Xrandr loop with gnome-settings-daemon [WAS: Re: Intel GM45: Loop of continuously triggered output detections]

[Peter Clifton]

On Wed, 2009-01-14 at 10:14 +0000, Peter Clifton wrote:
> On Tue, 2009-01-13 at 18:32 +0000, Peter Clifton wrote:
> > On Tue, 2009-01-13 at 09:08 -0800, Jesse Barnes wrote:
> > > On Tuesday, January 13, 2009 6:58 am Peter Clifton wrote:
> > > > On Tue, 2009-01-13 at 17:26 +0800, Jin, Gordon wrote:
> > > > > Peter Clifton wrote on Tuesday, January 13, 2009 11:45 AM:
> > > > > > On Tue, 2009-01-13 at 01:55 +0000, Peter Clifton wrote:
> > > > > >> Testing git HEAD intel drivers, also recent Xorg:
> > > > > >>
> > > > > >>
> > > > > >> After the problem with miss-detected TV-out, I killed Xorg with a
> > > > > >> Ctrl +Alt+Backspace (I've got zapping re-enabled in my xorg.conf),
> > > > > >> and the outputs detected properly, with no TV output detected as
> > > > > >> being connected.
> > > > > >>
> > > > > >> The performance was very slow, however, and with the characteristic
> > > > > >> "jiggle" / jittering of the mouse cursor position which I've
> > > > >
> > > > > noticed
> > > > >
> > > > > >> on both my Intel based machines during output detection.
> > > > > >>
> > > > > >> Trying xrandr, adjusting brightness, had no effect. A couple of VT
> > > > > >> switches to VT1 and back to Xorg finally stopped the detection
> > > > >
> > > > > loop,
> > > > >
> > > > > >> although during that process, one of the the switches to VT1 left
> > > > >
> > > > > me
> > > > >
> > > > > >> with a corrupted console. (Possibly scanning out from the wrong
> > > > >
> > > > > part
> > > > >
> > > > > >> of the frame-buffer, perhaps with the wrong sync settings?).
> > > > > >>
> > > > > >> I've attached the log. It does show a page-table problem with the
> > > > > >> last VT switch.
> > > > > >
> > > > > > I managed to re-trigger this bug by pulling the laptop's AC power
> > > > > > adaptor out, and plugging it back in again. I suspect either an ACPI
> > > > > > event, or something inside HP's SMM BIOS code triggered it. My old
> > > > >
> > > > > HP
> > > > >
> > > > > > nc 6320 didn't properly respect _DOS bit 4, so would always fiddle
> > > > > > with the graphics hardware when you plugged / unplugged the AC
> > > > > > adaptor.
> > > > > >
> > > > > > I've not dug deeply into this one, so I'm not quite blaming the BIOS
> > > > > > yet, however it is looking somewhat guilty.
> > > > >
> > > > > This looks similar to
> > > > > http://bugs.freedesktop.org/show_bug.cgi?id=19431, interesting bug.
> > > >
> > > > It only bears very supercficial similarities as far as I can see.
> > > >
> > > > Yes, I had a problem with intermittent TV out detection, but that
> > > > doesn't appear to be dependent on battery state.
> > > >
> > > > My problem is that "something" (often triggered by an AC state change,
> > > > but sometimes just when I boot up) is triggering a storm of probes to
> > > > detect outputs. I did wonder if this might be due to a faulty detection
> > > > routine trying to spot that I inserted a cable in one of the outputs,
> > > > however this backtrace I grabbed whilst the problem was occuring
> > > > suggests that it is being dispatched through the X server:
> > > >
> > > > #0  0xb809e430 in __kernel_vsyscall ()
> > > > #1  0xb7ce7700 in __nanosleep_nocancel () from /lib/tls/i686/cmov/libc.so.6
> > > > #2  0xb7d24ffc in usleep () from /lib/tls/i686/cmov/libc.so.6
> > > > #3  0xb7ab826e in i830WaitForVblank (pScreen=0xa197040) at
