Commit 493008a8 authored by Tejun Heo's avatar Tejun Heo
Browse files

workqueue: drop WQ_RESCUER and test workqueue->rescuer for NULL instead 



WQ_RESCUER is superflous.  WQ_MEM_RECLAIM indicates that the user
wants a rescuer and testing wq->rescuer for NULL can answer whether a
given workqueue has a rescuer or not.  Drop WQ_RESCUER and test
wq->rescuer directly.

This will help simplifying __alloc_workqueue_key() failure path by
allowing it to use destroy_workqueue() on a partially constructed
workqueue, which in turn will help implementing dynamic management of
pool_workqueues.

While at it, clear wq->rescuer after freeing it in
destroy_workqueue().  This is a precaution as scheduled changes will
make destruction more complex.

This patch doesn't introduce any functional changes.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reviewed-by: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
parent ac6104cd

include/linux/workqueue.h

+0 −1
Original line number Diff line number Diff line
@@ -295,7 +295,6 @@ enum { 
	WQ_CPU_INTENSIVE	= 1 << 5, /* cpu instensive workqueue */



	WQ_DRAINING		= 1 << 6, /* internal: workqueue is draining */

	WQ_RESCUER		= 1 << 7, /* internal: workqueue has rescuer */



	WQ_MAX_ACTIVE		= 512,	  /* I like 512, better ideas? */

	WQ_MAX_UNBOUND_PER_CPU	= 4,	  /* 4 * #cpus for unbound wq */

kernel/workqueue.c

+10 −12
Original line number Diff line number Diff line
@@ -1827,7 +1827,7 @@ static void send_mayday(struct work_struct *work) 


	lockdep_assert_held(&workqueue_lock);



	if (!(wq->flags & WQ_RESCUER))

	if (!wq->rescuer)

		return;



	/* mayday mayday mayday */
@@ -2285,7 +2285,7 @@ sleep: 
 * @__rescuer: self

 *

 * Workqueue rescuer thread function.  There's one rescuer for each

 * workqueue which has WQ_RESCUER set.

 * workqueue which has WQ_MEM_RECLAIM set.

 *

 * Regular work processing on a pool may block trying to create a new

 * worker which uses GFP_KERNEL allocation which has slight chance of
@@ -2769,7 +2769,7 @@ static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr) 
	 * flusher is not running on the same workqueue by verifying write

	 * access.

	 */

	if (pwq->wq->saved_max_active == 1 || pwq->wq->flags & WQ_RESCUER)

	if (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)

		lock_map_acquire(&pwq->wq->lockdep_map);

	else

		lock_map_acquire_read(&pwq->wq->lockdep_map);
@@ -3412,13 +3412,6 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt, 
	va_end(args);

	va_end(args1);



	/*

	 * Workqueues which may be used during memory reclaim should

	 * have a rescuer to guarantee forward progress.

	 */

	if (flags & WQ_MEM_RECLAIM)

		flags |= WQ_RESCUER;



	max_active = max_active ?: WQ_DFL_ACTIVE;

	max_active = wq_clamp_max_active(max_active, flags, wq->name);
@@ -3449,7 +3442,11 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt, 
	}

	local_irq_enable();



	if (flags & WQ_RESCUER) {

	/*

	 * Workqueues which may be used during memory reclaim should

	 * have a rescuer to guarantee forward progress.

	 */

	if (flags & WQ_MEM_RECLAIM) {

		struct worker *rescuer;



		wq->rescuer = rescuer = alloc_worker();
@@ -3533,9 +3530,10 @@ void destroy_workqueue(struct workqueue_struct *wq) 


	spin_unlock_irq(&workqueue_lock);



	if (wq->flags & WQ_RESCUER) {

	if (wq->rescuer) {

		kthread_stop(wq->rescuer->task);

		kfree(wq->rescuer);

		wq->rescuer = NULL;

	}



	/*

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