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Commit f2d5a0ee authored by Tejun Heo's avatar Tejun Heo
Browse files

workqueue: drop CPU_DYING notifier operation 



Workqueue used CPU_DYING notification to mark GCWQ_DISASSOCIATED.
This was necessary because workqueue's CPU_DOWN_PREPARE happened
before other DOWN_PREPARE notifiers and workqueue needed to stay
associated across the rest of DOWN_PREPARE.

After the previous patch, workqueue's DOWN_PREPARE happens after
others and can set GCWQ_DISASSOCIATED directly.  Drop CPU_DYING and
let the trustee set GCWQ_DISASSOCIATED after disabling concurrency
management.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatar"Rafael J. Wysocki" <rjw@sisk.pl>
parent 65758202

kernel/workqueue.c

+13 −16
Original line number Diff line number Diff line
@@ -1250,11 +1250,11 @@ static void worker_leave_idle(struct worker *worker) 
 * verbatim as it's best effort and blocking and gcwq may be

 * [dis]associated in the meantime.

 *

 * This function tries set_cpus_allowed() and locks gcwq and verifies

 * the binding against GCWQ_DISASSOCIATED which is set during

 * CPU_DYING and cleared during CPU_ONLINE, so if the worker enters

 * idle state or fetches works without dropping lock, it can guarantee

 * the scheduling requirement described in the first paragraph.

 * This function tries set_cpus_allowed() and locks gcwq and verifies the

 * binding against %GCWQ_DISASSOCIATED which is set during

 * %CPU_DOWN_PREPARE and cleared during %CPU_ONLINE, so if the worker

 * enters idle state or fetches works without dropping lock, it can

 * guarantee the scheduling requirement described in the first paragraph.

 *

 * CONTEXT:

 * Might sleep.  Called without any lock but returns with gcwq->lock
@@ -3349,6 +3349,12 @@ static int __cpuinit trustee_thread(void *__gcwq) 
	rc = trustee_wait_event(!gcwq_is_managing_workers(gcwq));

	BUG_ON(rc < 0);



	/*

	 * We've claimed all manager positions.  Make all workers unbound

	 * and set DISASSOCIATED.  Before this, all workers except for the

	 * ones which are still executing works from before the last CPU

	 * down must be on the cpu.  After this, they may become diasporas.

	 */

	for_each_worker_pool(pool, gcwq) {

		pool->flags |= POOL_MANAGING_WORKERS;
@@ -3359,6 +3365,8 @@ static int __cpuinit trustee_thread(void *__gcwq) 
	for_each_busy_worker(worker, i, pos, gcwq)

		worker->flags |= WORKER_ROGUE;



	gcwq->flags |= GCWQ_DISASSOCIATED;



	/*

	 * Call schedule() so that we cross rq->lock and thus can

	 * guarantee sched callbacks see the rogue flag.  This is
@@ -3582,16 +3590,6 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb, 
		}

		break;



	case CPU_DYING:

		/*

		 * Before this, the trustee and all workers except for

		 * the ones which are still executing works from

		 * before the last CPU down must be on the cpu.  After

		 * this, they'll all be diasporas.

		 */

		gcwq->flags |= GCWQ_DISASSOCIATED;

		break;



	case CPU_POST_DEAD:

		gcwq->trustee_state = TRUSTEE_BUTCHER;

		/* fall through */
@@ -3672,7 +3670,6 @@ static int __devinit workqueue_cpu_down_callback(struct notifier_block *nfb, 
{

	switch (action & ~CPU_TASKS_FROZEN) {

	case CPU_DOWN_PREPARE:

	case CPU_DYING:

	case CPU_POST_DEAD:

		return workqueue_cpu_callback(nfb, action, hcpu);

	}