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Commit 9a6b06c8 authored by Petr Mladek's avatar Petr Mladek Committed by Linus Torvalds
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kthread: allow to modify delayed kthread work 

There are situations when we need to modify the delay of a delayed kthread
work. For example, when the work depends on an event and the initial delay
means a timeout. Then we want to queue the work immediately when the event
happens.

This patch implements kthread_mod_delayed_work() as inspired workqueues.
It cancels the timer, removes the work from any worker list and queues it
again with the given timeout.

A very special case is when the work is being canceled at the same time.
It might happen because of the regular kthread_cancel_delayed_work_sync()
or by another kthread_mod_delayed_work(). In this case, we do nothing and
let the other operation win. This should not normally happen as the caller
is supposed to synchronize these operations a reasonable way.

Link: http://lkml.kernel.org/r/1470754545-17632-11-git-send-email-pmladek@suse.com


Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Borislav Petkov <bp@suse.de>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 37be45d4

include/linux/kthread.h

+4 −0
Original line number Diff line number Diff line
@@ -168,6 +168,10 @@ bool kthread_queue_delayed_work(struct kthread_worker *worker, 
				struct kthread_delayed_work *dwork,

				unsigned long delay);



bool kthread_mod_delayed_work(struct kthread_worker *worker,

			      struct kthread_delayed_work *dwork,

			      unsigned long delay);



void kthread_flush_work(struct kthread_work *work);

void kthread_flush_worker(struct kthread_worker *worker);

kernel/kthread.c

+53 −0
Original line number Diff line number Diff line
@@ -976,6 +976,59 @@ static bool __kthread_cancel_work(struct kthread_work *work, bool is_dwork, 
	return false;

}



/**

 * kthread_mod_delayed_work - modify delay of or queue a kthread delayed work

 * @worker: kthread worker to use

 * @dwork: kthread delayed work to queue

 * @delay: number of jiffies to wait before queuing

 *

 * If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise,

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

 * @work is guaranteed to be queued immediately.

 *

 * Return: %true if @dwork was pending and its timer was modified,

 * %false otherwise.

 *

 * A special case is when the work is being canceled in parallel.

 * It might be caused either by the real kthread_cancel_delayed_work_sync()

 * or yet another kthread_mod_delayed_work() call. We let the other command

 * win and return %false here. The caller is supposed to synchronize these

 * operations a reasonable way.

 *

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

 * See __kthread_cancel_work() and kthread_delayed_work_timer_fn()

 * for details.

 */

bool kthread_mod_delayed_work(struct kthread_worker *worker,

			      struct kthread_delayed_work *dwork,

			      unsigned long delay)

{

	struct kthread_work *work = &dwork->work;

	unsigned long flags;

	int ret = false;



	spin_lock_irqsave(&worker->lock, flags);



	/* Do not bother with canceling when never queued. */

	if (!work->worker)

		goto fast_queue;



	/* Work must not be used with >1 worker, see kthread_queue_work() */

	WARN_ON_ONCE(work->worker != worker);



	/* Do not fight with another command that is canceling this work. */

	if (work->canceling)

		goto out;



	ret = __kthread_cancel_work(work, true, &flags);

fast_queue:

	__kthread_queue_delayed_work(worker, dwork, delay);

out:

	spin_unlock_irqrestore(&worker->lock, flags);

	return ret;

}

EXPORT_SYMBOL_GPL(kthread_mod_delayed_work);



static bool __kthread_cancel_work_sync(struct kthread_work *work, bool is_dwork)

{

	struct kthread_worker *worker = work->worker;