From da863cddd831b0f4bf2d067f8b75254f1be94590 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Fri, 17 Feb 2012 23:39:33 +0100 Subject: [PATCH] PM / Sleep: Fix race conditions related to wakeup source timer function MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit If __pm_wakeup_event() has been used (with a nonzero timeout) to report a wakeup event and then __pm_relax() immediately followed by __pm_stay_awake() is called or __pm_wakeup_event() is called once again for the same wakeup source object before its timer expires, the timer function pm_wakeup_timer_fn() may still be run as a result of the previous __pm_wakeup_event() call. In either of those cases it may mistakenly deactivate the wakeup source that has just been activated. To prevent that from happening, make wakeup_source_deactivate() clear the wakeup source's timer_expires field and make pm_wakeup_timer_fn() check if timer_expires is different from zero and if it's not in future before calling wakeup_source_deactivate() (if timer_expires is 0, it means that the timer has just been deleted and if timer_expires is in future, it means that the timer has just been rescheduled to a different time). Reported-by: Arve Hjønnevåg Signed-off-by: Rafael J. Wysocki --- drivers/base/power/wakeup.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c index d279f46..b38bb9a 100644 --- a/drivers/base/power/wakeup.c +++ b/drivers/base/power/wakeup.c @@ -433,6 +433,7 @@ static void wakeup_source_deactivate(struct wakeup_source *ws) ws->max_time = duration; del_timer(&ws->timer); + ws->timer_expires = 0; /* * Increment the counter of registered wakeup events and decrement the @@ -487,11 +488,22 @@ EXPORT_SYMBOL_GPL(pm_relax); * pm_wakeup_timer_fn - Delayed finalization of a wakeup event. * @data: Address of the wakeup source object associated with the event source. * - * Call __pm_relax() for the wakeup source whose address is stored in @data. + * Call wakeup_source_deactivate() for the wakeup source whose address is stored + * in @data if it is currently active and its timer has not been canceled and + * the expiration time of the timer is not in future. */ static void pm_wakeup_timer_fn(unsigned long data) { - __pm_relax((struct wakeup_source *)data); + struct wakeup_source *ws = (struct wakeup_source *)data; + unsigned long flags; + + spin_lock_irqsave(&ws->lock, flags); + + if (ws->active && ws->timer_expires + && time_after_eq(jiffies, ws->timer_expires)) + wakeup_source_deactivate(ws); + + spin_unlock_irqrestore(&ws->lock, flags); } /** -- 2.7.4