clockevents: Stop unused clockevent devices (d2540875) · Commits · 戴 / test

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:

Viresh 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:

Thomas Gleixner <tglx@linutronix.de>

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);
		}

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