Re: [PATCH 17/18] drm/radeon: make radeon_mn_get wait for mmap_sem killable

[Vlastimil Babka]

On 02/29/2016 02:26 PM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@xxxxxxxx>
>
> radeon_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: Alex Deucher <alexander.deucher@xxxxxxx>
> Cc: "Christian KÃnig" <christian.koenig@xxxxxxx>
> Cc: David Airlie <airlied@xxxxxxxx>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>

Acked-by: Vlastimil Babka <vbabka@xxxxxxx>

> ---
>   drivers/gpu/drm/radeon/radeon_mn.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/radeon/radeon_mn.c b/drivers/gpu/drm/radeon/radeon_mn.c
> index eef006c48584..896f2cf51e4e 100644
> --- a/drivers/gpu/drm/radeon/radeon_mn.c
> +++ b/drivers/gpu/drm/radeon/radeon_mn.c
> @@ -186,7 +186,9 @@ static struct radeon_mn *radeon_mn_get(struct radeon_device *rdev)
>   	struct radeon_mn *rmn;
>   	int r;
>
> -	down_write(&mm->mmap_sem);
> +	if (down_write_killable(&mm->mmap_sem))
> +		return ERR_PTR(-EINTR);
> +
>   	mutex_lock(&rdev->mn_lock);
>
>   	hash_for_each_possible(rdev->mn_hash, rmn, node, (unsigned long)mm)