PM-runtime: Fix deadlock when canceling hrtimer

When rpm_resume() desactivates the autosuspend timer, it should only
try to cancel hrtimer but not wait for the handler to finish, because
both rpm_resume() and pm_suspend_timer_fn() take the power.lock.

A deadlock is possible as follows:

CPU0                              CPU1
rpm_resume()
  spin_lock_irqsave
                                  pm_suspend_timer_fn()
                                    spin_lock_irqsave
  pm_runtime_deactivate_timer()
    hrtimer_cancel()

It is sufficient to call hrtimer_try_to_cancel() from
pm_runtime_deactivate_timer(), because dev->power.timer_expires
reset to 0 by it, so use that function instead of hrtimer_cancel().

Fixes: 8234f6734c5d ("PM-runtime: Switch autosuspend over to using hrtimers")
Reported-by: Sunzhaosheng Sun(Zhaosheng) <sunzhaosheng@hisilicon.com>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
[ rjw: Changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index 0ea2139..ccd296d 100644 (file)
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -95,7 +95,7 @@ static void __update_runtime_status(struct device *dev, enum rpm_status status)
 static void pm_runtime_deactivate_timer(struct device *dev)
 {
        if (dev->power.timer_expires > 0) {
-               hrtimer_cancel(&dev->power.suspend_timer);
+               hrtimer_try_to_cancel(&dev->power.suspend_timer);
                dev->power.timer_expires = 0;
        }
 }