[PATCH 13/27] drm/i915/guc: Take context ref when cancelling request

[Daniele Ceraolo Spurio]

On 8/18/2021 11:16 PM, Matthew Brost wrote:
> A context can get destroyed after cancelling a request so take a
> reference to context when cancelling a request.

What's the exact race? AFAICS __i915_request_skip does not have a 
context_put().

Daniele

>
> Fixes: 62eaf0ae217d ("drm/i915/guc: Support request cancellation")
> Signed-off-by: Matthew Brost <matthew.brost at intel.com>
> ---
>   drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> 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 e0e85e4ad512..85f96d325048 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> @@ -1620,8 +1620,10 @@ static void guc_context_cancel_request(struct intel_context *ce,
>   				       struct i915_request *rq)
>   {
>   	if (i915_sw_fence_signaled(&rq->submit)) {
> -		struct i915_sw_fence *fence = guc_context_block(ce);
> +		struct i915_sw_fence *fence;
>   
> +		intel_context_get(ce);
> +		fence = guc_context_block(ce);
>   		i915_sw_fence_wait(fence);
>   		if (!i915_request_completed(rq)) {
>   			__i915_request_skip(rq);
> @@ -1636,6 +1638,7 @@ static void guc_context_cancel_request(struct intel_context *ce,
>   		flush_work(&ce_to_guc(ce)->ct.requests.worker);
>   
>   		guc_context_unblock(ce);
> +		intel_context_put(ce);
>   	}
>   }
>