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Commit d2540875 authored by Viresh Kumar's avatar Viresh Kumar Committed by Thomas Gleixner
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clockevents: Stop unused clockevent devices 



To avoid getting spurious interrupts on a tickless CPU, clockevent
device can now be stopped by switching to ONESHOT_STOPPED state.

The natural place for handling this transition is tick_program_event().

On 'expires == KTIME_MAX', we skip programming the event and so we need
to fix such call sites as well, to always call tick_program_event()
irrespective of the expires value.

Once the clockevent device is required again, check if it was earlier
put into ONESHOT_STOPPED state. If yes, switch its state to ONESHOT
before programming its event.

To make sure we haven't missed any corner case, add a WARN() for the
case where we try to reprogram clockevent device while we aren't
configured in ONESHOT_STOPPED state.

Signed-off-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
Cc: linaro-kernel@lists.linaro.org
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/5146b07be7f0bc497e0ebae036590ec2fa73e540.1428031396.git.viresh.kumar@linaro.org


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 8fff52fd

kernel/time/clockevents.c

+4 −0
Original line number Diff line number Diff line
@@ -331,6 +331,10 @@ int clockevents_program_event(struct clock_event_device *dev, ktime_t expires, 
	if (dev->state == CLOCK_EVT_STATE_SHUTDOWN)

		return 0;



	/* We must be in ONESHOT state here */

	WARN_ONCE(dev->state != CLOCK_EVT_STATE_ONESHOT, "Current state: %d\n",

		  dev->state);



	/* Shortcut for clockevent devices that can deal with ktime. */

	if (dev->features & CLOCK_EVT_FEAT_KTIME)

		return dev->set_next_ktime(expires, dev);

kernel/time/hrtimer.c

+2 −4
Original line number Diff line number Diff line
@@ -550,7 +550,6 @@ hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base, int skip_equal) 
	if (cpu_base->hang_detected)

		return;



	if (cpu_base->expires_next.tv64 != KTIME_MAX)

	tick_program_event(cpu_base->expires_next, 1);

}
@@ -1237,8 +1236,7 @@ retry: 
	raw_spin_unlock(&cpu_base->lock);



	/* Reprogramming necessary ? */

	if (expires_next.tv64 == KTIME_MAX ||

	    !tick_program_event(expires_next, 0)) {

	if (!tick_program_event(expires_next, 0)) {

		cpu_base->hang_detected = 0;

		return;

	}

kernel/time/tick-oneshot.c

+16 −0
Original line number Diff line number Diff line
@@ -28,6 +28,22 @@ int tick_program_event(ktime_t expires, int force) 
{

	struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);



	if (unlikely(expires.tv64 == KTIME_MAX)) {

		/*

		 * We don't need the clock event device any more, stop it.

		 */

		clockevents_set_state(dev, CLOCK_EVT_STATE_ONESHOT_STOPPED);

		return 0;

	}



	if (unlikely(dev->state == CLOCK_EVT_STATE_ONESHOT_STOPPED)) {

		/*

		 * We need the clock event again, configure it in ONESHOT mode

		 * before using it.

		 */

		clockevents_set_state(dev, CLOCK_EVT_STATE_ONESHOT);

	}



	return clockevents_program_event(dev, expires, force);

}