[Intel-gfx] [PATCH] drm/i915: Skip an engine reset if it recovered before our preparations

[Michel Thierry]

Hi,

On 12/15/2017 3:52 PM, Chris Wilson wrote:
> At the beginning of a reset, we disable the submission method and find
> the stuck request. We expect to find a stuck request for we have
> declared the engine stalled. However, if we find no active request, the
> engine must have recovered from its stall before we could issue a reset,
> so let the engine continue on without a reset. If the engine is truly
> stuck, we will back soon enough with the next reset attempt.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Michel Thierry <michel.thierry at intel.com>
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> ---
>   drivers/gpu/drm/i915/i915_drv.c | 14 +++++++-------
>   1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index ca9f4b2862eb..6f24435ddffe 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -2011,19 +2011,19 @@ int i915_reset_engine(struct intel_engine_cs *engine, unsigned int flags)
>   
>   	GEM_BUG_ON(!test_bit(I915_RESET_ENGINE + engine->id, &error->flags));
>   
> -	if (!(flags & I915_RESET_QUIET)) {
> -		dev_notice(engine->i915->drm.dev,
> -			   "Resetting %s after gpu hang\n", engine->name);
> -	}
> -	error->reset_engine_count[engine->id]++;
> -
>   	active_request = i915_gem_reset_prepare_engine(engine);
> -	if (IS_ERR(active_request)) {
> +	if (IS_ERR_OR_NULL(active_request)) {
>   		DRM_DEBUG_DRIVER("Previous reset failed, promote to full reset\n");
>   		ret = PTR_ERR(active_request);

Will a static checker complain about PTR_ERR(NULL)?
And the DRM_DEBUG_DRIVER isn't also correct in that case.

>   		goto out;
>   	}
>   
> +	if (!(flags & I915_RESET_QUIET)) {
> +		dev_notice(engine->i915->drm.dev,
> +			   "Resetting %s after gpu hang\n", engine->name);
> +	}
> +	error->reset_engine_count[engine->id]++;
> +
>   	if (!engine->i915->guc.execbuf_client)
>   		ret = intel_gt_reset_engine(engine->i915, engine);
>   	else
>