> ---------------------------------------------------------------------- > > Message: 1 > Date: Tue, 1 Jun 2010 12:25:42 -0700 (PDT) > From: bugzilla-daemon at freedesktop.org > Subject: [Bug 28341] Flickering screen in Neverball on > drm-radeon-testing > To: dri-devel at lists.freedesktop.org > Message-ID: <20100601192542.ACE5B1300E8 at annarchy.freedesktop.org> > Content-Type: text/plain; charset="UTF-8" > > https://bugs.freedesktop.org/show_bug.cgi?id=28341 > > --- Comment #3 from Magnus Jensen <magnus at jensenligan.se> > 2010-06-01 12:25:42 PDT --- > Sorry. ignore my last attachment. These errors continue to spawn > and i don't > think they are related to neverball. i'm going to recompile mesa > and ddx, and > post another dmesg soon. > Just waiting for a kernel compile to finish. >
I saw a similar flickering with latest Xorg stack (mesa master, xserver, ddx etc. master) and the 2.6.34 tree from radeon testing with my own toolkit on a R600 gpu. This setup uses the new dri sync & swap bits and changes how glXSwapbuffers works. My best hunch would be that submission of new rendering commands by the direct rendering client to the gpu doesn't block after a glXSwapbuffers() call until the bufferswap completed, i.e., some synchronization is missing there. This shows flickering, but load and timing dependent... .... glXXX rendering commands to draw image. glXSwapBuffers(); glBegin(GL_POINTS); glVertex2i(10,10); glEnd(); glFinish(); Take a swap completion timestamp here. glClear(); ...more rendering commands -> I use this glVertex2i, .... glFinish() sequence to wait for swap completion and get a timestamp. This works on any os/gpu combo ever tested, but doesn't seem to work reliably anymore with the new radeon sync & swap bits in place. Display flickers, presumably because the glClear() executes almost immediately after the glXSwapBuffers is scheduled, and before the bufferswap has actually taken place -> Clear the backbuffer before swapping. This however: .... glXXX rendering commands to draw image. glXSwapBuffers(); glXWaitForSbcOML(...); glClear(); ... does work, because the new glXWaitForSbcOML() blocks the client until swap completion, so glClear() can only get submitted to the gpu after the swap completed. [Except that glXWaitForSbcOML itself currently has a bug, for which i'll send a patch for xorg master/1.8.1 soon]. Didn't do detailed testing, but maybe this points into the right direction? best, -mario ********************************************************************* Mario Kleiner Max Planck Institute for Biological Cybernetics Spemannstr. 38 72076 Tuebingen Germany e-mail: mario.kleiner at tuebingen.mpg.de office: +49 (0)7071/601-1623 fax: +49 (0)7071/601-616 www: http://www.kyb.tuebingen.mpg.de/~kleinerm ********************************************************************* "For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." (Richard Feynman)
