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> Tested-by: Mark Rutland <mark.rutland@xxxxxxx> Tested-by: Sören Brinkmann <soren.brinkmann@xxxxxxxxxx> Acked-by: Marc Zyngier <marc.zyngier@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 | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c index 5d3fb10..3da62de 100644 --- a/kernel/time/tick-common.c +++ b/kernel/time/tick-common.c @@ -254,9 +254,10 @@ static int tick_check_new_device(struct clock_event_device *newdev) !(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) goto out_bc; /* - * Check the rating + * Check the rating, but prefer CPU local devices */ - if (curdev->rating >= newdev->rating) + if (curdev->rating >= newdev->rating && + cpumask_equal(curdev->cpumask, newdev->cpumask)) goto out_bc; } -- The Qualcomm Innovation Center, Inc. is a member of the 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
