Re: [PATCH] drm/i915/gt: Confirm the context survives execution

[Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>]

On 14/10/2020 09:43, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2020-10-14 09:36:08)
> > On 13/10/2020 16:35, Chris Wilson wrote:
> > > Repeat our sanitychecks from before execution to after execution. One
> > > expects that if we were to see these, the gpu would already be on fire,
> > > but the timing may be informative.
> > >
> > > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > > ---
> > >    drivers/gpu/drm/i915/gt/intel_lrc.c | 10 +++++++---
> > >    1 file changed, 7 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> > > index 287537089c77..3dbdd5d0cb60 100644
> > > --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> > > +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> > > @@ -1216,7 +1216,8 @@ static void intel_engine_context_out(struct intel_engine_cs *engine)
> > >    
> > >    static void
> > >    execlists_check_context(const struct intel_context *ce,
> > > -                     const struct intel_engine_cs *engine)
> > > +                     const struct intel_engine_cs *engine,
> > > +                     const char *when)
> > >    {
> > >        const struct intel_ring *ring = ce->ring;
> > >        u32 *regs = ce->lrc_reg_state;
> > > @@ -1251,7 +1252,7 @@ execlists_check_context(const struct intel_context *ce,
> > >                valid = false;
> > >        }
> > >    
> > > -     WARN_ONCE(!valid, "Invalid lrc state found before submission\n");
> > > +     WARN_ONCE(!valid, "Invalid lrc state found %s submission\n", when);
> > >    }
> > >    
> > >    static void restore_default_state(struct intel_context *ce,
> > > @@ -1347,7 +1348,7 @@ __execlists_schedule_in(struct i915_request *rq)
> > >                reset_active(rq, engine);
> > >    
> > >        if (IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
> > > -             execlists_check_context(ce, engine);
> > > +             execlists_check_context(ce, engine, "before");
> > >    
> > >        if (ce->tag) {
> > >                /* Use a fixed tag for OA and friends */
> > > @@ -1418,6 +1419,9 @@ __execlists_schedule_out(struct i915_request *rq,
> > >         * refrain from doing non-trivial work here.
> > >         */
> > >    
> > > +     if (IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
> > > +             execlists_check_context(ce, engine, "after");
> > > +
> >
> > CI failures here are either something super scary or a simple mistake
> > which I cannot see. Or is engine retire, possible queued up before,
> > racing with current schedule_out?
>
> It's the unpark while the process_csb is not yet flushed, so we scrub
> the kernel_context before it is scheduled-out. It could in theory be a
> real problem with our scrubbing to simulate an issue causing an issue,
> but the timing is quite slim.

Unpark with unflushed process_csb? I thought maybe you meant park, but 
poisoning is indeed in unpark. Put pending process_csb means engine is 
supposed to be unparked already. Or you are saying it went through the 
parked-unparked cycle all with pending process_csb?

Regards,

Tvrtko


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