PM / Sleep: Fix possible infinite loop during wakeup source destruction
If wakeup_source_destroy() is called for an active wakeup source that is never deactivated, it will spin forever. To prevent that from happening, make wakeup_source_destroy() call __pm_relax() for the wakeup source object it is about to free instead of waiting until it will be deactivated by someone else. However, for this to work it also needs to make sure that the timer function will not be executed after the final __pm_relax(), so make it run del_timer_sync() on the wakeup source's timer beforehand. Additionally, update the kerneldoc comment to document the requirement that __pm_stay_awake() and __pm_wakeup_event() must not be run in parallel with wakeup_source_destroy(). Reported-by: Arve Hjønnevåg <arve@android.com> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
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@ -74,22 +74,17 @@ EXPORT_SYMBOL_GPL(wakeup_source_create);
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/**
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* wakeup_source_destroy - Destroy a struct wakeup_source object.
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* @ws: Wakeup source to destroy.
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*
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* Callers must ensure that __pm_stay_awake() or __pm_wakeup_event() will never
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* be run in parallel with this function for the same wakeup source object.
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*/
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void wakeup_source_destroy(struct wakeup_source *ws)
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{
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if (!ws)
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return;
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spin_lock_irq(&ws->lock);
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while (ws->active) {
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spin_unlock_irq(&ws->lock);
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schedule_timeout_interruptible(msecs_to_jiffies(TIMEOUT));
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spin_lock_irq(&ws->lock);
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}
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spin_unlock_irq(&ws->lock);
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del_timer_sync(&ws->timer);
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__pm_relax(ws);
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kfree(ws->name);
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kfree(ws);
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}
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