path: root/kernel
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authorStephen Boyd <sboyd@codeaurora.org>2013-06-13 11:39:50 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-12-08 07:29:27 -0800
commit7281bb5614bcdbf6789e9559420b814689b122e3 (patch)
tree404589dbfeafa8b21f4a4cc47d95aef382662290 /kernel
parent9bae8ea0544becdd8e6716b318c1844aeea41a69 (diff)
clockevents: Prefer CPU local devices over global devices
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@arm.com> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> Tested-by: soren.brinkmann@xilinx.com Cc: John Stultz <john.stultz@linaro.org> Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: linux-arm-kernel@lists.infradead.org Cc: John Stultz <john.stultz@linaro.org> Link: http://lkml.kernel.org/r/20130613183950.GA32061@codeaurora.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Kim Phillips <kim.phillips@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
1 files changed, 7 insertions, 2 deletions
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index e91f1019d66..086216c433f 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -234,8 +234,13 @@ static bool tick_check_preferred(struct clock_event_device *curdev,
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);