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

From: Vlastimil Babka
Date: Fri Mar 11 2016 - 10:29:39 EST

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;

- 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)