X server not responding when querying X pointer position

[Daniel Stone]

Hi,

On Thu, Jul 07, 2011 at 11:17:57AM +0200, Thierry Reding wrote:
> I see strange behaviour with a program I'm developing. Basically the program
> embeds WebKit to display a graphical user-interface. Sometimes during testing
> (which is just playing around with some buttons on the screen) it happens that
> the GUI gets stuck completely.
> 
> Attaching to the program at runtime after reproducing the hang, I was able to
> get the following backtrace (paths shortened for readability):
> 
> 	(gdb) bt
> 	#2  0xb56939aa in poll () from /lib/libc.so.6
> 	#3  0xb55c2640 in _xcb_conn_wait (c=0x867a748, cond=0xbfe46ec0, vector=0x0, count=0x0)
> 	    at .../build/packages/xorg/lib/xcb/libxcb-1.7/src/xcb_conn.c:313
> 	#4  0xb55c3f87 in xcb_wait_for_reply (c=0x867a748, request=6396, e=0xbfe46f5c)
> 	    at .../build/packages/xorg/lib/xcb/libxcb-1.7/src/xcb_in.c:378
> 	#5  0xb761b458 in _XReply () from /usr/lib/libX11.so.6
> 	#6  0xb7610b5e in XQueryPointer () from /usr/lib/libX11.so.6
>       [...]
> 
> Looking at this there seems to be a problem when trying to display tooltips,
> possibly for one of the buttons being pressed/hovered over. My best guess is
> that for some reason, the X server is not responding to the XQueryPointer
> request.
> 
> I'm running this on X.Org server 1.10.2, with libX11 1.4.3 and libxcb 1.7. I'm
> also cross-compiling this from x86_64 to i786 if that is at all important.
> 
> Does anybody have any ideas about what might be the cause or do you have any
> pointers as to where I should look further? I can provide more information if
> needed. Also I wasn't sure whether or not to Cc the XCB mailing list on this
> because it seems more of an X server problem. I could be completely wrong of
> course.

The two most pertinent questions I can think of are:
    * are you using threads at all?
    * has someone else called XGrabServer()?

Cheers,
Daniel