[Bug 13938] New: i915 vblank interrupts not always working

[<bug...@fr...>]

http://bugs.freedesktop.org/show_bug.cgi?id=13938

           Summary: i915 vblank interrupts not always working
           Product: Mesa
           Version: CVS
          Platform: Other
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Drivers/DRI/i915
        AssignedTo: dri...@li...
        ReportedBy: ds...@sc...


chipset: 945GM
versions: * from git master

When running anything GL related on the CRT output, I get:

do_wait: drmWaitVBlank returned -1, IRQs don't seem to be working correctly.
Try running with LIBGL_THROTTLE_REFRESH and LIBL_SYNC_REFRESH unset.

This appears after a 3 second timeout.  Backtrace during the timeout:

ginger:~/xorg/jhbuild/git/mesa/progs/xdemos$ gdb ./glxgears
GNU gdb 6.6-debian
Copyright (C) 2006 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i486-linux-gnu"...
Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".
(gdb) r
Starting program: /home/ds/xorg/jhbuild/git/mesa/progs/xdemos/glxgears 
[Thread debugging using libthread_db enabled]
[New Thread -1214105920 (LWP 7690)]

Program received signal SIGINT, Interrupt.
[Switching to Thread -1214105920 (LWP 7690)]
0xffffe410 in __kernel_vsyscall ()
(gdb) bt
#0  0xffffe410 in __kernel_vsyscall ()
#1  0xb7d3e8b9 in ioctl () from /lib/tls/i686/cmov/libc.so.6
#2  0xb7a4b9ae in drmWaitVBlank (fd=6, vbl=0xbfb21d24) at xf86drm.c:1857
#3  0xb780d1a2 in do_wait (vbl=0xfffffffc, vbl_seq=0xbfb21d24, fd=-1072667590)
    at ../common/vblank.c:282
#4  0xb780d27c in driDrawableInitVBlank (priv=0x8056e98)
    at ../common/vblank.c:336
#5  0xb7830d6f in intelMakeCurrent (driContextPriv=0x80536b0, 
    driDrawPriv=0x8056e98, driReadPriv=0x8056e98) at intel_context.c:679
#6  0xb780df84 in driBindContext (ctx=0x80570c4, pdraw=0x8085cc0, 
    pread=0x8085cc0) at ../common/dri_util.c:213
#7  0xb7e1642e in MakeContextCurrent (dpy=0x804c008, draw=58720258, 
    read=58720258, gc=0x8057010) at glxext.c:1647
#8  0xb7e166fc in glXMakeCurrent (dpy=0x804c008, draw=58720258, gc=0x8057010)
    at glxext.c:1822
#9  0x0804a3fe in main (argc=1, argv=0xbfb220d4) at glxgears.c:601


Right after an X restart, the LVDS output does not show this problem.  However,
after running xrandr several times, they both show the problem.


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