linux-kernel - Re: [PATCH RFC] dma-buf: To check DMA_FENCE_FLAG_ENABLE_SIGNAL

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Date:   Mon, 8 Aug 2022 21:44:11 +0200
From:   Christian König <christian.koenig@....com>
To:     Arvind Yadav <Arvind.Yadav@....com>, andrey.grodzovsky@....com,
        shashank.sharma@....com, amaranath.somalapuram@....com,
        Luben.Tuikov@....com, Alexander.Deucher@....com,
        sumit.semwal@...aro.org, linux-media@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
        linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org
Subject: Re: [PATCH RFC] dma-buf: To check DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT
 status on debug



Am 04.08.22 um 14:19 schrieb Arvind Yadav:
> If core DMA-buf framework forgets to call dma_fence_enable_signaling()
> before calling the dma_fence_is_signaled(). To handle this scenario on
> debug kernel the DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT needs to be checked
> before checking the actual signaling status.
>
> Signed-off-by: Arvind Yadav <Arvind.Yadav@....com>
> ---
>   include/linux/dma-fence.h | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
> index 775cdc0b4f24..7c95c8d5e5f5 100644
> --- a/include/linux/dma-fence.h
> +++ b/include/linux/dma-fence.h
> @@ -428,6 +428,10 @@ dma_fence_is_signaled_locked(struct dma_fence *fence)
>   static inline bool
>   dma_fence_is_signaled(struct dma_fence *fence)
>   {
> +#ifdef CONFIG_DEBUG_FS
> +	if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags))
> +		return true;

The logic is just inverted. The test should be !test_bit(...) return false;

And please give that some testing as well.

Regards,
Christian.

> +#endif
>   	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
>   		return true;
>