linux-kernel - Re: [PATCH v4 6/6] dma-buf: Check status of enable-signaling bit on debug

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Message-ID: <893fc57d-7a49-4b39-ff74-867579141b22@amd.com>
Date:   Thu, 15 Sep 2022 14:06:49 +0200
From:   Christian König <christian.koenig@....com>
To:     Arvind Yadav <Arvind.Yadav@....com>, andrey.grodzovsky@....com,
        shashank.sharma@....com, amaranath.somalapuram@....com,
        Arunpravin.PaneerSelvam@....com, sumit.semwal@...aro.org,
        gustavo@...ovan.org, airlied@...ux.ie, daniel@...ll.ch,
        linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 6/6] dma-buf: Check status of enable-signaling bit on
 debug

Am 14.09.22 um 18:43 schrieb Arvind Yadav:
> Fence signaling must be enabled to make sure that
> the dma_fence_is_signaled() function ever returns true.
> Since drivers and implementations sometimes mess this up,
> this ensures correct behaviour when DMABUF_DEBUG_ENABLE_SIGNALING
> is used during debugging.
> This should make any implementation bugs resulting in not
> signaled fences much more obvious.
>
> Signed-off-by: Arvind Yadav <Arvind.Yadav@....com>

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

> ---
>
> Changes in v1,v2 :
> 1- Addressing Christian's comment to replace
> CONFIG_DEBUG_WW_MUTEX_SLOWPATH instead of CONFIG_DEBUG_FS.
> 2- As per Christian's comment moving this patch at last so
> The version of this patch is also changed and previously
> it was [PATCH 1/4]
>
> Changes in v3:
> 1 - Adding new config DMABUF_DEBUG_ENABLE_SIGNALING.
> 2 - Replace CONFIG_DEBUG_WW_MUTEX_SLOWPATH to new
> CONFIG_DMABUF_DEBUG_ENABLE_SIGNALING.
>
> ---
>   drivers/dma-buf/Kconfig   | 7 +++++++
>   include/linux/dma-fence.h | 5 +++++
>   2 files changed, 12 insertions(+)
>
> diff --git a/drivers/dma-buf/Kconfig b/drivers/dma-buf/Kconfig
> index e4dc53a36428..c991e6a51510 100644
> --- a/drivers/dma-buf/Kconfig
> +++ b/drivers/dma-buf/Kconfig
> @@ -65,6 +65,13 @@ config DMABUF_SELFTESTS
>   	default n
>   	depends on DMA_SHARED_BUFFER
>   
> +config DMABUF_DEBUG_ENABLE_SIGNALING
> +	bool "DMA Fence enable signaling debug checks"
> +	default n
> +	depends on DMA_SHARED_BUFFER
> +	help
> +	  This option enables additional checks for software signaling of fence.
> +
>   menuconfig DMABUF_HEAPS
>   	bool "DMA-BUF Userland Memory Heaps"
>   	select DMA_SHARED_BUFFER
> diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
> index 775cdc0b4f24..01e1fa4d3cec 100644
> --- a/include/linux/dma-fence.h
> +++ b/include/linux/dma-fence.h
> @@ -428,6 +428,11 @@ dma_fence_is_signaled_locked(struct dma_fence *fence)
>   static inline bool
>   dma_fence_is_signaled(struct dma_fence *fence)
>   {
> +#ifdef CONFIG_DMABUF_DEBUG_ENABLE_SIGNALING
> +	if (!test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags))
> +		return false;
> +#endif
> +
>   	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
>   		return true;
>