[Xcb] xcb 1.1 dead lock

Jamey Sharp jamey at minilop.net
Sat Dec 15 21:39:03 PST 2007

Hash: SHA1

On 12/13/07, Todd Goyen <tgoyen at swri.org> wrote:
> Hello All,

Hi Todd!

> I am using Debian Unstable with XCB 1.1 from experimental.

I assume you mean libX11 from experimental, and libxcb 1.1 from
unstable? If you're still running libxcb 1.0, please make sure you can
reproduce this bug with libxcb 1.1. We did fix a deadlock in that
release, but I think not this deadlock.

> I have seen a dead lock with the following backtraces. The program
> uses QT-4.3.3 and calls XInitThreads before anything else is
> performed. The threads are used with the nVidia driver to  separate
> OpenGL contexts and keep them synced to VBlank. In this case there
> were 24 threads 11 of which are OpenGL rendering threads, 1 is the
> GUI, and 12 are timers. It appears as though XTranslateCoordinates in
> the main GUI thread caused the deadlock. Any ideas would be helpful.

Augh. I believe I've seen this same deadlock using `ico -threads 3` or
higher, but I haven't been able to work out the cause, let alone a fix.
Since an application that matters is encountering it, I guess we'd
better hurry up and fix it, eh? sigh. If you have experience debugging
deadlocks, I believe the problem is mostly confined to process_responses
in xcb_io.c, and any insight you can provide would be appreciated.

Thanks for the complete backtrace. We'll let you know when there's a fix
you can test; in the meantime, is this application one that we can get a
copy of?

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