[PATCH 1/1] reservation: wait only with non-zero timeout specified (v2)

[Zhou, Jammy]

Hi Maarten,

> Can't you simply add if (!timeout) return !reservation_object_test_signaled_rcu(obj, wait_all); to the beginning instead?
Hmm, after looking into it, I think that can achieve the same purpose. I will update the patch with this.

> Also why do you need this? Why not simply return 0 with timeout = 0.
The major purpose here is to use reservation_object_wait_timeout_rcu to handle all possible timeout values (and just to check status with timeout==0). If we simply return 0, we cannot determine the fence is signaled or not with the return value.

Regards,
Jammy

-----Original Message-----
From: Maarten Lankhorst [mailto:maarten.lankhorst at canonical.com] 
Sent: Tuesday, January 13, 2015 2:50 PM
To: Zhou, Jammy
Cc: dri-devel at lists.freedesktop.org; Christian König; Deucher, Alexander
Subject: Re: [PATCH 1/1] reservation: wait only with non-zero timeout specified (v2)

Hey,

Can't you simply add if (!timeout) return !reservation_object_test_signaled_rcu(obj, wait_all); to the beginning instead?
Waiting with timeout = 0 is not really defined. Look at fence_default_wait for example. It returns timeout if the fence is signaled, but since this is 0 you can't distinguish between timed out wait and succesful wait.

Also why do you need this? Why not simply return 0 with timeout = 0.

~Maarten

On 13-01-15 06:50, Jammy Zhou wrote:
> When the timeout value passed to reservation_object_wait_timeout_rcu
> is zero, no wait should be done if the fences are not signaled.
> 
> Return '1' for idle and '0' for busy if the specified timeout is '0'
> to keep consistent with the case of non-zero timeout.
> 
> v2: call fence_put if not signaled in the case of timeout==0
> 
> Signed-off-by: Jammy Zhou <Jammy.Zhou at amd.com>
> Reviewed-by: Christian König <christian.koenig at amd.com>
> Reviewed-by: Alex Deucher <alexander.deucher at amd.com>
> ---
>  drivers/dma-buf/reservation.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/dma-buf/reservation.c 
> b/drivers/dma-buf/reservation.c index 3c97c8f..b1d554f 100644
> --- a/drivers/dma-buf/reservation.c
> +++ b/drivers/dma-buf/reservation.c
> @@ -380,12 +380,19 @@ retry:
>  	}
>  
>  	rcu_read_unlock();
> -	if (fence) {
> +	if (fence && timeout) {
>  		ret = fence_wait_timeout(fence, intr, ret);
>  		fence_put(fence);
>  		if (ret > 0 && wait_all && (i + 1 < shared_count))
>  			goto retry;
>  	}
> +
> +	if (fence && !timeout)
> +		fence_put(fence);
> +
> +	if (!fence && !timeout)
> +		ret = 1;
> +
>  	return ret;
>  
>  unlock_retry:
>