* @work: job to be done
*
* This puts a job on a specific cpu
*/
bool schedule_work_on(int cpu, struct work_struct *work)
{
return queue_work_on(cpu, system_wq, work);
}
EXPORT_SYMBOL(schedule_work_on);
/**
* schedule_work - put work task in global workqueue
* @work: job to be done
*
* Returns %false if @work was already on the kernel-global workqueue and
* %true otherwise.
*
* This puts a job in the kernel-global workqueue if it was not already
* queued and leaves it in the same position on the kernel-global
* workqueue otherwise.
*/
bool schedule_work(struct work_struct *work)
{
return queue_work(system_wq, work);
}
EXPORT_SYMBOL(schedule_work);
/**
* schedule_delayed_work_on - queue work in global workqueue on CPU after delay
* @cpu: cpu to use
* @dwork: job to be done
* @delay: number of jiffies to wait
*
* After waiting for a given time this puts a job in the kernel-global
* workqueue on the specified CPU.
*/
bool schedule_delayed_work_on(int cpu, struct delayed_work *dwork,
unsigned long delay)
{
return queue_delayed_work_on(cpu, system_wq, dwork, delay);
}
EXPORT_SYMBOL(schedule_delayed_work_on);
/**
* schedule_delayed_work - put work task in global workqueue after delay
* @dwork: job to be done
* @delay: number of jiffies to wait or 0 for immediate execution
*
* After waiting for a given time this puts a job in the kernel-global
* workqueue.
*/
bool schedule_delayed_work(struct delayed_work *dwork, unsigned long delay)
{
return queue_delayed_work(system_wq, dwork, delay);
}
EXPORT_SYMBOL(schedule_delayed_work);
/**
* schedule_on_each_cpu - execute a function synchronously on each online CPU
* @func: the function to call
*
* schedule_on_each_cpu() executes @func on each online CPU using the
* system workqueue and blocks until all CPUs have completed.
* schedule_on_each_cpu() is very slow.
*
* RETURNS:
* 0 on success, -errno on failure.
*/
int schedule_on_each_cpu(work_func_t func)
{
int cpu;
struct work_struct __percpu *works;
works = alloc_percpu(struct work_struct);
if (!works)
return -ENOMEM;
get_online_cpus();
for_each_online_cpu(cpu) {
struct work_struct *work = per_cpu_ptr(works, cpu);
INIT_WORK(work, func);
schedule_work_on(cpu, work);
}
for_each_online_cpu(cpu)
flush_work(per_cpu_ptr(works, cpu));
put_online_cpus();
free_percpu(works);
return 0;
}
/**
* flush_scheduled_work - ensure that any scheduled work has run to completion.
*
* Forces execution of the kernel-global workqueue and blocks until its
* completion.
*
* Think twice before calling this function! It's very easy to get into
* trouble if you don't take great care. Either of the following situations
* will lead to deadlock:
*
* One of the work items currently on the workqueue needs to acquire
* a lock held by your code or its caller.
*
* Your code is running in the context of a work routine.
*
* They will be detected by lockdep when they occur, but the first might not
* occur very often. It depends on what work items are on the workqueue and
* what locks they need, which you have no control over.
*
* In most situations flushing the entire workqueue is overkill; you merely
* need to know that a particular work item isn't queued and isn't running.
* In such cases you should use cancel_delayed_work_sync() or
* cancel_work_sync() instead.
*/
void flush_scheduled_work(void)
{
flush_workqueue(system_wq);
}
EXPORT_SYMBOL(flush_scheduled_work);
/**
* execute_in_process_context - reliably execute the routine with user context
* @fn: the function to execute
* @ew: guaranteed storage for the execute work structure (must
* be available when the work executes)
*
* Executes the function immediately if process context is available,
* otherwise schedules the function for delayed execution.
