linux-kernel - [PATCH 3.16.y-ckt 009/128] drm/ttm: Fixed a read/write lock imbalance

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Message-Id: <1453672883-2708-10-git-send-email-luis.henriques@canonical.com>
Date:	Sun, 24 Jan 2016 21:59:24 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Thomas Hellstrom <thellstrom@...are.com>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 009/128] drm/ttm: Fixed a read/write lock imbalance

3.16.7-ckt23 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Thomas Hellstrom <thellstrom@...are.com>

commit 025af189fb44250206dd8a32fa4a682392af3301 upstream.

In ttm_write_lock(), the uninterruptible path should call
__ttm_write_lock() not __ttm_read_lock().  This fixes a vmwgfx hang
on F23 start up.

syeh: Extracted this from one of Thomas' internal patches.

Signed-off-by: Thomas Hellstrom <thellstrom@...are.com>
Reviewed-by: Sinclair Yeh <syeh@...are.com>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 drivers/gpu/drm/ttm/ttm_lock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/ttm/ttm_lock.c b/drivers/gpu/drm/ttm/ttm_lock.c
index 6a954544727f..f154fb1929bd 100644
--- a/drivers/gpu/drm/ttm/ttm_lock.c
+++ b/drivers/gpu/drm/ttm/ttm_lock.c
@@ -180,7 +180,7 @@ int ttm_write_lock(struct ttm_lock *lock, bool interruptible)
 			spin_unlock(&lock->lock);
 		}
 	} else
-		wait_event(lock->queue, __ttm_read_lock(lock));
+		wait_event(lock->queue, __ttm_write_lock(lock));
 
 	return ret;
 }