PM-runtime: Fix deadlock when canceling hrtimer

vingu-linaro · rafaeljw · commit 74fb44863084 · 2019-02-21T10:29:00.000+01:00
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: 8234f67 ("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
@@ -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;
 	}
 }

Original file line number	Diff line number	Diff line change
`@@ -95,7 +95,7 @@ static void __update_runtime_status(struct device *dev, enum rpm_status status)`
`95`	`95`	`static void pm_runtime_deactivate_timer(struct device *dev)`
`96`	`96`	`{`
`97`	`97`	`if (dev->power.timer_expires > 0) {`
`98`		`- hrtimer_cancel(&dev->power.suspend_timer);`
	`98`	`+ hrtimer_try_to_cancel(&dev->power.suspend_timer);`
`99`	`99`	`dev->power.timer_expires = 0;`
`100`	`100`	`}`
`101`	`101`	`}`