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Commit 474beb57 authored by NeilBrown's avatar NeilBrown Committed by Shaohua Li
Browse files

md/raid1,raid10: silence warning about wait-within-wait 



If you prepare_to_wait() after a previous prepare_to_wait(),
but before calling schedule(), you get warning:

  do not call blocking ops when !TASK_RUNNING; state=2

This is appropriate as it is often a bug.  The event that the
first prepare_to_wait() expects might wake up the schedule following
the second prepare_to_wait(), which could be confusing.

However if both prepare_to_wait()s are part of simple wait_event()
loops, and if the inner one is rarely called, then there is
no problem.  The inner loop is too simple to get confused by
a stray wakeup, and the outer loop won't spin unduly because the
inner doesnt affect it often.

This pattern occurs in both raid1.c and raid10.c in the use of
flush_pending_writes().

The warning can be silenced by setting current->state to TASK_RUNNING.

Signed-off-by: default avatarNeilBrown <neilb@suse.com>
Signed-off-by: default avatarShaohua Li <shli@fb.com>
parent d5d885fd

drivers/md/raid1.c

+11 −0
Original line number Diff line number Diff line
@@ -815,6 +815,17 @@ static void flush_pending_writes(struct r1conf *conf) 
		bio = bio_list_get(&conf->pending_bio_list);

		conf->pending_count = 0;

		spin_unlock_irq(&conf->device_lock);



		/*

		 * As this is called in a wait_event() loop (see freeze_array),

		 * current->state might be TASK_UNINTERRUPTIBLE which will

		 * cause a warning when we prepare to wait again.  As it is

		 * rare that this path is taken, it is perfectly safe to force

		 * us to go around the wait_event() loop again, so the warning

		 * is a false-positive.  Silence the warning by resetting

		 * thread state

		 */

		__set_current_state(TASK_RUNNING);

		blk_start_plug(&plug);

		flush_bio_list(conf, bio);

		blk_finish_plug(&plug);

drivers/md/raid10.c

+12 −0
Original line number Diff line number Diff line
@@ -900,6 +900,18 @@ static void flush_pending_writes(struct r10conf *conf) 
		bio = bio_list_get(&conf->pending_bio_list);

		conf->pending_count = 0;

		spin_unlock_irq(&conf->device_lock);



		/*

		 * As this is called in a wait_event() loop (see freeze_array),

		 * current->state might be TASK_UNINTERRUPTIBLE which will

		 * cause a warning when we prepare to wait again.  As it is

		 * rare that this path is taken, it is perfectly safe to force

		 * us to go around the wait_event() loop again, so the warning

		 * is a false-positive. Silence the warning by resetting

		 * thread state

		 */

		__set_current_state(TASK_RUNNING);



		blk_start_plug(&plug);

		/* flush any pending bitmap writes to disk

		 * before proceeding w/ I/O */