Re: [PATCH v2] drm/i915: Stop automatically retiring requests after a GPU hang

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> [ text/plain ]
> Following a GPU hang, we break out of the request loop in order to
> unlock the struct_mutex for use by the GPU reset. However, if we retire
> all the requests at that moment, we cannot identify the guilty request
> after performing the reset.
>
> v2: Not automatically retiring requests forces us to recheck for
> available ringspace.
>
> Fixes: f4457ae71fd6 ("drm/i915: Prevent leaking of -EIO from i915_wait_request()")
> Testcase: igt/gem_reset_stats

Testcase: igt/gem_reset_stats/ban-*
Tested-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>

> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Mika Kuoppala <mika.kuoppala@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_gem.c         | 8 ++++++--
>  drivers/gpu/drm/i915/intel_ringbuffer.c | 2 ++
>  2 files changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 6e61738fab31..a3d826bb216b 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1462,7 +1462,10 @@ i915_wait_request(struct drm_i915_gem_request *req)
>  	if (ret)
>  		return ret;
>  
> -	__i915_gem_request_retire__upto(req);
> +	/* If the GPU hung, we want to keep the requests to find the guilty. */
> +	if (req->reset_counter == i915_reset_counter(&dev_priv->gpu_error))
> +		__i915_gem_request_retire__upto(req);
> +
>  	return 0;
>  }
>  
> @@ -1519,7 +1522,8 @@ i915_gem_object_retire_request(struct drm_i915_gem_object *obj,
>  	else if (obj->last_write_req == req)
>  		i915_gem_object_retire__write(obj);
>  
> -	__i915_gem_request_retire__upto(req);
> +	if (req->reset_counter == i915_reset_counter(&req->i915->gpu_error))
> +		__i915_gem_request_retire__upto(req);
>  }
>  
>  /* A nonblocking variant of the above wait. This is a highly dangerous routine
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index 0618dd34c3ec..8d35a3978f9b 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -2450,6 +2450,8 @@ int intel_ring_begin(struct drm_i915_gem_request *req, int num_dwords)
>  			return ret;
>  
>  		intel_ring_update_space(ringbuf);
> +		if (unlikely(ringbuf->space < wait_bytes))
> +			return -EAGAIN;
>  	}
>  
>  	if (unlikely(need_wrap)) {
> -- 
> 2.8.1
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