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    Subject[PATCH 2/3] PM / Sleep: Fix race conditions related to wakeup source timer function
    From: Rafael J. Wysocki <>

    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

    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(-)

    Index: linux/drivers/base/power/wakeup.c
    --- linux.orig/drivers/base/power/wakeup.c
    +++ linux/drivers/base/power/wakeup.c
    @@ -433,6 +433,7 @@ static void wakeup_source_deactivate(str
    ws->max_time = duration;

    + 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);

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      Last update: 2012-02-15 23:23    [W:0.024 / U:5.160 seconds]
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