Red Hat Bugzilla – Bug 427810
libxcb deadlocks and ioerrors
Last modified: 2009-07-14 10:58:34 EDT
Description of problem:
multi threaded applications using a listener thread deadlock in libxcb
Version-Release number of selected component (if applicable):
libxcb-1.0.4 and forward
Try to start cinelerra, nearly every thread set deadlocks
Steps to Reproduce:
1. access cinelerra 1.2, compile, and run
several deadlocks, XNextEvent listener threads receive replies for
XTranslateCoordinates, but XNextEvent thread holds c->xlib.lock and
is not c->xlib.thread and so is locked by pthread_cond_wait(&c->xlib.cond,
&c->iolock), since reply thread cant access lock program hangs.
No deadlocks delivering reply
The loop that enforces current thread as requester is not needed. The principle
reason for the reply/event queues seem to be so that this operation is not required.
Additionally, when an error reply is returned, read_packet errantly updates
c->in.request_completed, causing poll_for_reply to later return a null reply
(if(request == c->in.request_completed)). This returns a few levels and causes
_XReply to report an errant IOError. It is not clear what the calling thread
should return from the code when a listener thread intercepts an error reply.
The patch was not well tested.
Created attachment 290986 [details]
Changing version to '9' as part of upcoming Fedora 9 GA.
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Fedora 9 changed to end-of-life (EOL) status on 2009-07-10. Fedora 9 is
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