On Thu, Jun 13, 2013 at 07:39:50PM +0100, Stephen Boyd wrote: > 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> I've just tested this atop of tip/timers/core on a tc2, using only the sp804. As previously, without the patch boot hangs, and with the patch I'm able to reach userspace and do useful things. Tested-by: Mark Rutland <mark.rutland@xxxxxxx> Thanks for working on this, Stephen. Mark. > --- > 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
