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From: "Christian König" <christian.koenig@amd.com>
To: Muhammad Falak R Wani <falakreyaz@gmail.com>,
	David Airlie <airlied@linux.ie>
Cc: Alex Deucher <alexander.deucher@amd.com>,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org
Subject: Re: [PATCH] drm/amdgpu: Replace rcu_assign_pointer() with RCU_INIT_POINTER()
Date: Sun, 1 May 2016 17:26:54 +0200	[thread overview]
Message-ID: <5726203E.7060308@amd.com> (raw)
In-Reply-To: <1462042824-10851-1-git-send-email-falakreyaz@gmail.com>

Am 30.04.2016 um 21:00 schrieb Muhammad Falak R Wani:
> The rcu_assign_pointer() ensures that the initialization of a structure
> is carried out before storing a pointer to that structre. It is always
> safe to use RCU_INIT_POINTER() to NULL a pointer, instead of
> rcu_assign_pointer().
> This results in slightly smaller/faster code.

Thanks for the detailed explanation, I was already wondering what the 
difference is between the two.

>
> The following semantic patch was used:
> <smpl>
>
> @@
> @@
>
> - rcu_assign_pointer
> + RCU_INIT_POINTER
>    (..., NULL)
>
> </smpl>
>
> Signed-off-by: Muhammad Falak R Wani <falakreyaz@gmail.com>

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

Regards,
Christian.

> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> index d81f1f4..4500ff1 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> @@ -198,7 +198,7 @@ void amdgpu_fence_process(struct amdgpu_ring *ring)
>   
>   		/* There is always exactly one thread signaling this fence slot */
>   		fence = rcu_dereference_protected(*ptr, 1);
> -		rcu_assign_pointer(*ptr, NULL);
> +		RCU_INIT_POINTER(*ptr, NULL);
>   
>   		BUG_ON(!fence);
>   

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WARNING: multiple messages have this Message-ID (diff)
From: "Christian König" <christian.koenig@amd.com>
To: Muhammad Falak R Wani <falakreyaz@gmail.com>,
	David Airlie <airlied@linux.ie>
Cc: Chunming Zhou <David1.Zhou@amd.com>,
	Alex Deucher <alexander.deucher@amd.com>,
	<dri-devel@lists.freedesktop.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] drm/amdgpu: Replace rcu_assign_pointer() with RCU_INIT_POINTER()
Date: Sun, 1 May 2016 17:26:54 +0200	[thread overview]
Message-ID: <5726203E.7060308@amd.com> (raw)
In-Reply-To: <1462042824-10851-1-git-send-email-falakreyaz@gmail.com>

Am 30.04.2016 um 21:00 schrieb Muhammad Falak R Wani:
> The rcu_assign_pointer() ensures that the initialization of a structure
> is carried out before storing a pointer to that structre. It is always
> safe to use RCU_INIT_POINTER() to NULL a pointer, instead of
> rcu_assign_pointer().
> This results in slightly smaller/faster code.

Thanks for the detailed explanation, I was already wondering what the 
difference is between the two.

>
> The following semantic patch was used:
> <smpl>
>
> @@
> @@
>
> - rcu_assign_pointer
> + RCU_INIT_POINTER
>    (..., NULL)
>
> </smpl>
>
> Signed-off-by: Muhammad Falak R Wani <falakreyaz@gmail.com>

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

Regards,
Christian.

> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> index d81f1f4..4500ff1 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> @@ -198,7 +198,7 @@ void amdgpu_fence_process(struct amdgpu_ring *ring)
>   
>   		/* There is always exactly one thread signaling this fence slot */
>   		fence = rcu_dereference_protected(*ptr, 1);
> -		rcu_assign_pointer(*ptr, NULL);
> +		RCU_INIT_POINTER(*ptr, NULL);
>   
>   		BUG_ON(!fence);
>   

  reply	other threads:[~2016-05-01 15:42 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-04-30 19:00 [PATCH] drm/amdgpu: Replace rcu_assign_pointer() with RCU_INIT_POINTER() Muhammad Falak R Wani
2016-05-01 15:26 ` Christian König [this message]
2016-05-01 15:26   ` Christian König
2016-05-02 14:46   ` Alex Deucher
2016-05-02 14:46     ` Alex Deucher

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