2
* kernel/workqueue.c - generic async execution with shared worker pool
4
* Copyright (C) 2002 Ingo Molnar
6
* Derived from the taskqueue/keventd code by:
7
* David Woodhouse <dwmw2@infradead.org>
9
* Kai Petzke <wpp@marie.physik.tu-berlin.de>
10
* Theodore Ts'o <tytso@mit.edu>
12
* Made to use alloc_percpu by Christoph Lameter.
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* Copyright (C) 2010 SUSE Linux Products GmbH
15
* Copyright (C) 2010 Tejun Heo <tj@kernel.org>
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* This is the generic async execution mechanism. Work items as are
18
* executed in process context. The worker pool is shared and
19
* automatically managed. There is one worker pool for each CPU and
20
* one extra for works which are better served by workers which are
21
* not bound to any specific CPU.
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* Please read Documentation/workqueue.txt for details.
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#include <linux/export.h>
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#include <linux/kernel.h>
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#include <linux/sched.h>
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#include <linux/init.h>
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#include <linux/signal.h>
31
#include <linux/completion.h>
32
#include <linux/workqueue.h>
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#include <linux/slab.h>
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#include <linux/cpu.h>
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#include <linux/notifier.h>
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#include <linux/kthread.h>
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#include <linux/hardirq.h>
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#include <linux/mempolicy.h>
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#include <linux/freezer.h>
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#include <linux/kallsyms.h>
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#include <linux/debug_locks.h>
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#include <linux/lockdep.h>
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#include <linux/idr.h>
45
#include "workqueue_sched.h"
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/* global_cwq flags */
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GCWQ_MANAGE_WORKERS = 1 << 0, /* need to manage workers */
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GCWQ_MANAGING_WORKERS = 1 << 1, /* managing workers */
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GCWQ_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
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GCWQ_FREEZING = 1 << 3, /* freeze in progress */
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GCWQ_HIGHPRI_PENDING = 1 << 4, /* highpri works on queue */
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WORKER_STARTED = 1 << 0, /* started */
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WORKER_DIE = 1 << 1, /* die die die */
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WORKER_IDLE = 1 << 2, /* is idle */
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WORKER_PREP = 1 << 3, /* preparing to run works */
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WORKER_ROGUE = 1 << 4, /* not bound to any cpu */
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WORKER_REBIND = 1 << 5, /* mom is home, come back */
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WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
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WORKER_UNBOUND = 1 << 7, /* worker is unbound */
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WORKER_NOT_RUNNING = WORKER_PREP | WORKER_ROGUE | WORKER_REBIND |
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WORKER_CPU_INTENSIVE | WORKER_UNBOUND,
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/* gcwq->trustee_state */
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TRUSTEE_START = 0, /* start */
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TRUSTEE_IN_CHARGE = 1, /* trustee in charge of gcwq */
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TRUSTEE_BUTCHER = 2, /* butcher workers */
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TRUSTEE_RELEASE = 3, /* release workers */
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TRUSTEE_DONE = 4, /* trustee is done */
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BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
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BUSY_WORKER_HASH_SIZE = 1 << BUSY_WORKER_HASH_ORDER,
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BUSY_WORKER_HASH_MASK = BUSY_WORKER_HASH_SIZE - 1,
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MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
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IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
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MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2,
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/* call for help after 10ms
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MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
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CREATE_COOLDOWN = HZ, /* time to breath after fail */
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TRUSTEE_COOLDOWN = HZ / 10, /* for trustee draining */
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* Rescue workers are used only on emergencies and shared by
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RESCUER_NICE_LEVEL = -20,
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* Structure fields follow one of the following exclusion rules.
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* I: Modifiable by initialization/destruction paths and read-only for
102
* P: Preemption protected. Disabling preemption is enough and should
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* only be modified and accessed from the local cpu.
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* L: gcwq->lock protected. Access with gcwq->lock held.
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* X: During normal operation, modification requires gcwq->lock and
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* should be done only from local cpu. Either disabling preemption
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* on local cpu or grabbing gcwq->lock is enough for read access.
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* If GCWQ_DISASSOCIATED is set, it's identical to L.
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* F: wq->flush_mutex protected.
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* W: workqueue_lock protected.
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* The poor guys doing the actual heavy lifting. All on-duty workers
121
* are either serving the manager role, on idle list or on busy hash.
124
/* on idle list while idle, on busy hash table while busy */
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struct list_head entry; /* L: while idle */
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struct hlist_node hentry; /* L: while busy */
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struct work_struct *current_work; /* L: work being processed */
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struct cpu_workqueue_struct *current_cwq; /* L: current_work's cwq */
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struct list_head scheduled; /* L: scheduled works */
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struct task_struct *task; /* I: worker task */
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struct global_cwq *gcwq; /* I: the associated gcwq */
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/* 64 bytes boundary on 64bit, 32 on 32bit */
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unsigned long last_active; /* L: last active timestamp */
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unsigned int flags; /* X: flags */
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int id; /* I: worker id */
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struct work_struct rebind_work; /* L: rebind worker to cpu */
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* Global per-cpu workqueue. There's one and only one for each cpu
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* and all works are queued and processed here regardless of their
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spinlock_t lock; /* the gcwq lock */
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struct list_head worklist; /* L: list of pending works */
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unsigned int cpu; /* I: the associated cpu */
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unsigned int flags; /* L: GCWQ_* flags */
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int nr_workers; /* L: total number of workers */
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int nr_idle; /* L: currently idle ones */
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/* workers are chained either in the idle_list or busy_hash */
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struct list_head idle_list; /* X: list of idle workers */
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struct hlist_head busy_hash[BUSY_WORKER_HASH_SIZE];
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/* L: hash of busy workers */
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struct timer_list idle_timer; /* L: worker idle timeout */
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struct timer_list mayday_timer; /* L: SOS timer for dworkers */
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struct ida worker_ida; /* L: for worker IDs */
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struct task_struct *trustee; /* L: for gcwq shutdown */
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unsigned int trustee_state; /* L: trustee state */
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wait_queue_head_t trustee_wait; /* trustee wait */
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struct worker *first_idle; /* L: first idle worker */
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} ____cacheline_aligned_in_smp;
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* The per-CPU workqueue. The lower WORK_STRUCT_FLAG_BITS of
174
* work_struct->data are used for flags and thus cwqs need to be
175
* aligned at two's power of the number of flag bits.
177
struct cpu_workqueue_struct {
178
struct global_cwq *gcwq; /* I: the associated gcwq */
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struct workqueue_struct *wq; /* I: the owning workqueue */
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int work_color; /* L: current color */
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int flush_color; /* L: flushing color */
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int nr_in_flight[WORK_NR_COLORS];
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/* L: nr of in_flight works */
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int nr_active; /* L: nr of active works */
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int max_active; /* L: max active works */
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struct list_head delayed_works; /* L: delayed works */
190
* Structure used to wait for workqueue flush.
193
struct list_head list; /* F: list of flushers */
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int flush_color; /* F: flush color waiting for */
195
struct completion done; /* flush completion */
199
* All cpumasks are assumed to be always set on UP and thus can't be
200
* used to determine whether there's something to be done.
203
typedef cpumask_var_t mayday_mask_t;
204
#define mayday_test_and_set_cpu(cpu, mask) \
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cpumask_test_and_set_cpu((cpu), (mask))
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#define mayday_clear_cpu(cpu, mask) cpumask_clear_cpu((cpu), (mask))
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#define for_each_mayday_cpu(cpu, mask) for_each_cpu((cpu), (mask))
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#define alloc_mayday_mask(maskp, gfp) zalloc_cpumask_var((maskp), (gfp))
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#define free_mayday_mask(mask) free_cpumask_var((mask))
211
typedef unsigned long mayday_mask_t;
212
#define mayday_test_and_set_cpu(cpu, mask) test_and_set_bit(0, &(mask))
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#define mayday_clear_cpu(cpu, mask) clear_bit(0, &(mask))
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#define for_each_mayday_cpu(cpu, mask) if ((cpu) = 0, (mask))
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#define alloc_mayday_mask(maskp, gfp) true
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#define free_mayday_mask(mask) do { } while (0)
220
* The externally visible workqueue abstraction is an array of
221
* per-CPU workqueues:
223
struct workqueue_struct {
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unsigned int flags; /* W: WQ_* flags */
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struct cpu_workqueue_struct __percpu *pcpu;
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struct cpu_workqueue_struct *single;
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} cpu_wq; /* I: cwq's */
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struct list_head list; /* W: list of all workqueues */
232
struct mutex flush_mutex; /* protects wq flushing */
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int work_color; /* F: current work color */
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int flush_color; /* F: current flush color */
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atomic_t nr_cwqs_to_flush; /* flush in progress */
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struct wq_flusher *first_flusher; /* F: first flusher */
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struct list_head flusher_queue; /* F: flush waiters */
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struct list_head flusher_overflow; /* F: flush overflow list */
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mayday_mask_t mayday_mask; /* cpus requesting rescue */
241
struct worker *rescuer; /* I: rescue worker */
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int nr_drainers; /* W: drain in progress */
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int saved_max_active; /* W: saved cwq max_active */
245
const char *name; /* I: workqueue name */
246
#ifdef CONFIG_LOCKDEP
247
struct lockdep_map lockdep_map;
251
struct workqueue_struct *system_wq __read_mostly;
252
struct workqueue_struct *system_long_wq __read_mostly;
253
struct workqueue_struct *system_nrt_wq __read_mostly;
254
struct workqueue_struct *system_unbound_wq __read_mostly;
255
struct workqueue_struct *system_freezable_wq __read_mostly;
256
EXPORT_SYMBOL_GPL(system_wq);
257
EXPORT_SYMBOL_GPL(system_long_wq);
258
EXPORT_SYMBOL_GPL(system_nrt_wq);
259
EXPORT_SYMBOL_GPL(system_unbound_wq);
260
EXPORT_SYMBOL_GPL(system_freezable_wq);
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#define CREATE_TRACE_POINTS
263
#include <trace/events/workqueue.h>
265
#define for_each_busy_worker(worker, i, pos, gcwq) \
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for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++) \
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hlist_for_each_entry(worker, pos, &gcwq->busy_hash[i], hentry)
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static inline int __next_gcwq_cpu(int cpu, const struct cpumask *mask,
272
if (cpu < nr_cpu_ids) {
274
cpu = cpumask_next(cpu, mask);
275
if (cpu < nr_cpu_ids)
279
return WORK_CPU_UNBOUND;
281
return WORK_CPU_NONE;
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static inline int __next_wq_cpu(int cpu, const struct cpumask *mask,
285
struct workqueue_struct *wq)
287
return __next_gcwq_cpu(cpu, mask, !(wq->flags & WQ_UNBOUND) ? 1 : 2);
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* An extra gcwq is defined for an invalid cpu number
294
* (WORK_CPU_UNBOUND) to host workqueues which are not bound to any
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* specific CPU. The following iterators are similar to
296
* for_each_*_cpu() iterators but also considers the unbound gcwq.
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* for_each_gcwq_cpu() : possible CPUs + WORK_CPU_UNBOUND
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* for_each_online_gcwq_cpu() : online CPUs + WORK_CPU_UNBOUND
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* for_each_cwq_cpu() : possible CPUs for bound workqueues,
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* WORK_CPU_UNBOUND for unbound workqueues
303
#define for_each_gcwq_cpu(cpu) \
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for ((cpu) = __next_gcwq_cpu(-1, cpu_possible_mask, 3); \
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(cpu) < WORK_CPU_NONE; \
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(cpu) = __next_gcwq_cpu((cpu), cpu_possible_mask, 3))
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#define for_each_online_gcwq_cpu(cpu) \
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for ((cpu) = __next_gcwq_cpu(-1, cpu_online_mask, 3); \
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(cpu) < WORK_CPU_NONE; \
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(cpu) = __next_gcwq_cpu((cpu), cpu_online_mask, 3))
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#define for_each_cwq_cpu(cpu, wq) \
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for ((cpu) = __next_wq_cpu(-1, cpu_possible_mask, (wq)); \
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(cpu) < WORK_CPU_NONE; \
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(cpu) = __next_wq_cpu((cpu), cpu_possible_mask, (wq)))
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#ifdef CONFIG_DEBUG_OBJECTS_WORK
320
static struct debug_obj_descr work_debug_descr;
322
static void *work_debug_hint(void *addr)
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return ((struct work_struct *) addr)->func;
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* fixup_init is called when:
329
* - an active object is initialized
331
static int work_fixup_init(void *addr, enum debug_obj_state state)
333
struct work_struct *work = addr;
336
case ODEBUG_STATE_ACTIVE:
337
cancel_work_sync(work);
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debug_object_init(work, &work_debug_descr);
346
* fixup_activate is called when:
347
* - an active object is activated
348
* - an unknown object is activated (might be a statically initialized object)
350
static int work_fixup_activate(void *addr, enum debug_obj_state state)
352
struct work_struct *work = addr;
356
case ODEBUG_STATE_NOTAVAILABLE:
358
* This is not really a fixup. The work struct was
359
* statically initialized. We just make sure that it
360
* is tracked in the object tracker.
362
if (test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work))) {
363
debug_object_init(work, &work_debug_descr);
364
debug_object_activate(work, &work_debug_descr);
370
case ODEBUG_STATE_ACTIVE:
379
* fixup_free is called when:
380
* - an active object is freed
382
static int work_fixup_free(void *addr, enum debug_obj_state state)
384
struct work_struct *work = addr;
387
case ODEBUG_STATE_ACTIVE:
388
cancel_work_sync(work);
389
debug_object_free(work, &work_debug_descr);
396
static struct debug_obj_descr work_debug_descr = {
397
.name = "work_struct",
398
.debug_hint = work_debug_hint,
399
.fixup_init = work_fixup_init,
400
.fixup_activate = work_fixup_activate,
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.fixup_free = work_fixup_free,
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static inline void debug_work_activate(struct work_struct *work)
406
debug_object_activate(work, &work_debug_descr);
409
static inline void debug_work_deactivate(struct work_struct *work)
411
debug_object_deactivate(work, &work_debug_descr);
414
void __init_work(struct work_struct *work, int onstack)
417
debug_object_init_on_stack(work, &work_debug_descr);
419
debug_object_init(work, &work_debug_descr);
421
EXPORT_SYMBOL_GPL(__init_work);
423
void destroy_work_on_stack(struct work_struct *work)
425
debug_object_free(work, &work_debug_descr);
427
EXPORT_SYMBOL_GPL(destroy_work_on_stack);
430
static inline void debug_work_activate(struct work_struct *work) { }
431
static inline void debug_work_deactivate(struct work_struct *work) { }
434
/* Serializes the accesses to the list of workqueues. */
435
static DEFINE_SPINLOCK(workqueue_lock);
436
static LIST_HEAD(workqueues);
437
static bool workqueue_freezing; /* W: have wqs started freezing? */
440
* The almighty global cpu workqueues. nr_running is the only field
441
* which is expected to be used frequently by other cpus via
442
* try_to_wake_up(). Put it in a separate cacheline.
