Keith Whitwell wrote: > On Tue, 2009-03-17 at 03:56 -0700, José Fonseca wrote: > >> On Tue, 2009-03-17 at 03:39 -0700, Thomas Hellstrom wrote: >> >>> Thomas Hellström wrote: >>> >>>> Hi! >>>> >>>> I'm currently looking into the thread-safety of the dri drivers. In >>>> particular the calls to libX11. >>>> >>>> It appears that many of the applications I've tried have issues with >>>> deadlocks in the XCB code. >>>> It looks like this might be an issue with the locking order of >>>> XLockDisplay() and driver mutexes. >>>> >>>> In particular, if the application protects all glx calls with >>>> XLockDisplay() the driver might deadlock in a normal GL call: >>>> >>>> Thread A: >>>> XLockDisplay() -> glxXXX -> driver mutex -> Xlib call -> Xcb >>>> XLockdisplay(). >>>> Thread B >>>> Normal GL call -> driver mutex -> Xlib call -> Xcb XLockDisplay(). >>>> >>>> So we have a locking order reversal between the driver mutex and >>>> XLockDisplay which causes a deadlock. >>>> >>>> Now, it seems like a simple away around this would be to omit the >>>> application XLockDisplays() completely. However, that seems to cause >>>> issues with XPending and XNextEvent eating the reply data meant for >>>> XSync(), leaving XSync waiting locked in a select(). >>>> >>>> I guess the remedy is to have the DRI utility routines and drivers >>>> protect _all_ X calls with XLockDisplay(). >>>> >>>> Does anyone have thoughts / insights about this? >>>> >>>> Thanks, >>>> Thomas >>>> >>>> >>>> >>>> >>> Hmm, >>> I installed a non-XCB Xlib and all problems just vanished... >>> Don't mind the above. >>> >> So is this a XCB problem? >> > > XCB is pretty much the default now & given that it was supposed to > resolve the threading issues with old Xlib, I don't think that this > means the issue goes away... > > Keith > > Yes, as far as I can tell, this is an xcb problem, and it should pretty much affect all our drivers.
I guess this needs to be fixed asap. I'll see if I can come up with a non-GL X app that reproduces the problem. Basically it should show up if the main thread is running a loop that calls XNextEvent(), while other threads are calling XSync / XGetGeometry() on windows. /Thomas ------------------------------------------------------------------------------ Apps built with the Adobe(R) Flex(R) framework and Flex Builder(TM) are powering Web 2.0 with engaging, cross-platform capabilities. Quickly and easily build your RIAs with Flex Builder, the Eclipse(TM)based development software that enables intelligent coding and step-through debugging. Download the free 60 day trial. http://p.sf.net/sfu/www-adobe-com _______________________________________________ Mesa3d-dev mailing list Mesa3d-dev@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mesa3d-dev
