linux-kernel - [patch 07/20] posix-timers: Set k_itimer::it

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Message-ID: <20230425183313.196462644@linutronix.de>
Date:   Tue, 25 Apr 2023 20:49:06 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Frederic Weisbecker <frederic@...nel.org>,
        Anna-Maria Behnsen <anna-maria@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Sebastian Siewior <bigeasy@...utronix.de>,
        syzbot+5c54bd3eb218bb595aa9@...kaller.appspotmail.com,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Michael Kerrisk <mtk.manpages@...il.com>
Subject: [patch 07/20] posix-timers: Set k_itimer::it_signal to NULL on exit()

Technically it's not required to set k_itimer::it_signal to NULL on exit()
because there is no other thread anymore which could lookup the timer
concurrently.

Set it to NULL for consistency sake and add a comment to that effect.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 kernel/time/posix-timers.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -1107,6 +1107,14 @@ static void itimer_delete(struct k_itime
 	}
 	list_del(&timer->list);
 
+	/*
+	 * Setting timer::it_signal to NULL is technically not required
+	 * here as nothing can access the timer anymore legitimately via
+	 * the hash table. Set it to NULL nevertheless so that all deletion
+	 * paths are consistent.
+	 */
+	WRITE_ONCE(timer->it_signal, NULL);
+
 	spin_unlock_irqrestore(&timer->it_lock, flags);
 	release_posix_timer(timer, IT_ID_SET);
 }