444
static DEFINE_PER_CPU(struct global_cwq, global_cwq);
445
static DEFINE_PER_CPU_SHARED_ALIGNED(atomic_t, gcwq_nr_running);
448
* Global cpu workqueue and nr_running counter for unbound gcwq. The
449
* gcwq is always online, has GCWQ_DISASSOCIATED set, and all its
450
* workers have WORKER_UNBOUND set.
452
static struct global_cwq unbound_global_cwq;
453
static atomic_t unbound_gcwq_nr_running = ATOMIC_INIT(0); /* always 0 */
455
static int worker_thread(void *__worker);
457
static struct global_cwq *get_gcwq(unsigned int cpu)
459
if (cpu != WORK_CPU_UNBOUND)
460
return &per_cpu(global_cwq, cpu);
462
return &unbound_global_cwq;
465
static atomic_t *get_gcwq_nr_running(unsigned int cpu)
467
if (cpu != WORK_CPU_UNBOUND)
468
return &per_cpu(gcwq_nr_running, cpu);
470
return &unbound_gcwq_nr_running;
473
static struct cpu_workqueue_struct *get_cwq(unsigned int cpu,
474
struct workqueue_struct *wq)
476
if (!(wq->flags & WQ_UNBOUND)) {
477
if (likely(cpu < nr_cpu_ids)) {
479
return per_cpu_ptr(wq->cpu_wq.pcpu, cpu);
481
return wq->cpu_wq.single;
484
} else if (likely(cpu == WORK_CPU_UNBOUND))
485
return wq->cpu_wq.single;
489
static unsigned int work_color_to_flags(int color)
491
return color << WORK_STRUCT_COLOR_SHIFT;
494
static int get_work_color(struct work_struct *work)
496
return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) &
497
((1 << WORK_STRUCT_COLOR_BITS) - 1);
500
static int work_next_color(int color)
502
return (color + 1) % WORK_NR_COLORS;
506
* A work's data points to the cwq with WORK_STRUCT_CWQ set while the
507
* work is on queue. Once execution starts, WORK_STRUCT_CWQ is
508
* cleared and the work data contains the cpu number it was last on.
510
* set_work_{cwq|cpu}() and clear_work_data() can be used to set the
511
* cwq, cpu or clear work->data. These functions should only be
512
* called while the work is owned - ie. while the PENDING bit is set.
514
* get_work_[g]cwq() can be used to obtain the gcwq or cwq
515
* corresponding to a work. gcwq is available once the work has been
516
* queued anywhere after initialization. cwq is available only from
517
* queueing until execution starts.
519
static inline void set_work_data(struct work_struct *work, unsigned long data,
522
BUG_ON(!work_pending(work));
523
atomic_long_set(&work->data, data | flags | work_static(work));
526
static void set_work_cwq(struct work_struct *work,
527
struct cpu_workqueue_struct *cwq,
528
unsigned long extra_flags)
530
set_work_data(work, (unsigned long)cwq,
531
WORK_STRUCT_PENDING | WORK_STRUCT_CWQ | extra_flags);
534
static void set_work_cpu(struct work_struct *work, unsigned int cpu)
536
set_work_data(work, cpu << WORK_STRUCT_FLAG_BITS, WORK_STRUCT_PENDING);
539
static void clear_work_data(struct work_struct *work)
541
set_work_data(work, WORK_STRUCT_NO_CPU, 0);
544
static struct cpu_workqueue_struct *get_work_cwq(struct work_struct *work)
546
unsigned long data = atomic_long_read(&work->data);
548
if (data & WORK_STRUCT_CWQ)
549
return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
554
static struct global_cwq *get_work_gcwq(struct work_struct *work)
556
unsigned long data = atomic_long_read(&work->data);
559
if (data & WORK_STRUCT_CWQ)
560
return ((struct cpu_workqueue_struct *)
561
(data & WORK_STRUCT_WQ_DATA_MASK))->gcwq;
563
cpu = data >> WORK_STRUCT_FLAG_BITS;
564
if (cpu == WORK_CPU_NONE)
567
BUG_ON(cpu >= nr_cpu_ids && cpu != WORK_CPU_UNBOUND);
568
return get_gcwq(cpu);
572
* Policy functions. These define the policies on how the global
573
* worker pool is managed. Unless noted otherwise, these functions
574
* assume that they're being called with gcwq->lock held.
577
static bool __need_more_worker(struct global_cwq *gcwq)
579
return !atomic_read(get_gcwq_nr_running(gcwq->cpu)) ||
580
gcwq->flags & GCWQ_HIGHPRI_PENDING;
584
* Need to wake up a worker? Called from anything but currently
587
static bool need_more_worker(struct global_cwq *gcwq)
589
return !list_empty(&gcwq->worklist) && __need_more_worker(gcwq);
592
/* Can I start working? Called from busy but !running workers. */
593
static bool may_start_working(struct global_cwq *gcwq)
595
return gcwq->nr_idle;
598
/* Do I need to keep working? Called from currently running workers. */
599
static bool keep_working(struct global_cwq *gcwq)
601
atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu);
603
return !list_empty(&gcwq->worklist) &&
604
(atomic_read(nr_running) <= 1 ||
605
gcwq->flags & GCWQ_HIGHPRI_PENDING);
608
/* Do we need a new worker? Called from manager. */
609
static bool need_to_create_worker(struct global_cwq *gcwq)
611
return need_more_worker(gcwq) && !may_start_working(gcwq);
614
/* Do I need to be the manager? */
615
static bool need_to_manage_workers(struct global_cwq *gcwq)
617
return need_to_create_worker(gcwq) || gcwq->flags & GCWQ_MANAGE_WORKERS;
620
/* Do we have too many workers and should some go away? */
621
static bool too_many_workers(struct global_cwq *gcwq)
623
bool managing = gcwq->flags & GCWQ_MANAGING_WORKERS;
624
int nr_idle = gcwq->nr_idle + managing; /* manager is considered idle */
625
int nr_busy = gcwq->nr_workers - nr_idle;
627
return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
634
/* Return the first worker. Safe with preemption disabled */
635
static struct worker *first_worker(struct global_cwq *gcwq)
637
if (unlikely(list_empty(&gcwq->idle_list)))
640
return list_first_entry(&gcwq->idle_list, struct worker, entry);
644
* wake_up_worker - wake up an idle worker
645
* @gcwq: gcwq to wake worker for
647
* Wake up the first idle worker of @gcwq.
650
* spin_lock_irq(gcwq->lock).
652
static void wake_up_worker(struct global_cwq *gcwq)
654
struct worker *worker = first_worker(gcwq);
657
wake_up_process(worker->task);
661
* wq_worker_waking_up - a worker is waking up
662
* @task: task waking up
663
* @cpu: CPU @task is waking up to
665
* This function is called during try_to_wake_up() when a worker is
669
* spin_lock_irq(rq->lock)
671
void wq_worker_waking_up(struct task_struct *task, unsigned int cpu)
673
struct worker *worker = kthread_data(task);
675
if (!(worker->flags & WORKER_NOT_RUNNING))
676
atomic_inc(get_gcwq_nr_running(cpu));
680
* wq_worker_sleeping - a worker is going to sleep
681
* @task: task going to sleep
682
* @cpu: CPU in question, must be the current CPU number
684
* This function is called during schedule() when a busy worker is
685
* going to sleep. Worker on the same cpu can be woken up by
686
* returning pointer to its task.
689
* spin_lock_irq(rq->lock)
692
* Worker task on @cpu to wake up, %NULL if none.
694
struct task_struct *wq_worker_sleeping(struct task_struct *task,
697
struct worker *worker = kthread_data(task), *to_wakeup = NULL;
698
struct global_cwq *gcwq = get_gcwq(cpu);
699
atomic_t *nr_running = get_gcwq_nr_running(cpu);
701
if (worker->flags & WORKER_NOT_RUNNING)
704
/* this can only happen on the local cpu */
705
BUG_ON(cpu != raw_smp_processor_id());
708
* The counterpart of the following dec_and_test, implied mb,
709
* worklist not empty test sequence is in insert_work().
710
* Please read comment there.
712
* NOT_RUNNING is clear. This means that trustee is not in
713
* charge and we're running on the local cpu w/ rq lock held
714
* and preemption disabled, which in turn means that none else
715
* could be manipulating idle_list, so dereferencing idle_list
716
* without gcwq lock is safe.
718
if (atomic_dec_and_test(nr_running) && !list_empty(&gcwq->worklist))
719
to_wakeup = first_worker(gcwq);
720
return to_wakeup ? to_wakeup->task : NULL;
724
* worker_set_flags - set worker flags and adjust nr_running accordingly
726
* @flags: flags to set
727
* @wakeup: wakeup an idle worker if necessary
729
* Set @flags in @worker->flags and adjust nr_running accordingly. If
730
* nr_running becomes zero and @wakeup is %true, an idle worker is
734
* spin_lock_irq(gcwq->lock)
736
static inline void worker_set_flags(struct worker *worker, unsigned int flags,
739
struct global_cwq *gcwq = worker->gcwq;
741
WARN_ON_ONCE(worker->task != current);
744
* If transitioning into NOT_RUNNING, adjust nr_running and
745
* wake up an idle worker as necessary if requested by
748
if ((flags & WORKER_NOT_RUNNING) &&
749
!(worker->flags & WORKER_NOT_RUNNING)) {
750
atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu);
753
if (atomic_dec_and_test(nr_running) &&
754
!list_empty(&gcwq->worklist))
755
wake_up_worker(gcwq);
757
atomic_dec(nr_running);
760
worker->flags |= flags;
764
* worker_clr_flags - clear worker flags and adjust nr_running accordingly
766
* @flags: flags to clear
768
* Clear @flags in @worker->flags and adjust nr_running accordingly.
771
* spin_lock_irq(gcwq->lock)
773
static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
775
struct global_cwq *gcwq = worker->gcwq;
776
unsigned int oflags = worker->flags;
778
WARN_ON_ONCE(worker->task != current);
780
worker->flags &= ~flags;
783
* If transitioning out of NOT_RUNNING, increment nr_running. Note
784
* that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
785
* of multiple flags, not a single flag.
787
if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
788
if (!(worker->flags & WORKER_NOT_RUNNING))
789
atomic_inc(get_gcwq_nr_running(gcwq->cpu));
793
* busy_worker_head - return the busy hash head for a work
794
* @gcwq: gcwq of interest
795
* @work: work to be hashed
797
* Return hash head of @gcwq for @work.
800
* spin_lock_irq(gcwq->lock).
803
* Pointer to the hash head.
805
static struct hlist_head *busy_worker_head(struct global_cwq *gcwq,
806
struct work_struct *work)
808
const int base_shift = ilog2(sizeof(struct work_struct));
809
unsigned long v = (unsigned long)work;
811
/* simple shift and fold hash, do we need something better? */
813
v += v >> BUSY_WORKER_HASH_ORDER;
814
v &= BUSY_WORKER_HASH_MASK;
816
return &gcwq->busy_hash[v];
820
* __find_worker_executing_work - find worker which is executing a work
821
* @gcwq: gcwq of interest
822
* @bwh: hash head as returned by busy_worker_head()
823
* @work: work to find worker for
825
* Find a worker which is executing @work on @gcwq. @bwh should be
826
* the hash head obtained by calling busy_worker_head() with the same
830
* spin_lock_irq(gcwq->lock).
833
* Pointer to worker which is executing @work if found, NULL
836
static struct worker *__find_worker_executing_work(struct global_cwq *gcwq,
837
struct hlist_head *bwh,
838
struct work_struct *work)
840
struct worker *worker;
841
struct hlist_node *tmp;
843
hlist_for_each_entry(worker, tmp, bwh, hentry)
844
if (worker->current_work == work)
850
* find_worker_executing_work - find worker which is executing a work
851
* @gcwq: gcwq of interest
852
* @work: work to find worker for
854
* Find a worker which is executing @work on @gcwq. This function is
855
* identical to __find_worker_executing_work() except that this
856
* function calculates @bwh itself.
859
* spin_lock_irq(gcwq->lock).
862
* Pointer to worker which is executing @work if found, NULL
865
static struct worker *find_worker_executing_work(struct global_cwq *gcwq,
866
struct work_struct *work)
868
return __find_worker_executing_work(gcwq, busy_worker_head(gcwq, work),
873
* gcwq_determine_ins_pos - find insertion position
874
* @gcwq: gcwq of interest
875
* @cwq: cwq a work is being queued for
877
* A work for @cwq is about to be queued on @gcwq, determine insertion
878
* position for the work. If @cwq is for HIGHPRI wq, the work is
879
* queued at the head of the queue but in FIFO order with respect to
880
* other HIGHPRI works; otherwise, at the end of the queue. This
881
* function also sets GCWQ_HIGHPRI_PENDING flag to hint @gcwq that
882
* there are HIGHPRI works pending.
885
* spin_lock_irq(gcwq->lock).
888
* Pointer to inserstion position.
890
static inline struct list_head *gcwq_determine_ins_pos(struct global_cwq *gcwq,
891
struct cpu_workqueue_struct *cwq)
893
struct work_struct *twork;
895
if (likely(!(cwq->wq->flags & WQ_HIGHPRI)))
896
return &gcwq->worklist;
898
list_for_each_entry(twork, &gcwq->worklist, entry) {
899
struct cpu_workqueue_struct *tcwq = get_work_cwq(twork);
901
if (!(tcwq->wq->flags & WQ_HIGHPRI))
905
gcwq->flags |= GCWQ_HIGHPRI_PENDING;
906
return &twork->entry;
910
* insert_work - insert a work into gcwq
911
* @cwq: cwq @work belongs to
912
* @work: work to insert
913
* @head: insertion point
914
* @extra_flags: extra WORK_STRUCT_* flags to set
916
* Insert @work which belongs to @cwq into @gcwq after @head.
