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Merge branch 'for-5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 

Pull workqueue updates from Tejun Heo:
 "Nothing major. Just follow-up cleanups from Lai after the earlier
  synchronization simplification"

* 'for-5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
  workqueue: Convert the type of pool->nr_running to int
  workqueue: Use wake_up_worker() in wq_worker_sleeping() instead of open code
  workqueue: Change the comments of the synchronization about the idle_list
  workqueue: Remove the mb() pair between wq_worker_sleeping() and insert_work()
This commit is contained in:
Linus Torvalds 2022-03-23 12:40:51 -07:00
parent c5c009e250 bc35f7ef96
commit 7838316260
1 changed files with 20 additions and 38 deletions
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58
kernel/workqueue.c
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@ -154,15 +154,20 @@ struct worker_pool {
unsigned long watchdog_ts; /* L: watchdog timestamp */
/* The current concurrency level. */
atomic_t nr_running;
/*
* The counter is incremented in a process context on the associated CPU
* w/ preemption disabled, and decremented or reset in the same context
* but w/ pool->lock held. The readers grab pool->lock and are
* guaranteed to see if the counter reached zero.
*/
int nr_running;
struct list_head worklist; /* L: list of pending works */
int nr_workers; /* L: total number of workers */
int nr_idle; /* L: currently idle workers */
struct list_head idle_list; /* X: list of idle workers */
struct list_head idle_list; /* L: list of idle workers */
struct timer_list idle_timer; /* L: worker idle timeout */
struct timer_list mayday_timer; /* L: SOS timer for workers */
@ -777,7 +782,7 @@ static bool work_is_canceling(struct work_struct *work)
static bool __need_more_worker(struct worker_pool *pool)
{
return !atomic_read(&pool->nr_running);
return !pool->nr_running;
}
/*
@ -802,8 +807,7 @@ static bool may_start_working(struct worker_pool *pool)
/* Do I need to keep working? Called from currently running workers. */
static bool keep_working(struct worker_pool *pool)
{
return !list_empty(&pool->worklist) &&
atomic_read(&pool->nr_running) <= 1;
return !list_empty(&pool->worklist) && (pool->nr_running <= 1);
}
/* Do we need a new worker? Called from manager. */
@ -826,7 +830,7 @@ static bool too_many_workers(struct worker_pool *pool)
* Wake up functions.
*/
/* Return the first idle worker. Safe with preemption disabled */
/* Return the first idle worker. Called with pool->lock held. */
static struct worker *first_idle_worker(struct worker_pool *pool)
{
if (unlikely(list_empty(&pool->idle_list)))
@ -873,7 +877,7 @@ void wq_worker_running(struct task_struct *task)
*/
preempt_disable();
if (!(worker->flags & WORKER_NOT_RUNNING))
atomic_inc(&worker->pool->nr_running);
worker->pool->nr_running++;
preempt_enable();
worker->sleeping = 0;
}
@ -887,7 +891,7 @@ void wq_worker_running(struct task_struct *task)
*/
void wq_worker_sleeping(struct task_struct *task)
{
struct worker *next, *worker = kthread_data(task);
struct worker *worker = kthread_data(task);
struct worker_pool *pool;
/*
@ -917,23 +921,9 @@ void wq_worker_sleeping(struct task_struct *task)
return;
}
/*
* The counterpart of the following dec_and_test, implied mb,
* worklist not empty test sequence is in insert_work().
* Please read comment there.
*
* NOT_RUNNING is clear. This means that we're bound to and
* running on the local cpu w/ rq lock held and preemption
* disabled, which in turn means that none else could be
* manipulating idle_list, so dereferencing idle_list without pool
* lock is safe.
*/
if (atomic_dec_and_test(&pool->nr_running) &&
!list_empty(&pool->worklist)) {
next = first_idle_worker(pool);
if (next)
wake_up_process(next->task);
}
pool->nr_running--;
if (need_more_worker(pool))
wake_up_worker(pool);
raw_spin_unlock_irq(&pool->lock);
}
@ -987,7 +977,7 @@ static inline void worker_set_flags(struct worker *worker, unsigned int flags)
/* If transitioning into NOT_RUNNING, adjust nr_running. */
if ((flags & WORKER_NOT_RUNNING) &&
!(worker->flags & WORKER_NOT_RUNNING)) {
atomic_dec(&pool->nr_running);
pool->nr_running--;
}
worker->flags |= flags;
@ -1019,7 +1009,7 @@ static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
*/
if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
if (!(worker->flags & WORKER_NOT_RUNNING))
atomic_inc(&pool->nr_running);
pool->nr_running++;
}
/**
@ -1372,13 +1362,6 @@ static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
list_add_tail(&work->entry, head);
get_pwq(pwq);
/*
* Ensure either wq_worker_sleeping() sees the above
* list_add_tail() or we see zero nr_running to avoid workers lying
* around lazily while there are works to be processed.
*/
smp_mb();
if (__need_more_worker(pool))
wake_up_worker(pool);
}
@ -1827,8 +1810,7 @@ static void worker_enter_idle(struct worker *worker)
mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
/* Sanity check nr_running. */
WARN_ON_ONCE(pool->nr_workers == pool->nr_idle &&
atomic_read(&pool->nr_running));
WARN_ON_ONCE(pool->nr_workers == pool->nr_idle && pool->nr_running);
}
/**
@ -5006,7 +4988,7 @@ static void unbind_workers(int cpu)
* an unbound (in terms of concurrency management) pool which
* are served by workers tied to the pool.
*/
atomic_set(&pool->nr_running, 0);
pool->nr_running = 0;
/*
* With concurrency management just turned off, a busy