Re: [Intel-gfx] [PATCH] drm/i915: fix remaining_timeout in intel_gt_retire_requests_timeout

[Matthew Brost <matthew.brost@intel.com>]

On Fri, Mar 25, 2022 at 10:58:39AM -0700, Daniele Ceraolo Spurio wrote:
> In intel_gt_wait_for_idle, we use the remaining timeout returned from
> intel_gt_retire_requests_timeout to wait on the GuC being idle. However,
> the returned variable can have a negative value if something goes wrong
> during the wait, leading to us hitting a GEM_BUG_ON in the GuC wait
> function.
> To fix this, make sure to only return the timeout if it is positive.
> 
> Fixes: b97060a99b01b ("drm/i915/guc: Update intel_gt_wait_for_idle to work with GuC")
> Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: John Harrison <john.c.harrison@intel.com>

Reviewed-by: Matthew Brost <matthew.brost@intel.com>

> ---
>  drivers/gpu/drm/i915/gt/intel_gt_requests.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_requests.c b/drivers/gpu/drm/i915/gt/intel_gt_requests.c
> index edb881d756309..ef70c209976d8 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_requests.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_requests.c
> @@ -197,7 +197,7 @@ out_active:	spin_lock(&timelines->lock);
>  		active_count++;
>  
>  	if (remaining_timeout)
> -		*remaining_timeout = timeout;
> +		*remaining_timeout = timeout > 0 ? timeout : 0;
>  
>  	return active_count ? timeout : 0;
>  }
> -- 
> 2.25.1
>