Bug#616301: xserver-xorg-video-radeon:screen goes black, system hangs after 2sec:[youtube(FF/Opera)-reset req.]

[Alex Deucher]

On Sun, Mar 6, 2011 at 1:36 PM, Ben Hutchings <ben at decadent.org.uk> wrote:
> On Sun, 2011-03-06 at 13:08 -0500, Alex Deucher wrote:
>> On Fri, Mar 4, 2011 at 8:50 PM, Ben Hutchings <ben at decadent.org.uk> wrote:
>> > On Fri, 2011-03-04 at 21:01 +0200, Faidon Liambotis wrote:
>> >> severity 616301 critical
>> >> thanks
>> >
>> > No, not unless it will affect a large proportion of users.
>> >
>> >> My system locks up whenever I click on a YouTube video link since
>> >> yesterday. I can probably live without YouTube :), but in any case this
>> >> shouldn't happen.
>> >>
>> >> This isn't a singled out case nor in exotic, possibly faulty, hardware.
>> >> It's on a standard 1½-year old Dell OptiPlex 780 desktop with a Radeon
>> >> HD card (one of the standard configurations) and this is on a stock
>> >> squeeze system.
>> >>
>> >> The findings so far seem to suggest this is a Mesa issue; I'd probably
>> >> file it under "Linux kernel bugs" (or even DoS bugs) but I'm not sure
>> >> where to properly file such bugs in the post-KMS stack world.
>> >
>> > If there is a kernel driver involved then it should be assigned to the
>> > kernel.  Even without KMS, a Mesa driver should be considered untrusted
>> > and should not be able to trigger a crash or hang.  With KMS, this
>> > applies to the X driver too.
>> >
>>
>> With or without KMS, the userspace acceleration drivers can certainly
>> cause GPU hangs if the 3D engine is programmed with some combination
>> of commands it doesn't like.
>
> You can't solve the halting problem but you can implement a watchdog,
> can't you?

We have lockup detection and asic reset support, but depending on the
lockup it may or may not be able to successfully reset the asic.
Also, as for the command buffer checking, we try to protect against
basic stupidity, but the chips are just too complex to check for every
possible scenario that might cause a hang.

Alex

>
> Ben.
>
> --
> Ben Hutchings
> Once a job is fouled up, anything done to improve it makes it worse.
>