linux-kernel - [PATCH rcu v2 10/10] refscale: Move shutdown from wait_event() to wait_event

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Message-Id: <20230323043935.1221184-11-boqun.feng@gmail.com>
Date:   Wed, 22 Mar 2023 21:39:35 -0700
From:   Boqun Feng <boqun.feng@...il.com>
To:     rcu@...r.kernel.org
Cc:     Davidlohr Bueso <dave@...olabs.net>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Josh Triplett <josh@...htriplett.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Shuah Khan <shuah@...nel.org>,
        Bhaskar Chowdhury <unixbhaskar@...il.com>,
        Boqun Feng <boqun.feng@...il.com>,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: [PATCH rcu v2 10/10] refscale: Move shutdown from wait_event() to wait_event_idle()

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

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>
---
 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 afa3e1a2f690..1970ce5f22d4 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();
-- 
2.38.1