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Commit 18aa9eff authored by Tejun Heo's avatar Tejun Heo
Browse files

workqueue: implement WQ_NON_REENTRANT 



With gcwq managing all the workers and work->data pointing to the last
gcwq it was on, non-reentrance can be easily implemented by checking
whether the work is still running on the previous gcwq on queueing.
Implement it.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 7a22ad75

include/linux/workqueue.h

+1 −0
Original line number Diff line number Diff line
@@ -225,6 +225,7 @@ static inline unsigned int work_static(struct work_struct *work) { return 0; } 
enum {

	WQ_FREEZEABLE		= 1 << 0, /* freeze during suspend */

	WQ_SINGLE_CPU		= 1 << 1, /* only single cpu at a time */

	WQ_NON_REENTRANT	= 1 << 2, /* guarantee non-reentrance */

};



extern struct workqueue_struct *

kernel/workqueue.c

+29 −3
Original line number Diff line number Diff line
@@ -534,10 +534,36 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq, 


	debug_work_activate(work);



	/* determine gcwq to use */

	/*

	 * Determine gcwq to use.  SINGLE_CPU is inherently

	 * NON_REENTRANT, so test it first.

	 */

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

		/* just use the requested cpu for multicpu workqueues */

		struct global_cwq *last_gcwq;



		/*

		 * It's multi cpu.  If @wq is non-reentrant and @work

		 * was previously on a different cpu, it might still

		 * be running there, in which case the work needs to

		 * be queued on that cpu to guarantee non-reentrance.

		 */

		gcwq = get_gcwq(cpu);

		if (wq->flags & WQ_NON_REENTRANT &&

		    (last_gcwq = get_work_gcwq(work)) && last_gcwq != gcwq) {

			struct worker *worker;



			spin_lock_irqsave(&last_gcwq->lock, flags);



			worker = find_worker_executing_work(last_gcwq, work);



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

				gcwq = last_gcwq;

			else {

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

				spin_unlock_irqrestore(&last_gcwq->lock, flags);

				spin_lock_irqsave(&gcwq->lock, flags);

			}

		} else

			spin_lock_irqsave(&gcwq->lock, flags);

	} else {

		unsigned int req_cpu = cpu;