On Thu, Jul 31, 2014 at 04:37:14PM +0000, Mcaulay, Alistair wrote:
> Hi Daniel,
>
> Something more like this then? (and revert the change to intel_ring_begin(),
> putting it back to how it was )
Yeah, roughly. Except that I would place the reload_in_reset wrapping in
the i915_reset function. It is paramount that we never leak this outside
of the dev->struct_mutex protection so that other threads can't ever
observe this to be set. So putting it right next to the mutex locking is
better.
Also I think you've wrapped the wrong function - the re-init is done in
i915_gem_init_hw, this here just resets the software state (mostly) and is
done before the actual gpu hw reset is done. gem_init_hw is only run if
the reset succeeds.
-Daniel
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 991b663..b811ff2 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1217,6 +1217,9 @@ struct i915_gpu_error {
>
> /* For missed irq/seqno simulation. */
> unsigned int test_irq_rings;
> +
> + /* Used to prevent gem_check_wedged returning -EAGAIN during gpu reset
> */
> + bool reload_in_progress;
> };
>
> enum modeset_restore {
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index b38e086..a25d3b5 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1085,7 +1085,9 @@ i915_gem_check_wedge(struct i915_gpu_error *error,
> if (i915_terminally_wedged(error))
> return -EIO;
>
> - return -EAGAIN;
> + /* Check if GPU Reset is in progress */
> + if (!error->reload_in_reset)
> + return -EAGAIN;
> }
>
> return 0;
> @@ -2579,6 +2581,8 @@ void i915_gem_reset(struct drm_device *dev)
> struct intel_engine_cs *ring;
> int i;
>
> + /* Used to prevent gem_check_wedged returning -EAGAIN during gpu reset
> */
> + dev_priv->gpu_error.reload_in_reset = true;
> /*
> * Before we free the objects from the requests, we need to inspect
> * them for finding the guilty party. As the requests only borrow
> @@ -2591,6 +2595,8 @@ void i915_gem_reset(struct drm_device *dev)
> i915_gem_reset_ring_cleanup(dev_priv, ring);
>
> i915_gem_restore_fences(dev);
> +
> + dev_priv->gpu_error.reload_in_reset = false;
> }
>
>
> -----Original Message-----
> From: Daniel Vetter [mailto:[email protected]] On Behalf Of Daniel Vetter
> Sent: Wednesday, July 30, 2014 10:01 PM
> To: Mcaulay, Alistair
> Cc: Daniel Vetter; Chris Wilson; Ben Widawsky; [email protected]
> Subject: Re: [Intel-gfx] [PATCH] drm/i915: Rework GPU reset sequence to match
> driver load & thaw
>
> On Wed, Jul 30, 2014 at 04:59:33PM +0000, Mcaulay, Alistair wrote:
> > Hi Daniel,
> >
> > could you please be clearer on the change you mean. I think you mean
> > something functionally equivalent to the code below, but done in a less
> > hacky way.
> > (This slight change has made no change to test results) Or is the idea
> > to return at a different point to this?
> > I couldn't find " dev_priv->mm.reload_in_reset or similar" in the
> > code. The only thing I can find is error->reset_counter, which is used
> > in check_wedge(). Bottom bit set means RESET_IN_PROGRESS, top bit
> > means WEDGED
>
> Well I've meant that you have to add a new dev_prive->mm.realod_in_reset.
> And the below won't work since in all other places but when doing a gpu reset
> we want the -EAGAIN to reach callers. Actually it's really important that if
> we have an -EGAIN we don't eat it.
>
> And I guess the check for mm.reload_in_reset should actually be in
> gem_check_wedged.
> -Daniel
>
> >
> >
> > --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> > +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> > @@ -1832,7 +1832,9 @@ int intel_ring_begin(struct intel_engine_cs
> > *ring,
> >
> > ret = i915_gem_check_wedge(&dev_priv->gpu_error,
> > dev_priv->mm.interruptible);
> > - if (ret)
> > +
> > + /* -EAGAIN means a reset is in progress, it is Ok to return */
> > + if (ret == -EAGAIN)
> > + return 0;
> > + if (ret)
> > + return ret;
> >
> > ret = __intel_ring_prepare(ring, num_dwords * sizeof(uint32_t));
> >
> > Alistair.
> >
> > -----Original Message-----
> > From: Intel-gfx [mailto:[email protected]] On
> > Behalf Of Daniel Vetter
> > Sent: Tuesday, July 29, 2014 11:33 AM
> > To: Chris Wilson; Daniel Vetter; Ben Widawsky;
> > [email protected]
> > Subject: Re: [Intel-gfx] [PATCH] drm/i915: Rework GPU reset sequence
> > to match driver load & thaw
> >
> > On Tue, Jul 29, 2014 at 08:36:33AM +0100, Chris Wilson wrote:
> > > On Mon, Jul 28, 2014 at 11:26:38AM +0200, Daniel Vetter wrote:
> > > > Oh, I guess that's the tricky bit why the old approach never
> > > > worked
> > > > - because reset_in_progress is set we failed the context/ppgtt
> > > > loading through the rings and screwed up.
> > > >
> > > > Problem with your approach is that we want to bail out here if a
> > > > reset is in progress, so we can't just eat the EAGAIN. If we do
> > > > that we potentially deadlock or overflow the ring.
> > > >
> > > > I think we need a different hack here, and a few layers down (i.e.
> > > > at the place where we actually generate that offending -EAGAIN).
> > > >
> > > > - Around the re-init sequence in the reset function we set
> > > > dev_priv->mm.reload_in_reset or similar
> >
> > . Since we hold dev->struct_mutex
> > > > no one will see that, as long as we never leak it out of the critical
> > > > section.
> > > >
> > > > - In the ring_begin code that checks for gpu hangs we ignore
> > > > reset_in_progress if this bit is set.
> > > >
> > > > - Both places need fairly big comments to explain what exactly is going
> > > > on.
> > >
> > > This is going from bad to worse. I think you can do better if you
> > > looked at the problem afresh.
> >
> > Well we can't really reset reset_in_progress at that point, since not all
> > reset is done yet. Especially the modeset stuff. So I don't think that
> > reordering the reset sequence would get us out of this ugly spot. And I
> > don't see any other solution really. Do you?
> > -Daniel
> > --
> > Daniel Vetter
> > Software Engineer, Intel Corporation
> > +41 (0) 79 365 57 48 - http://blog.ffwll.ch
> > _______________________________________________
> > Intel-gfx mailing list
> > [email protected]
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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