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

Christian König
2022-09-15T12:07:03Z

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@amd.com>

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