Re: [PATCH 18/18] drm/amdgpu: make amdgpu_mn_get wait for mmap_sem killable

[Vlastimil Babka]

On 02/29/2016 02:26 PM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@xxxxxxxx>
>
> amdgpu_mn_get which is called during ioct path relies on mmap_sem for
> write. If the waiting task gets killed by the oom killer it would block
> oom_reaper from asynchronous address space reclaim and reduce the
> chances of timely OOM resolving. Wait for the lock in the killable mode
> and return with EINTR if the task got killed while waiting.
>
> Cc: David Airlie <airlied@xxxxxxxx>
> Cc: Alex Deucher <alexander.deucher@xxxxxxx>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>


Acked-by: Vlastimil Babka <vbabka@xxxxxxx>

> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
> index d7ec9bd6755f..6f44f1c23be3 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
> @@ -181,7 +181,10 @@ static struct amdgpu_mn *amdgpu_mn_get(struct amdgpu_device *adev)
>   	int r;
>
>   	mutex_lock(&adev->mn_lock);
> -	down_write(&mm->mmap_sem);
> +	if (down_write_killable(&mm->mmap_sem)) {
> +		mutex_unlock(&adev->mn_lock);
> +		return -EINTR;
> +	}
>
>   	hash_for_each_possible(adev->mn_hash, rmn, node, (unsigned long)mm)
>   		if (rmn->mm == mm)