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Commit 5f7dabfd authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Tejun Heo
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workqueue: WORKER_REBIND is no longer necessary for idle rebinding 



Now both worker destruction and idle rebinding remove the worker from
idle list while it's still idle, so list_empty(&worker->entry) can be
used to test whether either is pending and WORKER_DIE to distinguish
between the two instead making WORKER_REBIND unnecessary.

Use list_empty(&worker->entry) to determine whether destruction or
rebinding is pending.  This simplifies worker state transitions.

WORKER_REBIND is not needed anymore.  Remove it.

tj: Updated comments and description.

Signed-off-by: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent eab6d828

kernel/workqueue.c

+15 −26
Original line number Diff line number Diff line
@@ -73,11 +73,10 @@ enum { 
	WORKER_DIE		= 1 << 1,	/* die die die */

	WORKER_IDLE		= 1 << 2,	/* is idle */

	WORKER_PREP		= 1 << 3,	/* preparing to run works */

	WORKER_REBIND		= 1 << 5,	/* mom is home, come back */

	WORKER_CPU_INTENSIVE	= 1 << 6,	/* cpu intensive */

	WORKER_UNBOUND		= 1 << 7,	/* worker is unbound */



	WORKER_NOT_RUNNING	= WORKER_PREP | WORKER_REBIND | WORKER_UNBOUND |

	WORKER_NOT_RUNNING	= WORKER_PREP | WORKER_UNBOUND |

				  WORKER_CPU_INTENSIVE,



	NR_WORKER_POOLS		= 2,		/* # worker pools per gcwq */
@@ -1618,20 +1617,15 @@ __acquires(&gcwq->lock) 


/*

 * Rebind an idle @worker to its CPU.  worker_thread() will test

 * %WORKER_REBIND before leaving idle and call this function.

 * list_empty(@worker->entry) before leaving idle and call this function.

 */

static void idle_worker_rebind(struct worker *worker)

{

	struct global_cwq *gcwq = worker->pool->gcwq;



	/*

	 * CPU may go down again inbetween.  If rebinding fails, reinstate

	 * UNBOUND.  We're off idle_list and nobody else can do it for us.

	 */

	if (!worker_maybe_bind_and_lock(worker))

		worker->flags |= WORKER_UNBOUND;



	worker_clr_flags(worker, WORKER_REBIND);

	/* CPU may go down again inbetween, clear UNBOUND only on success */

	if (worker_maybe_bind_and_lock(worker))

		worker_clr_flags(worker, WORKER_UNBOUND);



	/* rebind complete, become available again */

	list_add(&worker->entry, &worker->pool->idle_list);
@@ -1689,16 +1683,9 @@ static void rebind_workers(struct global_cwq *gcwq) 
	for_each_worker_pool(pool, gcwq)

		lockdep_assert_held(&pool->manager_mutex);



	/* set REBIND and kick idle ones */

	/* dequeue and kick idle ones */

	for_each_worker_pool(pool, gcwq) {

		list_for_each_entry_safe(worker, n, &pool->idle_list, entry) {

			unsigned long worker_flags = worker->flags;



			/* morph UNBOUND to REBIND atomically */

			worker_flags &= ~WORKER_UNBOUND;

			worker_flags |= WORKER_REBIND;

			ACCESS_ONCE(worker->flags) = worker_flags;



			/*

			 * idle workers should be off @pool->idle_list

			 * until rebind is complete to avoid receiving
@@ -1706,7 +1693,10 @@ static void rebind_workers(struct global_cwq *gcwq) 
			 */

			list_del_init(&worker->entry);



			/* worker_thread() will call idle_worker_rebind() */

			/*

			 * worker_thread() will see the above dequeuing

			 * and call idle_worker_rebind().

			 */

			wake_up_process(worker->task);

		}

	}
@@ -2176,7 +2166,7 @@ __acquires(&gcwq->lock) 
	 * necessary to avoid spurious warnings from rescuers servicing the

	 * unbound or a disassociated gcwq.

	 */

	WARN_ON_ONCE(!(worker->flags & (WORKER_UNBOUND | WORKER_REBIND)) &&

	WARN_ON_ONCE(!(worker->flags & WORKER_UNBOUND) &&

		     !(gcwq->flags & GCWQ_DISASSOCIATED) &&

		     raw_smp_processor_id() != gcwq->cpu);
@@ -2300,18 +2290,17 @@ static int worker_thread(void *__worker) 
woke_up:

	spin_lock_irq(&gcwq->lock);



	/*

	 * DIE can be set only while idle and REBIND set while busy has

	 * @worker->rebind_work scheduled.  Checking here is enough.

	 */

	if (unlikely(worker->flags & (WORKER_REBIND | WORKER_DIE))) {

	/* we are off idle list if destruction or rebind is requested */

	if (unlikely(list_empty(&worker->entry))) {

		spin_unlock_irq(&gcwq->lock);



		/* if DIE is set, destruction is requested */

		if (worker->flags & WORKER_DIE) {

			worker->task->flags &= ~PF_WQ_WORKER;

			return 0;

		}



		/* otherwise, rebind */

		idle_worker_rebind(worker);

		goto woke_up;

	}