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Commit 8376fe22 authored by Tejun Heo's avatar Tejun Heo
Browse files

workqueue: implement mod_delayed_work[_on]() 



Workqueue was lacking a mechanism to modify the timeout of an already
pending delayed_work.  delayed_work users have been working around
this using several methods - using an explicit timer + work item,
messing directly with delayed_work->timer, and canceling before
re-queueing, all of which are error-prone and/or ugly.

This patch implements mod_delayed_work[_on]() which behaves similarly
to mod_timer() - if the delayed_work is idle, it's queued with the
given delay; otherwise, its timeout is modified to the new value.
Zero @delay guarantees immediate execution.

v2: Updated to reflect try_to_grab_pending() changes.  Now safe to be
    called from bh context.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
parent bbb68dfa

include/linux/workqueue.h

+4 −0
Original line number Diff line number Diff line
@@ -390,6 +390,10 @@ extern bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq, 
			struct delayed_work *work, unsigned long delay);

extern bool queue_delayed_work(struct workqueue_struct *wq,

			struct delayed_work *work, unsigned long delay);

extern bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,

			struct delayed_work *dwork, unsigned long delay);

extern bool mod_delayed_work(struct workqueue_struct *wq,

			struct delayed_work *dwork, unsigned long delay);



extern void flush_workqueue(struct workqueue_struct *wq);

extern void drain_workqueue(struct workqueue_struct *wq);

kernel/workqueue.c

+53 −0
Original line number Diff line number Diff line
@@ -1413,6 +1413,59 @@ bool queue_delayed_work(struct workqueue_struct *wq, 
}

EXPORT_SYMBOL_GPL(queue_delayed_work);



/**

 * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU

 * @cpu: CPU number to execute work on

 * @wq: workqueue to use

 * @dwork: work to queue

 * @delay: number of jiffies to wait before queueing

 *

 * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,

 * modify @dwork's timer so that it expires after @delay.  If @delay is

 * zero, @work is guaranteed to be scheduled immediately regardless of its

 * current state.

 *

 * Returns %false if @dwork was idle and queued, %true if @dwork was

 * pending and its timer was modified.

 *

 * This function is safe to call from any context other than IRQ handler.

 * See try_to_grab_pending() for details.

 */

bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,

			 struct delayed_work *dwork, unsigned long delay)

{

	unsigned long flags;

	int ret;



	do {

		ret = try_to_grab_pending(&dwork->work, true, &flags);

	} while (unlikely(ret == -EAGAIN));



	if (likely(ret >= 0)) {

		__queue_delayed_work(cpu, wq, dwork, delay);

		local_irq_restore(flags);

	}



	/* -ENOENT from try_to_grab_pending() becomes %true */

	return ret;

}

EXPORT_SYMBOL_GPL(mod_delayed_work_on);



/**

 * mod_delayed_work - modify delay of or queue a delayed work

 * @wq: workqueue to use

 * @dwork: work to queue

 * @delay: number of jiffies to wait before queueing

 *

 * mod_delayed_work_on() on local CPU.

 */

bool mod_delayed_work(struct workqueue_struct *wq, struct delayed_work *dwork,

		      unsigned long delay)

{

	return mod_delayed_work_on(WORK_CPU_UNBOUND, wq, dwork, delay);

}

EXPORT_SYMBOL_GPL(mod_delayed_work);



/**

 * worker_enter_idle - enter idle state

 * @worker: worker which is entering idle state