Re: [PATCH 2/2] drm/i915: Set guilty-flag on fence after detecting a hang

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 03/01/2017 11:05, Chris Wilson wrote:
> The struct dma_fence carries a status field exposed to userspace by
> sync_file. This is inspected after the fence is signaled and can convey
> whether or not the request completed successfully, or in our case if we
> detected a hang during the request (signaled via -EIO in
> SYNC_IOC_FILE_INFO).
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/i915_gem.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 204c4a673bf3..bc99c0e292d8 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -2757,10 +2757,12 @@ static void i915_gem_reset_engine(struct intel_engine_cs *engine)
>  		ring_hung = false;
>  	}
>
> -	if (ring_hung)
> +	if (ring_hung) {
>  		i915_gem_context_mark_guilty(request->ctx);
> -	else
> +		request->fence.status = -EIO;
> +	} else {
>  		i915_gem_context_mark_innocent(request->ctx);
> +	}
>
>  	if (!ring_hung)
>  		return;
>

Reading what happens later in this function, should we set the status of 
all the other requests we are about to clear?

However one thing I don't understand is how this scheme interacts with 
the current userspace. We will clear/no-nop some of the submitted 
requests since the state is corrupt. But how will userspace notice this 
before it submits more requets?

Regards,

Tvrtko

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