On 06/13, Thomas Gleixner wrote: > On Thu, 13 Jun 2013, Daniel Lezcano wrote: > > I prefer Thomas to have a look at it and ack it. I changed Cc to To for > > Thomas. > > The patch does not apply on tip timers/core. The code has been > reworked a month ago. Please work against tip timers/core. That's > where this stuff ends up. > Ah, I thought your patch series had stalled. Here is a refreshed patch. Every other patch in this series applies cleanly to tip timers/core so I don't want to resend them again unless absolutely necessary. -----8<----- Subject: [PATCH v8] clockevents: Prefer CPU local devices over global devices 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-by: Mark Rutland <mark.rutland@xxxxxxx> Cc: John Stultz <john.stultz@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> Signed-off-by: Stephen Boyd <sboyd@xxxxxxxxxxxxxx> --- kernel/time/tick-common.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c index 5edfb48..edd45f6 100644 --- a/kernel/time/tick-common.c +++ b/kernel/time/tick-common.c @@ -243,8 +243,13 @@ 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); } /* -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
