[PATCH] radeon: avoid copying over itself ddx fb

[j.glisse at gmail.com]

From: Jerome Glisse <jglisse at redhat.com>

In some rare case it seems that the old fb could already be the
ddx fb. As copying from the same bo will trigger a ttm deadlck
detection which will result in infinite kernel/userspace loop.
Avoid doing any copy as anyway it's useless.

Signed-off-by: Jerome Glisse <jglisse at redhat.com>
---
 src/drmmode_display.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/drmmode_display.c b/src/drmmode_display.c
index dc608de..15407fe 100644
--- a/src/drmmode_display.c
+++ b/src/drmmode_display.c
@@ -292,6 +292,15 @@ void drmmode_copy_fb(ScrnInfoPtr pScrn, drmmode_ptr drmmode)
 	if (!fbcon_id)
 		goto fallback;
 
+	if (fbcon_id == drmmode->fb_id) {
+		/* in some rare case there might be no fbcon and we might already
+		 * be the one with the current fb to avoid a false deadlck in
+		 * kernel ttm code just do nothing as anyway there is nothing
+		 * to do
+		 */
+		return;
+	}
+
 	src = create_pixmap_for_fbcon(drmmode, pScrn, fbcon_id);
 	if (!src)
 		goto fallback;
-- 
1.7.11.7