linux/kernel/workqueue.c
Tejun Heo 8852aac25e workqueue: mod_delayed_work_on() shouldn't queue timer on 0 delay
8376fe22c7 ("workqueue: implement mod_delayed_work[_on]()")
implemented mod_delayed_work[_on]() using the improved
try_to_grab_pending().  The function is later used, among others, to
replace [__]candel_delayed_work() + queue_delayed_work() combinations.

Unfortunately, a delayed_work item w/ zero @delay is handled slightly
differently by mod_delayed_work_on() compared to
queue_delayed_work_on().  The latter skips timer altogether and
directly queues it using queue_work_on() while the former schedules
timer which will expire on the closest tick.  This means, when @delay
is zero, that [__]cancel_delayed_work() + queue_delayed_work_on()
makes the target item immediately executable while
mod_delayed_work_on() may induce delay of upto a full tick.

This somewhat subtle difference breaks some of the converted users.
e.g. block queue plugging uses delayed_work for deferred processing
and uses mod_delayed_work_on() when the queue needs to be immediately
unplugged.  The above problem manifested as noticeably higher number
of context switches under certain circumstances.

The difference in behavior was caused by missing special case handling
for 0 delay in mod_delayed_work_on() compared to
queue_delayed_work_on().  Joonsoo Kim posted a patch to add it -
("workqueue: optimize mod_delayed_work_on() when @delay == 0")[1].
The patch was queued for 3.8 but it was described as optimization and
I missed that it was a correctness issue.

As both queue_delayed_work_on() and mod_delayed_work_on() use
__queue_delayed_work() for queueing, it seems that the better approach
is to move the 0 delay special handling to the function instead of
duplicating it in mod_delayed_work_on().

Fix the problem by moving 0 delay special case handling from
queue_delayed_work_on() to __queue_delayed_work().  This replaces
Joonsoo's patch.

[1] http://thread.gmane.org/gmane.linux.kernel/1379011/focus=1379012

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-and-tested-by: Anders Kaseorg <andersk@MIT.EDU>
Reported-and-tested-by: Zlatko Calusic <zlatko.calusic@iskon.hr>
LKML-Reference: <alpine.DEB.2.00.1211280953350.26602@dr-wily.mit.edu>
LKML-Reference: <50A78AA9.5040904@iskon.hr>
Cc: Joonsoo Kim <js1304@gmail.com>
2012-12-01 16:43:18 -08:00

3901 lines
106 KiB
C

/*
* 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 "workqueue_sched.h"
enum {
/*
* global_cwq flags
*
* A bound gcwq 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 gcwq behaves as an unbound one.
*
* Note that DISASSOCIATED can be flipped only while holding
* assoc_mutex of all pools on the gcwq to avoid changing binding
* state while create_worker() is in progress.
*/
GCWQ_DISASSOCIATED = 1 << 0, /* cpu can't serve workers */
GCWQ_FREEZING = 1 << 1, /* freeze in progress */
/* pool flags */
POOL_MANAGE_WORKERS = 1 << 0, /* need to manage workers */
POOL_MANAGING_WORKERS = 1 << 1, /* managing workers */
/* 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_WORKER_POOLS = 2, /* # worker pools per gcwq */
BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
BUSY_WORKER_HASH_SIZE = 1 << BUSY_WORKER_HASH_ORDER,
BUSY_WORKER_HASH_MASK = BUSY_WORKER_HASH_SIZE - 1,
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: gcwq->lock protected. Access with gcwq->lock held.
*
* X: During normal operation, modification requires gcwq->lock and
* should be done only from local cpu. Either disabling preemption
* on local cpu or grabbing gcwq->lock is enough for read access.
* If GCWQ_DISASSOCIATED is set, it's identical to L.
*
* F: wq->flush_mutex protected.
*
* W: workqueue_lock protected.
*/
struct global_cwq;
struct worker_pool;
/*
* The poor guys doing the actual heavy lifting. All on-duty workers
* are either serving the manager role, on idle list or on busy hash.
*/
struct worker {
/* on idle list while idle, on busy hash table while busy */
union {
struct list_head entry; /* L: while idle */
struct hlist_node hentry; /* L: while busy */
};
struct work_struct *current_work; /* L: work being processed */
struct cpu_workqueue_struct *current_cwq; /* L: current_work's cwq */
struct list_head scheduled; /* L: scheduled works */
struct task_struct *task; /* I: worker task */
struct worker_pool *pool; /* I: the associated pool */
/* 64 bytes boundary on 64bit, 32 on 32bit */
unsigned long last_active; /* L: last active timestamp */
unsigned int flags; /* X: flags */
int id; /* I: worker id */
/* for rebinding worker to CPU */
struct work_struct rebind_work; /* L: for busy worker */
};
struct worker_pool {
struct global_cwq *gcwq; /* I: the owning gcwq */
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 */
struct mutex assoc_mutex; /* protect GCWQ_DISASSOCIATED */
struct ida worker_ida; /* L: for worker IDs */
};
/*
* Global per-cpu workqueue. There's one and only one for each cpu
* and all works are queued and processed here regardless of their
* target workqueues.
*/
struct global_cwq {
spinlock_t lock; /* the gcwq lock */
unsigned int cpu; /* I: the associated cpu */
unsigned int flags; /* L: GCWQ_* flags */
/* workers are chained either in busy_hash or pool idle_list */
struct hlist_head busy_hash[BUSY_WORKER_HASH_SIZE];
/* L: hash of busy workers */
struct worker_pool pools[NR_WORKER_POOLS];
/* normal and highpri pools */
} ____cacheline_aligned_in_smp;
/*
* The per-CPU workqueue. The lower WORK_STRUCT_FLAG_BITS of
* work_struct->data are used for flags and thus cwqs need to be
* aligned at two's power of the number of flag bits.
*/
struct cpu_workqueue_struct {
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 */
};
/*
* 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 cpu_workqueue_struct __percpu *pcpu;
struct cpu_workqueue_struct *single;
unsigned long v;
} cpu_wq; /* I: cwq'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_cwqs_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 cwq max_active */
#ifdef CONFIG_LOCKDEP
struct lockdep_map lockdep_map;
#endif
char name[]; /* I: workqueue name */
};
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_worker_pool(pool, gcwq) \
for ((pool) = &(gcwq)->pools[0]; \
(pool) < &(gcwq)->pools[NR_WORKER_POOLS]; (pool)++)
#define for_each_busy_worker(worker, i, pos, gcwq) \
for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++) \
hlist_for_each_entry(worker, pos, &gcwq->busy_hash[i], hentry)
static inline int __next_gcwq_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_NONE;
}
static inline int __next_wq_cpu(int cpu, const struct cpumask *mask,
struct workqueue_struct *wq)
{
return __next_gcwq_cpu(cpu, mask, !(wq->flags & WQ_UNBOUND) ? 1 : 2);
}
/*
* CPU iterators
*
* An extra gcwq is defined for 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 gcwq.
