Re: [Intel-gfx] [PATCH] drm/i915/guc: Remove racey GEM_BUG_ON

[Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>]

On 12/9/2021 10:51 AM, Matthew Brost wrote:
> A full GT can race with the last context put resulting in the context
> ref count being zero but the destroyed bit not yet being set. Remove
> GEM_BUG_ON in scrub_guc_desc_for_outstanding_g2h that asserts the
> destroyed bit must be set in ref count is zero.
>
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> ---
>   drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c | 2 --
>   1 file changed, 2 deletions(-)
>
> 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 9b7b4f4e0d91..0f99bb83293a 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> @@ -1040,8 +1040,6 @@ static void scrub_guc_desc_for_outstanding_g2h(struct intel_guc *guc)
>   
>   		spin_unlock(&ce->guc_state.lock);
>   
> -		GEM_BUG_ON(!do_put && !destroyed);
> -

Do we need to re-queue/flush the destroyer work to make sure it runs 
before we reset, or is it ok for that to run in parallel?

Daniele

>   		if (pending_enable || destroyed || deregister) {
>   			decr_outstanding_submission_g2h(guc);
>   			if (deregister)