This is a note to let you know that I've just added the patch titled
clockevents: Prefer CPU local devices over global devices
to the 3.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
clockevents-prefer-cpu-local-devices-over-global-devices.patch
and it can be found in the queue-3.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 70e5975d3a04be5479a28eec4a2fb10f98ad2785 Mon Sep 17 00:00:00 2001
From: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>
Date: Thu, 13 Jun 2013 11:39:50 -0700
Subject: clockevents: Prefer CPU local devices over global devices
From: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>
commit 70e5975d3a04be5479a28eec4a2fb10f98ad2785 upstream.
On an SMP system with only one global clockevent and a dummy
clockevent per CPU we run into problems. We want the dummy
clockevents to be registered as the per CPU tick devices, but
we can only achieve that if we register the dummy clockevents
before the global clockevent or if we artificially inflate the
rating of the dummy clockevents to be higher than the rating
of the global clockevent. Failure to do so leads to boot
hangs when the dummy timers are registered on all other CPUs
besides the CPU that accepted the global clockevent as its tick
device and there is no broadcast timer to poke the dummy
devices.
If we're registering multiple clockevents and one clockevent is
global and the other is local to a particular CPU we should
choose to use the local clockevent regardless of the rating of
the device. This way, if the clockevent is a dummy it will take
the tick device duty as long as there isn't a higher rated tick
device and any global clockevent will be bumped out into
broadcast mode, fixing the problem described above.
Reported-and-tested-by: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>
Tested-by: soren.brinkmann@xxxxxxxxxx
Cc: John Stultz <john.stultz@xxxxxxxxxx>
Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: John Stultz <john.stultz@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/20130613183950.GA32061@xxxxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Kim Phillips <kim.phillips@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/time/tick-common.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -234,8 +234,13 @@ static bool tick_check_preferred(struct
return false;
}
- /* Use the higher rated one */
- return !curdev || newdev->rating > curdev->rating;
+ /*
+ * Use the higher rated one, but prefer a CPU local device with a lower
+ * rating than a non-CPU local device
+ */
+ return !curdev ||
+ newdev->rating > curdev->rating ||
+ !cpumask_equal(curdev->cpumask, newdev->cpumask);
}
/*
Patches currently in stable-queue which might be from sboyd@xxxxxxxxxxxxxx are
queue-3.10/clockevents-prefer-cpu-local-devices-over-global-devices.patch
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