*
* for_each_gcwq_cpu() : possible CPUs + WORK_CPU_UNBOUND
* for_each_online_gcwq_cpu() : online CPUs + WORK_CPU_UNBOUND
* for_each_cwq_cpu() : possible CPUs for bound workqueues,
* WORK_CPU_UNBOUND for unbound workqueues
*/
#define for_each_gcwq_cpu(cpu) \
for ((cpu) = __next_gcwq_cpu(-1, cpu_possible_mask, 3); \
(cpu) < WORK_CPU_NONE; \
(cpu) = __next_gcwq_cpu((cpu), cpu_possible_mask, 3))
#define for_each_online_gcwq_cpu(cpu) \
for ((cpu) = __next_gcwq_cpu(-1, cpu_online_mask, 3); \
(cpu) < WORK_CPU_NONE; \
(cpu) = __next_gcwq_cpu((cpu), cpu_online_mask, 3))
#define for_each_cwq_cpu(cpu, wq) \
for ((cpu) = __next_wq_cpu(-1, cpu_possible_mask, (wq)); \
(cpu) < WORK_CPU_NONE; \
(cpu) = __next_wq_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 almighty global cpu workqueues. nr_running is the only field
* which is expected to be used frequently by other cpus via
* try_to_wake_up(). Put it in a separate cacheline.
*/
static DEFINE_PER_CPU(struct global_cwq, global_cwq);
static DEFINE_PER_CPU_SHARED_ALIGNED(atomic_t, pool_nr_running[NR_WORKER_POOLS]);
/*
* Global cpu workqueue and nr_running counter for unbound gcwq. The
* gcwq is always online, has GCWQ_DISASSOCIATED set, and all its
* workers have WORKER_UNBOUND set.
*/
static struct global_cwq unbound_global_cwq;
static atomic_t unbound_pool_nr_running[NR_WORKER_POOLS] = {
[0 ... NR_WORKER_POOLS - 1] = ATOMIC_INIT(0), /* always 0 */
};
static int worker_thread(void *__worker);
static int worker_pool_pri(struct worker_pool *pool)
{
return pool - pool->gcwq->pools;
}
static struct global_cwq *get_gcwq(unsigned int cpu)
{
if (cpu != WORK_CPU_UNBOUND)
return &per_cpu(global_cwq, cpu);
else
return &unbound_global_cwq;
}
static atomic_t *get_pool_nr_running(struct worker_pool *pool)
{
int cpu = pool->gcwq->cpu;
int idx = worker_pool_pri(pool);
if (cpu != WORK_CPU_UNBOUND)
return &per_cpu(pool_nr_running, cpu)[idx];
else
return &unbound_pool_nr_running[idx];
}
static struct cpu_workqueue_struct *get_cwq(unsigned int cpu,
struct workqueue_struct *wq)
{
if (!(wq->flags & WQ_UNBOUND)) {
if (likely(cpu < nr_cpu_ids))
return per_cpu_ptr(wq->cpu_wq.pcpu, cpu);
} else if (likely(cpu == WORK_CPU_UNBOUND))
return wq->cpu_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_CWQ is set and non flag bits of a work's data
* contain the pointer to the queued cwq. Once execution starts, the flag
* is cleared and the high bits contain OFFQ flags and CPU number.
*
* set_work_cwq(), set_work_cpu_and_clear_pending(), mark_work_canceling()
* and clear_work_data() can be used to set the cwq, cpu or clear
* work->data. These functions should only be called while the work is
* owned - ie. while the PENDING bit is set.
*
* get_work_[g]cwq() can be used to obtain the gcwq or cwq corresponding to
* a work. gcwq is available once the work has been queued anywhere after
* initialization until it is sync canceled. cwq 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)
{
BUG_ON(!work_pending(work));
atomic_long_set(&work->data, data | flags | work_static(work));
}
static void set_work_cwq(struct work_struct *work,
struct cpu_workqueue_struct *cwq,
unsigned long extra_flags)
{
set_work_data(work, (unsigned long)cwq,
WORK_STRUCT_PENDING | WORK_STRUCT_CWQ | extra_flags);
}
static void set_work_cpu_and_clear_pending(struct work_struct *work,
unsigned int cpu)
{
/*
* 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)cpu << WORK_OFFQ_CPU_SHIFT, 0);
}
static void clear_work_data(struct work_struct *work)
{
smp_wmb(); /* see set_work_cpu_and_clear_pending() */
set_work_data(work, WORK_STRUCT_NO_CPU, 0);
}
static struct cpu_workqueue_struct *get_work_cwq(struct work_struct *work)
{
unsigned long data = atomic_long_read(&work->data);
if (data & WORK_STRUCT_CWQ)
return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
else
return NULL;
}
static struct global_cwq *get_work_gcwq(struct work_struct *work)
{
unsigned long data = atomic_long_read(&work->data);
unsigned int cpu;
if (data & WORK_STRUCT_CWQ)
return ((struct cpu_workqueue_struct *)
(data & WORK_STRUCT_WQ_DATA_MASK))->pool->gcwq;
cpu = data >> WORK_OFFQ_CPU_SHIFT;
if (cpu == WORK_CPU_NONE)
return NULL;
BUG_ON(cpu >= nr_cpu_ids && cpu != WORK_CPU_UNBOUND);
return get_gcwq(cpu);
}
static void mark_work_canceling(struct work_struct *work)
{
struct global_cwq *gcwq = get_work_gcwq(work);
unsigned long cpu = gcwq ? gcwq->cpu : WORK_CPU_NONE;
set_work_data(work, (cpu << WORK_OFFQ_CPU_SHIFT) | 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_CWQ) && (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 gcwq->lock held.
*/
static bool __need_more_worker(struct worker_pool *pool)
{
return !atomic_read(get_pool_nr_running(pool));
}
/*
* 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 gcwq 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)
{
atomic_t *nr_running = get_pool_nr_running(pool);
return !list_empty(&pool->worklist) && atomic_read(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(gcwq->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))
atomic_inc(get_pool_nr_running(worker->pool));
}
/**
* 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 = worker->pool;
atomic_t *nr_running = get_pool_nr_running(pool);
if (worker->flags & WORKER_NOT_RUNNING)
return NULL;
/* this can only happen on the local cpu */
BUG_ON(cpu != raw_smp_processor_id());
/*
* 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 gcwq
* lock is safe.