917
* @extra_flags is or'd to work_struct flags.
920
* spin_lock_irq(gcwq->lock).
922
static void insert_work(struct cpu_workqueue_struct *cwq,
923
struct work_struct *work, struct list_head *head,
924
unsigned int extra_flags)
926
struct global_cwq *gcwq = cwq->gcwq;
928
/* we own @work, set data and link */
929
set_work_cwq(work, cwq, extra_flags);
932
* Ensure that we get the right work->data if we see the
933
* result of list_add() below, see try_to_grab_pending().
937
list_add_tail(&work->entry, head);
940
* Ensure either worker_sched_deactivated() sees the above
941
* list_add_tail() or we see zero nr_running to avoid workers
942
* lying around lazily while there are works to be processed.
946
if (__need_more_worker(gcwq))
947
wake_up_worker(gcwq);
951
* Test whether @work is being queued from another work executing on the
952
* same workqueue. This is rather expensive and should only be used from
955
static bool is_chained_work(struct workqueue_struct *wq)
960
for_each_gcwq_cpu(cpu) {
961
struct global_cwq *gcwq = get_gcwq(cpu);
962
struct worker *worker;
963
struct hlist_node *pos;
966
spin_lock_irqsave(&gcwq->lock, flags);
967
for_each_busy_worker(worker, i, pos, gcwq) {
968
if (worker->task != current)
970
spin_unlock_irqrestore(&gcwq->lock, flags);
972
* I'm @worker, no locking necessary. See if @work
973
* is headed to the same workqueue.
975
return worker->current_cwq->wq == wq;
977
spin_unlock_irqrestore(&gcwq->lock, flags);
982
static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
983
struct work_struct *work)
985
struct global_cwq *gcwq;
986
struct cpu_workqueue_struct *cwq;
987
struct list_head *worklist;
988
unsigned int work_flags;
991
debug_work_activate(work);
993
/* if dying, only works from the same workqueue are allowed */
994
if (unlikely(wq->flags & WQ_DRAINING) &&
995
WARN_ON_ONCE(!is_chained_work(wq)))
998
/* determine gcwq to use */
999
if (!(wq->flags & WQ_UNBOUND)) {
1000
struct global_cwq *last_gcwq;
1002
if (unlikely(cpu == WORK_CPU_UNBOUND))
1003
cpu = raw_smp_processor_id();
1006
* It's multi cpu. If @wq is non-reentrant and @work
1007
* was previously on a different cpu, it might still
1008
* be running there, in which case the work needs to
1009
* be queued on that cpu to guarantee non-reentrance.
1011
gcwq = get_gcwq(cpu);
1012
if (wq->flags & WQ_NON_REENTRANT &&
1013
(last_gcwq = get_work_gcwq(work)) && last_gcwq != gcwq) {
1014
struct worker *worker;
1016
spin_lock_irqsave(&last_gcwq->lock, flags);
1018
worker = find_worker_executing_work(last_gcwq, work);
1020
if (worker && worker->current_cwq->wq == wq)
1023
/* meh... not running there, queue here */
1024
spin_unlock_irqrestore(&last_gcwq->lock, flags);
1025
spin_lock_irqsave(&gcwq->lock, flags);
1028
spin_lock_irqsave(&gcwq->lock, flags);
1030
gcwq = get_gcwq(WORK_CPU_UNBOUND);
1031
spin_lock_irqsave(&gcwq->lock, flags);
1034
/* gcwq determined, get cwq and queue */
1035
cwq = get_cwq(gcwq->cpu, wq);
1036
trace_workqueue_queue_work(cpu, cwq, work);
1038
BUG_ON(!list_empty(&work->entry));
1040
cwq->nr_in_flight[cwq->work_color]++;
1041
work_flags = work_color_to_flags(cwq->work_color);
1043
if (likely(cwq->nr_active < cwq->max_active)) {
1044
trace_workqueue_activate_work(work);
1046
worklist = gcwq_determine_ins_pos(gcwq, cwq);
1048
work_flags |= WORK_STRUCT_DELAYED;
1049
worklist = &cwq->delayed_works;
1052
insert_work(cwq, work, worklist, work_flags);
1054
spin_unlock_irqrestore(&gcwq->lock, flags);
1058
* queue_work - queue work on a workqueue
1059
* @wq: workqueue to use
1060
* @work: work to queue
1062
* Returns 0 if @work was already on a queue, non-zero otherwise.
1064
* We queue the work to the CPU on which it was submitted, but if the CPU dies
1065
* it can be processed by another CPU.
1067
int queue_work(struct workqueue_struct *wq, struct work_struct *work)
1071
ret = queue_work_on(get_cpu(), wq, work);
1076
EXPORT_SYMBOL_GPL(queue_work);
1079
* queue_work_on - queue work on specific cpu
1080
* @cpu: CPU number to execute work on
1081
* @wq: workqueue to use
1082
* @work: work to queue
1084
* Returns 0 if @work was already on a queue, non-zero otherwise.
1086
* We queue the work to a specific CPU, the caller must ensure it
1090
queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work)
1094
if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1095
__queue_work(cpu, wq, work);
1100
EXPORT_SYMBOL_GPL(queue_work_on);
1102
static void delayed_work_timer_fn(unsigned long __data)
1104
struct delayed_work *dwork = (struct delayed_work *)__data;
1105
struct cpu_workqueue_struct *cwq = get_work_cwq(&dwork->work);
1107
__queue_work(smp_processor_id(), cwq->wq, &dwork->work);
1111
* queue_delayed_work - queue work on a workqueue after delay
1112
* @wq: workqueue to use
1113
* @dwork: delayable work to queue
1114
* @delay: number of jiffies to wait before queueing
1116
* Returns 0 if @work was already on a queue, non-zero otherwise.
1118
int queue_delayed_work(struct workqueue_struct *wq,
1119
struct delayed_work *dwork, unsigned long delay)
1122
return queue_work(wq, &dwork->work);
1124
return queue_delayed_work_on(-1, wq, dwork, delay);
1126
EXPORT_SYMBOL_GPL(queue_delayed_work);
1129
* queue_delayed_work_on - queue work on specific CPU after delay
1130
* @cpu: CPU number to execute work on
1131
* @wq: workqueue to use
1132
* @dwork: work to queue
1133
* @delay: number of jiffies to wait before queueing
1135
* Returns 0 if @work was already on a queue, non-zero otherwise.
1137
int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1138
struct delayed_work *dwork, unsigned long delay)
1141
struct timer_list *timer = &dwork->timer;
1142
struct work_struct *work = &dwork->work;
1144
if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1147
BUG_ON(timer_pending(timer));
1148
BUG_ON(!list_empty(&work->entry));
1150
timer_stats_timer_set_start_info(&dwork->timer);
1153
* This stores cwq for the moment, for the timer_fn.
1154
* Note that the work's gcwq is preserved to allow
1155
* reentrance detection for delayed works.
1157
if (!(wq->flags & WQ_UNBOUND)) {
1158
struct global_cwq *gcwq = get_work_gcwq(work);
1160
if (gcwq && gcwq->cpu != WORK_CPU_UNBOUND)
1163
lcpu = raw_smp_processor_id();
1165
lcpu = WORK_CPU_UNBOUND;
1167
set_work_cwq(work, get_cwq(lcpu, wq), 0);
1169
timer->expires = jiffies + delay;
1170
timer->data = (unsigned long)dwork;
1171
timer->function = delayed_work_timer_fn;
1173
if (unlikely(cpu >= 0))
1174
add_timer_on(timer, cpu);
1181
EXPORT_SYMBOL_GPL(queue_delayed_work_on);
1184
* worker_enter_idle - enter idle state
1185
* @worker: worker which is entering idle state
1187
* @worker is entering idle state. Update stats and idle timer if
1191
* spin_lock_irq(gcwq->lock).
1193
static void worker_enter_idle(struct worker *worker)
1195
struct global_cwq *gcwq = worker->gcwq;
1197
BUG_ON(worker->flags & WORKER_IDLE);
1198
BUG_ON(!list_empty(&worker->entry) &&
1199
(worker->hentry.next || worker->hentry.pprev));
1201
/* can't use worker_set_flags(), also called from start_worker() */
1202
worker->flags |= WORKER_IDLE;
1204
worker->last_active = jiffies;
1206
/* idle_list is LIFO */
1207
list_add(&worker->entry, &gcwq->idle_list);
1209
if (likely(!(worker->flags & WORKER_ROGUE))) {
1210
if (too_many_workers(gcwq) && !timer_pending(&gcwq->idle_timer))
1211
mod_timer(&gcwq->idle_timer,
1212
jiffies + IDLE_WORKER_TIMEOUT);
1214
wake_up_all(&gcwq->trustee_wait);
1216
/* sanity check nr_running */
1217
WARN_ON_ONCE(gcwq->nr_workers == gcwq->nr_idle &&
1218
atomic_read(get_gcwq_nr_running(gcwq->cpu)));
1222
* worker_leave_idle - leave idle state
1223
* @worker: worker which is leaving idle state
1225
* @worker is leaving idle state. Update stats.
1228
* spin_lock_irq(gcwq->lock).
1230
static void worker_leave_idle(struct worker *worker)
1232
struct global_cwq *gcwq = worker->gcwq;
1234
BUG_ON(!(worker->flags & WORKER_IDLE));
1235
worker_clr_flags(worker, WORKER_IDLE);
1237
list_del_init(&worker->entry);
1241
* worker_maybe_bind_and_lock - bind worker to its cpu if possible and lock gcwq
1244
* Works which are scheduled while the cpu is online must at least be
1245
* scheduled to a worker which is bound to the cpu so that if they are
1246
* flushed from cpu callbacks while cpu is going down, they are
1247
* guaranteed to execute on the cpu.
1249
* This function is to be used by rogue workers and rescuers to bind
1250
* themselves to the target cpu and may race with cpu going down or
1251
* coming online. kthread_bind() can't be used because it may put the
1252
* worker to already dead cpu and set_cpus_allowed_ptr() can't be used
1253
* verbatim as it's best effort and blocking and gcwq may be
1254
* [dis]associated in the meantime.
1256
* This function tries set_cpus_allowed() and locks gcwq and verifies
1257
* the binding against GCWQ_DISASSOCIATED which is set during
1258
* CPU_DYING and cleared during CPU_ONLINE, so if the worker enters
1259
* idle state or fetches works without dropping lock, it can guarantee
1260
* the scheduling requirement described in the first paragraph.
1263
* Might sleep. Called without any lock but returns with gcwq->lock
1267
* %true if the associated gcwq is online (@worker is successfully
1268
* bound), %false if offline.
1270
static bool worker_maybe_bind_and_lock(struct worker *worker)
1271
__acquires(&gcwq->lock)
1273
struct global_cwq *gcwq = worker->gcwq;
1274
struct task_struct *task = worker->task;
1278
* The following call may fail, succeed or succeed
1279
* without actually migrating the task to the cpu if
1280
* it races with cpu hotunplug operation. Verify
1281
* against GCWQ_DISASSOCIATED.
1283
if (!(gcwq->flags & GCWQ_DISASSOCIATED))
1284
set_cpus_allowed_ptr(task, get_cpu_mask(gcwq->cpu));
1286
spin_lock_irq(&gcwq->lock);
1287
if (gcwq->flags & GCWQ_DISASSOCIATED)
1289
if (task_cpu(task) == gcwq->cpu &&
1290
cpumask_equal(¤t->cpus_allowed,
1291
get_cpu_mask(gcwq->cpu)))
1293
spin_unlock_irq(&gcwq->lock);
1296
* We've raced with CPU hot[un]plug. Give it a breather
1297
* and retry migration. cond_resched() is required here;
1298
* otherwise, we might deadlock against cpu_stop trying to
1299
* bring down the CPU on non-preemptive kernel.
1307
* Function for worker->rebind_work used to rebind rogue busy workers
1308
* to the associated cpu which is coming back online. This is
1309
* scheduled by cpu up but can race with other cpu hotplug operations
1310
* and may be executed twice without intervening cpu down.
1312
static void worker_rebind_fn(struct work_struct *work)
1314
struct worker *worker = container_of(work, struct worker, rebind_work);
1315
struct global_cwq *gcwq = worker->gcwq;
1317
if (worker_maybe_bind_and_lock(worker))
1318
worker_clr_flags(worker, WORKER_REBIND);
1320
spin_unlock_irq(&gcwq->lock);
1323
static struct worker *alloc_worker(void)
1325
struct worker *worker;
1327
worker = kzalloc(sizeof(*worker), GFP_KERNEL);
1329
INIT_LIST_HEAD(&worker->entry);
1330
INIT_LIST_HEAD(&worker->scheduled);
1331
INIT_WORK(&worker->rebind_work, worker_rebind_fn);
1332
/* on creation a worker is in !idle && prep state */
1333
worker->flags = WORKER_PREP;
1339
* create_worker - create a new workqueue worker
1340
* @gcwq: gcwq the new worker will belong to
1341
* @bind: whether to set affinity to @cpu or not
1343
* Create a new worker which is bound to @gcwq. The returned worker
1344
* can be started by calling start_worker() or destroyed using
1348
* Might sleep. Does GFP_KERNEL allocations.
1351
* Pointer to the newly created worker.
1353
static struct worker *create_worker(struct global_cwq *gcwq, bool bind)
1355
bool on_unbound_cpu = gcwq->cpu == WORK_CPU_UNBOUND;
1356
struct worker *worker = NULL;
1359
spin_lock_irq(&gcwq->lock);
1360
while (ida_get_new(&gcwq->worker_ida, &id)) {
1361
spin_unlock_irq(&gcwq->lock);
1362
if (!ida_pre_get(&gcwq->worker_ida, GFP_KERNEL))
1364
spin_lock_irq(&gcwq->lock);
1366
spin_unlock_irq(&gcwq->lock);
1368
worker = alloc_worker();
1372
worker->gcwq = gcwq;
1375
if (!on_unbound_cpu)
1376
worker->task = kthread_create_on_node(worker_thread,
1378
cpu_to_node(gcwq->cpu),
1379
"kworker/%u:%d", gcwq->cpu, id);
1381
worker->task = kthread_create(worker_thread, worker,
1382
"kworker/u:%d", id);
1383
if (IS_ERR(worker->task))
1387
* A rogue worker will become a regular one if CPU comes
1388
* online later on. Make sure every worker has
1389
* PF_THREAD_BOUND set.
