On 06/03/2013 10:33 PM, Stephen Boyd wrote: > 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. It is not clear the connection between the changelog, the patch and the comment. Could you clarify a bit ? Thanks -- Daniel > 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; > } > > -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog -- 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
