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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: 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>
This commit is contained in:
Viresh Kumar 2015-04-03 09:04:05 +05:30 committed by Thomas Gleixner
parent 8fff52fd50
commit d25408756a
3 changed files with 22 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
kernel/time/clockevents.c
View File

@ -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);

6
kernel/time/hrtimer.c
View File

@ -550,8 +550,7 @@ 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);
tick_program_event(cpu_base->expires_next, 1);
}
/*
@ -1237,8 +1236,7 @@ void hrtimer_interrupt(struct clock_event_device *dev)
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;
}

16
kernel/time/tick-oneshot.c
View File

@ -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);
}