*/
if (atomic_dec_and_test(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(gcwq->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)) {
atomic_t *nr_running = get_pool_nr_running(pool);
if (wakeup) {
if (atomic_dec_and_test(nr_running) &&
!list_empty(&pool->worklist))
wake_up_worker(pool);
} else
atomic_dec(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(gcwq->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(get_pool_nr_running(pool));
}
/**
* busy_worker_head - return the busy hash head for a work
* @gcwq: gcwq of interest
* @work: work to be hashed
*
* Return hash head of @gcwq for @work.
*
* CONTEXT:
* spin_lock_irq(gcwq->lock).
*
* RETURNS:
* Pointer to the hash head.
*/
static struct hlist_head *busy_worker_head(struct global_cwq *gcwq,
struct work_struct *work)
{
const int base_shift = ilog2(sizeof(struct work_struct));
unsigned long v = (unsigned long)work;
/* simple shift and fold hash, do we need something better? */
v >>= base_shift;
v += v >> BUSY_WORKER_HASH_ORDER;
v &= BUSY_WORKER_HASH_MASK;
return &gcwq->busy_hash[v];
}
/**
* __find_worker_executing_work - find worker which is executing a work
* @gcwq: gcwq of interest
* @bwh: hash head as returned by busy_worker_head()
* @work: work to find worker for
*
* Find a worker which is executing @work on @gcwq. @bwh should be
* the hash head obtained by calling busy_worker_head() with the same
* work.
*
* CONTEXT:
* spin_lock_irq(gcwq->lock).
*
* RETURNS:
* Pointer to worker which is executing @work if found, NULL
* otherwise.
*/
static struct worker *__find_worker_executing_work(struct global_cwq *gcwq,
struct hlist_head *bwh,
struct work_struct *work)
{
struct worker *worker;
struct hlist_node *tmp;
hlist_for_each_entry(worker, tmp, bwh, hentry)
if (worker->current_work == work)
return worker;
return NULL;
}
/**
* find_worker_executing_work - find worker which is executing a work
* @gcwq: gcwq of interest
* @work: work to find worker for
*
* Find a worker which is executing @work on @gcwq. This function is
* identical to __find_worker_executing_work() except that this
* function calculates @bwh itself.
*
* CONTEXT:
* spin_lock_irq(gcwq->lock).
*
* RETURNS:
* Pointer to worker which is executing @work if found, NULL
* otherwise.
*/
static struct worker *find_worker_executing_work(struct global_cwq *gcwq,
struct work_struct *work)
{
return __find_worker_executing_work(gcwq, busy_worker_head(gcwq, work),
work);
}
/**
* 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(gcwq->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 cwq_activate_delayed_work(struct work_struct *work)
{
struct cpu_workqueue_struct *cwq = get_work_cwq(work);
trace_workqueue_activate_work(work);
move_linked_works(work, &cwq->pool->worklist, NULL);
__clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
cwq->nr_active++;
}
static void cwq_activate_first_delayed(struct cpu_workqueue_struct *cwq)
{
struct work_struct *work = list_first_entry(&cwq->delayed_works,
struct work_struct, entry);
cwq_activate_delayed_work(work);
}
/**
* cwq_dec_nr_in_flight - decrement cwq's nr_in_flight
* @cwq: cwq 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 cwq and handle workqueue flushing.
*
* CONTEXT:
* spin_lock_irq(gcwq->lock).
*/
static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color)
{
/* ignore uncolored works */
if (color == WORK_NO_COLOR)
return;
cwq->nr_in_flight[color]--;
cwq->nr_active--;
if (!list_empty(&cwq->delayed_works)) {
/* one down, submit a delayed one */
if (cwq->nr_active < cwq->max_active)
cwq_activate_first_delayed(cwq);
}
/* is flush in progress and are we at the flushing tip? */
if (likely(cwq->flush_color != color))
return;
/* are there still in-flight works? */
if (cwq->nr_in_flight[color])
return;
/* this cwq is done, clear flush_color */
cwq->flush_color = -1;
/*
* If this was the last cwq, wake up the first flusher. It
* will handle the rest.
*/
if (atomic_dec_and_test(&cwq->wq->nr_cwqs_to_flush))
complete(&cwq->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 global_cwq *gcwq;
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.
*/
gcwq = get_work_gcwq(work);
if (!gcwq)
goto fail;
spin_lock(&gcwq->lock);
if (!list_empty(&work->entry)) {
/*
* This work is queued, but perhaps we locked the wrong gcwq.
* In that case we must see the new value after rmb(), see
* insert_work()->wmb().
*/
smp_rmb();
if (gcwq == get_work_gcwq(work)) {
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
* cwq->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)
cwq_activate_delayed_work(work);
list_del_init(&work->entry);
cwq_dec_nr_in_flight(get_work_cwq(work),
get_work_color(work));
spin_unlock(&gcwq->lock);
return 1;
}
}
spin_unlock(&gcwq->lock);
fail:
local_irq_restore(*flags);
if (work_is_canceling(work))
return -ENOENT;
cpu_relax();
return -EAGAIN;
}
/**
* insert_work - insert a work into gcwq
* @cwq: cwq @work belongs to
* @work: work to insert
* @head: insertion point
* @extra_flags: extra WORK_STRUCT_* flags to set
*
* Insert @work which belongs to @cwq into @gcwq after @head.
* @extra_flags is or'd to work_struct flags.
*
* CONTEXT:
* spin_lock_irq(gcwq->lock).
*/
static void insert_work(struct cpu_workqueue_struct *cwq,
struct work_struct *work, struct list_head *head,
unsigned int extra_flags)
{
struct worker_pool *pool = cwq->pool;
/* we own @work, set data and link */
set_work_cwq(work, cwq, extra_flags);
/*
* Ensure that we get the right work->data if we see the
* result of list_add() below, see try_to_grab_pending().
*/
smp_wmb();
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. This is rather expensive and should only be used from
* cold paths.
*/
static bool is_chained_work(struct workqueue_struct *wq)
{
unsigned long flags;
unsigned int cpu;
for_each_gcwq_cpu(cpu) {
struct global_cwq *gcwq = get_gcwq(cpu);
struct worker *worker;
struct hlist_node *pos;
int i;
spin_lock_irqsave(&gcwq->lock, flags);
for_each_busy_worker(worker, i, pos, gcwq) {
if (worker->task != current)
continue;
spin_unlock_irqrestore(&gcwq->lock, flags);
/*
* I'm @worker, no locking necessary. See if @work
* is headed to the same workqueue.