*
* Returns: 0 - function was executed
* 1 - function was scheduled for execution
*/
int execute_in_process_context(work_func_t fn, struct execute_work *ew)
{
if (!in_interrupt()) {
fn(&ew->work);
return 0;
}
INIT_WORK(&ew->work, fn);
schedule_work(&ew->work);
return 1;
}
EXPORT_SYMBOL_GPL(execute_in_process_context);
int keventd_up(void)
{
return system_wq != NULL;
}
static int alloc_pwqs(struct workqueue_struct *wq)
{
if (!(wq->flags & WQ_UNBOUND))
wq->pool_wq.pcpu = alloc_percpu(struct pool_workqueue);
else
wq->pool_wq.single = kmem_cache_zalloc(pwq_cache, GFP_KERNEL);
return wq->pool_wq.v ? 0 : -ENOMEM;
}
static void free_pwqs(struct workqueue_struct *wq)
{
if (!(wq->flags & WQ_UNBOUND))
free_percpu(wq->pool_wq.pcpu);
else
kmem_cache_free(pwq_cache, wq->pool_wq.single);
}
static int wq_clamp_max_active(int max_active, unsigned int flags,
const char *name)
{
int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
if (max_active < 1 || max_active > lim)
pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
max_active, name, 1, lim);
return clamp_val(max_active, 1, lim);
}
struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
unsigned int flags,
int max_active,
struct lock_class_key *key,
const char *lock_name, ...)
{
va_list args, args1;
struct workqueue_struct *wq;
unsigned int cpu;
size_t namelen;
/* determine namelen, allocate wq and format name */
va_start(args, lock_name);
va_copy(args1, args);
namelen = vsnprintf(NULL, 0, fmt, args) + 1;
wq = kzalloc(sizeof(*wq) + namelen, GFP_KERNEL);
if (!wq)
goto err;
vsnprintf(wq->name, namelen, fmt, args1);
va_end(args);
va_end(args1);
/*
* Workqueues which may be used during memory reclaim should
* have a rescuer to guarantee forward progress.
*/
if (flags & WQ_MEM_RECLAIM)
flags |= WQ_RESCUER;
max_active = max_active ?: WQ_DFL_ACTIVE;
max_active = wq_clamp_max_active(max_active, flags, wq->name);
/* init wq */
wq->flags = flags;
wq->saved_max_active = max_active;
mutex_init(&wq->flush_mutex);
atomic_set(&wq->nr_pwqs_to_flush, 0);
INIT_LIST_HEAD(&wq->flusher_queue);
INIT_LIST_HEAD(&wq->flusher_overflow);
lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
INIT_LIST_HEAD(&wq->list);
if (alloc_pwqs(wq) < 0)
goto err;
for_each_pwq_cpu(cpu, wq) {
struct pool_workqueue *pwq = get_pwq(cpu, wq);
BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);
pwq->pool = get_std_worker_pool(cpu, flags & WQ_HIGHPRI);
pwq->wq = wq;
pwq->flush_color = -1;
pwq->max_active = max_active;
INIT_LIST_HEAD(&pwq->delayed_works);
}
if (flags & WQ_RESCUER) {
struct worker *rescuer;
if (!alloc_mayday_mask(&wq->mayday_mask, GFP_KERNEL))
goto err;
wq->rescuer = rescuer = alloc_worker();
if (!rescuer)
goto err;
rescuer->rescue_wq = wq;
rescuer->task = kthread_create(rescuer_thread, rescuer, "%s",
wq->name);
if (IS_ERR(rescuer->task))
goto err;
rescuer->task->flags |= PF_THREAD_BOUND;
wake_up_process(rescuer->task);
}
/*
* workqueue_lock protects global freeze state and workqueues
* list. Grab it, set max_active accordingly and add the new
* workqueue to workqueues list.