1391
if (bind && !on_unbound_cpu)
1392
kthread_bind(worker->task, gcwq->cpu);
1394
worker->task->flags |= PF_THREAD_BOUND;
1396
worker->flags |= WORKER_UNBOUND;
1402
spin_lock_irq(&gcwq->lock);
1403
ida_remove(&gcwq->worker_ida, id);
1404
spin_unlock_irq(&gcwq->lock);
1411
* start_worker - start a newly created worker
1412
* @worker: worker to start
1414
* Make the gcwq aware of @worker and start it.
1417
* spin_lock_irq(gcwq->lock).
1419
static void start_worker(struct worker *worker)
1421
worker->flags |= WORKER_STARTED;
1422
worker->gcwq->nr_workers++;
1423
worker_enter_idle(worker);
1424
wake_up_process(worker->task);
1428
* destroy_worker - destroy a workqueue worker
1429
* @worker: worker to be destroyed
1431
* Destroy @worker and adjust @gcwq stats accordingly.
1434
* spin_lock_irq(gcwq->lock) which is released and regrabbed.
1436
static void destroy_worker(struct worker *worker)
1438
struct global_cwq *gcwq = worker->gcwq;
1439
int id = worker->id;
1441
/* sanity check frenzy */
1442
BUG_ON(worker->current_work);
1443
BUG_ON(!list_empty(&worker->scheduled));
1445
if (worker->flags & WORKER_STARTED)
1447
if (worker->flags & WORKER_IDLE)
1450
list_del_init(&worker->entry);
1451
worker->flags |= WORKER_DIE;
1453
spin_unlock_irq(&gcwq->lock);
1455
kthread_stop(worker->task);
1458
spin_lock_irq(&gcwq->lock);
1459
ida_remove(&gcwq->worker_ida, id);
1462
static void idle_worker_timeout(unsigned long __gcwq)
1464
struct global_cwq *gcwq = (void *)__gcwq;
1466
spin_lock_irq(&gcwq->lock);
1468
if (too_many_workers(gcwq)) {
1469
struct worker *worker;
1470
unsigned long expires;
1472
/* idle_list is kept in LIFO order, check the last one */
1473
worker = list_entry(gcwq->idle_list.prev, struct worker, entry);
1474
expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1476
if (time_before(jiffies, expires))
1477
mod_timer(&gcwq->idle_timer, expires);
1479
/* it's been idle for too long, wake up manager */
1480
gcwq->flags |= GCWQ_MANAGE_WORKERS;
1481
wake_up_worker(gcwq);
1485
spin_unlock_irq(&gcwq->lock);
1488
static bool send_mayday(struct work_struct *work)
1490
struct cpu_workqueue_struct *cwq = get_work_cwq(work);
1491
struct workqueue_struct *wq = cwq->wq;
1494
if (!(wq->flags & WQ_RESCUER))
1497
/* mayday mayday mayday */
1498
cpu = cwq->gcwq->cpu;
1499
/* WORK_CPU_UNBOUND can't be set in cpumask, use cpu 0 instead */
1500
if (cpu == WORK_CPU_UNBOUND)
1502
if (!mayday_test_and_set_cpu(cpu, wq->mayday_mask))
1503
wake_up_process(wq->rescuer->task);
1507
static void gcwq_mayday_timeout(unsigned long __gcwq)
1509
struct global_cwq *gcwq = (void *)__gcwq;
1510
struct work_struct *work;
1512
spin_lock_irq(&gcwq->lock);
1514
if (need_to_create_worker(gcwq)) {
1516
* We've been trying to create a new worker but
1517
* haven't been successful. We might be hitting an
1518
* allocation deadlock. Send distress signals to
1521
list_for_each_entry(work, &gcwq->worklist, entry)
1525
spin_unlock_irq(&gcwq->lock);
1527
mod_timer(&gcwq->mayday_timer, jiffies + MAYDAY_INTERVAL);
1531
* maybe_create_worker - create a new worker if necessary
1532
* @gcwq: gcwq to create a new worker for
1534
* Create a new worker for @gcwq if necessary. @gcwq is guaranteed to
1535
* have at least one idle worker on return from this function. If
1536
* creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
1537
* sent to all rescuers with works scheduled on @gcwq to resolve
1538
* possible allocation deadlock.
1540
* On return, need_to_create_worker() is guaranteed to be false and
1541
* may_start_working() true.
1544
* spin_lock_irq(gcwq->lock) which may be released and regrabbed
1545
* multiple times. Does GFP_KERNEL allocations. Called only from
1549
* false if no action was taken and gcwq->lock stayed locked, true
1552
static bool maybe_create_worker(struct global_cwq *gcwq)
1553
__releases(&gcwq->lock)
1554
__acquires(&gcwq->lock)
1556
if (!need_to_create_worker(gcwq))
1559
spin_unlock_irq(&gcwq->lock);
1561
/* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
1562
mod_timer(&gcwq->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
1565
struct worker *worker;
1567
worker = create_worker(gcwq, true);
1569
del_timer_sync(&gcwq->mayday_timer);
1570
spin_lock_irq(&gcwq->lock);
1571
start_worker(worker);
1572
BUG_ON(need_to_create_worker(gcwq));
1576
if (!need_to_create_worker(gcwq))
1579
__set_current_state(TASK_INTERRUPTIBLE);
1580
schedule_timeout(CREATE_COOLDOWN);
1582
if (!need_to_create_worker(gcwq))
1586
del_timer_sync(&gcwq->mayday_timer);
1587
spin_lock_irq(&gcwq->lock);
1588
if (need_to_create_worker(gcwq))
1594
* maybe_destroy_worker - destroy workers which have been idle for a while
1595
* @gcwq: gcwq to destroy workers for
1597
* Destroy @gcwq workers which have been idle for longer than
1598
* IDLE_WORKER_TIMEOUT.
1601
* spin_lock_irq(gcwq->lock) which may be released and regrabbed
1602
* multiple times. Called only from manager.
1605
* false if no action was taken and gcwq->lock stayed locked, true
1608
static bool maybe_destroy_workers(struct global_cwq *gcwq)
1612
while (too_many_workers(gcwq)) {
1613
struct worker *worker;
1614
unsigned long expires;
1616
worker = list_entry(gcwq->idle_list.prev, struct worker, entry);
1617
expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1619
if (time_before(jiffies, expires)) {
1620
mod_timer(&gcwq->idle_timer, expires);
1624
destroy_worker(worker);
1632
* manage_workers - manage worker pool
1635
* Assume the manager role and manage gcwq worker pool @worker belongs
1636
* to. At any given time, there can be only zero or one manager per
1637
* gcwq. The exclusion is handled automatically by this function.
1639
* The caller can safely start processing works on false return. On
1640
* true return, it's guaranteed that need_to_create_worker() is false
1641
* and may_start_working() is true.
1644
* spin_lock_irq(gcwq->lock) which may be released and regrabbed
1645
* multiple times. Does GFP_KERNEL allocations.
1648
* false if no action was taken and gcwq->lock stayed locked, true if
1649
* some action was taken.
1651
static bool manage_workers(struct worker *worker)
1653
struct global_cwq *gcwq = worker->gcwq;
1656
if (gcwq->flags & GCWQ_MANAGING_WORKERS)
1659
gcwq->flags &= ~GCWQ_MANAGE_WORKERS;
1660
gcwq->flags |= GCWQ_MANAGING_WORKERS;
1663
* Destroy and then create so that may_start_working() is true
1666
ret |= maybe_destroy_workers(gcwq);
1667
ret |= maybe_create_worker(gcwq);
1669
gcwq->flags &= ~GCWQ_MANAGING_WORKERS;
1672
* The trustee might be waiting to take over the manager
1673
* position, tell it we're done.
1675
if (unlikely(gcwq->trustee))
1676
wake_up_all(&gcwq->trustee_wait);
1682
* move_linked_works - move linked works to a list
1683
* @work: start of series of works to be scheduled
1684
* @head: target list to append @work to
1685
* @nextp: out paramter for nested worklist walking
1687
* Schedule linked works starting from @work to @head. Work series to
1688
* be scheduled starts at @work and includes any consecutive work with
1689
* WORK_STRUCT_LINKED set in its predecessor.
1691
* If @nextp is not NULL, it's updated to point to the next work of
1692
* the last scheduled work. This allows move_linked_works() to be
1693
* nested inside outer list_for_each_entry_safe().
1696
* spin_lock_irq(gcwq->lock).
1698
static void move_linked_works(struct work_struct *work, struct list_head *head,
1699
struct work_struct **nextp)
1701
struct work_struct *n;
1704
* Linked worklist will always end before the end of the list,
1705
* use NULL for list head.
1707
list_for_each_entry_safe_from(work, n, NULL, entry) {
1708
list_move_tail(&work->entry, head);
1709
if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1714
* If we're already inside safe list traversal and have moved
1715
* multiple works to the scheduled queue, the next position
1716
* needs to be updated.
1722
static void cwq_activate_first_delayed(struct cpu_workqueue_struct *cwq)
1724
struct work_struct *work = list_first_entry(&cwq->delayed_works,
1725
struct work_struct, entry);
1726
struct list_head *pos = gcwq_determine_ins_pos(cwq->gcwq, cwq);
1728
trace_workqueue_activate_work(work);
1729
move_linked_works(work, pos, NULL);
1730
__clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
1735
* cwq_dec_nr_in_flight - decrement cwq's nr_in_flight
1736
* @cwq: cwq of interest
1737
* @color: color of work which left the queue
1738
* @delayed: for a delayed work
1740
* A work either has completed or is removed from pending queue,
1741
* decrement nr_in_flight of its cwq and handle workqueue flushing.
1744
* spin_lock_irq(gcwq->lock).
1746
static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color,
1749
/* ignore uncolored works */
1750
if (color == WORK_NO_COLOR)
1753
cwq->nr_in_flight[color]--;
1757
if (!list_empty(&cwq->delayed_works)) {
1758
/* one down, submit a delayed one */
1759
if (cwq->nr_active < cwq->max_active)
1760
cwq_activate_first_delayed(cwq);
1764
/* is flush in progress and are we at the flushing tip? */
1765
if (likely(cwq->flush_color != color))
1768
/* are there still in-flight works? */
1769
if (cwq->nr_in_flight[color])
1772
/* this cwq is done, clear flush_color */
1773
cwq->flush_color = -1;
1776
* If this was the last cwq, wake up the first flusher. It
1777
* will handle the rest.
1779
if (atomic_dec_and_test(&cwq->wq->nr_cwqs_to_flush))
1780
complete(&cwq->wq->first_flusher->done);
1784
* process_one_work - process single work
1786
* @work: work to process
1788
* Process @work. This function contains all the logics necessary to
1789
* process a single work including synchronization against and
1790
* interaction with other workers on the same cpu, queueing and
1791
* flushing. As long as context requirement is met, any worker can
1792
* call this function to process a work.
1795
* spin_lock_irq(gcwq->lock) which is released and regrabbed.
1797
static void process_one_work(struct worker *worker, struct work_struct *work)
1798
__releases(&gcwq->lock)
1799
__acquires(&gcwq->lock)
1801
struct cpu_workqueue_struct *cwq = get_work_cwq(work);
1802
struct global_cwq *gcwq = cwq->gcwq;
1803
struct hlist_head *bwh = busy_worker_head(gcwq, work);
1804
bool cpu_intensive = cwq->wq->flags & WQ_CPU_INTENSIVE;
1805
work_func_t f = work->func;
1807
struct worker *collision;
1808
#ifdef CONFIG_LOCKDEP
1810
* It is permissible to free the struct work_struct from
1811
* inside the function that is called from it, this we need to
1812
* take into account for lockdep too. To avoid bogus "held
1813
* lock freed" warnings as well as problems when looking into
1814
* work->lockdep_map, make a copy and use that here.
1816
struct lockdep_map lockdep_map = work->lockdep_map;
1819
* A single work shouldn't be executed concurrently by
1820
* multiple workers on a single cpu. Check whether anyone is
1821
* already processing the work. If so, defer the work to the
1822
* currently executing one.
1824
collision = __find_worker_executing_work(gcwq, bwh, work);
1825
if (unlikely(collision)) {
1826
move_linked_works(work, &collision->scheduled, NULL);
1830
/* claim and process */
1831
debug_work_deactivate(work);
1832
hlist_add_head(&worker->hentry, bwh);
1833
worker->current_work = work;
1834
worker->current_cwq = cwq;
1835
work_color = get_work_color(work);
1837
/* record the current cpu number in the work data and dequeue */
1838
set_work_cpu(work, gcwq->cpu);
1839
list_del_init(&work->entry);
1842
* If HIGHPRI_PENDING, check the next work, and, if HIGHPRI,
1843
* wake up another worker; otherwise, clear HIGHPRI_PENDING.
1845
if (unlikely(gcwq->flags & GCWQ_HIGHPRI_PENDING)) {
1846
struct work_struct *nwork = list_first_entry(&gcwq->worklist,
1847
struct work_struct, entry);
1849
if (!list_empty(&gcwq->worklist) &&
1850
get_work_cwq(nwork)->wq->flags & WQ_HIGHPRI)
1851
wake_up_worker(gcwq);
1853
gcwq->flags &= ~GCWQ_HIGHPRI_PENDING;
1857
* CPU intensive works don't participate in concurrency
1858
* management. They're the scheduler's responsibility.
1860
if (unlikely(cpu_intensive))
1861
worker_set_flags(worker, WORKER_CPU_INTENSIVE, true);
1863
spin_unlock_irq(&gcwq->lock);
1865
work_clear_pending(work);
1866
lock_map_acquire_read(&cwq->wq->lockdep_map);
1867
lock_map_acquire(&lockdep_map);
1868
trace_workqueue_execute_start(work);
1871
* While we must be careful to not use "work" after this, the trace
1872
* point will only record its address.
1874
trace_workqueue_execute_end(work);
1875
lock_map_release(&lockdep_map);
1876
lock_map_release(&cwq->wq->lockdep_map);
1878
if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
1879
printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
1881
current->comm, preempt_count(), task_pid_nr(current));
1882
printk(KERN_ERR " last function: ");
1883
print_symbol("%s\n", (unsigned long)f);
1884
debug_show_held_locks(current);
1888
spin_lock_irq(&gcwq->lock);
1890
/* clear cpu intensive status */
1891
if (unlikely(cpu_intensive))
1892
worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
1894
/* we're done with it, release */
1895
hlist_del_init(&worker->hentry);
1896
worker->current_work = NULL;
1897
worker->current_cwq = NULL;
1898
cwq_dec_nr_in_flight(cwq, work_color, false);
1902
* process_scheduled_works - process scheduled works
1905
* Process all scheduled works. Please note that the scheduled list
1906
* may change while processing a work, so this function repeatedly
1907
* fetches a work from the top and executes it.
