linux-kernel - Re: [PATCH 1/2] tick: broadcast: Deny per-cpu clockevents from being broadcast sources

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Message-ID: <53ddc00f-1033-481b-be37-978bd4410c10@TX2EHSMHS034.ehs.local>
Date:	Fri, 13 Sep 2013 08:25:19 -0700
From:	Sören Brinkmann <soren.brinkmann@...inx.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Rob Herring <rob.herring@...xeda.com>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Stephen Warren <swarren@...dotorg.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Russell King <linux@....linux.org.uk>,
	Michal Simek <michal.simek@...inx.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Stephen Boyd <sboyd@...eaurora.org>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/2] tick: broadcast: Deny per-cpu clockevents from being
 broadcast sources

On Fri, Sep 13, 2013 at 04:45:12PM +0200, Thomas Gleixner wrote:
> On Thu, 12 Sep 2013, Sören Brinkmann wrote:
> > On Thu, Sep 12, 2013 at 10:30:15PM +0200, Thomas Gleixner wrote:
> > I gave it a shot. Is this what you imagine:
> > diff --git a/drivers/clocksource/arm_global_timer.c b/drivers/clocksource/arm_global_timer.c
> > index b66c1f3..c639b1a 100644
> > --- a/drivers/clocksource/arm_global_timer.c
> > +++ b/drivers/clocksource/arm_global_timer.c
> > @@ -169,7 +169,8 @@ static int gt_clockevents_init(struct clock_event_device *clk)
> >         int cpu = smp_processor_id();
> >  
> >         clk->name = "arm_global_timer";
> > -       clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
> > +       clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
> > +               CLOCK_EVT_FEAT_PERCPU;
> >         clk->set_mode = gt_clockevent_set_mode;
> >         clk->set_next_event = gt_clockevent_set_next_event;
> >         clk->cpumask = cpumask_of(cpu);
> > diff --git a/include/linux/clockchips.h b/include/linux/clockchips.h
> > index 0857922..493aa02 100644
> > --- a/include/linux/clockchips.h
> > +++ b/include/linux/clockchips.h
> > @@ -60,6 +60,7 @@ enum clock_event_mode {
> >   * Core shall set the interrupt affinity dynamically in broadcast mode
> >   */
> >  #define CLOCK_EVT_FEAT_DYNIRQ          0x000020
> > +#define CLOCK_EVT_FEAT_PERCPU          0x000040
> >  
> >  /**
> >   * struct clock_event_device - clock event device descriptor
> > diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
> > index d3539e5..de4c5d8 100644
> > --- a/kernel/time/tick-broadcast.c
> > +++ b/kernel/time/tick-broadcast.c
> > @@ -70,16 +70,14 @@ static bool tick_check_broadcast_device(struct clock_event_device *curdev,
> >                                         struct clock_event_device *newdev)
> >  {
> >         if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
> > -           (newdev->features & CLOCK_EVT_FEAT_C3STOP))
> > +           (newdev->features & CLOCK_EVT_FEAT_C3STOP) ||
> > +           (newdev->features & CLOCK_EVT_FEAT_PERCPU))
> >                 return false;
> >  
> >         if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT &&
> >             !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
> >                 return false;
> >  
> > -       if (cpumask_equal(newdev->cpumask, cpumask_of(smp_processor_id())))
> > -               return false;
> > -
> >         return !curdev || newdev->rating > curdev->rating;
> >  }
> > 
> > If this is the way to go, I can prepare this in a v2.
> 
> Looks good to me. The last junk of the patch won't apply on mainline,
> but thats the least of my worries. :)

Of course. I'll split this into smaller chunks and send out a v2.

	Thanks,
	Sören


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