linux-kernel - [PATCH 1/2] nohz: Add hrtimer sanity check

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Message-Id: <1495201910-12466-2-git-send-email-fweisbec@gmail.com>
Date:   Fri, 19 May 2017 15:51:49 +0200
From:   Frederic Weisbecker <fweisbec@...il.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Rik van Riel <riel@...hat.com>,
        James Hartsock <hartsjc@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>, stable@...r.kernel.org,
        Tim Wright <tim@...bash.co.uk>, Pavel Machek <pavel@....cz>
Subject: [PATCH 1/2] nohz: Add hrtimer sanity check

Make sure that the clockevent device is never programmed to a deadline
later than the tick.

Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Tim Wright <tim@...bash.co.uk>
Cc: Pavel Machek <pavel@....cz>
Cc: James Hartsock <hartsjc@...hat.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Rik van Riel <riel@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/time/tick-sched.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 64c97fc..d212bb6 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -771,8 +771,13 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
 	tick = expires;
 
 	/* Skip reprogram of event if its not changed */
-	if (ts->tick_stopped && (expires == dev->next_event))
-		goto out;
+	if (ts->tick_stopped) {
+		if (hrtimer_active(&ts->sched_timer))
+			WARN_ON_ONCE(hrtimer_get_expires(&ts->sched_timer) < dev->next_event);
+
+		if (expires == dev->next_event)
+			goto out;
+	}
 
 	/*
 	 * nohz_stop_sched_tick can be called several times before
-- 
2.7.4