linux-kernel - Re: [PATCH v2] drm/amdgpu: fix double reference dropping

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Message-ID: <a3b2cc0c-2c0a-fcae-3750-9e51da46b872@amd.com>
Date:   Wed, 6 Nov 2019 12:48:50 +0000
From:   "Koenig, Christian" <Christian.Koenig@....com>
To:     Pan Bian <bianpan2016@....com>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "Zhou, David(ChunMing)" <David1.Zhou@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Sam Ravnborg <sam@...nborg.org>
CC:     "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] drm/amdgpu: fix double reference dropping

Am 06.11.19 um 12:35 schrieb Pan Bian:
> The reference to object fence is dropped at the end of the loop.
> However, it is dropped again outside the loop. The reference can be
> dropped immediately after calling dma_fence_wait() in the loop and
> thus the dropping operation outside the loop can be removed.
>
> Signed-off-by: Pan Bian <bianpan2016@....com>

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

> ---
> v2: fix the bug in a more concise way
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_benchmark.c | 6 ++----
>   1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_benchmark.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_benchmark.c
> index 649e68c4479b..d1495e1c9289 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_benchmark.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_benchmark.c
> @@ -33,7 +33,7 @@ static int amdgpu_benchmark_do_move(struct amdgpu_device *adev, unsigned size,
>   {
>   	unsigned long start_jiffies;
>   	unsigned long end_jiffies;
> -	struct dma_fence *fence = NULL;
> +	struct dma_fence *fence;
>   	int i, r;
>   
>   	start_jiffies = jiffies;
> @@ -44,16 +44,14 @@ static int amdgpu_benchmark_do_move(struct amdgpu_device *adev, unsigned size,
>   		if (r)
>   			goto exit_do_move;
>   		r = dma_fence_wait(fence, false);
> +		dma_fence_put(fence);
>   		if (r)
>   			goto exit_do_move;
> -		dma_fence_put(fence);
>   	}
>   	end_jiffies = jiffies;
>   	r = jiffies_to_msecs(end_jiffies - start_jiffies);
>   
>   exit_do_move:
> -	if (fence)
> -		dma_fence_put(fence);
>   	return r;
>   }
>