Bug 427810

Summary: libxcb deadlocks and ioerrors
Product: [Fedora] Fedora Reporter: William P. Morrow <morroww6>
Component: libxcbAssignee: Adam Jackson <ajax>
Status: CLOSED WONTFIX QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: medium Docs Contact:
Priority: low    
Version: 9   
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Hardware: All   
OS: Linux   
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Last Closed: 2009-07-14 14:58:34 UTC Type: ---
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Description Flags
deadlocks/ioerrors patch none

Description William P. Morrow 2008-01-07 17:26:39 UTC 
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

How reproducible:
Try to start cinelerra, nearly every thread set deadlocks

Steps to Reproduce:
1. access cinelerra 1.2, compile, and run
 
Actual results:
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.

Expected results:
No deadlocks delivering reply

Additional info:
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.
Comment 1 William P. Morrow 2008-01-07 17:26:39 UTC 
Created attachment 290986 [details]
deadlocks/ioerrors patch
Comment 2 Bug Zapper 2008-05-14 04:19:35 UTC 
Changing version to '9' as part of upcoming Fedora 9 GA.
More information and reason for this action is here:
http://fedoraproject.org/wiki/BugZappers/HouseKeeping
Comment 3 Bug Zapper 2009-06-09 23:21:08 UTC 
This message is a reminder that Fedora 9 is nearing its end of life.
Approximately 30 (thirty) days from now Fedora will stop maintaining
and issuing updates for Fedora 9.  It is Fedora's policy to close all
bug reports from releases that are no longer maintained.  At that time
this bug will be closed as WONTFIX if it remains open with a Fedora 
'version' of '9'.

Package Maintainer: If you wish for this bug to remain open because you
plan to fix it in a currently maintained version, simply change the 'version' 
to a later Fedora version prior to Fedora 9's end of life.

Bug Reporter: Thank you for reporting this issue and we are sorry that 
we may not be able to fix it before Fedora 9 is end of life.  If you 
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Comment 4 Bug Zapper 2009-07-14 14:58:34 UTC 
Fedora 9 changed to end-of-life (EOL) status on 2009-07-10. Fedora 9 is 
no longer maintained, which means that it will not receive any further 
security or bug fix updates. As a result we are closing this bug.

If you can reproduce this bug against a currently maintained version of 
Fedora please feel free to reopen this bug against that version.

Thank you for reporting this bug and we are sorry it could not be fixed.