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From: Sudeep Holla <>
To:, Thomas Gleixner <>
Cc: Sudeep Holla <>,
	Frederic Weisbecker <>
Subject: [PATCH] tick: prefer a lower rating device only if it's CPU local device
Date: Wed,  9 May 2018 17:02:08 +0100	[thread overview]
Message-ID: <> (raw)

Checking the equality of cpumask for both new and old tick device doesn't
ensure that it's CPU local device. This will cause issue if a low rating
clockevent tick device is registered first followed by the registration
of higher rating clockevent tick device.

In such case, clockevents_released list will never get emptied as both
the devices get selected as preferred one and we will loop forever in

Cc: Frederic Weisbecker <>
Cc: Thomas Gleixner <>
Signed-off-by: Sudeep Holla <>
 kernel/time/tick-common.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Hi Thomas,

I am seeing this issue on my Juno devboard, where system wide timers
with rating 300 and 400 are registered in same order and we get stuck in
a loop in clockevents_notify_released. Let me know if this looks sane or
you have any suggestions that I can try out.


diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 49edc1c4f3e6..78e598334007 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -277,7 +277,8 @@ static bool tick_check_preferred(struct clock_event_device *curdev,
 	return !curdev ||
 		newdev->rating > curdev->rating ||
-	       !cpumask_equal(curdev->cpumask, newdev->cpumask);
+	       (!cpumask_equal(curdev->cpumask, newdev->cpumask) &&
+	        !tick_check_percpu(curdev, newdev, smp_processor_id()));


             reply	other threads:[~2018-05-09 16:02 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-09 16:02 Sudeep Holla [this message]
2018-05-13 13:09 ` [tip:timers/core] tick: Prefer " tip-bot for Sudeep Holla
2018-07-02 23:44 ` [PATCH] tick: prefer " Kevin Hilman
2018-07-03 10:53   ` Sudeep Holla
2018-07-03 15:04     ` Kevin Hilman
2018-07-03 15:44       ` Sudeep Holla
2018-07-03 16:08         ` Thomas Gleixner
2018-07-03 16:48           ` Sudeep Holla
2018-07-08 20:59             ` Martin Blumenstingl
2018-07-09 15:12               ` Sudeep Holla

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