linux-kernel - [PATCH AUTOSEL 6.3 1/3] refscale: Move shutdown from wait_event() to wait_event

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Date:   Fri, 28 Apr 2023 21:58:48 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     "Paul E. McKenney" <paulmck@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Sasha Levin <sashal@...nel.org>, dave@...olabs.net,
        josh@...htriplett.org, frederic@...nel.org,
        quic_neeraju@...cinc.com, rcu@...r.kernel.org
Subject: [PATCH AUTOSEL 6.3 1/3] refscale: Move shutdown from wait_event() to wait_event_idle()

From: "Paul E. McKenney" <paulmck@...nel.org>

[ 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@...nel.org>
Signed-off-by: Boqun Feng <boqun.feng@...il.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 afa3e1a2f6902..1970ce5f22d40 100644
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -1031,7 +1031,7 @@ 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