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Date:   Thu, 11 May 2023 21:41:30 +0000
In-Reply-To: <20230406194053.876844-1-arve@android.com>
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References: <20230406194053.876844-1-arve@android.com>
Message-ID: <20230511214144.1924757-1-jstultz@google.com>
Subject: [PATCH] sched/wait: Fix a kthread_park race with wait_woken()
From:   John Stultz <jstultz@google.com>
To:     LKML <linux-kernel@vger.kernel.org>
Cc:     "=?UTF-8?q?Arve=20Hj=C3=B8nnev=C3=A5g?=" <arve@android.com>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Valentin Schneider <vschneid@redhat.com>,
        John Stultz <jstultz@google.com>
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From: Arve Hj=C3=B8nnev=C3=A5g <arve@android.com>

kthread_park and wait_woken have a similar race that kthread_stop and
wait_woken used to have before it was fixed in
cb6538e740d7543cd989128625cf8cac4b471e0a. Extend that fix to also cover
kthread_park.

Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Signed-off-by: Arve Hj=C3=B8nnev=C3=A5g <arve@android.com>
Signed-off-by: John Stultz <jstultz@google.com>
---
This seemingly slipped by, so I wanted to resend it
for review.
---
 kernel/sched/wait.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
index 133b74730738..a9cf49da884b 100644
--- a/kernel/sched/wait.c
+++ b/kernel/sched/wait.c
@@ -425,9 +425,9 @@ int autoremove_wake_function(struct wait_queue_entry *w=
q_entry, unsigned mode, i
 }
 EXPORT_SYMBOL(autoremove_wake_function);
=20
-static inline bool is_kthread_should_stop(void)
+static inline bool is_kthread_should_stop_or_park(void)
 {
-	return (current->flags & PF_KTHREAD) && kthread_should_stop();
+	return (current->flags & PF_KTHREAD) && (kthread_should_stop() || kthread=
_should_park());
 }
=20
 /*
@@ -459,7 +459,7 @@ long wait_woken(struct wait_queue_entry *wq_entry, unsi=
gned mode, long timeout)
 	 * or woken_wake_function() sees our store to current->state.
 	 */
 	set_current_state(mode); /* A */
-	if (!(wq_entry->flags & WQ_FLAG_WOKEN) && !is_kthread_should_stop())
+	if (!(wq_entry->flags & WQ_FLAG_WOKEN) && !is_kthread_should_stop_or_park=
())
 		timeout =3D schedule_timeout(timeout);
 	__set_current_state(TASK_RUNNING);
=20
--=20
2.40.1.606.ga4b1b128d6-goog