linux-kernel - Re: [PATCH] reservation: don't wait when timeout=0

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Date:   Tue, 21 Nov 2017 15:27:26 +0100
From:   Christian König <ckoenig.leichtzumerken@...il.com>
To:     Rob Clark <robdclark@...il.com>, dri-devel@...ts.freedesktop.org
Cc:     linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org,
        linux-media@...r.kernel.org
Subject: Re: [PATCH] reservation: don't wait when timeout=0

Am 21.11.2017 um 15:08 schrieb Rob Clark:
> If we are testing if a reservation object's fences have been
> signaled with timeout=0 (non-blocking), we need to pass 0 for
> timeout to dma_fence_wait_timeout().
>
> Plus bonus spelling correction.
>
> Signed-off-by: Rob Clark <robdclark@...il.com>

Reviewed-by: Christian König <christian.koenig@....com>

> ---
>   drivers/dma-buf/reservation.c | 11 +++++++++--
>   1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c
> index dec3a815455d..71f51140a9ad 100644
> --- a/drivers/dma-buf/reservation.c
> +++ b/drivers/dma-buf/reservation.c
> @@ -420,7 +420,7 @@ EXPORT_SYMBOL_GPL(reservation_object_get_fences_rcu);
>    *
>    * RETURNS
>    * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
> - * greater than zer on success.
> + * greater than zero on success.
>    */
>   long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
>   					 bool wait_all, bool intr,
> @@ -483,7 +483,14 @@ long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
>   			goto retry;
>   		}
>   
> -		ret = dma_fence_wait_timeout(fence, intr, ret);
> +		/*
> +		 * Note that dma_fence_wait_timeout() will return 1 if
> +		 * the fence is already signaled, so in the wait_all
> +		 * case when we go through the retry loop again, ret
> +		 * will be greater than 0 and we don't want this to
> +		 * cause _wait_timeout() to block
> +		 */
> +		ret = dma_fence_wait_timeout(fence, intr, timeout ? ret : 0);
>   		dma_fence_put(fence);
>   		if (ret > 0 && wait_all && (i + 1 < shared_count))
>   			goto retry;