linux-kernel - Re: [PATCH 1/2] dma-buf: Add __dma_fence_is

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Message-ID: <4255f9a9-be17-4a9a-b7cf-8e3d4f93b38b@igalia.com>
Date: Fri, 23 May 2025 15:47:06 +0100
From: Tvrtko Ursulin <tvrtko.ursulin@...lia.com>
To: Philipp Stanner <phasta@...nel.org>, Lyude Paul <lyude@...hat.com>,
 Danilo Krummrich <dakr@...nel.org>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, Sumit Semwal <sumit.semwal@...aro.org>,
 Christian König <christian.koenig@....com>
Cc: dri-devel@...ts.freedesktop.org, nouveau@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, linux-media@...r.kernel.org
Subject: Re: [PATCH 1/2] dma-buf: Add __dma_fence_is_signaled()


On 22/05/2025 12:25, Philipp Stanner wrote:
> Some parties want to check whether a function is already signaled
> without actually signaling the fence, which is what
> dma_fence_is_signaled() might due if the fence ops 'signaled' callback

s/due/do/

> is implemented.
> 
> Add __dma_fence_is_signaled(), which _only_ checks whether a fence is
> signaled. Use it internally.
> 
> Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@...lia.com>
> Signed-off-by: Philipp Stanner <phasta@...nel.org>
> ---
>   include/linux/dma-fence.h | 24 ++++++++++++++++++++++--
>   1 file changed, 22 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
> index 48b5202c531d..ac951a54a007 100644
> --- a/include/linux/dma-fence.h
> +++ b/include/linux/dma-fence.h
> @@ -381,6 +381,26 @@ bool dma_fence_remove_callback(struct dma_fence *fence,
>   			       struct dma_fence_cb *cb);
>   void dma_fence_enable_sw_signaling(struct dma_fence *fence);
>   
> +/**
> + * __dma_fence_is_signaled - Only check whether a fence is signaled yet.
> + * @fence: the fence to check
> + *
> + * This function just checks whether @fence is signaled, without interacting
> + * with the fence in any way. The user must, therefore, ensure through other

s/user/caller/ ?

Otherwise looks good to me. For if/when Christian approves you can add my:

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@...lia.com>

Regards,

Tvrtko

> + * means that fences get signaled eventually.
> + *
> + * This function does not require locking.
> + *
> + * See also dma_fence_is_signaled().
> + *
> + * Return: true if signaled, false otherwise.
> + */
> +static inline bool
> +__dma_fence_is_signaled(struct dma_fence *fence)
> +{
> +	return test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags);
> +}
> +
>   /**
>    * dma_fence_is_signaled_locked - Return an indication if the fence
>    *                                is signaled yet.
> @@ -398,7 +418,7 @@ void dma_fence_enable_sw_signaling(struct dma_fence *fence);
>   static inline bool
>   dma_fence_is_signaled_locked(struct dma_fence *fence)
>   {
> -	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
> +	if (__dma_fence_is_signaled(fence))
>   		return true;
>   
>   	if (fence->ops->signaled && fence->ops->signaled(fence)) {
> @@ -428,7 +448,7 @@ dma_fence_is_signaled_locked(struct dma_fence *fence)
>   static inline bool
>   dma_fence_is_signaled(struct dma_fence *fence)
>   {
> -	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
> +	if (__dma_fence_is_signaled(fence))
>   		return true;
>   
>   	if (fence->ops->signaled && fence->ops->signaled(fence)) {