libX11/XCB problems in Hardy

[Bryce Harrington]

On Sat, Jun 21, 2008 at 01:13:22PM +0200, Stefan Potyra wrote:
> Now this might be a red herring, and not related with this at all, but
> I've been having troubles with xcb in FAUmachine with hardy as well. It turned 
> out that file descriptors registered in blocking mode caused a hang in xcb 
> (which wasn't a problem in gutsy yet). Relevant file is at [1], and the diff 
> which solved it is [2].

While it's not evident to me either, it would not surprise me if the
root cause of this was related, since they both deal with blocking
situations.

Do the FAUmachine troubles occur 100% of the time or intermittently?
The Xubuntu folks were finding the issue to be intermittent, making us
think it's a race condition of some sort.

> If you think, that this might somehow be connected, and digging in that 
> direction might bring us closer to the issue, I could try to boild down the 
> relevant code parts to a minimal test case.

That would be great - it'd give us something we could give to upstream
to test against, and so we can validate new code from them to make sure
it doesn't have this problem.

(If anyone else knows of or has run across suspected libxcb issues,
I'll extend this to a general offer - send me your test cases and I'll
see to it that they pass before we put new libx11/xcb code into ubuntu.)

Bryce