Shell locks up

[Michal Hruby]

Shell can randomly lock up after a while of playing with it, see the attached trace of all threads when the lock up happened (of note are threads 5 and 13, which are waiting on a condition variable and semaphore).

[Michał Sawicz (saviq)]

It's obviously pretty difficult to reproduce. Thanks for the trace, Michal. Both look like Qt lockups, look like they will be pretty difficult to track down :/

[Michał Sawicz (saviq)]

One other effect of this seems to be "empty scope views". I.e. you can switch between scopes, but some of them are just empty.

Would be good to verify this still happens with Qt 5.1.

[Michał Sawicz (saviq)]

Please, anyone, put steps to reproduce, if found...

[Pat McGowan (pat-mcgowan)]

I saw this twice in the past two days on image 60. In both cases the shell restarted first and then soon after when using it more it hung.
I had around 5 or 6 apps open, just using normally.

[Albert Astals Cid (aacid)]

In thread 5 we have QQuickRenderThreadSingleContextWindowManager which is gone in Qt 5.1 in a commit whose text says:

commit ebe8b9408cfcd953fae80514aa67e49221541bed
Author: Gunnar Sletta <email address hidden>
Date: Wed Dec 5 06:27:47 2012 -0800

    Complete rewrite of threaded render loop.

    This change starts using the superior implementation of the scene graph
    render loop which has been worked on in the scenegraph-playground
    project for a while. It uses a far more straightforward locking/sync
    paradigm compared to the existing one and is less deadlock and error
    prone. It also enables the scene graph thread to run on its own when
    the GUI thread is blocked, enabling threaded animations.

    This changes also introduces a naming change inside Qt Quick from
    "Window Manager" -> "Render Loop" as that fits better to what the
    code does.

    Change-Id: I1c2170ee04fcbef79660bd7dae6cace647cdb276
    Reviewed-by: Samuel Rødal <email address hidden>

Note the "is less deadlock and error prone"

[Daniel Holbach (dholbach)]

For me this happened in image 65 on maguro when I tried to close some apps. Saviq and tsdgeos have the core file of the unity8 process, when it happened.

[Launchpad Janitor (janitor)]

[Expired for Unity 8 because there has been no activity for 60 days.]