[PATCH] drm/i915/gt: Ensure irqs' status does not change with spin_unlock

[Krzysztof Karas]

Hi Maciej,

> > diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > index 12f1ba7ca9c1..e9102f7246f5 100644
> > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > @@ -4338,10 +4338,11 @@ static void guc_bump_inflight_request_prio(struct i915_request *rq,
> >   static void guc_retire_inflight_request_prio(struct i915_request *rq)
> >   {
> >   	struct intel_context *ce = request_to_scheduling_context(rq);
> > +	unsigned long flags;
> > -	spin_lock(&ce->guc_state.lock);
> > +	spin_lock_irqsave(&ce->guc_state.lock, flags);
> >   	guc_prio_fini(rq, ce);
> > -	spin_unlock(&ce->guc_state.lock);
> > +	spin_unlock_irqrestore(&ce->guc_state.lock, flags);
> >   }
> >   static void sanitize_hwsp(struct intel_engine_cs *engine)
> 
> The guc_retire_inflight_request_prio is called in intel_breadcrumbs.c
> signal_irq_work().
> 
> There is a similar situation
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c?h=v6.13-rc7#n255
> 
> There is also spin_(un)lock while potentially IRQs are disabled.
> 
> Should it also be addressed?
Thanks for spotting this. Yes, I believe we should also address
other spin locks/unlocks on this path
(inside list_for_each_entry_rcu loops for example), as they
might cause similar problems. I will include these in v2.

Krzysztof
> 
> Regards,
> 
> Maciej
>