1910
* spin_lock_irq(gcwq->lock) which may be released and regrabbed
1913
static void process_scheduled_works(struct worker *worker)
1915
while (!list_empty(&worker->scheduled)) {
1916
struct work_struct *work = list_first_entry(&worker->scheduled,
1917
struct work_struct, entry);
1918
process_one_work(worker, work);
1923
* worker_thread - the worker thread function
1926
* The gcwq worker thread function. There's a single dynamic pool of
1927
* these per each cpu. These workers process all works regardless of
1928
* their specific target workqueue. The only exception is works which
1929
* belong to workqueues with a rescuer which will be explained in
1932
static int worker_thread(void *__worker)
1934
struct worker *worker = __worker;
1935
struct global_cwq *gcwq = worker->gcwq;
1937
/* tell the scheduler that this is a workqueue worker */
1938
worker->task->flags |= PF_WQ_WORKER;
1940
spin_lock_irq(&gcwq->lock);
1942
/* DIE can be set only while we're idle, checking here is enough */
1943
if (worker->flags & WORKER_DIE) {
1944
spin_unlock_irq(&gcwq->lock);
1945
worker->task->flags &= ~PF_WQ_WORKER;
1949
worker_leave_idle(worker);
1951
/* no more worker necessary? */
1952
if (!need_more_worker(gcwq))
1955
/* do we need to manage? */
1956
if (unlikely(!may_start_working(gcwq)) && manage_workers(worker))
1960
* ->scheduled list can only be filled while a worker is
1961
* preparing to process a work or actually processing it.
1962
* Make sure nobody diddled with it while I was sleeping.
1964
BUG_ON(!list_empty(&worker->scheduled));
1967
* When control reaches this point, we're guaranteed to have
1968
* at least one idle worker or that someone else has already
1969
* assumed the manager role.
1971
worker_clr_flags(worker, WORKER_PREP);
1974
struct work_struct *work =
1975
list_first_entry(&gcwq->worklist,
1976
struct work_struct, entry);
1978
if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
1979
/* optimization path, not strictly necessary */
1980
process_one_work(worker, work);
1981
if (unlikely(!list_empty(&worker->scheduled)))
1982
process_scheduled_works(worker);
1984
move_linked_works(work, &worker->scheduled, NULL);
1985
process_scheduled_works(worker);
1987
} while (keep_working(gcwq));
1989
worker_set_flags(worker, WORKER_PREP, false);
1991
if (unlikely(need_to_manage_workers(gcwq)) && manage_workers(worker))
1995
* gcwq->lock is held and there's no work to process and no
1996
* need to manage, sleep. Workers are woken up only while
1997
* holding gcwq->lock or from local cpu, so setting the
1998
* current state before releasing gcwq->lock is enough to
1999
* prevent losing any event.
2001
worker_enter_idle(worker);
2002
__set_current_state(TASK_INTERRUPTIBLE);
2003
spin_unlock_irq(&gcwq->lock);
2009
* rescuer_thread - the rescuer thread function
2010
* @__wq: the associated workqueue
2012
* Workqueue rescuer thread function. There's one rescuer for each
2013
* workqueue which has WQ_RESCUER set.
2015
* Regular work processing on a gcwq may block trying to create a new
2016
* worker which uses GFP_KERNEL allocation which has slight chance of
2017
* developing into deadlock if some works currently on the same queue
2018
* need to be processed to satisfy the GFP_KERNEL allocation. This is
2019
* the problem rescuer solves.
2021
* When such condition is possible, the gcwq summons rescuers of all
2022
* workqueues which have works queued on the gcwq and let them process
2023
* those works so that forward progress can be guaranteed.
2025
* This should happen rarely.
2027
static int rescuer_thread(void *__wq)
2029
struct workqueue_struct *wq = __wq;
2030
struct worker *rescuer = wq->rescuer;
2031
struct list_head *scheduled = &rescuer->scheduled;
2032
bool is_unbound = wq->flags & WQ_UNBOUND;
2035
set_user_nice(current, RESCUER_NICE_LEVEL);
2037
set_current_state(TASK_INTERRUPTIBLE);
2039
if (kthread_should_stop())
2043
* See whether any cpu is asking for help. Unbounded
2044
* workqueues use cpu 0 in mayday_mask for CPU_UNBOUND.
2046
for_each_mayday_cpu(cpu, wq->mayday_mask) {
2047
unsigned int tcpu = is_unbound ? WORK_CPU_UNBOUND : cpu;
2048
struct cpu_workqueue_struct *cwq = get_cwq(tcpu, wq);
2049
struct global_cwq *gcwq = cwq->gcwq;
2050
struct work_struct *work, *n;
2052
__set_current_state(TASK_RUNNING);
2053
mayday_clear_cpu(cpu, wq->mayday_mask);
2055
/* migrate to the target cpu if possible */
2056
rescuer->gcwq = gcwq;
2057
worker_maybe_bind_and_lock(rescuer);
2060
* Slurp in all works issued via this workqueue and
2063
BUG_ON(!list_empty(&rescuer->scheduled));
2064
list_for_each_entry_safe(work, n, &gcwq->worklist, entry)
2065
if (get_work_cwq(work) == cwq)
2066
move_linked_works(work, scheduled, &n);
2068
process_scheduled_works(rescuer);
2071
* Leave this gcwq. If keep_working() is %true, notify a
2072
* regular worker; otherwise, we end up with 0 concurrency
2073
* and stalling the execution.
2075
if (keep_working(gcwq))
2076
wake_up_worker(gcwq);
2078
spin_unlock_irq(&gcwq->lock);
2086
struct work_struct work;
2087
struct completion done;
2090
static void wq_barrier_func(struct work_struct *work)
2092
struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2093
complete(&barr->done);
2097
* insert_wq_barrier - insert a barrier work
2098
* @cwq: cwq to insert barrier into
2099
* @barr: wq_barrier to insert
2100
* @target: target work to attach @barr to
2101
* @worker: worker currently executing @target, NULL if @target is not executing
2103
* @barr is linked to @target such that @barr is completed only after
2104
* @target finishes execution. Please note that the ordering
2105
* guarantee is observed only with respect to @target and on the local
2108
* Currently, a queued barrier can't be canceled. This is because
2109
* try_to_grab_pending() can't determine whether the work to be
2110
* grabbed is at the head of the queue and thus can't clear LINKED
2111
* flag of the previous work while there must be a valid next work
2112
* after a work with LINKED flag set.
2114
* Note that when @worker is non-NULL, @target may be modified
2115
* underneath us, so we can't reliably determine cwq from @target.
2118
* spin_lock_irq(gcwq->lock).
2120
static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
2121
struct wq_barrier *barr,
2122
struct work_struct *target, struct worker *worker)
2124
struct list_head *head;
2125
unsigned int linked = 0;
2128
* debugobject calls are safe here even with gcwq->lock locked
2129
* as we know for sure that this will not trigger any of the
2130
* checks and call back into the fixup functions where we
2133
INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
2134
__set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
2135
init_completion(&barr->done);
2138
* If @target is currently being executed, schedule the
2139
* barrier to the worker; otherwise, put it after @target.
2142
head = worker->scheduled.next;
2144
unsigned long *bits = work_data_bits(target);
2146
head = target->entry.next;
2147
/* there can already be other linked works, inherit and set */
2148
linked = *bits & WORK_STRUCT_LINKED;
2149
__set_bit(WORK_STRUCT_LINKED_BIT, bits);
2152
debug_work_activate(&barr->work);
2153
insert_work(cwq, &barr->work, head,
2154
work_color_to_flags(WORK_NO_COLOR) | linked);
2158
* flush_workqueue_prep_cwqs - prepare cwqs for workqueue flushing
2159
* @wq: workqueue being flushed
2160
* @flush_color: new flush color, < 0 for no-op
2161
* @work_color: new work color, < 0 for no-op
2163
* Prepare cwqs for workqueue flushing.
2165
* If @flush_color is non-negative, flush_color on all cwqs should be
2166
* -1. If no cwq has in-flight commands at the specified color, all
2167
* cwq->flush_color's stay at -1 and %false is returned. If any cwq
2168
* has in flight commands, its cwq->flush_color is set to
2169
* @flush_color, @wq->nr_cwqs_to_flush is updated accordingly, cwq
2170
* wakeup logic is armed and %true is returned.
2172
* The caller should have initialized @wq->first_flusher prior to
2173
* calling this function with non-negative @flush_color. If
2174
* @flush_color is negative, no flush color update is done and %false
2177
* If @work_color is non-negative, all cwqs should have the same
2178
* work_color which is previous to @work_color and all will be
2179
* advanced to @work_color.
2182
* mutex_lock(wq->flush_mutex).
2185
* %true if @flush_color >= 0 and there's something to flush. %false
2188
static bool flush_workqueue_prep_cwqs(struct workqueue_struct *wq,
2189
int flush_color, int work_color)
2194
if (flush_color >= 0) {
2195
BUG_ON(atomic_read(&wq->nr_cwqs_to_flush));
2196
atomic_set(&wq->nr_cwqs_to_flush, 1);
2199
for_each_cwq_cpu(cpu, wq) {
2200
struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
2201
struct global_cwq *gcwq = cwq->gcwq;
2203
spin_lock_irq(&gcwq->lock);
2205
if (flush_color >= 0) {
2206
BUG_ON(cwq->flush_color != -1);
2208
if (cwq->nr_in_flight[flush_color]) {
2209
cwq->flush_color = flush_color;
2210
atomic_inc(&wq->nr_cwqs_to_flush);
2215
if (work_color >= 0) {
2216
BUG_ON(work_color != work_next_color(cwq->work_color));
2217
cwq->work_color = work_color;
2220
spin_unlock_irq(&gcwq->lock);
2223
if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_cwqs_to_flush))
2224
complete(&wq->first_flusher->done);
2230
* flush_workqueue - ensure that any scheduled work has run to completion.
2231
* @wq: workqueue to flush
2233
* Forces execution of the workqueue and blocks until its completion.
2234
* This is typically used in driver shutdown handlers.
2236
* We sleep until all works which were queued on entry have been handled,
2237
* but we are not livelocked by new incoming ones.
2239
void flush_workqueue(struct workqueue_struct *wq)
2241
struct wq_flusher this_flusher = {
2242
.list = LIST_HEAD_INIT(this_flusher.list),
2244
.done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done),
2248
lock_map_acquire(&wq->lockdep_map);
2249
lock_map_release(&wq->lockdep_map);
2251
mutex_lock(&wq->flush_mutex);
2254
* Start-to-wait phase
2256
next_color = work_next_color(wq->work_color);
2258
if (next_color != wq->flush_color) {
2260
* Color space is not full. The current work_color
2261
* becomes our flush_color and work_color is advanced
2264
BUG_ON(!list_empty(&wq->flusher_overflow));
2265
this_flusher.flush_color = wq->work_color;
2266
wq->work_color = next_color;
2268
if (!wq->first_flusher) {
2269
/* no flush in progress, become the first flusher */
2270
BUG_ON(wq->flush_color != this_flusher.flush_color);
2272
wq->first_flusher = &this_flusher;
2274
if (!flush_workqueue_prep_cwqs(wq, wq->flush_color,
2276
/* nothing to flush, done */
2277
wq->flush_color = next_color;
2278
wq->first_flusher = NULL;
2283
BUG_ON(wq->flush_color == this_flusher.flush_color);
2284
list_add_tail(&this_flusher.list, &wq->flusher_queue);
2285
flush_workqueue_prep_cwqs(wq, -1, wq->work_color);
2289
* Oops, color space is full, wait on overflow queue.
2290
* The next flush completion will assign us
2291
* flush_color and transfer to flusher_queue.
2293
list_add_tail(&this_flusher.list, &wq->flusher_overflow);
2296
mutex_unlock(&wq->flush_mutex);
2298
wait_for_completion(&this_flusher.done);
2301
* Wake-up-and-cascade phase
2303
* First flushers are responsible for cascading flushes and
2304
* handling overflow. Non-first flushers can simply return.
2306
if (wq->first_flusher != &this_flusher)
2309
mutex_lock(&wq->flush_mutex);
2311
/* we might have raced, check again with mutex held */
2312
if (wq->first_flusher != &this_flusher)
2315
wq->first_flusher = NULL;
2317
BUG_ON(!list_empty(&this_flusher.list));
2318
BUG_ON(wq->flush_color != this_flusher.flush_color);
2321
struct wq_flusher *next, *tmp;
2323
/* complete all the flushers sharing the current flush color */
2324
list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
2325
if (next->flush_color != wq->flush_color)
2327
list_del_init(&next->list);
2328
complete(&next->done);
2331
BUG_ON(!list_empty(&wq->flusher_overflow) &&
2332
wq->flush_color != work_next_color(wq->work_color));
2334
/* this flush_color is finished, advance by one */
2335
wq->flush_color = work_next_color(wq->flush_color);
2337
/* one color has been freed, handle overflow queue */
2338
if (!list_empty(&wq->flusher_overflow)) {
2340
* Assign the same color to all overflowed
2341
* flushers, advance work_color and append to
2342
* flusher_queue. This is the start-to-wait
2343
* phase for these overflowed flushers.
2345
list_for_each_entry(tmp, &wq->flusher_overflow, list)
2346
tmp->flush_color = wq->work_color;
2348
wq->work_color = work_next_color(wq->work_color);
2350
list_splice_tail_init(&wq->flusher_overflow,
2351
&wq->flusher_queue);
2352
flush_workqueue_prep_cwqs(wq, -1, wq->work_color);
2355
if (list_empty(&wq->flusher_queue)) {
2356
BUG_ON(wq->flush_color != wq->work_color);
2361
* Need to flush more colors. Make the next flusher
2362
* the new first flusher and arm cwqs.
2364
BUG_ON(wq->flush_color == wq->work_color);
2365
BUG_ON(wq->flush_color != next->flush_color);
2367
list_del_init(&next->list);
2368
wq->first_flusher = next;
2370
if (flush_workqueue_prep_cwqs(wq, wq->flush_color, -1))
2374
* Meh... this color is already done, clear first
2375
* flusher and repeat cascading.
