Commit a357fc03 authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Tejun Heo
Browse files

workqueue: protect wq->saved_max_active with wq->mutex 



We're expanding wq->mutex to cover all fields specific to each
workqueue with the end goal of replacing pwq_lock which will make
locking simpler and easier to understand.

This patch makes wq->saved_max_active protected by wq->mutex instead
of pwq_lock.  As pwq_lock locking around pwq_adjust_mac_active() is no
longer necessary, this patch also replaces pwq_lock lockings of
for_each_pwq() around pwq_adjust_max_active() to wq->mutex.

tj: Rebased on top of the current dev branch.  Updated description.

Signed-off-by: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent b09f4fd3

kernel/workqueue.c

+16 −17
Original line number Diff line number Diff line
@@ -243,7 +243,7 @@ struct workqueue_struct { 
	struct worker		*rescuer;	/* I: rescue worker */



	int			nr_drainers;	/* WQ: drain in progress */

	int			saved_max_active; /* PW: saved pwq max_active */

	int			saved_max_active; /* WQ: saved pwq max_active */



#ifdef CONFIG_SYSFS

	struct wq_device	*wq_dev;	/* I: for sysfs interface */
@@ -3579,13 +3579,13 @@ static void pwq_adjust_max_active(struct pool_workqueue *pwq) 
	bool freezable = wq->flags & WQ_FREEZABLE;



	/* for @wq->saved_max_active */

	lockdep_assert_held(&pwq_lock);

	lockdep_assert_held(&wq->mutex);



	/* fast exit for non-freezable wqs */

	if (!freezable && pwq->max_active == wq->saved_max_active)

		return;



	spin_lock(&pwq->pool->lock);

	spin_lock_irq(&pwq->pool->lock);



	if (!freezable || !(pwq->pool->flags & POOL_FREEZING)) {

		pwq->max_active = wq->saved_max_active;
@@ -3603,7 +3603,7 @@ static void pwq_adjust_max_active(struct pool_workqueue *pwq) 
		pwq->max_active = 0;

	}



	spin_unlock(&pwq->pool->lock);

	spin_unlock_irq(&pwq->pool->lock);

}



static void init_and_link_pwq(struct pool_workqueue *pwq,
@@ -3622,7 +3622,6 @@ static void init_and_link_pwq(struct pool_workqueue *pwq, 
	INIT_WORK(&pwq->unbound_release_work, pwq_unbound_release_workfn);



	mutex_lock(&wq->mutex);

	spin_lock_irq(&pwq_lock);



	/*

	 * Set the matching work_color.  This is synchronized with
@@ -3636,9 +3635,10 @@ static void init_and_link_pwq(struct pool_workqueue *pwq, 
	pwq_adjust_max_active(pwq);



	/* link in @pwq */

	spin_lock_irq(&pwq_lock);

	list_add_rcu(&pwq->pwqs_node, &wq->pwqs);



	spin_unlock_irq(&pwq_lock);



	mutex_unlock(&wq->mutex);

}
@@ -3803,10 +3803,10 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt, 
	 */

	mutex_lock(&wq_pool_mutex);



	spin_lock_irq(&pwq_lock);

	mutex_lock(&wq->mutex);

	for_each_pwq(pwq, wq)

		pwq_adjust_max_active(pwq);

	spin_unlock_irq(&pwq_lock);

	mutex_unlock(&wq->mutex);



	list_add(&wq->list, &workqueues);
@@ -3917,14 +3917,14 @@ void workqueue_set_max_active(struct workqueue_struct *wq, int max_active) 


	max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);



	spin_lock_irq(&pwq_lock);

	mutex_lock(&wq->mutex);



	wq->saved_max_active = max_active;



	for_each_pwq(pwq, wq)

		pwq_adjust_max_active(pwq);



	spin_unlock_irq(&pwq_lock);

	mutex_unlock(&wq->mutex);

}

EXPORT_SYMBOL_GPL(workqueue_set_max_active);
@@ -4287,7 +4287,7 @@ EXPORT_SYMBOL_GPL(work_on_cpu); 
 * pool->worklist.

 *

 * CONTEXT:

 * Grabs and releases wq_pool_mutex, pwq_lock and pool->lock's.

 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.

 */

void freeze_workqueues_begin(void)

{
@@ -4309,13 +4309,12 @@ void freeze_workqueues_begin(void) 
		spin_unlock_irq(&pool->lock);

	}



	/* suppress further executions by setting max_active to zero */

	spin_lock_irq(&pwq_lock);

	list_for_each_entry(wq, &workqueues, list) {

		mutex_lock(&wq->mutex);

		for_each_pwq(pwq, wq)

			pwq_adjust_max_active(pwq);

		mutex_unlock(&wq->mutex);

	}

	spin_unlock_irq(&pwq_lock);



	mutex_unlock(&wq_pool_mutex);

}
@@ -4373,7 +4372,7 @@ out_unlock: 
 * frozen works are transferred to their respective pool worklists.

 *

 * CONTEXT:

 * Grabs and releases wq_pool_mutex, pwq_lock and pool->lock's.

 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.

 */

void thaw_workqueues(void)

{
@@ -4396,12 +4395,12 @@ void thaw_workqueues(void) 
	}



	/* restore max_active and repopulate worklist */

	spin_lock_irq(&pwq_lock);

	list_for_each_entry(wq, &workqueues, list) {

		mutex_lock(&wq->mutex);

		for_each_pwq(pwq, wq)

			pwq_adjust_max_active(pwq);

		mutex_unlock(&wq->mutex);

	}

	spin_unlock_irq(&pwq_lock);



	workqueue_freezing = false;

out_unlock:

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