linux-kernel - [PATCH 4.4 169/342] drm/vmwgfx: Fix an incorrect lock check

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Message-Id: <20160301234533.423471476@linuxfoundation.org>
Date:	Tue, 01 Mar 2016 23:54:40 +0000
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	<linux-kernel@...r.kernel.org>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	<stable@...r.kernel.org>, Thomas Hellstrom <thellstrom@...are.com>,
	Sinclair Yeh <syeh@...are.com>,
	Dave Airlie <airlied@...hat.com>
Subject: [PATCH 4.4 169/342] drm/vmwgfx: Fix an incorrect lock check

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

------------------

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

commit fb89ac5102ae2875d685c847e6b5dbc141622d43 upstream.

With CONFIG_SMP=n and CONFIG_DEBUG_SPINLOCK=y the vmwgfx kernel module
would unconditionally throw a bug when checking for a held spinlock
in the command buffer code. Fix this by using a lockdep check.

Reported-and-tested-by: Tetsuo Handa <penguin-kernel@...ove-sakura.ne.jp>
Signed-off-by: Thomas Hellstrom <thellstrom@...are.com>
Reviewed-by: Sinclair Yeh <syeh@...are.com>
Signed-off-by: Dave Airlie <airlied@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/vmwgfx/vmwgfx_cmdbuf.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/vmwgfx/vmwgfx_cmdbuf.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_cmdbuf.c
@@ -247,7 +247,7 @@ static void __vmw_cmdbuf_header_free(str
 {
 	struct vmw_cmdbuf_man *man = header->man;
 
-	BUG_ON(!spin_is_locked(&man->lock));
+	lockdep_assert_held_once(&man->lock);
 
 	if (header->inline_space) {
 		vmw_cmdbuf_header_inline_free(header);