2377
wq->first_flusher = NULL;
2381
mutex_unlock(&wq->flush_mutex);
2383
EXPORT_SYMBOL_GPL(flush_workqueue);
2386
* drain_workqueue - drain a workqueue
2387
* @wq: workqueue to drain
2389
* Wait until the workqueue becomes empty. While draining is in progress,
2390
* only chain queueing is allowed. IOW, only currently pending or running
2391
* work items on @wq can queue further work items on it. @wq is flushed
2392
* repeatedly until it becomes empty. The number of flushing is detemined
2393
* by the depth of chaining and should be relatively short. Whine if it
2396
void drain_workqueue(struct workqueue_struct *wq)
2398
unsigned int flush_cnt = 0;
2402
* __queue_work() needs to test whether there are drainers, is much
2403
* hotter than drain_workqueue() and already looks at @wq->flags.
2404
* Use WQ_DRAINING so that queue doesn't have to check nr_drainers.
2406
spin_lock(&workqueue_lock);
2407
if (!wq->nr_drainers++)
2408
wq->flags |= WQ_DRAINING;
2409
spin_unlock(&workqueue_lock);
2411
flush_workqueue(wq);
2413
for_each_cwq_cpu(cpu, wq) {
2414
struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
2417
spin_lock_irq(&cwq->gcwq->lock);
2418
drained = !cwq->nr_active && list_empty(&cwq->delayed_works);
2419
spin_unlock_irq(&cwq->gcwq->lock);
2424
if (++flush_cnt == 10 ||
2425
(flush_cnt % 100 == 0 && flush_cnt <= 1000))
2426
pr_warning("workqueue %s: flush on destruction isn't complete after %u tries\n",
2427
wq->name, flush_cnt);
2431
spin_lock(&workqueue_lock);
2432
if (!--wq->nr_drainers)
2433
wq->flags &= ~WQ_DRAINING;
2434
spin_unlock(&workqueue_lock);
2436
EXPORT_SYMBOL_GPL(drain_workqueue);
2438
static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
2439
bool wait_executing)
2441
struct worker *worker = NULL;
2442
struct global_cwq *gcwq;
2443
struct cpu_workqueue_struct *cwq;
2446
gcwq = get_work_gcwq(work);
2450
spin_lock_irq(&gcwq->lock);
2451
if (!list_empty(&work->entry)) {
2453
* See the comment near try_to_grab_pending()->smp_rmb().
2454
* If it was re-queued to a different gcwq under us, we
2455
* are not going to wait.
2458
cwq = get_work_cwq(work);
2459
if (unlikely(!cwq || gcwq != cwq->gcwq))
2461
} else if (wait_executing) {
2462
worker = find_worker_executing_work(gcwq, work);
2465
cwq = worker->current_cwq;
2469
insert_wq_barrier(cwq, barr, work, worker);
2470
spin_unlock_irq(&gcwq->lock);
2473
* If @max_active is 1 or rescuer is in use, flushing another work
2474
* item on the same workqueue may lead to deadlock. Make sure the
2475
* flusher is not running on the same workqueue by verifying write
2478
if (cwq->wq->saved_max_active == 1 || cwq->wq->flags & WQ_RESCUER)
2479
lock_map_acquire(&cwq->wq->lockdep_map);
2481
lock_map_acquire_read(&cwq->wq->lockdep_map);
2482
lock_map_release(&cwq->wq->lockdep_map);
2486
spin_unlock_irq(&gcwq->lock);
2491
* flush_work - wait for a work to finish executing the last queueing instance
2492
* @work: the work to flush
2494
* Wait until @work has finished execution. This function considers
2495
* only the last queueing instance of @work. If @work has been
2496
* enqueued across different CPUs on a non-reentrant workqueue or on
2497
* multiple workqueues, @work might still be executing on return on
2498
* some of the CPUs from earlier queueing.
2500
* If @work was queued only on a non-reentrant, ordered or unbound
2501
* workqueue, @work is guaranteed to be idle on return if it hasn't
2502
* been requeued since flush started.
2505
* %true if flush_work() waited for the work to finish execution,
2506
* %false if it was already idle.
2508
bool flush_work(struct work_struct *work)
2510
struct wq_barrier barr;
2512
if (start_flush_work(work, &barr, true)) {
2513
wait_for_completion(&barr.done);
2514
destroy_work_on_stack(&barr.work);
2519
EXPORT_SYMBOL_GPL(flush_work);
2521
static bool wait_on_cpu_work(struct global_cwq *gcwq, struct work_struct *work)
2523
struct wq_barrier barr;
2524
struct worker *worker;
2526
spin_lock_irq(&gcwq->lock);
2528
worker = find_worker_executing_work(gcwq, work);
2529
if (unlikely(worker))
2530
insert_wq_barrier(worker->current_cwq, &barr, work, worker);
2532
spin_unlock_irq(&gcwq->lock);
2534
if (unlikely(worker)) {
2535
wait_for_completion(&barr.done);
2536
destroy_work_on_stack(&barr.work);
2542
static bool wait_on_work(struct work_struct *work)
2549
lock_map_acquire(&work->lockdep_map);
2550
lock_map_release(&work->lockdep_map);
2552
for_each_gcwq_cpu(cpu)
2553
ret |= wait_on_cpu_work(get_gcwq(cpu), work);
2558
* flush_work_sync - wait until a work has finished execution
2559
* @work: the work to flush
2561
* Wait until @work has finished execution. On return, it's
2562
* guaranteed that all queueing instances of @work which happened
2563
* before this function is called are finished. In other words, if
2564
* @work hasn't been requeued since this function was called, @work is
2565
* guaranteed to be idle on return.
2568
* %true if flush_work_sync() waited for the work to finish execution,
2569
* %false if it was already idle.
2571
bool flush_work_sync(struct work_struct *work)
2573
struct wq_barrier barr;
2574
bool pending, waited;
2576
/* we'll wait for executions separately, queue barr only if pending */
2577
pending = start_flush_work(work, &barr, false);
2579
/* wait for executions to finish */
2580
waited = wait_on_work(work);
2582
/* wait for the pending one */
2584
wait_for_completion(&barr.done);
2585
destroy_work_on_stack(&barr.work);
2588
return pending || waited;
2590
EXPORT_SYMBOL_GPL(flush_work_sync);
2593
* Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,
2594
* so this work can't be re-armed in any way.
2596
static int try_to_grab_pending(struct work_struct *work)
2598
struct global_cwq *gcwq;
2601
if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
2605
* The queueing is in progress, or it is already queued. Try to
2606
* steal it from ->worklist without clearing WORK_STRUCT_PENDING.
2608
gcwq = get_work_gcwq(work);
2612
spin_lock_irq(&gcwq->lock);
2613
if (!list_empty(&work->entry)) {
2615
* This work is queued, but perhaps we locked the wrong gcwq.
2616
* In that case we must see the new value after rmb(), see
2617
* insert_work()->wmb().
2620
if (gcwq == get_work_gcwq(work)) {
2621
debug_work_deactivate(work);
2622
list_del_init(&work->entry);
2623
cwq_dec_nr_in_flight(get_work_cwq(work),
2624
get_work_color(work),
2625
*work_data_bits(work) & WORK_STRUCT_DELAYED);
2629
spin_unlock_irq(&gcwq->lock);
2634
static bool __cancel_work_timer(struct work_struct *work,
2635
struct timer_list* timer)
2640
ret = (timer && likely(del_timer(timer)));
2642
ret = try_to_grab_pending(work);
2644
} while (unlikely(ret < 0));
2646
clear_work_data(work);
2651
* cancel_work_sync - cancel a work and wait for it to finish
2652
* @work: the work to cancel
2654
* Cancel @work and wait for its execution to finish. This function
2655
* can be used even if the work re-queues itself or migrates to
2656
* another workqueue. On return from this function, @work is
2657
* guaranteed to be not pending or executing on any CPU.
2659
* cancel_work_sync(&delayed_work->work) must not be used for
2660
* delayed_work's. Use cancel_delayed_work_sync() instead.
2662
* The caller must ensure that the workqueue on which @work was last
2663
* queued can't be destroyed before this function returns.
2666
* %true if @work was pending, %false otherwise.
2668
bool cancel_work_sync(struct work_struct *work)
2670
return __cancel_work_timer(work, NULL);
2672
EXPORT_SYMBOL_GPL(cancel_work_sync);
2675
* flush_delayed_work - wait for a dwork to finish executing the last queueing
2676
* @dwork: the delayed work to flush
2678
* Delayed timer is cancelled and the pending work is queued for
2679
* immediate execution. Like flush_work(), this function only
2680
* considers the last queueing instance of @dwork.
2683
* %true if flush_work() waited for the work to finish execution,
2684
* %false if it was already idle.
2686
bool flush_delayed_work(struct delayed_work *dwork)
2688
if (del_timer_sync(&dwork->timer))
2689
__queue_work(raw_smp_processor_id(),
2690
get_work_cwq(&dwork->work)->wq, &dwork->work);
2691
return flush_work(&dwork->work);
2693
EXPORT_SYMBOL(flush_delayed_work);
2696
* flush_delayed_work_sync - wait for a dwork to finish
2697
* @dwork: the delayed work to flush
2699
* Delayed timer is cancelled and the pending work is queued for
2700
* execution immediately. Other than timer handling, its behavior
2701
* is identical to flush_work_sync().
2704
* %true if flush_work_sync() waited for the work to finish execution,
2705
* %false if it was already idle.
2707
bool flush_delayed_work_sync(struct delayed_work *dwork)
2709
if (del_timer_sync(&dwork->timer))
2710
__queue_work(raw_smp_processor_id(),
2711
get_work_cwq(&dwork->work)->wq, &dwork->work);
2712
return flush_work_sync(&dwork->work);
2714
EXPORT_SYMBOL(flush_delayed_work_sync);
2717
* cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
2718
* @dwork: the delayed work cancel
2720
* This is cancel_work_sync() for delayed works.
2723
* %true if @dwork was pending, %false otherwise.
2725
bool cancel_delayed_work_sync(struct delayed_work *dwork)
2727
return __cancel_work_timer(&dwork->work, &dwork->timer);
2729
EXPORT_SYMBOL(cancel_delayed_work_sync);
2732
* schedule_work - put work task in global workqueue
2733
* @work: job to be done
2735
* Returns zero if @work was already on the kernel-global workqueue and
2736
* non-zero otherwise.
2738
* This puts a job in the kernel-global workqueue if it was not already
2739
* queued and leaves it in the same position on the kernel-global
2740
* workqueue otherwise.
2742
int schedule_work(struct work_struct *work)
2744
return queue_work(system_wq, work);
2746
EXPORT_SYMBOL(schedule_work);
2749
* schedule_work_on - put work task on a specific cpu
2750
* @cpu: cpu to put the work task on
2751
* @work: job to be done
2753
* This puts a job on a specific cpu
2755
int schedule_work_on(int cpu, struct work_struct *work)
2757
return queue_work_on(cpu, system_wq, work);
2759
EXPORT_SYMBOL(schedule_work_on);
2762
* schedule_delayed_work - put work task in global workqueue after delay
2763
* @dwork: job to be done
2764
* @delay: number of jiffies to wait or 0 for immediate execution
2766
* After waiting for a given time this puts a job in the kernel-global
2769
int schedule_delayed_work(struct delayed_work *dwork,
2770
unsigned long delay)
2772
return queue_delayed_work(system_wq, dwork, delay);
2774
EXPORT_SYMBOL(schedule_delayed_work);
2777
* schedule_delayed_work_on - queue work in global workqueue on CPU after delay
2779
* @dwork: job to be done
2780
* @delay: number of jiffies to wait
2782
* After waiting for a given time this puts a job in the kernel-global
2783
* workqueue on the specified CPU.
2785
int schedule_delayed_work_on(int cpu,
2786
struct delayed_work *dwork, unsigned long delay)
2788
return queue_delayed_work_on(cpu, system_wq, dwork, delay);
2790
EXPORT_SYMBOL(schedule_delayed_work_on);
2793
* schedule_on_each_cpu - execute a function synchronously on each online CPU
2794
* @func: the function to call
2796
* schedule_on_each_cpu() executes @func on each online CPU using the
2797
* system workqueue and blocks until all CPUs have completed.
2798
* schedule_on_each_cpu() is very slow.
2801
* 0 on success, -errno on failure.
2803
int schedule_on_each_cpu(work_func_t func)
2806
struct work_struct __percpu *works;
2808
works = alloc_percpu(struct work_struct);
2814
for_each_online_cpu(cpu) {
2815
struct work_struct *work = per_cpu_ptr(works, cpu);
2817
INIT_WORK(work, func);
2818
schedule_work_on(cpu, work);
2821
for_each_online_cpu(cpu)
2822
flush_work(per_cpu_ptr(works, cpu));
2830
* flush_scheduled_work - ensure that any scheduled work has run to completion.
2832
* Forces execution of the kernel-global workqueue and blocks until its
2835
* Think twice before calling this function! It's very easy to get into
2836
* trouble if you don't take great care. Either of the following situations
2837
* will lead to deadlock:
2839
* One of the work items currently on the workqueue needs to acquire
2840
* a lock held by your code or its caller.
2842
* Your code is running in the context of a work routine.
2844
* They will be detected by lockdep when they occur, but the first might not
2845
* occur very often. It depends on what work items are on the workqueue and
2846
* what locks they need, which you have no control over.
2848
* In most situations flushing the entire workqueue is overkill; you merely
2849
* need to know that a particular work item isn't queued and isn't running.
2850
* In such cases you should use cancel_delayed_work_sync() or
2851
* cancel_work_sync() instead.
2853
void flush_scheduled_work(void)
2855
flush_workqueue(system_wq);
2857
EXPORT_SYMBOL(flush_scheduled_work);
2860
* execute_in_process_context - reliably execute the routine with user context
2861
* @fn: the function to execute
2862
* @ew: guaranteed storage for the execute work structure (must
2863
* be available when the work executes)
2865
* Executes the function immediately if process context is available,
2866
* otherwise schedules the function for delayed execution.
