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Re: XWin crash after the launch of startkde on a remote Red Hat 5 machine

On 18/09/2010 19:44, michel hummel wrote:
I have checked the code of the clipboard thread and the race condition
you talk about should not be a problem.
Before to start a new clipboard thread, the code waits for the end of
the first thread (pthread_join) then fixe the variable
g_fClipboardLaunched = FALSE;
g_fClipboardStarted = FALSE;

So the new thread will never be launched before the old one has terminated.

I have a proposition of modification to make the clipboard thread more robust.

1/ Adding a cleanup function which will be automaticaly called at the
end of the thread.
I purpose the use of the macro pthread_cleanup_push() pthread_cleanup_pop()

2/ You said that having a long-lived thread will be a good solution to
simplify the code.
I have an other proposition which needs less modification and can
simplify the code :
By using also here the macro pthread_cleanup_push() we can
automaticaly restart the thread on every unexpected exit.
We just have to delete this restart when the exit is expected (ie.
End of the function)
With this solution we don't have to take care about the thread
being killed by anyone, it will be restarted.

You will need to have some kind of back-off mechanism (i.e. a delay before retrying to connect) so that that this doesn't constantly try to connect if the server gets into a state where it can't accept the connection or the connection is constantly getting closed.

3/ An other thing I saw is that when the Xwindow part of the clipboard
is killed by an other application, the thread will still be alive but
the clipboard doesn't work anymore.
A solution can be :
when an winClipboardErrorHandler() is catched, check for
this Xwindow window and whenever this window doesn't exist anymore,
create a new one.

Would it not be simpler to restart the clipboard thread in this situation as well, rather than having code to recrate the window?

What do you think about my suggestions ?

I tested them and they seem to work as expected.
For example, I skipped the wrapper of XQueryTree (actualy needed for
xdmcp) and the clipboard is now working with xdmcp/gdm, etc.

If you don't like something in my propositions, please tell me what
and I will try to adapt it.

If you are interested in a patch doing this, I will be happy to give
it after a quick review and a clean

That would be great, thank you.

Volunteer Cygwin/X X Server maintainer

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