Re: [PATCHv7 01/11] clockevents: Prefer CPU local devices overglobal devices
From: Stephen Boyd
Date: Wed Jun 19 2013 - 12:30:55 EST
On 06/18, Mark Rutland wrote:
> 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.
Can you pick up the first two patches in this series please? And
preferably make a stable branch that can be pulled into arm-soc?
Then I can send the rest through the arm-soc tree.
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