> > > > ../../src/i830_display.c:379 #4  0xb7abaf80 in i830_crtc_mode_set
> > > > (crtc=0xa199b80, mode=0xbfdb9ea0, adjusted_mode=0xa4d70e8, x=0, y=0) at
> > > > ../../src/i830_display.c:1511 #5  0x080ed08d in xf86CrtcSetModeTransform
> > > > (crtc=0xa199b80, mode=0xbfdb9ea0, rotation=1, transform=0x0, x=0, y=0) at
> > > > ../../../../hw/xfree86/modes/xf86Crtc.c:366
> > > > #6  0x080ed6d6 in xf86CrtcSetMode (crtc=0xa199b80, mode=0xbfdb9ea0,
> > > > rotation=8180, x=0, y=0) at ../../../../hw/xfree86/modes/xf86Crtc.c:413 #7 
> > > > 0xb7ab956d in i830GetLoadDetectPipe (output=0xa19b618, mode=0xbfdb9ea0,
> > > > dpms_mode=0xbfdb9f78) at ../../src/i830_display.c:1811 #8  0xb7ad746d in
> > > > i830_tv_detect (output=0xa19b618) at ../../src/i830_tv.c:1376 #9 
> > > > 0x080eda90 in xf86ProbeOutputModes (scrn=0xa197040, maxX=4096, maxY=4096)
> > > > at ../../../../hw/xfree86/modes/xf86Crtc.c:1500 #10 0x080f56c0 in
> > > > xf86RandR12GetInfo12 (pScreen=0xa19c460, rotations=0xbfdba16a) at
> > > > ../../../../hw/xfree86/modes/xf86RandR12.c:1255 #11 0x08162e89 in RRGetInfo
> > > > (pScreen=0xa19c460) at ../../randr/rrinfo.c:196 #12 0x08167084 in
> > > > ProcRRGetScreenSizeRange (client=0xa3d2208) at ../../randr/rrscreen.c:227
> > > > #13 0x0815f305 in ProcRRDispatch (client=0x0) at ../../randr/randr.c:473
> > > > #14 0x0808cdbf in Dispatch () at ../../dix/dispatch.c:437
> > > > #15 0x08071aad in main (argc=10, argv=0xbfdba324, envp=Cannot access memory
> > > > at address 0x8 ) at ../../dix/main.c:383
> > > >
> > > >
> > > > Does anyone know if there is an easy way to ascertain from a backtrace,
> > > > which client caused a particular dispatch? (Perhaps chasing back
> > > > through /proc/ or netstat to find out more info on the actual process
> > > > involved?
> > > 
> > > Well, the randr functions are in the backtrace, so it's possible some 
> > > application is triggering the re-probe.  That doesn't mean your BIOS isn't 
> > > causing trouble though: it could be sending ACPI events that are getting 
> > > picked up by some app which is then doing a re-probe.  You should be able to 
> > > check out your ACPI daemon log or use acpi_listen to see if that's happening.
> > 
> > Turns out that the problem probes are sent by gnome-settings-daemon.
> > I've yet to figure out why they are triggered.
> > 
> > acpi_listen didn't show anything untoward (other than that my HP 6730
> > laptop doesn't bother emitting LID events when I open / close the lid).
> > 
> > Killing gnome-settings daemon and then restarting it from within my
> > session seems to have calmed it down somewhat. I can't persuade the loop
> > to re-trigger again this session since I did that.
> 
> Ok, seems that every time I change brightness with a hotkey, I get an
> Xrandr notification, which cause gnome-settings-daemon to round-trip,
> requesting XRRGetScreenSizeRange, which in turn causes a monitor
> reprobe.

Also, it might be useful to note, that I only tend to get the corrupted
console symptom when doing a VT switch whilst this Xrandr probe loop is
running. Once I've killed gnome-settings-daemon, I can VT switch
(usually giving a corrupt console), at which point, any backlog of
events appears to be dropped. Further VT7 / VT1 switches don't appear to
result in corruption.


-- 
Peter Clifton

Electrical Engineering Division,
Engineering Department,
University of Cambridge,
9, JJ Thomson Avenue,
Cambridge
CB3 0FA

Tel: +44 (0)7729 980173 - (No signal in the lab!)