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Commit 8594fade authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Tejun Heo
Browse files

workqueue: pick cwq instead of pool in __queue_work() 



Currently, __queue_work() chooses the pool to queue a work item to and
then determines cwq from the target wq and the chosen pool.  This is a
bit backwards in that we can determine cwq first and simply use
cwq->pool.  This way, we can skip get_std_worker_pool() in queueing
path which will be a hurdle when implementing custom worker pools.

Update __queue_work() such that it chooses the target cwq and then use
cwq->pool instead of the other way around.  While at it, add missing
{} in an if statement.

This patch doesn't introduce any functional changes.

tj: The original patch had two get_cwq() calls - the first to
    determine the pool by doing get_cwq(cpu, wq)->pool and the second
    to determine the matching cwq from get_cwq(pool->cpu, wq).
    Updated the function such that it chooses cwq instead of pool and
    removed the second call.  Rewrote the description.

Signed-off-by: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 54d5b7d0

kernel/workqueue.c

+13 −16
Original line number Diff line number Diff line
@@ -1193,8 +1193,6 @@ static bool is_chained_work(struct workqueue_struct *wq) 
static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,

			 struct work_struct *work)

{

	bool highpri = wq->flags & WQ_HIGHPRI;

	struct worker_pool *pool;

	struct cpu_workqueue_struct *cwq;

	struct list_head *worklist;

	unsigned int work_flags;
@@ -1215,7 +1213,7 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq, 
	    WARN_ON_ONCE(!is_chained_work(wq)))

		return;



	/* determine pool to use */

	/* determine the cwq to use */

	if (!(wq->flags & WQ_UNBOUND)) {

		struct worker_pool *last_pool;
@@ -1228,37 +1226,36 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq, 
		 * work needs to be queued on that cpu to guarantee

		 * non-reentrancy.

		 */

		pool = get_std_worker_pool(cpu, highpri);

		cwq = get_cwq(cpu, wq);

		last_pool = get_work_pool(work);



		if (last_pool && last_pool != pool) {

		if (last_pool && last_pool != cwq->pool) {

			struct worker *worker;



			spin_lock(&last_pool->lock);



			worker = find_worker_executing_work(last_pool, work);



			if (worker && worker->current_cwq->wq == wq)

				pool = last_pool;

			else {

			if (worker && worker->current_cwq->wq == wq) {

				cwq = get_cwq(last_pool->cpu, wq);

			} else {

				/* meh... not running there, queue here */

				spin_unlock(&last_pool->lock);

				spin_lock(&pool->lock);

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

			}

		} else {

			spin_lock(&pool->lock);

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

		}

	} else {

		pool = get_std_worker_pool(WORK_CPU_UNBOUND, highpri);

		spin_lock(&pool->lock);

		cwq = get_cwq(WORK_CPU_UNBOUND, wq);

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

	}



	/* pool determined, get cwq and queue */

	cwq = get_cwq(pool->cpu, wq);

	/* cwq determined, queue */

	trace_workqueue_queue_work(req_cpu, cwq, work);



	if (WARN_ON(!list_empty(&work->entry))) {

		spin_unlock(&pool->lock);

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

		return;

	}
@@ -1276,7 +1273,7 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq, 


	insert_work(cwq, work, worklist, work_flags);



	spin_unlock(&pool->lock);

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

}



/**