Quoting Ville Syrjälä (2019-09-11 11:52:29)
> On Wed, Sep 11, 2019 at 11:19:59AM +0100, Chris Wilson wrote:
> > If the display is inactive, we need not worry about the gpu reset
> > clobbering the display! To prevent the display changing state between us
> > checking the active state and doing the hard reset, we introduce the
> > lightweight reset lock to the atomic commit for the affected (legacy)
> > platforms.
> >
> > Testcase: igt/gem_eio/kms
> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/display/intel_display.c | 11 +++++++++++
> > drivers/gpu/drm/i915/gt/intel_reset.c | 18 +++++++++++++++++-
> > 2 files changed, 28 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> > index 4ee750fa3ef0..a92487d8f4cf 100644
> > --- a/drivers/gpu/drm/i915/display/intel_display.c
> > +++ b/drivers/gpu/drm/i915/display/intel_display.c
> > @@ -13986,6 +13986,7 @@ static void intel_atomic_commit_tail(struct intel_atomic_state *state)
> > struct intel_crtc *crtc;
> > u64 put_domains[I915_MAX_PIPES] = {};
> > intel_wakeref_t wakeref = 0;
> > + int srcu;
> > int i;
> >
> > intel_atomic_commit_fence_wait(state);
> > @@ -14005,6 +14006,12 @@ static void intel_atomic_commit_tail(struct intel_atomic_state *state)
> > }
> > }
> >
> > + /* Prevent starting a GPU reset while we change global display state */
> > + srcu = -ENODEV;
> > + if (INTEL_INFO(dev_priv)->gpu_reset_clobbers_display)
> > + /* only fails if interrupted */
> > + srcu = intel_gt_reset_trylock(&dev_priv->gt);
>
> Hmm. What happens if we're holding the modeset locks and there's an
> ongoing reset blocked on said locks?
I was about to say it's the inner lock in both cases, but it's not.
Anyway doesn't that interaction (intel_prepare_reset) prevent
crtc->active changing as we use it from inside intel_gt_reset (which
calls intel_gt_unset_wedged)?
-Chris
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