linux-kernel - Re: [PATCH 3/3] dma-buf: Check status of enable-signaling bit on debug

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Message-ID: <59d4d647-f451-061c-79b5-0ffc4e33fc58@amd.com>
Date:   Thu, 29 Sep 2022 20:18:35 +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 3/3] dma-buf: Check status of enable-signaling bit on
 debug

Am 27.09.22 um 19:24 schrieb Arvind Yadav:
> Fence signaling must be enabled to make sure that
> the dma_fence_is_signaled_locked() 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.

Are all IGT tests now passing with this? That would be a bit unfortunate 
because it means we still have missed the bug in drm_syncobj.

Christian.

>
> Signed-off-by: Arvind Yadav <Arvind.Yadav@....com>
> ---
>   include/linux/dma-fence.h | 5 +++++
>   1 file changed, 5 insertions(+)
>
> diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
> index 775cdc0b4f24..5156dc6be0a6 100644
> --- a/include/linux/dma-fence.h
> +++ b/include/linux/dma-fence.h
> @@ -398,6 +398,11 @@ void dma_fence_enable_sw_signaling(struct dma_fence *fence);
>   static inline bool
>   dma_fence_is_signaled_locked(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;
>