[PATCH v2 2/2] drm/i915: Never return 0 if not all requests retired

[Das, Nirmoy]

On 11/18/2022 11:42 AM, Janusz Krzysztofik wrote:
> Users of intel_gt_retire_requests_timeout() expect 0 return value on
> success.  However, we have no protection from passing back 0 potentially
> returned by a call to dma_fence_wait_timeout() when it succedes right
> after its timeout has expired.
>
> Replace 0 with -ETIME before potentially using the timeout value as return
> code, so -ETIME is returned if there are still some requests not retired
> after timeout, 0 otherwise.
>
> v2: Move the added lines down so flush_submission() is not affected.
>
> Fixes: f33a8a51602c ("drm/i915: Merge wait_for_timelines with retire_request")
> Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik at linux.intel.com>
> Cc: stable at vger.kernel.org # v5.5+
> ---
>   drivers/gpu/drm/i915/gt/intel_gt_requests.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_requests.c b/drivers/gpu/drm/i915/gt/intel_gt_requests.c
> index edb881d756309..3ac4603eeb4ee 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_requests.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_requests.c
> @@ -199,6 +199,9 @@ out_active:	spin_lock(&timelines->lock);
>   	if (remaining_timeout)
>   		*remaining_timeout = timeout;
>   
> +	if (!timeout)
> +		timeout = -ETIME;

This will return error, -ETIME when 0 timeout is passed, 
intel_gt_retire_requests().

We don't want that. I think you can use a separate variable to store 
return val from the dma_fence_wait_timeout()


Regards,

Nirmoy

> +
>   	return active_count ? timeout : 0;
>   }
>