2868
* Returns: 0 - function was executed
2869
* 1 - function was scheduled for execution
2871
int execute_in_process_context(work_func_t fn, struct execute_work *ew)
2873
if (!in_interrupt()) {
2878
INIT_WORK(&ew->work, fn);
2879
schedule_work(&ew->work);
2883
EXPORT_SYMBOL_GPL(execute_in_process_context);
2885
int keventd_up(void)
2887
return system_wq != NULL;
2890
static int alloc_cwqs(struct workqueue_struct *wq)
2893
* cwqs are forced aligned according to WORK_STRUCT_FLAG_BITS.
2894
* Make sure that the alignment isn't lower than that of
2895
* unsigned long long.
2897
const size_t size = sizeof(struct cpu_workqueue_struct);
2898
const size_t align = max_t(size_t, 1 << WORK_STRUCT_FLAG_BITS,
2899
__alignof__(unsigned long long));
2901
bool percpu = !(wq->flags & WQ_UNBOUND);
2903
bool percpu = false;
2907
wq->cpu_wq.pcpu = __alloc_percpu(size, align);
2912
* Allocate enough room to align cwq and put an extra
2913
* pointer at the end pointing back to the originally
2914
* allocated pointer which will be used for free.
2916
ptr = kzalloc(size + align + sizeof(void *), GFP_KERNEL);
2918
wq->cpu_wq.single = PTR_ALIGN(ptr, align);
2919
*(void **)(wq->cpu_wq.single + 1) = ptr;
2923
/* just in case, make sure it's actually aligned */
2924
BUG_ON(!IS_ALIGNED(wq->cpu_wq.v, align));
2925
return wq->cpu_wq.v ? 0 : -ENOMEM;
2928
static void free_cwqs(struct workqueue_struct *wq)
2931
bool percpu = !(wq->flags & WQ_UNBOUND);
2933
bool percpu = false;
2937
free_percpu(wq->cpu_wq.pcpu);
2938
else if (wq->cpu_wq.single) {
2939
/* the pointer to free is stored right after the cwq */
2940
kfree(*(void **)(wq->cpu_wq.single + 1));
2944
static int wq_clamp_max_active(int max_active, unsigned int flags,
2947
int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
2949
if (max_active < 1 || max_active > lim)
2950
printk(KERN_WARNING "workqueue: max_active %d requested for %s "
2951
"is out of range, clamping between %d and %d\n",
2952
max_active, name, 1, lim);
2954
return clamp_val(max_active, 1, lim);
2957
struct workqueue_struct *__alloc_workqueue_key(const char *name,
2960
struct lock_class_key *key,
2961
const char *lock_name)
2963
struct workqueue_struct *wq;
2967
* Workqueues which may be used during memory reclaim should
2968
* have a rescuer to guarantee forward progress.
2970
if (flags & WQ_MEM_RECLAIM)
2971
flags |= WQ_RESCUER;
2974
* Unbound workqueues aren't concurrency managed and should be
2975
* dispatched to workers immediately.
2977
if (flags & WQ_UNBOUND)
2978
flags |= WQ_HIGHPRI;
2980
max_active = max_active ?: WQ_DFL_ACTIVE;
2981
max_active = wq_clamp_max_active(max_active, flags, name);
2983
wq = kzalloc(sizeof(*wq), GFP_KERNEL);
2988
wq->saved_max_active = max_active;
2989
mutex_init(&wq->flush_mutex);
2990
atomic_set(&wq->nr_cwqs_to_flush, 0);
2991
INIT_LIST_HEAD(&wq->flusher_queue);
2992
INIT_LIST_HEAD(&wq->flusher_overflow);
2995
lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
2996
INIT_LIST_HEAD(&wq->list);
2998
if (alloc_cwqs(wq) < 0)
3001
for_each_cwq_cpu(cpu, wq) {
3002
struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3003
struct global_cwq *gcwq = get_gcwq(cpu);
3005
BUG_ON((unsigned long)cwq & WORK_STRUCT_FLAG_MASK);
3008
cwq->flush_color = -1;
3009
cwq->max_active = max_active;
3010
INIT_LIST_HEAD(&cwq->delayed_works);
3013
if (flags & WQ_RESCUER) {
3014
struct worker *rescuer;
3016
if (!alloc_mayday_mask(&wq->mayday_mask, GFP_KERNEL))
3019
wq->rescuer = rescuer = alloc_worker();
3023
rescuer->task = kthread_create(rescuer_thread, wq, "%s", name);
3024
if (IS_ERR(rescuer->task))
3027
rescuer->task->flags |= PF_THREAD_BOUND;
3028
wake_up_process(rescuer->task);
3032
* workqueue_lock protects global freeze state and workqueues
3033
* list. Grab it, set max_active accordingly and add the new
3034
* workqueue to workqueues list.
3036
spin_lock(&workqueue_lock);
3038
if (workqueue_freezing && wq->flags & WQ_FREEZABLE)
3039
for_each_cwq_cpu(cpu, wq)
3040
get_cwq(cpu, wq)->max_active = 0;
3042
list_add(&wq->list, &workqueues);
3044
spin_unlock(&workqueue_lock);
3050
free_mayday_mask(wq->mayday_mask);
3056
EXPORT_SYMBOL_GPL(__alloc_workqueue_key);
3059
* destroy_workqueue - safely terminate a workqueue
3060
* @wq: target workqueue
3062
* Safely destroy a workqueue. All work currently pending will be done first.
3064
void destroy_workqueue(struct workqueue_struct *wq)
3068
/* drain it before proceeding with destruction */
3069
drain_workqueue(wq);
3072
* wq list is used to freeze wq, remove from list after
3073
* flushing is complete in case freeze races us.
3075
spin_lock(&workqueue_lock);
3076
list_del(&wq->list);
3077
spin_unlock(&workqueue_lock);
3080
for_each_cwq_cpu(cpu, wq) {
3081
struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3084
for (i = 0; i < WORK_NR_COLORS; i++)
3085
BUG_ON(cwq->nr_in_flight[i]);
3086
BUG_ON(cwq->nr_active);
3087
BUG_ON(!list_empty(&cwq->delayed_works));
3090
if (wq->flags & WQ_RESCUER) {
3091
kthread_stop(wq->rescuer->task);
3092
free_mayday_mask(wq->mayday_mask);
3099
EXPORT_SYMBOL_GPL(destroy_workqueue);
3102
* workqueue_set_max_active - adjust max_active of a workqueue
3103
* @wq: target workqueue
3104
* @max_active: new max_active value.
3106
* Set max_active of @wq to @max_active.
3109
* Don't call from IRQ context.
3111
void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
3115
max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
3117
spin_lock(&workqueue_lock);
3119
wq->saved_max_active = max_active;
3121
for_each_cwq_cpu(cpu, wq) {
3122
struct global_cwq *gcwq = get_gcwq(cpu);
3124
spin_lock_irq(&gcwq->lock);
3126
if (!(wq->flags & WQ_FREEZABLE) ||
3127
!(gcwq->flags & GCWQ_FREEZING))
3128
get_cwq(gcwq->cpu, wq)->max_active = max_active;
3130
spin_unlock_irq(&gcwq->lock);
3133
spin_unlock(&workqueue_lock);
3135
EXPORT_SYMBOL_GPL(workqueue_set_max_active);
3138
* workqueue_congested - test whether a workqueue is congested
3139
* @cpu: CPU in question
3140
* @wq: target workqueue
3142
* Test whether @wq's cpu workqueue for @cpu is congested. There is
3143
* no synchronization around this function and the test result is
3144
* unreliable and only useful as advisory hints or for debugging.
3147
* %true if congested, %false otherwise.
3149
bool workqueue_congested(unsigned int cpu, struct workqueue_struct *wq)
3151
struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3153
return !list_empty(&cwq->delayed_works);
3155
EXPORT_SYMBOL_GPL(workqueue_congested);
3158
* work_cpu - return the last known associated cpu for @work
3159
* @work: the work of interest
3162
* CPU number if @work was ever queued. WORK_CPU_NONE otherwise.
3164
unsigned int work_cpu(struct work_struct *work)
3166
struct global_cwq *gcwq = get_work_gcwq(work);
3168
return gcwq ? gcwq->cpu : WORK_CPU_NONE;
3170
EXPORT_SYMBOL_GPL(work_cpu);
3173
* work_busy - test whether a work is currently pending or running
3174
* @work: the work to be tested
3176
* Test whether @work is currently pending or running. There is no
3177
* synchronization around this function and the test result is
3178
* unreliable and only useful as advisory hints or for debugging.
3179
* Especially for reentrant wqs, the pending state might hide the
3183
* OR'd bitmask of WORK_BUSY_* bits.
3185
unsigned int work_busy(struct work_struct *work)
3187
struct global_cwq *gcwq = get_work_gcwq(work);
3188
unsigned long flags;
3189
unsigned int ret = 0;
3194
spin_lock_irqsave(&gcwq->lock, flags);
3196
if (work_pending(work))
3197
ret |= WORK_BUSY_PENDING;
3198
if (find_worker_executing_work(gcwq, work))
3199
ret |= WORK_BUSY_RUNNING;
3201
spin_unlock_irqrestore(&gcwq->lock, flags);
3205
EXPORT_SYMBOL_GPL(work_busy);
3210
* There are two challenges in supporting CPU hotplug. Firstly, there
3211
* are a lot of assumptions on strong associations among work, cwq and
3212
* gcwq which make migrating pending and scheduled works very
3213
* difficult to implement without impacting hot paths. Secondly,
3214
* gcwqs serve mix of short, long and very long running works making
3215
* blocked draining impractical.
3217
* This is solved by allowing a gcwq to be detached from CPU, running
3218
* it with unbound (rogue) workers and allowing it to be reattached
3219
* later if the cpu comes back online. A separate thread is created
3220
* to govern a gcwq in such state and is called the trustee of the
3223
* Trustee states and their descriptions.
3225
* START Command state used on startup. On CPU_DOWN_PREPARE, a
3226
* new trustee is started with this state.
3228
* IN_CHARGE Once started, trustee will enter this state after
3229
* assuming the manager role and making all existing
3230
* workers rogue. DOWN_PREPARE waits for trustee to
3231
* enter this state. After reaching IN_CHARGE, trustee
3232
* tries to execute the pending worklist until it's empty
3233
* and the state is set to BUTCHER, or the state is set
3236
* BUTCHER Command state which is set by the cpu callback after
3237
* the cpu has went down. Once this state is set trustee
3238
* knows that there will be no new works on the worklist
3239
* and once the worklist is empty it can proceed to
3240
* killing idle workers.
3242
* RELEASE Command state which is set by the cpu callback if the
3243
* cpu down has been canceled or it has come online
3244
* again. After recognizing this state, trustee stops
3245
* trying to drain or butcher and clears ROGUE, rebinds
3246
* all remaining workers back to the cpu and releases
3249
* DONE Trustee will enter this state after BUTCHER or RELEASE
3252
* trustee CPU draining
3253
* took over down complete
3254
* START -----------> IN_CHARGE -----------> BUTCHER -----------> DONE
3256
* | CPU is back online v return workers |
3257
* ----------------> RELEASE --------------
3261
* trustee_wait_event_timeout - timed event wait for trustee
3262
* @cond: condition to wait for
3263
* @timeout: timeout in jiffies
3265
* wait_event_timeout() for trustee to use. Handles locking and
3266
* checks for RELEASE request.
3269
* spin_lock_irq(gcwq->lock) which may be released and regrabbed
3270
* multiple times. To be used by trustee.
3273
* Positive indicating left time if @cond is satisfied, 0 if timed
3274
* out, -1 if canceled.
3276
#define trustee_wait_event_timeout(cond, timeout) ({ \
3277
long __ret = (timeout); \
3278
while (!((cond) || (gcwq->trustee_state == TRUSTEE_RELEASE)) && \
3280
spin_unlock_irq(&gcwq->lock); \
3281
__wait_event_timeout(gcwq->trustee_wait, (cond) || \
3282
(gcwq->trustee_state == TRUSTEE_RELEASE), \
3284
spin_lock_irq(&gcwq->lock); \
3286
gcwq->trustee_state == TRUSTEE_RELEASE ? -1 : (__ret); \
3290
* trustee_wait_event - event wait for trustee
3291
* @cond: condition to wait for
3293
* wait_event() for trustee to use. Automatically handles locking and
3294
* checks for CANCEL request.
3297
* spin_lock_irq(gcwq->lock) which may be released and regrabbed
3298
* multiple times. To be used by trustee.
3301
* 0 if @cond is satisfied, -1 if canceled.
3303
#define trustee_wait_event(cond) ({ \
3305
__ret1 = trustee_wait_event_timeout(cond, MAX_SCHEDULE_TIMEOUT);\
3306
__ret1 < 0 ? -1 : 0; \
3309
static int __cpuinit trustee_thread(void *__gcwq)
3311
struct global_cwq *gcwq = __gcwq;
3312
struct worker *worker;
3313
struct work_struct *work;
3314
struct hlist_node *pos;
3318
BUG_ON(gcwq->cpu != smp_processor_id());
3320
spin_lock_irq(&gcwq->lock);
3322
* Claim the manager position and make all workers rogue.
3323
* Trustee must be bound to the target cpu and can't be
3326
BUG_ON(gcwq->cpu != smp_processor_id());
3327
rc = trustee_wait_event(!(gcwq->flags & GCWQ_MANAGING_WORKERS));
3330
gcwq->flags |= GCWQ_MANAGING_WORKERS;
3332
list_for_each_entry(worker, &gcwq->idle_list, entry)
3333
worker->flags |= WORKER_ROGUE;
3335
for_each_busy_worker(worker, i, pos, gcwq)
3336
worker->flags |= WORKER_ROGUE;
3339
* Call schedule() so that we cross rq->lock and thus can
3340
* guarantee sched callbacks see the rogue flag. This is
3341
* necessary as scheduler callbacks may be invoked from other
3344
spin_unlock_irq(&gcwq->lock);
3346
spin_lock_irq(&gcwq->lock);
3349
* Sched callbacks are disabled now. Zap nr_running. After
3350
* this, nr_running stays zero and need_more_worker() and
3351
* keep_working() are always true as long as the worklist is
3354
atomic_set(get_gcwq_nr_running(gcwq->cpu), 0);
3356
spin_unlock_irq(&gcwq->lock);
3357
del_timer_sync(&gcwq->idle_timer);
3358
spin_lock_irq(&gcwq->lock);
3361
* We're now in charge. Notify and proceed to drain. We need
3362
* to keep the gcwq running during the whole CPU down
3363
* procedure as other cpu hotunplug callbacks may need to
3364
* flush currently running tasks.
