[PATCH 2/7] md: fix a race condition when stopping the sync thread

[Mikulas Patocka <mpatocka@redhat.com>]

Note that md_wakeup_thread_directly is racy - it will do nothing if the
thread is already running or it may cause spurious wake-up if the thread
is blocked in another subsystem.

In order to eliminate the race condition, we will retry
md_wakeup_thread_directly after 0.1 seconds.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org	# v6.7
Fixes: 130443d60b1b ("md: refactor idle/frozen_sync_thread() to fix deadlock")

---
 drivers/md/md.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

Index: linux-2.6/drivers/md/md.c
===================================================================
--- linux-2.6.orig/drivers/md/md.c
+++ linux-2.6/drivers/md/md.c
@@ -4889,6 +4889,7 @@ static void stop_sync_thread(struct mdde
 
 	mddev_unlock(mddev);
 
+retry:
 	set_bit(MD_RECOVERY_INTR, &mddev->recovery);
 	/*
 	 * Thread might be blocked waiting for metadata update which will now
@@ -4898,9 +4899,11 @@ static void stop_sync_thread(struct mdde
 	if (work_pending(&mddev->sync_work))
 		flush_work(&mddev->sync_work);
 
-	wait_event(resync_wait,
+	if (!wait_event_timeout(resync_wait,
 		   !test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) ||
-		   (check_seq && sync_seq != atomic_read(&mddev->sync_seq)));
+		   (check_seq && sync_seq != atomic_read(&mddev->sync_seq)),
+		   HZ / 10))
+		goto retry;
 
 	if (locked)
 		mddev_lock_nointr(mddev);