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

[Michal Hocko]

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>
Reviewed-by: Christian KÃnig <christian.koenig@xxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
---
 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 9f4a45cd2aab..cf90686a50d1 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
@@ -232,7 +232,10 @@ 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)
-- 
2.8.0.rc3