[PATCH] drm/amdgpu: Replace rcu_assign_pointer() with RCU_INIT_POINTER()

[PATCH] drm/amdgpu: Replace rcu_assign_pointer() with RCU_INIT_POINTER()

[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.

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>
---
 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);
 
-- 
1.9.1

Re: [PATCH] drm/amdgpu: Replace rcu_assign_pointer() with RCU_INIT_POINTER()

[Christian König]

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);
>   

Re: [PATCH] drm/amdgpu: Replace rcu_assign_pointer() with RCU_INIT_POINTER()

[Alex Deucher]

On Sun, May 1, 2016 at 11:26 AM, Christian König
<christian.koenig@amd.com> wrote:
> 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>

Applied.  thanks!

Alex


>
> 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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