[Intel-gfx] [PATCH 02/40] drm: Fix syncobj handing of schedule() returning 0

[Tvrtko Ursulin]

On 19/09/2018 20:55, Chris Wilson wrote:
> After schedule() returns 0, we must do one last check of COND to
> determine the reason for the wakeup with 0 jiffies remaining before
> reporting the timeout -- otherwise we may lose the signal due to
> scheduler delays.
> 
> References: https://bugs.freedesktop.org/show_bug.cgi?id=106690
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>   drivers/gpu/drm/drm_syncobj.c | 41 +++++++++++++----------------------
>   1 file changed, 15 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
> index e254f97fed7d..5bcb3ef9b256 100644
> --- a/drivers/gpu/drm/drm_syncobj.c
> +++ b/drivers/gpu/drm/drm_syncobj.c
> @@ -672,7 +672,6 @@ static signed long drm_syncobj_array_wait_timeout(struct drm_syncobj **syncobjs,
>   {
>   	struct syncobj_wait_entry *entries;
>   	struct dma_fence *fence;
> -	signed long ret;
>   	uint32_t signaled_count, i;
>   
>   	entries = kcalloc(count, sizeof(*entries), GFP_KERNEL);
> @@ -692,7 +691,7 @@ static signed long drm_syncobj_array_wait_timeout(struct drm_syncobj **syncobjs,
>   			if (flags & DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT) {
>   				continue;
>   			} else {
> -				ret = -EINVAL;
> +				timeout = -EINVAL;
>   				goto cleanup_entries;
>   			}
>   		}
> @@ -704,12 +703,6 @@ static signed long drm_syncobj_array_wait_timeout(struct drm_syncobj **syncobjs,
>   		}
>   	}
>   
> -	/* Initialize ret to the max of timeout and 1.  That way, the
> -	 * default return value indicates a successful wait and not a
> -	 * timeout.
> -	 */
> -	ret = max_t(signed long, timeout, 1);
> -
>   	if (signaled_count == count ||
>   	    (signaled_count > 0 &&
>   	     !(flags & DRM_SYNCOBJ_WAIT_FLAGS_WAIT_ALL)))
> @@ -760,18 +753,17 @@ static signed long drm_syncobj_array_wait_timeout(struct drm_syncobj **syncobjs,
>   			goto done_waiting;
>   
>   		if (timeout == 0) {
> -			/* If we are doing a 0 timeout wait and we got
> -			 * here, then we just timed out.
> -			 */
> -			ret = 0;
> +			timeout = -ETIME;
>   			goto done_waiting;
>   		}
>   
> -		ret = schedule_timeout(ret);
> +		if (signal_pending(current)) {
> +			timeout = -ERESTARTSYS;
> +			goto done_waiting;
> +		}
>   
> -		if (ret > 0 && signal_pending(current))
> -			ret = -ERESTARTSYS;
> -	} while (ret > 0);
> +		timeout = schedule_timeout(timeout);
> +	} while (1);
>   
>   done_waiting:
>   	__set_current_state(TASK_RUNNING);
> @@ -788,7 +780,7 @@ static signed long drm_syncobj_array_wait_timeout(struct drm_syncobj **syncobjs,
>   	}
>   	kfree(entries);
>   
> -	return ret;
> +	return timeout;
>   }
>   
>   /**
> @@ -829,19 +821,16 @@ static int drm_syncobj_array_wait(struct drm_device *dev,
>   				  struct drm_syncobj **syncobjs)
>   {
>   	signed long timeout = drm_timeout_abs_to_jiffies(wait->timeout_nsec);
> -	signed long ret = 0;
>   	uint32_t first = ~0;
>   
> -	ret = drm_syncobj_array_wait_timeout(syncobjs,
> -					     wait->count_handles,
> -					     wait->flags,
> -					     timeout, &first);
> -	if (ret < 0)
> -		return ret;
> +	timeout = drm_syncobj_array_wait_timeout(syncobjs,
> +						 wait->count_handles,
> +						 wait->flags,
> +						 timeout, &first);
> +	if (timeout < 0)
> +		return timeout;
>   
>   	wait->first_signaled = first;
> -	if (ret == 0)
> -		return -ETIME;
>   	return 0;
>   }
>   
> 

LGTM.

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Regards,

Tvrtko