[Xcb] [Bug 23192] racy access to dpy->synchandler in libX11 >=

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Wed Apr 21 18:58:39 PDT 2010


--- Comment #10 from Jamey Sharp <jamey at minilop.net> 2010-04-21 18:58:39 PDT ---
(In reply to comment #9)
> One other thing I wondered at the time is to do with the assert( (dpy->flags &
> XlibDisplayPrivSync) != 0 )
> Are bitwise flag modifications gaurenteed to be atomic??? 
> Not all the other flags are modified within LockDisplays.
> ie Could a read/modify/write to one of the other flags make the
> XlibDisplayPrivSync flag un-thread-safe?

If dpy->flags is written to outside the lock, then yes, that's probably unsafe,
and theoretically ought to be fixed.

However, after the commit Josh mentioned, we don't use XlibDisplayPrivSync or
savedsynchandler at all in multi-threaded applications, so it is no longer a
problem for *this* part of the code. :-)

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