*/
spin_lock_irq(&workqueue_lock);
if (workqueue_freezing && wq->flags & WQ_FREEZABLE)
for_each_pwq_cpu(cpu, wq)
get_pwq(cpu, wq)->max_active = 0;
list_add(&wq->list, &workqueues);
spin_unlock_irq(&workqueue_lock);
return wq;
err:
if (wq) {
free_pwqs(wq);
free_mayday_mask(wq->mayday_mask);
kfree(wq->rescuer);
kfree(wq);
}
return NULL;
}
EXPORT_SYMBOL_GPL(__alloc_workqueue_key);
/**
* destroy_workqueue - safely terminate a workqueue
* @wq: target workqueue
*
* Safely destroy a workqueue. All work currently pending will be done first.
*/
void destroy_workqueue(struct workqueue_struct *wq)
{
unsigned int cpu;
/* drain it before proceeding with destruction */
drain_workqueue(wq);
/* sanity checks */
for_each_pwq_cpu(cpu, wq) {
struct pool_workqueue *pwq = get_pwq(cpu, wq);
int i;
for (i = 0; i < WORK_NR_COLORS; i++)
if (WARN_ON(pwq->nr_in_flight[i]))
return;
if (WARN_ON(pwq->nr_active) ||
WARN_ON(!list_empty(&pwq->delayed_works)))
return;
}
/*
* wq list is used to freeze wq, remove from list after
* flushing is complete in case freeze races us.
*/
spin_lock_irq(&workqueue_lock);
list_del(&wq->list);
spin_unlock_irq(&workqueue_lock);
if (wq->flags & WQ_RESCUER) {
kthread_stop(wq->rescuer->task);
free_mayday_mask(wq->mayday_mask);
kfree(wq->rescuer);
}
free_pwqs(wq);
kfree(wq);
}
EXPORT_SYMBOL_GPL(destroy_workqueue);
/**
* pwq_set_max_active - adjust max_active of a pwq
* @pwq: target pool_workqueue
* @max_active: new max_active value.
*
* Set @pwq->max_active to @max_active and activate delayed works if
* increased.
*
* CONTEXT:
* spin_lock_irq(pool->lock).
*/
static void pwq_set_max_active(struct pool_workqueue *pwq, int max_active)
{
pwq->max_active = max_active;
while (!list_empty(&pwq->delayed_works) &&
pwq->nr_active < pwq->max_active)
pwq_activate_first_delayed(pwq);
}
/**
* workqueue_set_max_active - adjust max_active of a workqueue
* @wq: target workqueue
* @max_active: new max_active value.
*
* Set max_active of @wq to @max_active.
*
* CONTEXT:
* Don't call from IRQ context.
*/
void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
{
unsigned int cpu;
max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
spin_lock_irq(&workqueue_lock);
wq->saved_max_active = max_active;
for_each_pwq_cpu(cpu, wq) {
struct pool_workqueue *pwq = get_pwq(cpu, wq);
struct worker_pool *pool = pwq->pool;
spin_lock(&pool->lock);
if (!(wq->flags & WQ_FREEZABLE) ||
!(pool->flags & POOL_FREEZING))
pwq_set_max_active(pwq, max_active);
spin_unlock(&pool->lock);
}
spin_unlock_irq(&workqueue_lock);
}
EXPORT_SYMBOL_GPL(workqueue_set_max_active);
/**
* workqueue_congested - test whether a workqueue is congested
* @cpu: CPU in question
* @wq: target workqueue
*
* Test whether @wq's cpu workqueue for @cpu is congested. There is
* no synchronization around this function and the test result is
* unreliable and only useful as advisory hints or for debugging.
*
* RETURNS:
* %true if congested, %false otherwise.
*/
bool workqueue_congested(unsigned int cpu, struct workqueue_struct *wq)
{
struct pool_workqueue *pwq = get_pwq(cpu, wq);
return !list_empty(&pwq->delayed_works);
}
EXPORT_SYMBOL_GPL(workqueue_congested);
/**
* work_busy - test whether a work is currently pending or running
* @work: the work to be tested
*
* Test whether @work is currently pending or running. There is no
* synchronization around this function and the test result is
* unreliable and only useful as advisory hints or for debugging.
