linux-kernel - Re: [PATCH v8 1/6] drm: amdgpu: Allow NULL pointers at amdgpu_vm_put_task

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Message-ID: <cc3f06c2-12f6-44b5-ab51-4f141a4c6e3e@amd.com>
Date: Mon, 16 Jun 2025 20:28:06 +0200
From: Christian König <christian.koenig@....com>
To: André Almeida <andrealmeid@...lia.com>,
 Alex Deucher <alexander.deucher@....com>, siqueira@...lia.com,
 airlied@...il.com, simona@...ll.ch, Raag Jadav <raag.jadav@...el.com>,
 rodrigo.vivi@...el.com, jani.nikula@...ux.intel.com,
 Xaver Hugl <xaver.hugl@...il.com>,
 Krzysztof Karas <krzysztof.karas@...el.com>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 kernel-dev@...lia.com, amd-gfx@...ts.freedesktop.org,
 intel-xe@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org
Subject: Re: [PATCH v8 1/6] drm: amdgpu: Allow NULL pointers at
 amdgpu_vm_put_task_info()



On 6/16/25 20:14, André Almeida wrote:
> Allow NULL pointers at amdgpu_vm_put_task_info() as it common practice
> for "put" or "free" functions. This avoid an extra check for NULL for
> callers.
> 
> Signed-off-by: André Almeida <andrealmeid@...lia.com>
> ---
> v8: New patch
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> index 3911c78f8282..dadf5633476c 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> @@ -2447,6 +2447,9 @@ amdgpu_vm_get_vm_from_pasid(struct amdgpu_device *adev, u32 pasid)
>   */
>  void amdgpu_vm_put_task_info(struct amdgpu_task_info *task_info)
>  {
> +	if (unlikely(ZERO_OR_NULL_PTR(task_info)))

Don't use ZERO_OR_NULL_PTR here, that is slab internal and not valid in this use case.

The usual code fragment used looks something like this

if (ptr)
	kref_put(&ptr->refcount, func);

See dma_fence_put() for an example.

Regards,
Christian.

> +		return;
> +
>  	kref_put(&task_info->refcount, amdgpu_vm_destroy_task_info);
>  }
>