[Xcb] xcb_wait_for_reply deadlocking with xcb_property_changed call

Nicholas Allen nick.allen at onlinehome.de
Sun Mar 28 05:45:17 PDT 2010

I added /usr/lib/debug/usr/lib to the start of the LD_LIBRARY_PATH
environment variable but now as soon as to run my program the JVM
crashes in Sun's native code where it tries to load the library.

So I'm not sure if I can get debug symbols for the stack traces but will
try a bit more and see if I can find some solution...


Jamey Sharp wrote:
> On Sat, Mar 27, 2010 at 4:30 AM, Nicholas Allen
> <nick.allen at onlinehome.de> wrote:
>> Unfortunately, I'm also experiencing these deadlocks when I call
>> xcb_wait_for_event even though I've called xcb_flush just before. I
>> thought it was only happening when I used the property util functions
>> but I now caught it under the debugger outside of this function. This
>> doesn't happen as often as with the property change helper library but
>> it still happens occasionally.
>> So it seems there is a major thread deadlocking bug in XCB. I don't
>> really know how to debug it though. Any suggestions? I'm not at all
>> familiar with the XCB code base so any pointers greatly appreciated...
> Can you get a wire protocol trace from a session that hangs? With
> xtrace, Wireshark, whatever.
> Also, can you "thread apply all bt full" in gdb once it hangs and send
> us that output? It'll help a lot if you have debugging symbols
> available for libxcb; on Debian systems, those are in the libxcb1-dbg
> package.
> As always, the most helpful thing would be a minimal C test case
> demonstrating the bug, but hopefully the protocol trace and the stack
> traces will be enough to start forming hypotheses about what's wrong.
> Jamey
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