*
* RETURNS:
* OR'd bitmask of WORK_BUSY_* bits.
*/
unsigned int work_busy(struct work_struct *work)
{
struct worker_pool *pool = get_work_pool(work);
unsigned long flags;
unsigned int ret = 0;
if (work_pending(work))
ret |= WORK_BUSY_PENDING;
if (pool) {
spin_lock_irqsave(&pool->lock, flags);
if (find_worker_executing_work(pool, work))
ret |= WORK_BUSY_RUNNING;
spin_unlock_irqrestore(&pool->lock, flags);
}
return ret;
}
EXPORT_SYMBOL_GPL(work_busy);
/*
* CPU hotplug.
*
* There are two challenges in supporting CPU hotplug. Firstly, there
* are a lot of assumptions on strong associations among work, pwq and
* pool which make migrating pending and scheduled works very
* difficult to implement without impacting hot paths. Secondly,
* worker pools serve mix of short, long and very long running works making
* blocked draining impractical.
*
* This is solved by allowing the pools to be disassociated from the CPU
* running as an unbound one and allowing it to be reattached later if the
* cpu comes back online.
*/
static void wq_unbind_fn(struct work_struct *work)
{
int cpu = smp_processor_id();
struct worker_pool *pool;
struct worker *worker;
int i;
for_each_std_worker_pool(pool, cpu) {
WARN_ON_ONCE(cpu != smp_processor_id());
mutex_lock(&pool->assoc_mutex);
spin_lock_irq(&pool->lock);
/*
* We've claimed all manager positions. Make all workers
* unbound and set DISASSOCIATED. Before this, all workers
* except for the ones which are still executing works from
* before the last CPU down must be on the cpu. After
* this, they may become diasporas.
*/
list_for_each_entry(worker, &pool->idle_list, entry)
worker->flags |= WORKER_UNBOUND;
for_each_busy_worker(worker, i, pool)
worker->flags |= WORKER_UNBOUND;
pool->flags |= POOL_DISASSOCIATED;
spin_unlock_irq(&pool->lock);
mutex_unlock(&pool->assoc_mutex);
}
/*
* Call schedule() so that we cross rq->lock and thus can guarantee
* sched callbacks see the %WORKER_UNBOUND flag. This is necessary
* as scheduler callbacks may be invoked from other cpus.
*/
schedule();
/*
* Sched callbacks are disabled now. Zap nr_running. After this,
* nr_running stays zero and need_more_worker() and keep_working()
* are always true as long as the worklist is not empty. Pools on
* @cpu now behave as unbound (in terms of concurrency management)
* pools which are served by workers tied to the CPU.
*
* On return from this function, the current worker would trigger
* unbound chain execution of pending work items if other workers
* didn't already.
*/
for_each_std_worker_pool(pool, cpu)
atomic_set(&pool->nr_running, 0);
}
/*
* Workqueues should be brought up before normal priority CPU notifiers.
* This will be registered high priority CPU notifier.
*/
static int __cpuinit workqueue_cpu_up_callback(struct notifier_block *nfb,
unsigned long action,
void *hcpu)
{
unsigned int cpu = (unsigned long)hcpu;
struct worker_pool *pool;
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_UP_PREPARE:
for_each_std_worker_pool(pool, cpu) {
struct worker *worker;
if (pool->nr_workers)
continue;
worker = create_worker(pool);
if (!worker)
return NOTIFY_BAD;
spin_lock_irq(&pool->lock);
start_worker(worker);
spin_unlock_irq(&pool->lock);
}
break;
case CPU_DOWN_FAILED:
case CPU_ONLINE:
for_each_std_worker_pool(pool, cpu) {
mutex_lock(&pool->assoc_mutex);
spin_lock_irq(&pool->lock);
pool->flags &= ~POOL_DISASSOCIATED;
rebind_workers(pool);
spin_unlock_irq(&pool->lock);
mutex_unlock(&pool->assoc_mutex);
}
break;
}
return NOTIFY_OK;
}
/*
* Workqueues should be brought down after normal priority CPU notifiers.
