linux-kernel - [PATCH 17/18] drm/radeon: make radeon_mn_get wait for mmap

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Date:	Tue, 26 Apr 2016 14:56:24 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	<linux-mm@...ck.org>, Andrew Morton <akpm@...ux-foundation.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Michal Hocko <mhocko@...e.com>,
	Alex Deucher <alexander.deucher@....com>,
	Christian König <christian.koenig@....com>,
	David Airlie <airlied@...ux.ie>,
	Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH 17/18] drm/radeon: make radeon_mn_get wait for mmap_sem killable

From: Michal Hocko <mhocko@...e.com>

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@....com>
Cc: "Christian König" <christian.koenig@....com>
Cc: David Airlie <airlied@...ux.ie>
Reviewed-by: Christian König <christian.koenig@....com>
Acked-by: Vlastimil Babka <vbabka@...e.cz>
Signed-off-by: Michal Hocko <mhocko@...e.com>
---
 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)
-- 
2.8.0.rc3