Commit 8db25e78 authored by Tejun Heo's avatar Tejun Heo
Browse files

workqueue: simplify CPU hotplug code 



With trustee gone, CPU hotplug code can be simplified.

* gcwq_claim/release_management() now grab and release gcwq lock too
  respectively and gained _and_lock and _and_unlock postfixes.

* All CPU hotplug logic was implemented in workqueue_cpu_callback()
  which was called by workqueue_cpu_up/down_callback() for the correct
  priority.  This was because up and down paths shared a lot of logic,
  which is no longer true.  Remove workqueue_cpu_callback() and move
  all hotplug logic into the two actual callbacks.

This patch doesn't make any functional changes.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatar"Rafael J. Wysocki" <rjw@sisk.pl>
parent 628c78e7

kernel/workqueue.c

+25 −54
Original line number Diff line number Diff line
@@ -3358,19 +3358,21 @@ EXPORT_SYMBOL_GPL(work_busy); 
 */



/* claim manager positions of all pools */

static void gcwq_claim_management(struct global_cwq *gcwq)

static void gcwq_claim_management_and_lock(struct global_cwq *gcwq)

{

	struct worker_pool *pool;



	for_each_worker_pool(pool, gcwq)

		mutex_lock_nested(&pool->manager_mutex, pool - gcwq->pools);

	spin_lock_irq(&gcwq->lock);

}



/* release manager positions */

static void gcwq_release_management(struct global_cwq *gcwq)

static void gcwq_release_management_and_unlock(struct global_cwq *gcwq)

{

	struct worker_pool *pool;



	spin_unlock_irq(&gcwq->lock);

	for_each_worker_pool(pool, gcwq)

		mutex_unlock(&pool->manager_mutex);

}
@@ -3385,8 +3387,7 @@ static void gcwq_unbind_fn(struct work_struct *work) 


	BUG_ON(gcwq->cpu != smp_processor_id());



	gcwq_claim_management(gcwq);

	spin_lock_irq(&gcwq->lock);

	gcwq_claim_management_and_lock(gcwq);



	/*

	 * We've claimed all manager positions.  Make all workers unbound
@@ -3403,8 +3404,7 @@ static void gcwq_unbind_fn(struct work_struct *work) 


	gcwq->flags |= GCWQ_DISASSOCIATED;



	spin_unlock_irq(&gcwq->lock);

	gcwq_release_management(gcwq);

	gcwq_release_management_and_unlock(gcwq);



	/*

	 * Call schedule() so that we cross rq->lock and thus can guarantee
@@ -3428,26 +3428,19 @@ static void gcwq_unbind_fn(struct work_struct *work) 
		atomic_set(get_pool_nr_running(pool), 0);

}



static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,

/*

 * Workqueues should be brought up before normal priority CPU notifiers.

 * This will be registered high priority CPU notifier.

 */

static int __devinit workqueue_cpu_up_callback(struct notifier_block *nfb,

					       unsigned long action,

					       void *hcpu)

{

	unsigned int cpu = (unsigned long)hcpu;

	struct global_cwq *gcwq = get_gcwq(cpu);

	struct worker_pool *pool;

	struct work_struct unbind_work;

	unsigned long flags;



	action &= ~CPU_TASKS_FROZEN;



	switch (action) {

	case CPU_DOWN_PREPARE:

		/* unbinding should happen on the local CPU */

		INIT_WORK_ONSTACK(&unbind_work, gcwq_unbind_fn);

		schedule_work_on(cpu, &unbind_work);

		flush_work(&unbind_work);

		break;



	switch (action & ~CPU_TASKS_FROZEN) {

	case CPU_UP_PREPARE:

		for_each_worker_pool(pool, gcwq) {

			struct worker *worker;
@@ -3463,45 +3456,16 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb, 
			start_worker(worker);

			spin_unlock_irq(&gcwq->lock);

		}

	}



	/* some are called w/ irq disabled, don't disturb irq status */

	spin_lock_irqsave(&gcwq->lock, flags);

		break;



	switch (action) {

	case CPU_DOWN_FAILED:

	case CPU_ONLINE:

		spin_unlock_irq(&gcwq->lock);

		gcwq_claim_management(gcwq);

		spin_lock_irq(&gcwq->lock);



		gcwq_claim_management_and_lock(gcwq);

		gcwq->flags &= ~GCWQ_DISASSOCIATED;



		rebind_workers(gcwq);



		gcwq_release_management(gcwq);

		gcwq_release_management_and_unlock(gcwq);

		break;

	}



	spin_unlock_irqrestore(&gcwq->lock, flags);



	return notifier_from_errno(0);

}



/*

 * Workqueues should be brought up before normal priority CPU notifiers.

 * This will be registered high priority CPU notifier.

 */

static int __devinit workqueue_cpu_up_callback(struct notifier_block *nfb,

					       unsigned long action,

					       void *hcpu)

{

	switch (action & ~CPU_TASKS_FROZEN) {

	case CPU_UP_PREPARE:

	case CPU_DOWN_FAILED:

	case CPU_ONLINE:

		return workqueue_cpu_callback(nfb, action, hcpu);

	}

	return NOTIFY_OK;

}
@@ -3513,9 +3477,16 @@ static int __devinit workqueue_cpu_down_callback(struct notifier_block *nfb, 
						 unsigned long action,

						 void *hcpu)

{

	unsigned int cpu = (unsigned long)hcpu;

	struct work_struct unbind_work;



	switch (action & ~CPU_TASKS_FROZEN) {

	case CPU_DOWN_PREPARE:

		return workqueue_cpu_callback(nfb, action, hcpu);

		/* unbinding should happen on the local CPU */

		INIT_WORK_ONSTACK(&unbind_work, gcwq_unbind_fn);

		schedule_work_on(cpu, &unbind_work);

		flush_work(&unbind_work);

		break;

	}

	return NOTIFY_OK;

}

CRA Git | Maintained and supported by SUSTech CRA and CCSE