*/
return worker->current_cwq->wq == wq;
}
spin_unlock_irqrestore(&gcwq->lock, flags);
}
return false;
}
static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
struct work_struct *work)
{
struct global_cwq *gcwq;
struct cpu_workqueue_struct *cwq;
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 gcwq to use */
if (!(wq->flags & WQ_UNBOUND)) {
struct global_cwq *last_gcwq;
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.
*/
gcwq = get_gcwq(cpu);
last_gcwq = get_work_gcwq(work);
if (last_gcwq && last_gcwq != gcwq) {
struct worker *worker;
spin_lock(&last_gcwq->lock);
worker = find_worker_executing_work(last_gcwq, work);
if (worker && worker->current_cwq->wq == wq)
gcwq = last_gcwq;
else {
/* meh... not running there, queue here */
spin_unlock(&last_gcwq->lock);
spin_lock(&gcwq->lock);
}
} else {
spin_lock(&gcwq->lock);
}
} else {
gcwq = get_gcwq(WORK_CPU_UNBOUND);
spin_lock(&gcwq->lock);
}
/* gcwq determined, get cwq and queue */
cwq = get_cwq(gcwq->cpu, wq);
trace_workqueue_queue_work(req_cpu, cwq, work);
if (WARN_ON(!list_empty(&work->entry))) {
spin_unlock(&gcwq->lock);
return;
}
cwq->nr_in_flight[cwq->work_color]++;
work_flags = work_color_to_flags(cwq->work_color);
if (likely(cwq->nr_active < cwq->max_active)) {
trace_workqueue_activate_work(work);
cwq->nr_active++;
worklist = &cwq->pool->worklist;
} else {
work_flags |= WORK_STRUCT_DELAYED;
worklist = &cwq->delayed_works;
}
insert_work(cwq, work, worklist, work_flags);
spin_unlock(&gcwq->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;
struct cpu_workqueue_struct *cwq = get_work_cwq(&dwork->work);
/* should have been called from irqsafe timer with irq already off */
__queue_work(dwork->cpu, cwq->wq, &dwork->work);
}
EXPORT_SYMBOL_GPL(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;
unsigned int lcpu;
WARN_ON_ONCE(timer->function != delayed_work_timer_fn ||
timer->data != (unsigned long)dwork);
BUG_ON(timer_pending(timer));
BUG_ON(!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);
/*
* This stores cwq for the moment, for the timer_fn. Note that the
* work's gcwq is preserved to allow reentrance detection for
* delayed works.
*/
if (!(wq->flags & WQ_UNBOUND)) {
struct global_cwq *gcwq = get_work_gcwq(work);
/*
* If we cannot get the last gcwq from @work directly,
* select the last CPU such that it avoids unnecessarily
* triggering non-reentrancy check in __queue_work().
*/
lcpu = cpu;
if (gcwq)
lcpu = gcwq->cpu;
if (lcpu == WORK_CPU_UNBOUND)
lcpu = raw_smp_processor_id();
} else {
lcpu = WORK_CPU_UNBOUND;
}
set_work_cwq(work, get_cwq(lcpu, wq), 0);
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(gcwq->lock).
*/
static void worker_enter_idle(struct worker *worker)
{
struct worker_pool *pool = worker->pool;
struct global_cwq *gcwq = pool->gcwq;
BUG_ON(worker->flags & WORKER_IDLE);
BUG_ON(!list_empty(&worker->entry) &&
(worker->hentry.next || worker->hentry.pprev));
/* 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 gcwq_unbind_fn() releases
* gcwq->lock between setting %WORKER_UNBOUND and zapping
* nr_running, the warning may trigger spuriously. Check iff
* unbind is not in progress.
*/
WARN_ON_ONCE(!(gcwq->flags & GCWQ_DISASSOCIATED) &&
pool->nr_workers == pool->nr_idle &&
atomic_read(get_pool_nr_running(pool)));
}
/**
* worker_leave_idle - leave idle state
* @worker: worker which is leaving idle state
*
* @worker is leaving idle state. Update stats.
*
* LOCKING:
* spin_lock_irq(gcwq->lock).
*/
static void worker_leave_idle(struct worker *worker)
{
struct worker_pool *pool = worker->pool;
BUG_ON(!(worker->flags & WORKER_IDLE));
worker_clr_flags(worker, WORKER_IDLE);
pool->nr_idle--;
list_del_init(&worker->entry);
}
/**
* worker_maybe_bind_and_lock - bind worker to its cpu if possible and lock gcwq
* @worker: self
*
* 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 rogue 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 gcwq may be
* [dis]associated in the meantime.
*
* This function tries set_cpus_allowed() and locks gcwq and verifies the
* binding against %GCWQ_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 gcwq->lock
* held.
*
* RETURNS:
* %true if the associated gcwq is online (@worker is successfully
* bound), %false if offline.
*/
static bool worker_maybe_bind_and_lock(struct worker *worker)
__acquires(&gcwq->lock)
{
struct global_cwq *gcwq = worker->pool->gcwq;
struct task_struct *task = worker->task;
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 GCWQ_DISASSOCIATED.
*/
if (!(gcwq->flags & GCWQ_DISASSOCIATED))
set_cpus_allowed_ptr(task, get_cpu_mask(gcwq->cpu));
spin_lock_irq(&gcwq->lock);
if (gcwq->flags & GCWQ_DISASSOCIATED)
return false;
if (task_cpu(task) == gcwq->cpu &&
cpumask_equal(&current->cpus_allowed,
get_cpu_mask(gcwq->cpu)))
return true;
spin_unlock_irq(&gcwq->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)
{
struct global_cwq *gcwq = worker->pool->gcwq;
/* CPU may go down again inbetween, clear UNBOUND only on success */
if (worker_maybe_bind_and_lock(worker))
worker_clr_flags(worker, WORKER_UNBOUND);
/* rebind complete, become available again */
list_add(&worker->entry, &worker->pool->idle_list);
spin_unlock_irq(&gcwq->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);
struct global_cwq *gcwq = worker->pool->gcwq;
if (worker_maybe_bind_and_lock(worker))
worker_clr_flags(worker, WORKER_UNBOUND);
spin_unlock_irq(&gcwq->lock);
}
/**
* rebind_workers - rebind all workers of a gcwq to the associated CPU
* @gcwq: gcwq of interest
*
* @gcwq->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 global_cwq *gcwq)
{
struct worker_pool *pool;
struct worker *worker, *n;
struct hlist_node *pos;
int i;
lockdep_assert_held(&gcwq->lock);
for_each_worker_pool(pool, gcwq)
lockdep_assert_held(&pool->assoc_mutex);
/* dequeue and kick idle ones */
for_each_worker_pool(pool, gcwq) {
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, pos, gcwq) {
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 @cwq->pool consistent for sanity.
