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

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Message-ID: <efce6f23-135d-d946-6677-0668d83a7831@amd.com>
Date:   Thu, 29 Sep 2022 20:32:08 +0200
From:   Christian König <christian.koenig@....com>
To:     "Yadav, Arvind" <arvyadav@....com>,
        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 29.09.22 um 20:30 schrieb Yadav, Arvind:
>
> On 9/29/2022 11:48 PM, Christian König wrote:
>> 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.
>>
> IGT has these test cases related to syncobj (syncobj_basic, 
> syncobj_timeline and syncobj_wait)and all are passing.
>
> I will check syncobj and let you know.

Maybe CC the Intel list and let their CI systems take a look. That's 
usually rather valuable.

Thanks,
Christian.

>
> ~Arvind
>
>> 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;
>>