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Commit 06ab015d authored by Petr Mladek's avatar Petr Mladek Committed by Sasha Levin
Browse files

kthread_worker: split code for canceling the delayed work timer 

commit 34b3d5344719d14fd2185b2d9459b3abcb8cf9d8 upstream.

Patch series "kthread_worker: Fix race between kthread_mod_delayed_work()
and kthread_cancel_delayed_work_sync()".

This patchset fixes the race between kthread_mod_delayed_work() and
kthread_cancel_delayed_work_sync() including proper return value
handling.

This patch (of 2):

Simple code refactoring as a preparation step for fixing a race between
kthread_mod_delayed_work() and kthread_cancel_delayed_work_sync().

It does not modify the existing behavior.

Link: https://lkml.kernel.org/r/20210610133051.15337-2-pmladek@suse.com


Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
Cc: <jenhaochen@google.com>
Cc: Martin Liu <liumartin@google.com>
Cc: Minchan Kim <minchan@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent d77c9c85

kernel/kthread.c

+29 −17
Original line number Diff line number Diff line
@@ -1020,20 +1020,15 @@ void kthread_flush_work(struct kthread_work *work) 
EXPORT_SYMBOL_GPL(kthread_flush_work);



/*

 * This function removes the work from the worker queue. Also it makes sure

 * that it won't get queued later via the delayed work's timer.

 *

 * The work might still be in use when this function finishes. See the

 * current_work proceed by the worker.

 * Make sure that the timer is neither set nor running and could

 * not manipulate the work list_head any longer.

 *

 * Return: %true if @work was pending and successfully canceled,

 *	%false if @work was not pending

 * The function is called under worker->lock. The lock is temporary

 * released but the timer can't be set again in the meantime.

 */

static bool __kthread_cancel_work(struct kthread_work *work, bool is_dwork,

static void kthread_cancel_delayed_work_timer(struct kthread_work *work,

					      unsigned long *flags)

{

	/* Try to cancel the timer if exists. */

	if (is_dwork) {

	struct kthread_delayed_work *dwork =

		container_of(work, struct kthread_delayed_work, work);

	struct kthread_worker *worker = work->worker;
@@ -1051,6 +1046,23 @@ static bool __kthread_cancel_work(struct kthread_work *work, bool is_dwork, 
	work->canceling--;

}



/*

 * This function removes the work from the worker queue. Also it makes sure

 * that it won't get queued later via the delayed work's timer.

 *

 * The work might still be in use when this function finishes. See the

 * current_work proceed by the worker.

 *

 * Return: %true if @work was pending and successfully canceled,

 *	%false if @work was not pending

 */

static bool __kthread_cancel_work(struct kthread_work *work, bool is_dwork,

				  unsigned long *flags)

{

	/* Try to cancel the timer if exists. */

	if (is_dwork)

		kthread_cancel_delayed_work_timer(work, flags);



	/*

	 * Try to remove the work from a worker list. It might either

	 * be from worker->work_list or from worker->delayed_work_list.