*/
if (worker_pool_pri(worker->pool))
wq = system_highpri_wq;
else
wq = system_wq;
insert_work(get_cwq(gcwq->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)
{
struct global_cwq *gcwq = pool->gcwq;
const char *pri = worker_pool_pri(pool) ? "H" : "";
struct worker *worker = NULL;
int id = -1;
spin_lock_irq(&gcwq->lock);
while (ida_get_new(&pool->worker_ida, &id)) {
spin_unlock_irq(&gcwq->lock);
if (!ida_pre_get(&pool->worker_ida, GFP_KERNEL))
goto fail;
spin_lock_irq(&gcwq->lock);
}
spin_unlock_irq(&gcwq->lock);
worker = alloc_worker();
if (!worker)
goto fail;
worker->pool = pool;
worker->id = id;
if (gcwq->cpu != WORK_CPU_UNBOUND)
worker->task = kthread_create_on_node(worker_thread,
worker, cpu_to_node(gcwq->cpu),
"kworker/%u:%d%s", gcwq->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 (worker_pool_pri(pool))
set_user_nice(worker->task, HIGHPRI_NICE_LEVEL);
/*
* Determine CPU binding of the new worker depending on
* %GCWQ_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 (!(gcwq->flags & GCWQ_DISASSOCIATED)) {
kthread_bind(worker->task, gcwq->cpu);
} else {
worker->task->flags |= PF_THREAD_BOUND;
worker->flags |= WORKER_UNBOUND;
}
return worker;
fail:
if (id >= 0) {
spin_lock_irq(&gcwq->lock);
ida_remove(&pool->worker_ida, id);
spin_unlock_irq(&gcwq->lock);
}
kfree(worker);
return NULL;
}
/**
* start_worker - start a newly created worker
* @worker: worker to start
*
* Make the gcwq aware of @worker and start it.
*
* CONTEXT:
* spin_lock_irq(gcwq->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 @gcwq stats accordingly.
*
* CONTEXT:
* spin_lock_irq(gcwq->lock) which is released and regrabbed.
*/
static void destroy_worker(struct worker *worker)
{
struct worker_pool *pool = worker->pool;
struct global_cwq *gcwq = pool->gcwq;
int id = worker->id;
/* sanity check frenzy */
BUG_ON(worker->current_work);
BUG_ON(!list_empty(&worker->scheduled));
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(&gcwq->lock);
kthread_stop(worker->task);
kfree(worker);
spin_lock_irq(&gcwq->lock);
ida_remove(&pool->worker_ida, id);
}
static void idle_worker_timeout(unsigned long __pool)
{
struct worker_pool *pool = (void *)__pool;
struct global_cwq *gcwq = pool->gcwq;
spin_lock_irq(&gcwq->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(&gcwq->lock);
}
static bool send_mayday(struct work_struct *work)
{
struct cpu_workqueue_struct *cwq = get_work_cwq(work);
struct workqueue_struct *wq = cwq->wq;
unsigned int cpu;
if (!(wq->flags & WQ_RESCUER))
return false;
/* mayday mayday mayday */
cpu = cwq->pool->gcwq->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 gcwq_mayday_timeout(unsigned long __pool)
{
struct worker_pool *pool = (void *)__pool;
struct global_cwq *gcwq = pool->gcwq;
struct work_struct *work;
spin_lock_irq(&gcwq->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(&gcwq->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(gcwq->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 gcwq->lock stayed locked, true
* otherwise.
*/
static bool maybe_create_worker(struct worker_pool *pool)
__releases(&gcwq->lock)
__acquires(&gcwq->lock)
{
struct global_cwq *gcwq = pool->gcwq;
if (!need_to_create_worker(pool))
return false;
restart:
spin_unlock_irq(&gcwq->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(&gcwq->lock);
start_worker(worker);
BUG_ON(need_to_create_worker(pool));
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(&gcwq->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(gcwq->lock) which may be released and regrabbed
* multiple times. Called only from manager.
*
* RETURNS:
* false if no action was taken and gcwq->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 gcwq worker pool @worker belongs
* to. At any given time, there can be only zero or one manager per
* gcwq. 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(gcwq->lock) which may be released and regrabbed
* multiple times. Does GFP_KERNEL allocations.
*
* RETURNS:
* false if no action was taken and gcwq->lock stayed locked, true if
* some action was taken.
*/
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 @gcwq->lock.
*/
if (unlikely(!mutex_trylock(&pool->assoc_mutex))) {
spin_unlock_irq(&pool->gcwq->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
* @gcwq'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 @gcwq's current state. Try it and adjust
* %WORKER_UNBOUND accordingly.
*/
if (worker_maybe_bind_and_lock(worker))
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(gcwq->lock) which is released and regrabbed.
*/
static void process_one_work(struct worker *worker, struct work_struct *work)
__releases(&gcwq->lock)
__acquires(&gcwq->lock)
{
struct cpu_workqueue_struct *cwq = get_work_cwq(work);
struct worker_pool *pool = worker->pool;
struct global_cwq *gcwq = pool->gcwq;
struct hlist_head *bwh = busy_worker_head(gcwq, work);
bool cpu_intensive = cwq->wq->flags & WQ_CPU_INTENSIVE;
work_func_t f = work->func;
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 gcwq.
*/
WARN_ON_ONCE(!(worker->flags & WORKER_UNBOUND) &&
!(gcwq->flags & GCWQ_DISASSOCIATED) &&
raw_smp_processor_id() != gcwq->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(gcwq, bwh, work);
if (unlikely(collision)) {
move_linked_works(work, &collision->scheduled, NULL);
return;
}
/* claim and dequeue */
debug_work_deactivate(work);
hlist_add_head(&worker->hentry, bwh);
worker->current_work = work;
worker->current_cwq = cwq;
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 gcwq 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 CPU and clear PENDING which should be the last
* update to @work. Also, do this inside @gcwq->lock so that
* PENDING and queued state changes happen together while IRQ is
* disabled.
*/
set_work_cpu_and_clear_pending(work, gcwq->cpu);
spin_unlock_irq(&gcwq->lock);
lock_map_acquire_read(&cwq->wq->lockdep_map);
lock_map_acquire(&lockdep_map);
trace_workqueue_execute_start(work);
f(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(&cwq->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), f);
debug_show_held_locks(current);
dump_stack();
}
spin_lock_irq(&gcwq->lock);
/* clear cpu intensive status */
if (unlikely(cpu_intensive))
worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
/* we're done with it, release */
hlist_del_init(&worker->hentry);
worker->current_work = NULL;
worker->current_cwq = NULL;
cwq_dec_nr_in_flight(cwq, 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(gcwq->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 gcwq worker thread function. There's a single dynamic pool 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;
struct global_cwq *gcwq = pool->gcwq;
/* tell the scheduler that this is a workqueue worker */
worker->task->flags |= PF_WQ_WORKER;
woke_up:
spin_lock_irq(&gcwq->lock);
/* we are off idle list if destruction or rebind is requested */
if (unlikely(list_empty(&worker->entry))) {
spin_unlock_irq(&gcwq->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.
