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Commit 00dfcaf7 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

workqueues: shrink cpu_populated_map when CPU dies 



When cpu_populated_map was introduced, it was supposed that cwq->thread can
survive after CPU_DEAD, that is why we never shrink cpu_populated_map.

This is not very nice, we can safely remove the already dead CPU from the map.
 The only required change is that destroy_workqueue() must hold the hotplug
lock until it destroys all cwq->thread's, to protect the cpu_populated_map.
We could make the local copy of cpu mask and drop the lock, but
sizeof(cpumask_t) may be very large.

Also, fix the comment near queue_work().  Unless _cpu_down() happens we do
guarantee the cpu-affinity of the work_struct, and we have users which rely on
this.

[akpm@linux-foundation.org: repair comment]
Signed-off-by: default avatarOleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 78608366

kernel/workqueue.c

+9 −4
Original line number Original line Diff line number Diff line
@@ -158,8 +158,8 @@ static void __queue_work(struct cpu_workqueue_struct *cwq, 
 *

 *

 * Returns 0 if @work was already on a queue, non-zero otherwise.

 * Returns 0 if @work was already on a queue, non-zero otherwise.

 *

 *

 * We queue the work to the CPU it was submitted, but there is no

 * We queue the work to the CPU on which it was submitted, but if the CPU dies

 * guarantee that it will be processed by that CPU.

 * it can be processed by another CPU.

 */

 */

int queue_work(struct workqueue_struct *wq, struct work_struct *work)

int queue_work(struct workqueue_struct *wq, struct work_struct *work)

{

{
@@ -815,12 +815,12 @@ void destroy_workqueue(struct workqueue_struct *wq) 
	spin_lock(&workqueue_lock);

	spin_lock(&workqueue_lock);

	list_del(&wq->list);

	list_del(&wq->list);

	spin_unlock(&workqueue_lock);

	spin_unlock(&workqueue_lock);

	put_online_cpus();





	for_each_cpu_mask(cpu, *cpu_map) {

	for_each_cpu_mask(cpu, *cpu_map) {

		cwq = per_cpu_ptr(wq->cpu_wq, cpu);

		cwq = per_cpu_ptr(wq->cpu_wq, cpu);

		cleanup_workqueue_thread(cwq, cpu);

		cleanup_workqueue_thread(cwq, cpu);

	}

	}

	put_online_cpus();





	free_percpu(wq->cpu_wq);

	free_percpu(wq->cpu_wq);

	kfree(wq);

	kfree(wq);
@@ -838,7 +838,6 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb, 
	action &= ~CPU_TASKS_FROZEN;

	action &= ~CPU_TASKS_FROZEN;





	switch (action) {

	switch (action) {



	case CPU_UP_PREPARE:

	case CPU_UP_PREPARE:

		cpu_set(cpu, cpu_populated_map);

		cpu_set(cpu, cpu_populated_map);

	}

	}
@@ -866,6 +865,12 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb, 
		}

		}

	}

	}





	switch (action) {

	case CPU_UP_CANCELED:

	case CPU_DEAD:

		cpu_clear(cpu, cpu_populated_map);

	}



	return NOTIFY_OK;

	return NOTIFY_OK;

}

}