* This will be registered as low priority CPU notifier.
*/
static int __cpuinit workqueue_cpu_down_callback(struct notifier_block *nfb,
unsigned long action,
void *hcpu)
{
unsigned int cpu = (unsigned long)hcpu;
struct work_struct unbind_work;
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_DOWN_PREPARE:
/* unbinding should happen on the local CPU */
INIT_WORK_ONSTACK(&unbind_work, wq_unbind_fn);
queue_work_on(cpu, system_highpri_wq, &unbind_work);
flush_work(&unbind_work);
break;
}
return NOTIFY_OK;
}
#ifdef CONFIG_SMP
struct work_for_cpu {
struct work_struct work;
long (*fn)(void *);
void *arg;
long ret;
};
static void work_for_cpu_fn(struct work_struct *work)
{
struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
wfc->ret = wfc->fn(wfc->arg);
}
/**
* work_on_cpu - run a function in user context on a particular cpu
* @cpu: the cpu to run on
* @fn: the function to run
* @arg: the function arg
*
* This will return the value @fn returns.
* It is up to the caller to ensure that the cpu doesn't go offline.
* The caller must not hold any locks which would prevent @fn from completing.
*/
long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
{
struct work_for_cpu wfc = { .fn = fn, .arg = arg };
INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn);
schedule_work_on(cpu, &wfc.work);
flush_work(&wfc.work);
return wfc.ret;
}
EXPORT_SYMBOL_GPL(work_on_cpu);
#endif /* CONFIG_SMP */
#ifdef CONFIG_FREEZER
/**
* freeze_workqueues_begin - begin freezing workqueues
*
* Start freezing workqueues. After this function returns, all freezable
* workqueues will queue new works to their frozen_works list instead of
* pool->worklist.
*
* CONTEXT:
* Grabs and releases workqueue_lock and pool->lock's.
*/
void freeze_workqueues_begin(void)
{
unsigned int cpu;
spin_lock_irq(&workqueue_lock);
WARN_ON_ONCE(workqueue_freezing);
workqueue_freezing = true;
for_each_wq_cpu(cpu) {
struct worker_pool *pool;
struct workqueue_struct *wq;
for_each_std_worker_pool(pool, cpu) {
spin_lock(&pool->lock);
WARN_ON_ONCE(pool->flags & POOL_FREEZING);
pool->flags |= POOL_FREEZING;
list_for_each_entry(wq, &workqueues, list) {
struct pool_workqueue *pwq = get_pwq(cpu, wq);
if (pwq && pwq->pool == pool &&
(wq->flags & WQ_FREEZABLE))
pwq->max_active = 0;
}
spin_unlock(&pool->lock);
}
}
spin_unlock_irq(&workqueue_lock);
}
/**
* freeze_workqueues_busy - are freezable workqueues still busy?
*
* Check whether freezing is complete. This function must be called
* between freeze_workqueues_begin() and thaw_workqueues().
*
* CONTEXT:
* Grabs and releases workqueue_lock.
*
* RETURNS:
* %true if some freezable workqueues are still busy. %false if freezing
* is complete.
*/
bool freeze_workqueues_busy(void)
{
unsigned int cpu;
bool busy = false;
spin_lock_irq(&workqueue_lock);
WARN_ON_ONCE(!workqueue_freezing);
for_each_wq_cpu(cpu) {
struct workqueue_struct *wq;
/*
* nr_active is monotonically decreasing. It's safe
* to peek without lock.
