Am 23.07.2014 10:01, schrieb Daniel Vetter:
On Wed, Jul 23, 2014 at 9:37 AM, Christian König
<christian.koenig@xxxxxxx> wrote:
Am 23.07.2014 09:31, schrieb Daniel Vetter:
On Wed, Jul 23, 2014 at 9:26 AM, Christian König
<deathsimple@xxxxxxxxxxx> wrote:
It's not a locking problem I'm talking about here. Radeons lockup
handling
kicks in when anything calls into the driver from the outside, if you
have a
fence wait function that's called from the outside but doesn't handle
lockups you essentially rely on somebody else calling another radeon
function for the lockup to be resolved.
So you don't have a timer in radeon that periodically checks whether
progress is still being made? That's the approach we're using in i915,
together with some tricks to kick any stuck waiters so that we can
reliably step in and grab locks for the reset.
We tried this approach, but it didn't worked at all.
I already considered trying it again because of the upcoming fence
implementation, but reconsidering that when a driver is forced to change
it's handling because of the fence implementation that's just another hint
that there is something wrong here.
Out of curiosity: What's the blocker for using a timer/scheduled work
to reset radeon? Getting this right on i915 has been fairly tricky and
we now have an elaborate multi-stage state machine to get the driver
through a reset. So always interested in different solutions.
IIRC we would have needed a quite advanced multi-stage state machine as
well and that was just to much overhead at this point.
One major problem was the power management in use back then, but that
got replaced by DPM in the meantime. So it might be a good idea to try
again.
What we currently do is marking the driver as "needs reset" and
returning -EAGAIN and then the next IOCTL starts the reset procedure
before doing anything else.
Christian.
-Daniel
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