linux-kernel - Re: [PATCH V2] amdgpu: optimization-- reduce noneed mutex

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Date:   Tue, 21 Apr 2020 00:20:29 -0400
From:   Felix Kuehling <felix.kuehling@....com>
To:     1587181464-114215-1-git-send-email-bernard@...o.com,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "David (ChunMing) Zhou" <David1.Zhou@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Cc:     opensource.kernel@...o.com, Bernard Zhao <bernard@...o.com>
Subject: Re: [PATCH V2] amdgpu: optimization-- reduce noneed mutex_lock area

Hi Bernard,

Thank you for the patch. Please see some comments inline.

Am 2020-04-20 um 10:25 p.m. schrieb Bernard Zhao:
> Maybe we could reduce the mutex_lock(&mem->lock)`s protected code area,
> and noneed to protect pr_debug.

Typo: noneed -> no need


>
> Signed-off-by: Bernard Zhao <bernard@...o.com>
>
> Changes since V1:
> *commit message improve
>
> Link for V1:
> *https://lore.kernel.org/patchwork/patch/1226588/
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> index 327317c54f7c..3c3769e57174 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> @@ -1285,17 +1285,18 @@ int amdgpu_amdkfd_gpuvm_free_memory_of_gpu(
>  	struct bo_vm_reservation_context ctx;
>  	struct ttm_validate_buffer *bo_list_entry;
>  	int ret;
> +	unsigned int mapped_to_gpu_memory;
>  
>  	mutex_lock(&mem->lock);
> +	mapped_to_gpu_memory = mem->mapped_to_gpu_memory;
> +	mutex_unlock(&mem->lock);
>  
> -	if (mem->mapped_to_gpu_memory > 0) {
> +	if (mapped_to_gpu_memory > 0) {
>  		pr_debug("BO VA 0x%llx size 0x%lx is still mapped.\n",
>  				mem->va, bo_size);
> -		mutex_unlock(&mem->lock);
>  		return -EBUSY;
>  	}
>  
> -	mutex_unlock(&mem->lock);
>  	/* lock is not needed after this, since mem is unused and will
>  	 * be freed anyway
>  	 */

Please move this comment along with the mutex_unlock.

Regards,
  Felix