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

[Daniele Ceraolo Spurio]

On 8/24/2021 8:42 AM, Matthew Brost wrote:
> On Fri, Aug 20, 2021 at 05:07:27PM -0700, Daniele Ceraolo Spurio wrote:
>>
>> 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().
> This commit message isn't quite right, it is really a context reset or a
> GT reset which could result in the context getting destroyed. I haven't
> actually seen this happen but this just being paranoid about ref
> counting. Can fix up the commit message.

ok, with an updated commit message:

Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>

Daniele

>
> Matt
>
>> 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);
>>>    	}
>>>    }