[PATCH v2] os: Fix timer race conditions

[Keith Packard]

Aaron Plattner <aplattner at nvidia.com> writes:

> From: Nikhil Mahale <nmahale at nvidia.com>
>
> Fixing following kind of race-conditions -
>
>     WaitForSomething()
>     |
>     ---->  // timers -> timer-1 -> timer-2 -> null
>            while (timers && (int) (timers->expires - now) <= 0)
>                // prototype - DoTimer(OsTimerPtr timer, CARD32 now, OsTimerPtr *prev)
>                DoTimer(timers, now, &timers)
>                |
>                |
>                ----> OsBlockSignals();  .... OS Signal comes just before blocking it,
>                                         .... timer-1 handler gets called.
>                                              // timer-1 gets served and scheduled again;
>                                              // timers -> timer-2 -> timer-1 -> null
>                                         ....
>                      *prev = timer->next;
>                       timer->next = NULL;   // timers -> null
>                       // timers list gets corrupted here and timer-2 gets removed from list.
>
> Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=86288
> Signed-off-by: Nikhil Mahale <nmahale at nvidia.com>
> Reviewed-by: Julien Cristau <jcristau at debian.org>
>
> v2: Apply warning fixes from Keith Packard <keithp at keithp.com>
>
> Reviewed-by: Aaron Plattner <aplattner at nvidia.com>
> Signed-off-by: Aaron Plattner <aplattner at nvidia.com>

Merged.
   58f28b0..fe4c774  master -> master

-- 
-keith
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