[regression] Deadlock in TimeoutFrameDroppingPolicy logic results in frozen unity8

[kevin gunn]

spawning from bug 1417773 "Unity8 completely frozen (unable to unlock, receive calls, etc)"

See Saviq's comment #4 & 5, duflu's comment #7 in bug 1417773

[Alan Griffiths (alan-griffiths)]

Is there any reason to believe that Saviq's comment #4 and Saviq's comment #5 relate to the same problem?

duflu's comment makes sense for https://bugs.launchpad.net/ubuntu-rtm/+source/unity8/+bug/1417773/comments/4 but not for https://bugs.launchpad.net/ubuntu-rtm/+source/unity8/+bug/1417773/comments/5 or the earlier comment by rsalveti.

[Cemil Azizoglu (cemil-azizoglu)]

Adding AlbertA's analysis.

<AlbertA> @vogons: looks like the issue is the TimerGSource aquires a read-lock, dispatches it (i.e. alarm fired), gets pre-empted
--> JohnLea_ (<email address hidden>) has joined #mir
<AlbertA> @vogons: compositor_release fires (from compositor thread), acquires buffer queue mutex
 @vogons: attempts to cancel alarm but deadlocks because the previous alarm handler is waiting for the buffer queue mutex and cannot aquire a write lock to the GTimerSource mutex

[Cemil Azizoglu (cemil-azizoglu)]

Attaching the relevant backtrace :

[PS Jenkins bot (ps-jenkins)]

Fix committed into lp:mir at revision None, scheduled for release in mir, milestone 0.12.0

[Daniel van Vugt (vanvugt)]

Alberto says this was a regression, introduced in 0.9.0 with glib main loop.

[Launchpad Janitor (janitor)]

This bug was fixed in the package mir - 0.12.0+15.04.20150228-0ubuntu1

---------------
mir (0.12.0+15.04.20150228-0ubuntu1) vivid; urgency=medium

  [ Alberto Aguirre ]
  * New upstream release 0.12.0 (https://launchpad.net/mir/+milestone/0.12.0)
    - Packaging changes:
      . Client platform packages now include the Mir client platform ABI
        number. Thusly, mir-client-platform-(mesa|android) is replaced by
        mir-client-platform-(mesa|android)2
      . Server graphics platform packages now include the Mir graphics
        platform ABI number. Thusly, mir-platform-graphics-(mesa|android)
        is replaced by mir-platform-graphics-(mesa|android)1
    - ABI summary: Servers need rebuilding, but clients do not;
      . Mirclient ABI unchanged at 8
      . Mircommon ABI unchanged at 3
      . Mirplatform ABI unchanged at 6
      . Mirserver ABI bumped to 30
    - Bug fixes:
      . [regression] Platform libraries and packages are not versioned thus
        are not installable in parallel (LP: #1423591)
      . [regression] Deadlock in TimeoutFrameDroppingPolicy logic (LP: #1421255)

  [ CI Train Bot ]
  * New rebuild forced.
 -- CI Train Bot <email address hidden> Sat, 28 Feb 2015 10:30:53 +0000