*/
list_for_each_entry(wq, &workqueues, list) {
struct pool_workqueue *pwq = get_pwq(cpu, wq);
if (!pwq || !(wq->flags & WQ_FREEZABLE))
continue;
WARN_ON_ONCE(pwq->nr_active < 0);
if (pwq->nr_active) {
busy = true;
goto out_unlock;
}
}
}
out_unlock:
spin_unlock_irq(&workqueue_lock);
return busy;
}
/**
* thaw_workqueues - thaw workqueues
*
* Thaw workqueues. Normal queueing is restored and all collected
* frozen works are transferred to their respective pool worklists.
*
* CONTEXT:
* Grabs and releases workqueue_lock and pool->lock's.
*/
void thaw_workqueues(void)
{
unsigned int cpu;
spin_lock_irq(&workqueue_lock);
if (!workqueue_freezing)
goto out_unlock;
for_each_wq_cpu(cpu) {
struct worker_pool *pool;
struct workqueue_struct *wq;
for_each_std_worker_pool(pool, cpu) {
spin_lock(&pool->lock);
WARN_ON_ONCE(!(pool->flags & POOL_FREEZING));
pool->flags &= ~POOL_FREEZING;
list_for_each_entry(wq, &workqueues, list) {
struct pool_workqueue *pwq = get_pwq(cpu, wq);
if (!pwq || pwq->pool != pool ||
!(wq->flags & WQ_FREEZABLE))
continue;
/* restore max_active and repopulate worklist */
pwq_set_max_active(pwq, wq->saved_max_active);
}
wake_up_worker(pool);
spin_unlock(&pool->lock);
}
}
workqueue_freezing = false;
out_unlock:
spin_unlock_irq(&workqueue_lock);
}
#endif /* CONFIG_FREEZER */
static int __init init_workqueues(void)
{
unsigned int cpu;
/* make sure we have enough bits for OFFQ pool ID */
BUILD_BUG_ON((1LU << (BITS_PER_LONG - WORK_OFFQ_POOL_SHIFT)) <
WORK_CPU_END * NR_STD_WORKER_POOLS);
WARN_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
cpu_notifier(workqueue_cpu_up_callback, CPU_PRI_WORKQUEUE_UP);
hotcpu_notifier(workqueue_cpu_down_callback, CPU_PRI_WORKQUEUE_DOWN);
/* initialize CPU pools */
for_each_wq_cpu(cpu) {
struct worker_pool *pool;
for_each_std_worker_pool(pool, cpu) {
spin_lock_init(&pool->lock);
pool->cpu = cpu;
pool->flags |= POOL_DISASSOCIATED;
INIT_LIST_HEAD(&pool->worklist);
INIT_LIST_HEAD(&pool->idle_list);
hash_init(pool->busy_hash);
init_timer_deferrable(&pool->idle_timer);
pool->idle_timer.function = idle_worker_timeout;
pool->idle_timer.data = (unsigned long)pool;
setup_timer(&pool->mayday_timer, pool_mayday_timeout,
(unsigned long)pool);
mutex_init(&pool->assoc_mutex);
ida_init(&pool->worker_ida);
/* alloc pool ID */
BUG_ON(worker_pool_assign_id(pool));
}
}
/* create the initial worker */
for_each_online_wq_cpu(cpu) {
struct worker_pool *pool;
for_each_std_worker_pool(pool, cpu) {
struct worker *worker;
if (cpu != WORK_CPU_UNBOUND)
pool->flags &= ~POOL_DISASSOCIATED;
worker = create_worker(pool);
BUG_ON(!worker);
spin_lock_irq(&pool->lock);
start_worker(worker);
spin_unlock_irq(&pool->lock);
}
}
system_wq = alloc_workqueue("events", 0, 0);
system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);
system_long_wq = alloc_workqueue("events_long", 0, 0);
system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
WQ_UNBOUND_MAX_ACTIVE);
system_freezable_wq = alloc_workqueue("events_freezable",
WQ_FREEZABLE, 0);
BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||
!system_unbound_wq || !system_freezable_wq);
return 0;
}
early_initcall(init_workqueues);
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