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Message-ID: <188a99e2-77bc-40b6-9d87-073a19497e20@amd.com>
Date: Wed, 3 Dec 2025 14:13:06 +0100
From: Christian König <christian.koenig@....com>
To: Philipp Stanner <phasta@...nel.org>,
Sumit Semwal <sumit.semwal@...aro.org>, Gustavo Padovan
<gustavo@...ovan.org>, Felix Kuehling <Felix.Kuehling@....com>,
Alex Deucher <alexander.deucher@....com>, David Airlie <airlied@...il.com>,
Simona Vetter <simona@...ll.ch>, Jani Nikula <jani.nikula@...ux.intel.com>,
Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
Rodrigo Vivi <rodrigo.vivi@...el.com>, Tvrtko Ursulin
<tursulin@...ulin.net>, Huang Rui <ray.huang@....com>,
Matthew Auld <matthew.auld@...el.com>,
Matthew Brost <matthew.brost@...el.com>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
Lucas De Marchi <lucas.demarchi@...el.com>,
Thomas Hellström <thomas.hellstrom@...ux.intel.com>
Cc: linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
intel-gfx@...ts.freedesktop.org, intel-xe@...ts.freedesktop.org
Subject: Re: [PATCH v2 7/8] dma-buf/dma-fence: Remove return code of
signaling-functions
On 12/1/25 11:50, Philipp Stanner wrote:
> All functions used for signaling a fence return an error code whose sole
> purpose is to tell whether a fence was already signaled.
>
> This is racy and has been used by almost no party in the kernel, and the
> few users have been removed in preceding cleanup commits.
>
> Turn all signaling-functions into void-functions.
>
> Suggested-by: Christian König <christian.koenig@....com>
> Signed-off-by: Philipp Stanner <phasta@...nel.org>
Reviewed-by: Christian König <christian.koenig@....com>
> ---
> drivers/dma-buf/dma-fence.c | 40 ++++++++++---------------------------
> include/linux/dma-fence.h | 9 ++++-----
> 2 files changed, 14 insertions(+), 35 deletions(-)
>
> diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
> index 146de62887cf..529a44371b35 100644
> --- a/drivers/dma-buf/dma-fence.c
> +++ b/drivers/dma-buf/dma-fence.c
> @@ -360,11 +360,8 @@ void __dma_fence_might_wait(void)
> *
> * Unlike dma_fence_signal_timestamp(), this function must be called with
> * &dma_fence.lock held.
> - *
> - * Returns 0 on success and a negative error value when @fence has been
> - * signalled already.
> */
> -int dma_fence_signal_timestamp_locked(struct dma_fence *fence,
> +void dma_fence_signal_timestamp_locked(struct dma_fence *fence,
> ktime_t timestamp)
> {
> struct dma_fence_cb *cur, *tmp;
> @@ -374,7 +371,7 @@ int dma_fence_signal_timestamp_locked(struct dma_fence *fence,
>
> if (unlikely(test_and_set_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
> &fence->flags)))
> - return -EINVAL;
> + return;
>
> /* Stash the cb_list before replacing it with the timestamp */
> list_replace(&fence->cb_list, &cb_list);
> @@ -387,8 +384,6 @@ int dma_fence_signal_timestamp_locked(struct dma_fence *fence,
> INIT_LIST_HEAD(&cur->node);
> cur->func(fence, cur);
> }
> -
> - return 0;
> }
> EXPORT_SYMBOL(dma_fence_signal_timestamp_locked);
>
> @@ -403,23 +398,17 @@ EXPORT_SYMBOL(dma_fence_signal_timestamp_locked);
> * can only go from the unsignaled to the signaled state and not back, it will
> * only be effective the first time. Set the timestamp provided as the fence
> * signal timestamp.
> - *
> - * Returns 0 on success and a negative error value when @fence has been
> - * signalled already.
> */
> -int dma_fence_signal_timestamp(struct dma_fence *fence, ktime_t timestamp)
> +void dma_fence_signal_timestamp(struct dma_fence *fence, ktime_t timestamp)
> {
> unsigned long flags;
> - int ret;
>
> if (WARN_ON(!fence))
> - return -EINVAL;
> + return;
>
> spin_lock_irqsave(fence->lock, flags);
> - ret = dma_fence_signal_timestamp_locked(fence, timestamp);
> + dma_fence_signal_timestamp_locked(fence, timestamp);
> spin_unlock_irqrestore(fence->lock, flags);
> -
> - return ret;
> }
> EXPORT_SYMBOL(dma_fence_signal_timestamp);
>
> @@ -435,13 +424,10 @@ EXPORT_SYMBOL(dma_fence_signal_timestamp);
> *
> * Unlike dma_fence_signal(), this function must be called with &dma_fence.lock
> * held.
> - *
> - * Returns 0 on success and a negative error value when @fence has been
> - * signalled already.
> */
> -int dma_fence_signal_locked(struct dma_fence *fence)
> +void dma_fence_signal_locked(struct dma_fence *fence)
> {
> - return dma_fence_signal_timestamp_locked(fence, ktime_get());
> + dma_fence_signal_timestamp_locked(fence, ktime_get());
> }
> EXPORT_SYMBOL(dma_fence_signal_locked);
>
> @@ -498,28 +484,22 @@ EXPORT_SYMBOL(dma_fence_check_and_signal);
> * dma_fence_add_callback(). Can be called multiple times, but since a fence
> * can only go from the unsignaled to the signaled state and not back, it will
> * only be effective the first time.
> - *
> - * Returns 0 on success and a negative error value when @fence has been
> - * signalled already.
> */
> -int dma_fence_signal(struct dma_fence *fence)
> +void dma_fence_signal(struct dma_fence *fence)
> {
> unsigned long flags;
> - int ret;
> bool tmp;
>
> if (WARN_ON(!fence))
> - return -EINVAL;
> + return;
>
> tmp = dma_fence_begin_signalling();
>
> spin_lock_irqsave(fence->lock, flags);
> - ret = dma_fence_signal_timestamp_locked(fence, ktime_get());
> + dma_fence_signal_timestamp_locked(fence, ktime_get());
> spin_unlock_irqrestore(fence->lock, flags);
>
> dma_fence_end_signalling(tmp);
> -
> - return ret;
> }
> EXPORT_SYMBOL(dma_fence_signal);
>
> diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
> index 0504afe52c2a..d4c92fd35092 100644
> --- a/include/linux/dma-fence.h
> +++ b/include/linux/dma-fence.h
> @@ -364,13 +364,12 @@ static inline void dma_fence_end_signalling(bool cookie) {}
> static inline void __dma_fence_might_wait(void) {}
> #endif
>
> -int dma_fence_signal(struct dma_fence *fence);
> +void dma_fence_signal(struct dma_fence *fence);
> bool dma_fence_check_and_signal(struct dma_fence *fence);
> bool dma_fence_check_and_signal_locked(struct dma_fence *fence);
> -int dma_fence_signal_locked(struct dma_fence *fence);
> -int dma_fence_signal_timestamp(struct dma_fence *fence, ktime_t timestamp);
> -int dma_fence_signal_timestamp_locked(struct dma_fence *fence,
> - ktime_t timestamp);
> +void dma_fence_signal_locked(struct dma_fence *fence);
> +void dma_fence_signal_timestamp(struct dma_fence *fence, ktime_t timestamp);
> +void dma_fence_signal_timestamp_locked(struct dma_fence *fence, ktime_t timestamp);
> signed long dma_fence_default_wait(struct dma_fence *fence,
> bool intr, signed long timeout);
> int dma_fence_add_callback(struct dma_fence *fence,
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