On Sun, Feb 08, 2015 at 02:10:07AM -0800, Kenneth Graunke wrote: > On Friday, February 06, 2015 08:25:44 AM Chris Wilson wrote: > > Once we have chosen the target CRTC, check for an error when querying > > the current MSC so we can report the error before attempting to record > > the uninitialised MSC/UST, and subsequently feeding garbage values to > > drmWaitVBlank. > > > > Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk> > > --- > > present/present.c | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/present/present.c b/present/present.c > > index 1ce587e..4a1cf0c 100644 > > --- a/present/present.c > > +++ b/present/present.c > > @@ -727,7 +727,9 @@ present_pixmap(WindowPtr window, > > else if (!target_crtc) > > target_crtc = present_get_crtc(window); > > > > - present_get_ust_msc(screen, target_crtc, &ust, &crtc_msc); > > + ret = present_get_ust_msc(screen, target_crtc, &ust, &crtc_msc); > > + if (ret) > > + return ret; > > > > target_msc = present_window_to_crtc_msc(window, target_crtc, > > window_msc, crtc_msc); > > You've definitely found a bug here. Some drivers' get_ust_msc hooks > (UXA, modesetting) return BadMatch and leave crtc_msc uninitialized. > At which point we'd happily continue and use rubbish values. > > I discovered this today as well, when using valgrind to try and debug > some crashes in xf86-video-modesetting using my 'pageflip' branch: > [term1]# valgrind --vgdb-error=1 X > [term2]# gdb > [term2](gdb) target remote | vgdb > [term2](gdb) c > [term3]$ DISPLAY=:0 glxgears -fullscreen & > [term3]$ DISPLAY=:0 xset force dpms off > <hit a key to DPMS on> > > valgrind will complain about the uninitialized values in the crtc_msc >= > target_msc branch. > > But...is an early return really the right thing to do? I tested this > with xf86-video-modesetting and my 'pageflip' branch, and it caused > "glxgears -fullscreen" to die from a BadMatch error after a single DPMS > cycle. I tried changing it to 'return Success', and that caused it to > stop drawing altogether. I also tried it with UXA+DRI3, and it seemed > to break there as well. So it seems like we need to do something more.
The previous patch fixes that bug. -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ xorg-devel@lists.x.org: X.Org development Archives: http://lists.x.org/archives/xorg-devel Info: http://lists.x.org/mailman/listinfo/xorg-devel