Bug 86288

Created attachment 109479 [details] [review]
[PATCH] os: Fix timer race conditions

Now patch is merged, should status be updated?

Reference: http://cgit.freedesktop.org/xorg/xserver/commit/?id=fe4c774c572e3f55a7417f0ca336ae1479a966ad

It would be great to update status so this flows to Ubuntu's bug tracker.

Yeah, it should.  Thanks for the ping.

Marking fixed with commit fe4c774c572e3f55a7417f0ca336ae1479a966ad
Author: Nikhil Mahale <nmahale@nvidia.com>
Date:   Sat Jan 24 17:06:59 2015 -0800

    os: Fix timer race conditions
    
    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@nvidia.com>
    Reviewed-by: Julien Cristau <jcristau@debian.org>
    
    v2: Apply warning fixes from Keith Packard <keithp@keithp.com>
    
    Reviewed-by: Aaron Plattner <aplattner@nvidia.com>
    Signed-off-by: Aaron Plattner <aplattner@nvidia.com>
    Signed-off-by: Keith Packard <keithp@keithp.com>

 os/WaitFor.c | 41 ++++++++++++++++++++++++++---------------
 1 file changed, 26 insertions(+), 15 deletions(-)