3366
gcwq->trustee_state = TRUSTEE_IN_CHARGE;
3367
wake_up_all(&gcwq->trustee_wait);
3370
* The original cpu is in the process of dying and may go away
3371
* anytime now. When that happens, we and all workers would
3372
* be migrated to other cpus. Try draining any left work. We
3373
* want to get it over with ASAP - spam rescuers, wake up as
3374
* many idlers as necessary and create new ones till the
3375
* worklist is empty. Note that if the gcwq is frozen, there
3376
* may be frozen works in freezable cwqs. Don't declare
3377
* completion while frozen.
3379
while (gcwq->nr_workers != gcwq->nr_idle ||
3380
gcwq->flags & GCWQ_FREEZING ||
3381
gcwq->trustee_state == TRUSTEE_IN_CHARGE) {
3384
list_for_each_entry(work, &gcwq->worklist, entry) {
3389
list_for_each_entry(worker, &gcwq->idle_list, entry) {
3392
wake_up_process(worker->task);
3395
if (need_to_create_worker(gcwq)) {
3396
spin_unlock_irq(&gcwq->lock);
3397
worker = create_worker(gcwq, false);
3398
spin_lock_irq(&gcwq->lock);
3400
worker->flags |= WORKER_ROGUE;
3401
start_worker(worker);
3405
/* give a breather */
3406
if (trustee_wait_event_timeout(false, TRUSTEE_COOLDOWN) < 0)
3411
* Either all works have been scheduled and cpu is down, or
3412
* cpu down has already been canceled. Wait for and butcher
3413
* all workers till we're canceled.
3416
rc = trustee_wait_event(!list_empty(&gcwq->idle_list));
3417
while (!list_empty(&gcwq->idle_list))
3418
destroy_worker(list_first_entry(&gcwq->idle_list,
3419
struct worker, entry));
3420
} while (gcwq->nr_workers && rc >= 0);
3423
* At this point, either draining has completed and no worker
3424
* is left, or cpu down has been canceled or the cpu is being
3425
* brought back up. There shouldn't be any idle one left.
3426
* Tell the remaining busy ones to rebind once it finishes the
3427
* currently scheduled works by scheduling the rebind_work.
3429
WARN_ON(!list_empty(&gcwq->idle_list));
3431
for_each_busy_worker(worker, i, pos, gcwq) {
3432
struct work_struct *rebind_work = &worker->rebind_work;
3435
* Rebind_work may race with future cpu hotplug
3436
* operations. Use a separate flag to mark that
3437
* rebinding is scheduled.
3439
worker->flags |= WORKER_REBIND;
3440
worker->flags &= ~WORKER_ROGUE;
3442
/* queue rebind_work, wq doesn't matter, use the default one */
3443
if (test_and_set_bit(WORK_STRUCT_PENDING_BIT,
3444
work_data_bits(rebind_work)))
3447
debug_work_activate(rebind_work);
3448
insert_work(get_cwq(gcwq->cpu, system_wq), rebind_work,
3449
worker->scheduled.next,
3450
work_color_to_flags(WORK_NO_COLOR));
3453
/* relinquish manager role */
3454
gcwq->flags &= ~GCWQ_MANAGING_WORKERS;
3456
/* notify completion */
3457
gcwq->trustee = NULL;
3458
gcwq->trustee_state = TRUSTEE_DONE;
3459
wake_up_all(&gcwq->trustee_wait);
3460
spin_unlock_irq(&gcwq->lock);
3465
* wait_trustee_state - wait for trustee to enter the specified state
3466
* @gcwq: gcwq the trustee of interest belongs to
3467
* @state: target state to wait for
3469
* Wait for the trustee to reach @state. DONE is already matched.
3472
* spin_lock_irq(gcwq->lock) which may be released and regrabbed
3473
* multiple times. To be used by cpu_callback.
3475
static void __cpuinit wait_trustee_state(struct global_cwq *gcwq, int state)
3476
__releases(&gcwq->lock)
3477
__acquires(&gcwq->lock)
3479
if (!(gcwq->trustee_state == state ||
3480
gcwq->trustee_state == TRUSTEE_DONE)) {
3481
spin_unlock_irq(&gcwq->lock);
3482
__wait_event(gcwq->trustee_wait,
3483
gcwq->trustee_state == state ||
3484
gcwq->trustee_state == TRUSTEE_DONE);
3485
spin_lock_irq(&gcwq->lock);
3489
static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
3490
unsigned long action,
3493
unsigned int cpu = (unsigned long)hcpu;
3494
struct global_cwq *gcwq = get_gcwq(cpu);
3495
struct task_struct *new_trustee = NULL;
3496
struct worker *uninitialized_var(new_worker);
3497
unsigned long flags;
3499
action &= ~CPU_TASKS_FROZEN;
3502
case CPU_DOWN_PREPARE:
3503
new_trustee = kthread_create(trustee_thread, gcwq,
3504
"workqueue_trustee/%d\n", cpu);
3505
if (IS_ERR(new_trustee))
3506
return notifier_from_errno(PTR_ERR(new_trustee));
3507
kthread_bind(new_trustee, cpu);
3509
case CPU_UP_PREPARE:
3510
BUG_ON(gcwq->first_idle);
3511
new_worker = create_worker(gcwq, false);
3514
kthread_stop(new_trustee);
3519
/* some are called w/ irq disabled, don't disturb irq status */
3520
spin_lock_irqsave(&gcwq->lock, flags);
3523
case CPU_DOWN_PREPARE:
3524
/* initialize trustee and tell it to acquire the gcwq */
3525
BUG_ON(gcwq->trustee || gcwq->trustee_state != TRUSTEE_DONE);
3526
gcwq->trustee = new_trustee;
3527
gcwq->trustee_state = TRUSTEE_START;
3528
wake_up_process(gcwq->trustee);
3529
wait_trustee_state(gcwq, TRUSTEE_IN_CHARGE);
3531
case CPU_UP_PREPARE:
3532
BUG_ON(gcwq->first_idle);
3533
gcwq->first_idle = new_worker;
3538
* Before this, the trustee and all workers except for
3539
* the ones which are still executing works from
3540
* before the last CPU down must be on the cpu. After
3541
* this, they'll all be diasporas.
3543
gcwq->flags |= GCWQ_DISASSOCIATED;
3547
gcwq->trustee_state = TRUSTEE_BUTCHER;
3549
case CPU_UP_CANCELED:
3550
destroy_worker(gcwq->first_idle);
3551
gcwq->first_idle = NULL;
3554
case CPU_DOWN_FAILED:
3556
gcwq->flags &= ~GCWQ_DISASSOCIATED;
3557
if (gcwq->trustee_state != TRUSTEE_DONE) {
3558
gcwq->trustee_state = TRUSTEE_RELEASE;
3559
wake_up_process(gcwq->trustee);
3560
wait_trustee_state(gcwq, TRUSTEE_DONE);
3564
* Trustee is done and there might be no worker left.
3565
* Put the first_idle in and request a real manager to
3568
spin_unlock_irq(&gcwq->lock);
3569
kthread_bind(gcwq->first_idle->task, cpu);
3570
spin_lock_irq(&gcwq->lock);
3571
gcwq->flags |= GCWQ_MANAGE_WORKERS;
3572
start_worker(gcwq->first_idle);
3573
gcwq->first_idle = NULL;
3577
spin_unlock_irqrestore(&gcwq->lock, flags);
3579
return notifier_from_errno(0);
3584
struct work_for_cpu {
3585
struct completion completion;
3591
static int do_work_for_cpu(void *_wfc)
3593
struct work_for_cpu *wfc = _wfc;
3594
wfc->ret = wfc->fn(wfc->arg);
3595
complete(&wfc->completion);
3600
* work_on_cpu - run a function in user context on a particular cpu
3601
* @cpu: the cpu to run on
3602
* @fn: the function to run
3603
* @arg: the function arg
3605
* This will return the value @fn returns.
3606
* It is up to the caller to ensure that the cpu doesn't go offline.
3607
* The caller must not hold any locks which would prevent @fn from completing.
3609
long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
3611
struct task_struct *sub_thread;
3612
struct work_for_cpu wfc = {
3613
.completion = COMPLETION_INITIALIZER_ONSTACK(wfc.completion),
3618
sub_thread = kthread_create(do_work_for_cpu, &wfc, "work_for_cpu");
3619
if (IS_ERR(sub_thread))
3620
return PTR_ERR(sub_thread);
3621
kthread_bind(sub_thread, cpu);
3622
wake_up_process(sub_thread);
3623
wait_for_completion(&wfc.completion);
3626
EXPORT_SYMBOL_GPL(work_on_cpu);
3627
#endif /* CONFIG_SMP */
3629
#ifdef CONFIG_FREEZER
3632
* freeze_workqueues_begin - begin freezing workqueues
3634
* Start freezing workqueues. After this function returns, all freezable
3635
* workqueues will queue new works to their frozen_works list instead of
3639
* Grabs and releases workqueue_lock and gcwq->lock's.
3641
void freeze_workqueues_begin(void)
3645
spin_lock(&workqueue_lock);
3647
BUG_ON(workqueue_freezing);
3648
workqueue_freezing = true;
3650
for_each_gcwq_cpu(cpu) {
3651
struct global_cwq *gcwq = get_gcwq(cpu);
3652
struct workqueue_struct *wq;
3654
spin_lock_irq(&gcwq->lock);
3656
BUG_ON(gcwq->flags & GCWQ_FREEZING);
3657
gcwq->flags |= GCWQ_FREEZING;
3659
list_for_each_entry(wq, &workqueues, list) {
3660
struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3662
if (cwq && wq->flags & WQ_FREEZABLE)
3663
cwq->max_active = 0;
3666
spin_unlock_irq(&gcwq->lock);
3669
spin_unlock(&workqueue_lock);
3673
* freeze_workqueues_busy - are freezable workqueues still busy?
3675
* Check whether freezing is complete. This function must be called
3676
* between freeze_workqueues_begin() and thaw_workqueues().
3679
* Grabs and releases workqueue_lock.
3682
* %true if some freezable workqueues are still busy. %false if freezing
3685
bool freeze_workqueues_busy(void)
3690
spin_lock(&workqueue_lock);
3692
BUG_ON(!workqueue_freezing);
3694
for_each_gcwq_cpu(cpu) {
3695
struct workqueue_struct *wq;
3697
* nr_active is monotonically decreasing. It's safe
3698
* to peek without lock.
3700
list_for_each_entry(wq, &workqueues, list) {
3701
struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3703
if (!cwq || !(wq->flags & WQ_FREEZABLE))
3706
BUG_ON(cwq->nr_active < 0);
3707
if (cwq->nr_active) {
3714
spin_unlock(&workqueue_lock);
3719
* thaw_workqueues - thaw workqueues
3721
* Thaw workqueues. Normal queueing is restored and all collected
3722
* frozen works are transferred to their respective gcwq worklists.
3725
* Grabs and releases workqueue_lock and gcwq->lock's.
3727
void thaw_workqueues(void)
3731
spin_lock(&workqueue_lock);
3733
if (!workqueue_freezing)
3736
for_each_gcwq_cpu(cpu) {
3737
struct global_cwq *gcwq = get_gcwq(cpu);
3738
struct workqueue_struct *wq;
3740
spin_lock_irq(&gcwq->lock);
3742
BUG_ON(!(gcwq->flags & GCWQ_FREEZING));
3743
gcwq->flags &= ~GCWQ_FREEZING;
3745
list_for_each_entry(wq, &workqueues, list) {
3746
struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3748
if (!cwq || !(wq->flags & WQ_FREEZABLE))
3751
/* restore max_active and repopulate worklist */
3752
cwq->max_active = wq->saved_max_active;
3754
while (!list_empty(&cwq->delayed_works) &&
3755
cwq->nr_active < cwq->max_active)
3756
cwq_activate_first_delayed(cwq);
3759
wake_up_worker(gcwq);
3761
spin_unlock_irq(&gcwq->lock);
3764
workqueue_freezing = false;
3766
spin_unlock(&workqueue_lock);
3768
#endif /* CONFIG_FREEZER */
3770
static int __init init_workqueues(void)
3775
cpu_notifier(workqueue_cpu_callback, CPU_PRI_WORKQUEUE);
3777
/* initialize gcwqs */
3778
for_each_gcwq_cpu(cpu) {
3779
struct global_cwq *gcwq = get_gcwq(cpu);
3781
spin_lock_init(&gcwq->lock);
3782
INIT_LIST_HEAD(&gcwq->worklist);
3784
gcwq->flags |= GCWQ_DISASSOCIATED;
3786
INIT_LIST_HEAD(&gcwq->idle_list);
3787
for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++)
3788
INIT_HLIST_HEAD(&gcwq->busy_hash[i]);
3790
init_timer_deferrable(&gcwq->idle_timer);
3791
gcwq->idle_timer.function = idle_worker_timeout;
3792
gcwq->idle_timer.data = (unsigned long)gcwq;
3794
setup_timer(&gcwq->mayday_timer, gcwq_mayday_timeout,
3795
(unsigned long)gcwq);
3797
ida_init(&gcwq->worker_ida);
3799
gcwq->trustee_state = TRUSTEE_DONE;
3800
init_waitqueue_head(&gcwq->trustee_wait);
3803
/* create the initial worker */
3804
for_each_online_gcwq_cpu(cpu) {
3805
struct global_cwq *gcwq = get_gcwq(cpu);
3806
struct worker *worker;
3808
if (cpu != WORK_CPU_UNBOUND)
3809
gcwq->flags &= ~GCWQ_DISASSOCIATED;
3810
worker = create_worker(gcwq, true);
3812
spin_lock_irq(&gcwq->lock);
3813
start_worker(worker);
3814
spin_unlock_irq(&gcwq->lock);
3817
system_wq = alloc_workqueue("events", 0, 0);
3818
system_long_wq = alloc_workqueue("events_long", 0, 0);
3819
system_nrt_wq = alloc_workqueue("events_nrt", WQ_NON_REENTRANT, 0);
3820
system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
3821
WQ_UNBOUND_MAX_ACTIVE);
3822
system_freezable_wq = alloc_workqueue("events_freezable",
3824
BUG_ON(!system_wq || !system_long_wq || !system_nrt_wq ||
3825
!system_unbound_wq || !system_freezable_wq);
3828
early_initcall(init_workqueues);