*/
BUG_ON(!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;
/*
* gcwq->lock is held and there's no work to process and no
* need to manage, sleep. Workers are woken up only while
* holding gcwq->lock or from local cpu, so setting the
* current state before releasing gcwq->lock is enough to
* prevent losing any event.
*/
worker_enter_idle(worker);
__set_current_state(TASK_INTERRUPTIBLE);
spin_unlock_irq(&gcwq->lock);
schedule();
goto woke_up;
}
/**
* rescuer_thread - the rescuer thread function
* @__wq: the associated workqueue
*
* Workqueue rescuer thread function. There's one rescuer for each
* workqueue which has WQ_RESCUER set.
*
* Regular work processing on a gcwq 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 gcwq summons rescuers of all
* workqueues which have works queued on the gcwq and let them process
* those works so that forward progress can be guaranteed.
*
* This should happen rarely.
*/
static int rescuer_thread(void *__wq)
{
struct workqueue_struct *wq = __wq;
struct worker *rescuer = wq->rescuer;
struct list_head *scheduled = &rescuer->scheduled;
bool is_unbound = wq->flags & WQ_UNBOUND;
unsigned int cpu;
set_user_nice(current, RESCUER_NICE_LEVEL);
repeat:
set_current_state(TASK_INTERRUPTIBLE);
if (kthread_should_stop()) {
__set_current_state(TASK_RUNNING);
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 cpu_workqueue_struct *cwq = get_cwq(tcpu, wq);
struct worker_pool *pool = cwq->pool;
struct global_cwq *gcwq = pool->gcwq;
struct work_struct *work, *n;
__set_current_state(TASK_RUNNING);
mayday_clear_cpu(cpu, wq->mayday_mask);
/* migrate to the target cpu if possible */
rescuer->pool = pool;
worker_maybe_bind_and_lock(rescuer);
/*
* Slurp in all works issued via this workqueue and
* process'em.
*/
BUG_ON(!list_empty(&rescuer->scheduled));
list_for_each_entry_safe(work, n, &pool->worklist, entry)
if (get_work_cwq(work) == cwq)
move_linked_works(work, scheduled, &n);
process_scheduled_works(rescuer);
/*
* Leave this gcwq. 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);
spin_unlock_irq(&gcwq->lock);
}
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
* @cwq: cwq 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 cwq from @target.
*
* CONTEXT:
* spin_lock_irq(gcwq->lock).
*/
static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
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 gcwq->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(cwq, &barr->work, head,
work_color_to_flags(WORK_NO_COLOR) | linked);
}
/**
* flush_workqueue_prep_cwqs - prepare cwqs 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 cwqs for workqueue flushing.
*
* If @flush_color is non-negative, flush_color on all cwqs should be
* -1. If no cwq has in-flight commands at the specified color, all
* cwq->flush_color's stay at -1 and %false is returned. If any cwq
* has in flight commands, its cwq->flush_color is set to
* @flush_color, @wq->nr_cwqs_to_flush is updated accordingly, cwq
* 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 cwqs 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_cwqs(struct workqueue_struct *wq,
int flush_color, int work_color)
{
bool wait = false;
unsigned int cpu;
if (flush_color >= 0) {
BUG_ON(atomic_read(&wq->nr_cwqs_to_flush));
atomic_set(&wq->nr_cwqs_to_flush, 1);
}
for_each_cwq_cpu(cpu, wq) {
struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
struct global_cwq *gcwq = cwq->pool->gcwq;
spin_lock_irq(&gcwq->lock);
if (flush_color >= 0) {
BUG_ON(cwq->flush_color != -1);
if (cwq->nr_in_flight[flush_color]) {
cwq->flush_color = flush_color;
atomic_inc(&wq->nr_cwqs_to_flush);
wait = true;
}
}
if (work_color >= 0) {
BUG_ON(work_color != work_next_color(cwq->work_color));
cwq->work_color = work_color;
}
spin_unlock_irq(&gcwq->lock);
}
if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_cwqs_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.
*/
BUG_ON(!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 */
BUG_ON(wq->flush_color != this_flusher.flush_color);
wq->first_flusher = &this_flusher;
if (!flush_workqueue_prep_cwqs(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 */
BUG_ON(wq->flush_color == this_flusher.flush_color);
list_add_tail(&this_flusher.list, &wq->flusher_queue);
flush_workqueue_prep_cwqs(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;
BUG_ON(!list_empty(&this_flusher.list));
BUG_ON(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);
}
BUG_ON(!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_cwqs(wq, -1, wq->work_color);
}
if (list_empty(&wq->flusher_queue)) {
BUG_ON(wq->flush_color != wq->work_color);
break;
}
/*
* Need to flush more colors. Make the next flusher
* the new first flusher and arm cwqs.
*/
BUG_ON(wq->flush_color == wq->work_color);
BUG_ON(wq->flush_color != next->flush_color);
list_del_init(&next->list);
wq->first_flusher = next;
if (flush_workqueue_prep_cwqs(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(&workqueue_lock);
if (!wq->nr_drainers++)
wq->flags |= WQ_DRAINING;
spin_unlock(&workqueue_lock);
reflush:
flush_workqueue(wq);
for_each_cwq_cpu(cpu, wq) {
struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
bool drained;
spin_lock_irq(&cwq->pool->gcwq->lock);
drained = !cwq->nr_active && list_empty(&cwq->delayed_works);
spin_unlock_irq(&cwq->pool->gcwq->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(&workqueue_lock);
if (!--wq->nr_drainers)
wq->flags &= ~WQ_DRAINING;
spin_unlock(&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 global_cwq *gcwq;
struct cpu_workqueue_struct *cwq;
might_sleep();
gcwq = get_work_gcwq(work);
if (!gcwq)
return false;
spin_lock_irq(&gcwq->lock);
if (!list_empty(&work->entry)) {
/*
* See the comment near try_to_grab_pending()->smp_rmb().
* If it was re-queued to a different gcwq under us, we
* are not going to wait.
