[PATCH AUTOSEL 5.15 1/2] refscale: Move shutdown from wait_event() to wait_event_idle()

[Sasha Levin]

From: "Paul E. McKenney" <paulmck@xxxxxxxxxx>

[ Upstream commit 6bc6e6b27524304aadb9c04611ddb1c84dd7617a ]

The ref_scale_shutdown() kthread/function uses wait_event() to wait for
the refscale test to complete.  However, although the read-side tests
are normally extremely fast, there is no law against specifying a very
large value for the refscale.loops module parameter or against having
a slow read-side primitive.  Either way, this might well trigger the
hung-task timeout.

This commit therefore replaces those wait_event() calls with calls to
wait_event_idle(), which do not trigger the hung-task timeout.

Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Signed-off-by: Boqun Feng <boqun.feng@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 kernel/rcu/refscale.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index 66dc14cf5687e..5abb0cf52803a 100644
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -777,7 +777,7 @@ ref_scale_cleanup(void)
 static int
 ref_scale_shutdown(void *arg)
 {
-	wait_event(shutdown_wq, shutdown_start);
+	wait_event_idle(shutdown_wq, shutdown_start);
 
 	smp_mb(); // Wake before output.
 	ref_scale_cleanup();
-- 
2.39.2