PM / Sleep: Fix race conditions related to wakeup source timer function
authorRafael J. Wysocki <rjw@sisk.pl>
Fri, 17 Feb 2012 22:39:33 +0000 (23:39 +0100)
committerArve Hjønnevåg <arve@android.com>
Sat, 17 Mar 2012 01:10:26 +0000 (18:10 -0700)
commit91b83809ffb978a4477c25dbef86a800149f2bd1
treed7a0b0e73e6640b165600bcf5559d8a9a63b5d41
parent649caa0ad80f49bbb7b90012433973809ead8826
PM / Sleep: Fix race conditions related to wakeup source timer function

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 <arve@android.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
drivers/base/power/wakeup.c