*/
smp_rmb();
cwq = get_work_cwq(work);
if (unlikely(!cwq || gcwq != cwq->pool->gcwq))
goto already_gone;
} else {
worker = find_worker_executing_work(gcwq, work);
if (!worker)
goto already_gone;
cwq = worker->current_cwq;
}
insert_wq_barrier(cwq, barr, work, worker);
spin_unlock_irq(&gcwq->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 (cwq->wq->saved_max_active == 1 || cwq->wq->flags & WQ_RESCUER)
lock_map_acquire(&cwq->wq->lockdep_map);
else
lock_map_acquire_read(&cwq->wq->lockdep_map);
lock_map_release(&cwq->wq->lockdep_map);
return true;
already_gone:
spin_unlock_irq(&gcwq->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,
get_work_cwq(&dwork->work)->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_cpu_and_clear_pending(&dwork->work, work_cpu(&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_cwqs(struct workqueue_struct *wq)
{
/*
* cwqs are forced aligned according to WORK_STRUCT_FLAG_BITS.
* Make sure that the alignment isn't lower than that of
* unsigned long long.
*/
const size_t size = sizeof(struct cpu_workqueue_struct);
const size_t align = max_t(size_t, 1 << WORK_STRUCT_FLAG_BITS,
__alignof__(unsigned long long));
if (!(wq->flags & WQ_UNBOUND))
wq->cpu_wq.pcpu = __alloc_percpu(size, align);
else {
void *ptr;
/*
* Allocate enough room to align cwq and put an extra
* pointer at the end pointing back to the originally
* allocated pointer which will be used for free.
*/
ptr = kzalloc(size + align + sizeof(void *), GFP_KERNEL);
if (ptr) {
wq->cpu_wq.single = PTR_ALIGN(ptr, align);
*(void **)(wq->cpu_wq.single + 1) = ptr;
}
}
/* just in case, make sure it's actually aligned */
BUG_ON(!IS_ALIGNED(wq->cpu_wq.v, align));
return wq->cpu_wq.v ? 0 : -ENOMEM;
}
static void free_cwqs(struct workqueue_struct *wq)
{
if (!(wq->flags & WQ_UNBOUND))
free_percpu(wq->cpu_wq.pcpu);
else if (wq->cpu_wq.single) {
/* the pointer to free is stored right after the cwq */
kfree(*(void **)(wq->cpu_wq.single + 1));
}
}
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_cwqs_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_cwqs(wq) < 0)
goto err;
for_each_cwq_cpu(cpu, wq) {
struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
struct global_cwq *gcwq = get_gcwq(cpu);
int pool_idx = (bool)(flags & WQ_HIGHPRI);
BUG_ON((unsigned long)cwq & WORK_STRUCT_FLAG_MASK);
cwq->pool = &gcwq->pools[pool_idx];
cwq->wq = wq;
cwq->flush_color = -1;
cwq->max_active = max_active;
INIT_LIST_HEAD(&cwq->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->task = kthread_create(rescuer_thread, wq, "%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(&workqueue_lock);
if (workqueue_freezing && wq->flags & WQ_FREEZABLE)
for_each_cwq_cpu(cpu, wq)
get_cwq(cpu, wq)->max_active = 0;
list_add(&wq->list, &workqueues);
spin_unlock(&workqueue_lock);
return wq;
err:
if (wq) {
free_cwqs(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);
/*
* wq list is used to freeze wq, remove from list after
* flushing is complete in case freeze races us.
*/
spin_lock(&workqueue_lock);
list_del(&wq->list);
spin_unlock(&workqueue_lock);
/* sanity check */
for_each_cwq_cpu(cpu, wq) {
struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
int i;
for (i = 0; i < WORK_NR_COLORS; i++)
BUG_ON(cwq->nr_in_flight[i]);
BUG_ON(cwq->nr_active);
BUG_ON(!list_empty(&cwq->delayed_works));
}
if (wq->flags & WQ_RESCUER) {
kthread_stop(wq->rescuer->task);
free_mayday_mask(wq->mayday_mask);
kfree(wq->rescuer);
}
free_cwqs(wq);
kfree(wq);
}
EXPORT_SYMBOL_GPL(destroy_workqueue);
/**
* cwq_set_max_active - adjust max_active of a cwq
* @cwq: target cpu_workqueue_struct
* @max_active: new max_active value.
*
* Set @cwq->max_active to @max_active and activate delayed works if
* increased.
*
* CONTEXT:
* spin_lock_irq(gcwq->lock).
*/
static void cwq_set_max_active(struct cpu_workqueue_struct *cwq, int max_active)
{
cwq->max_active = max_active;
while (!list_empty(&cwq->delayed_works) &&
cwq->nr_active < cwq->max_active)
cwq_activate_first_delayed(cwq);
}
/**
* 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(&workqueue_lock);
wq->saved_max_active = max_active;
for_each_cwq_cpu(cpu, wq) {
struct global_cwq *gcwq = get_gcwq(cpu);
spin_lock_irq(&gcwq->lock);
if (!(wq->flags & WQ_FREEZABLE) ||
!(gcwq->flags & GCWQ_FREEZING))
cwq_set_max_active(get_cwq(gcwq->cpu, wq), max_active);
spin_unlock_irq(&gcwq->lock);
}
spin_unlock(&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 cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
return !list_empty(&cwq->delayed_works);
}
EXPORT_SYMBOL_GPL(workqueue_congested);
/**
* work_cpu - return the last known associated cpu for @work
* @work: the work of interest
*
* RETURNS:
* CPU number if @work was ever queued. WORK_CPU_NONE otherwise.
*/
unsigned int work_cpu(struct work_struct *work)
{
struct global_cwq *gcwq = get_work_gcwq(work);
return gcwq ? gcwq->cpu : WORK_CPU_NONE;
}
EXPORT_SYMBOL_GPL(work_cpu);
/**
* 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.
* Especially for reentrant wqs, the pending state might hide the
* running state.
*
* RETURNS:
* OR'd bitmask of WORK_BUSY_* bits.
*/
unsigned int work_busy(struct work_struct *work)
{
struct global_cwq *gcwq = get_work_gcwq(work);
unsigned long flags;
unsigned int ret = 0;
if (!gcwq)
return false;
spin_lock_irqsave(&gcwq->lock, flags);
if (work_pending(work))
ret |= WORK_BUSY_PENDING;
if (find_worker_executing_work(gcwq, work))
ret |= WORK_BUSY_RUNNING;
spin_unlock_irqrestore(&gcwq->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, cwq and
* gcwq which make migrating pending and scheduled works very
* difficult to implement without impacting hot paths. Secondly,
* gcwqs serve mix of short, long and very long running works making
* blocked draining impractical.
*
* This is solved by allowing a gcwq to be disassociated from the CPU
* running as an unbound one and allowing it to be reattached later if the
* cpu comes back online.
