From: Thomas Hellstrom <thellstrom@vmware.com>
Date: Fri, 20 Nov 2015 19:43:50 +0000 (-0800)
Subject: drm/ttm: Fixed a read/write lock imbalance
X-Git-Tag: v3.16.35~811
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=23fe87e5a17ab204a85988d2f6d49e0a71e15a62;p=thirdparty%2Fkernel%2Fstable.git

drm/ttm: Fixed a read/write lock imbalance

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@vmware.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---

diff --git a/drivers/gpu/drm/ttm/ttm_lock.c b/drivers/gpu/drm/ttm/ttm_lock.c
index 6a954544727f3..f154fb1929bd1 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;
 }