application using Xv extension with multiple windows freezes the X server when these overlaps

[Amos Tibaldi]

Hello, I am trying to develop an application using more than one Xv
extension enabled window. These display images each one. All works
correctly except when the windows overlaps: the content of the window
are destroyed when the Expose Event of the window is managed with an
XShmPutImage. I have used valgrind checking for memory leakages and
for bad thread synchronization but everything is ok for that debugger.
So what am I suppose to try next? When the x server freezes the only
possibility is to reset the computer. The same is for an ubuntu 8.04
64bit and for an ubuntu 7.10 32bit, both with ati original driver and
fglrx.ko kernel object.

How can I debug the problem if the x server freezes? I have also tried
to use XSynchronize at xlib initialization and to define one my error
callback function but nothing has worked. May be there is some
debugging tool for debugging xlib in such situation?

Thanks in advance, any help is appreciated,

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Amos Tibaldi