*/
/* claim manager positions of all pools */
static void gcwq_claim_assoc_and_lock(struct global_cwq *gcwq)
{
struct worker_pool *pool;
for_each_worker_pool(pool, gcwq)
mutex_lock_nested(&pool->assoc_mutex, pool - gcwq->pools);
spin_lock_irq(&gcwq->lock);
}
/* release manager positions */
static void gcwq_release_assoc_and_unlock(struct global_cwq *gcwq)
{
struct worker_pool *pool;
spin_unlock_irq(&gcwq->lock);
for_each_worker_pool(pool, gcwq)
mutex_unlock(&pool->assoc_mutex);
}
static void gcwq_unbind_fn(struct work_struct *work)
{
struct global_cwq *gcwq = get_gcwq(smp_processor_id());
struct worker_pool *pool;
struct worker *worker;
struct hlist_node *pos;
int i;
BUG_ON(gcwq->cpu != smp_processor_id());
gcwq_claim_assoc_and_lock(gcwq);
/*
* 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.
*/
for_each_worker_pool(pool, gcwq)
list_for_each_entry(worker, &pool->idle_list, entry)
worker->flags |= WORKER_UNBOUND;
for_each_busy_worker(worker, i, pos, gcwq)
worker->flags |= WORKER_UNBOUND;
gcwq->flags |= GCWQ_DISASSOCIATED;
gcwq_release_assoc_and_unlock(gcwq);
/*
* 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. @gcwq now
* behaves as unbound (in terms of concurrency management) gcwq
* which is 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_worker_pool(pool, gcwq)
atomic_set(get_pool_nr_running(pool), 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 global_cwq *gcwq = get_gcwq(cpu);
struct worker_pool *pool;
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_UP_PREPARE:
for_each_worker_pool(pool, gcwq) {
struct worker *worker;
if (pool->nr_workers)
continue;
worker = create_worker(pool);
if (!worker)
return NOTIFY_BAD;
spin_lock_irq(&gcwq->lock);
start_worker(worker);
spin_unlock_irq(&gcwq->lock);
}
break;
case CPU_DOWN_FAILED:
case CPU_ONLINE:
gcwq_claim_assoc_and_lock(gcwq);
gcwq->flags &= ~GCWQ_DISASSOCIATED;
rebind_workers(gcwq);
gcwq_release_assoc_and_unlock(gcwq);
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, gcwq_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
* gcwq->worklist.
*
* CONTEXT:
* Grabs and releases workqueue_lock and gcwq->lock's.
*/
void freeze_workqueues_begin(void)
{
unsigned int cpu;
spin_lock(&workqueue_lock);
BUG_ON(workqueue_freezing);
workqueue_freezing = true;
for_each_gcwq_cpu(cpu) {
struct global_cwq *gcwq = get_gcwq(cpu);
struct workqueue_struct *wq;
spin_lock_irq(&gcwq->lock);
BUG_ON(gcwq->flags & GCWQ_FREEZING);
gcwq->flags |= GCWQ_FREEZING;
list_for_each_entry(wq, &workqueues, list) {
struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
if (cwq && wq->flags & WQ_FREEZABLE)
cwq->max_active = 0;
}
spin_unlock_irq(&gcwq->lock);
}
spin_unlock(&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(&workqueue_lock);
BUG_ON(!workqueue_freezing);
for_each_gcwq_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 cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
if (!cwq || !(wq->flags & WQ_FREEZABLE))
continue;
BUG_ON(cwq->nr_active < 0);
if (cwq->nr_active) {
busy = true;
goto out_unlock;
}
}
}
out_unlock:
spin_unlock(&workqueue_lock);
return busy;
}
/**
* thaw_workqueues - thaw workqueues
*
* Thaw workqueues. Normal queueing is restored and all collected
* frozen works are transferred to their respective gcwq worklists.
*
* CONTEXT:
* Grabs and releases workqueue_lock and gcwq->lock's.
*/
void thaw_workqueues(void)
{
unsigned int cpu;
spin_lock(&workqueue_lock);
if (!workqueue_freezing)
goto out_unlock;
for_each_gcwq_cpu(cpu) {
struct global_cwq *gcwq = get_gcwq(cpu);
struct worker_pool *pool;
struct workqueue_struct *wq;
spin_lock_irq(&gcwq->lock);
BUG_ON(!(gcwq->flags & GCWQ_FREEZING));
gcwq->flags &= ~GCWQ_FREEZING;
list_for_each_entry(wq, &workqueues, list) {
struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
if (!cwq || !(wq->flags & WQ_FREEZABLE))
continue;
/* restore max_active and repopulate worklist */
cwq_set_max_active(cwq, wq->saved_max_active);
}
for_each_worker_pool(pool, gcwq)
wake_up_worker(pool);
spin_unlock_irq(&gcwq->lock);
}
workqueue_freezing = false;
out_unlock:
spin_unlock(&workqueue_lock);
}
#endif /* CONFIG_FREEZER */
static int __init init_workqueues(void)
{
unsigned int cpu;
int i;
/* make sure we have enough bits for OFFQ CPU number */
BUILD_BUG_ON((1LU << (BITS_PER_LONG - WORK_OFFQ_CPU_SHIFT)) <
WORK_CPU_LAST);
cpu_notifier(workqueue_cpu_up_callback, CPU_PRI_WORKQUEUE_UP);
hotcpu_notifier(workqueue_cpu_down_callback, CPU_PRI_WORKQUEUE_DOWN);
/* initialize gcwqs */
for_each_gcwq_cpu(cpu) {
struct global_cwq *gcwq = get_gcwq(cpu);
struct worker_pool *pool;
spin_lock_init(&gcwq->lock);
gcwq->cpu = cpu;
gcwq->flags |= GCWQ_DISASSOCIATED;
for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++)
INIT_HLIST_HEAD(&gcwq->busy_hash[i]);
for_each_worker_pool(pool, gcwq) {
pool->gcwq = gcwq;
INIT_LIST_HEAD(&pool->worklist);
INIT_LIST_HEAD(&pool->idle_list);
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, gcwq_mayday_timeout,
(unsigned long)pool);
mutex_init(&pool->assoc_mutex);
ida_init(&pool->worker_ida);
}
}
/* create the initial worker */
for_each_online_gcwq_cpu(cpu) {
struct global_cwq *gcwq = get_gcwq(cpu);
struct worker_pool *pool;
if (cpu != WORK_CPU_UNBOUND)
gcwq->flags &= ~GCWQ_DISASSOCIATED;
for_each_worker_pool(pool, gcwq) {
struct worker *worker;
worker = create_worker(pool);
BUG_ON(!worker);
spin_lock_irq(&gcwq->lock);
start_worker(worker);
spin_unlock_irq(&gcwq->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);