linux-kernel - [PATCH 3.4 05/91] drm/vmwgfx: Fix a potential infinite spin waiting for fifo idle

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Date:	Wed, 28 Jan 2015 12:06:17 +0800
From:	lizf@...nel.org
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Thomas Hellstrom <thellstrom@...are.com>,
	Zefan Li <lizefan@...wei.com>
Subject: [PATCH 3.4 05/91] drm/vmwgfx: Fix a potential infinite spin waiting for fifo idle

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

3.4.105-rc1 review patch.  If anyone has any objections, please let me know.

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


commit f01ea0c3d9db536c64d47922716d8b3b8f21d850 upstream.

The code waiting for fifo idle was incorrect and could possibly spin
forever under certain circumstances.

Signed-off-by: Thomas Hellstrom <thellstrom@...are.com>
Reported-by: Mark Sheldon <markshel@...are.com>
Reviewed-by: Jakob Bornecrantz <jakob@...are.com>
Reivewed-by: Mark Sheldon <markshel@...are.com>
Signed-off-by: Zefan Li <lizefan@...wei.com>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c b/drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c
index a0c2f12..decca82 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c
@@ -163,8 +163,9 @@ void vmw_fifo_release(struct vmw_private *dev_priv, struct vmw_fifo_state *fifo)
 
 	mutex_lock(&dev_priv->hw_mutex);
 
+	vmw_write(dev_priv, SVGA_REG_SYNC, SVGA_SYNC_GENERIC);
 	while (vmw_read(dev_priv, SVGA_REG_BUSY) != 0)
-		vmw_write(dev_priv, SVGA_REG_SYNC, SVGA_SYNC_GENERIC);
+		;
 
 	dev_priv->last_read_seqno = ioread32(fifo_mem + SVGA_FIFO_FENCE);
 
-- 
1.9.1

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