linux-kernel - [PATCH v2 1/1] dm-delay: fix hung task introduced by kthread mode

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Date: Mon,  6 May 2024 09:25:23 +0200
From: Joel Colledge <joel.colledge@...bit.com>
To: Christian Loehle <christian.loehle@....com>
Cc: Benjamin Marzinski <bmarzins@...hat.com>,
	dm-devel@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/1] dm-delay: fix hung task introduced by kthread mode

If the worker thread is not woken due to a bio, then it is not woken at
all. This causes the hung task check to trigger. This occurs, for
instance, when no bios are submitted. Also when a delay of 0 is
configured, delay_bio() returns without waking the worker.

Prevent the hung task check from triggering by creating the thread with
kthread_run() instead of using kthread_create() directly.

Fixes: 70bbeb29fab0 ("dm delay: for short delays, use kthread instead of timers and wq")
Signed-off-by: Joel Colledge <joel.colledge@...bit.com>
---
 drivers/md/dm-delay.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/md/dm-delay.c b/drivers/md/dm-delay.c
index 5eabdb06c649..eac166405b6b 100644
--- a/drivers/md/dm-delay.c
+++ b/drivers/md/dm-delay.c
@@ -267,8 +267,7 @@ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 		 * In case of small requested delays, use kthread instead of
 		 * timers and workqueue to achieve better latency.
 		 */
-		dc->worker = kthread_create(&flush_worker_fn, dc,
-					    "dm-delay-flush-worker");
+		dc->worker = kthread_run(&flush_worker_fn, dc, "dm-delay-flush-worker");
 		if (IS_ERR(dc->worker)) {
 			ret = PTR_ERR(dc->worker);
 			dc->worker = NULL;
-- 
2.34.1