Re: [BISECTED] drm: random hang since 620f378 "drm: prune modes when ..."

[Dave Airlie <airlied@redhat.com>]

On Tue, 2009-12-08 at 22:59 +0100, Arnd Bergmann wrote:
> On Monday 07 December 2009, Arnd Bergmann wrote:
> > After upgrading one of my machines to 2.6.32, I saw hangs after one to thirty minutes after
> > booting, with random data written to parts of the frame buffer. I've bisected it down
> > to 620f37811d "drm: prune modes when output is disconnected.", which was merged
> > in 2.6.32-rc1. Connecting a serial console does not reveal any output at the time of
> > the crash.
> > 
> > The machine uses an Intel G45 chipset with the i915 kernel mode setting enabled.
> > 
> > I have no clue what that patch does or why reverting it fixes the problem but 2.6.32
> > with this revert applied has not shown these hangs yet.
> > 
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> 
> Scratch this, the machine crashed again in the same way, but only after
> a some hours of uptime (normally it took a few minutes). It still looks like
>  this commit makes the bug much more likely, but it could also be
> attributed to complete coincedence and bad timing. 2.6.31 certainly never
> showed the problem and the bisection clearly pointed in the general direction
> of i915.
> 
> I hate debugging sporadic hangs...
> 
> Sorry for blaming the wrong patch, especially if it already caused a lot 
> of work. I'll try blaming ec2a4c3fdc8 "drm/i915: get the bridge device
> once" now, that is the next-best candidate that my bisection pointed to,
> but I'll do more rigorous testing.
> 

Btw is this just a laptop with no monitor plugged in?

just want to rule out the patch you mentioned for any sort of memory
corruption.

Dave.