[PATCH]: Only start one xenfb kthread

[Chris Lalancette <clalance@redhat.com>]

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All,
     When doing save/restore testing with the linux-2.6.18-xen.hg tree,
it was discovered that every time a restore happened we would get a
new xenfb thread.  While the framebuffer continues to work, this is
an obvious resource leak.  The attached patch only starts up a new xenfb
thread the first time the backend connects, and continues to re-use that
in the future.  Jeremy's upstream LKML tree doesn't suffer from this
since it uses a completely different mechanism to do screen updates.
Original patch from John Haxby @ Oracle; slightly modified by me to apply
to the linux-2.6.18-xen.hg tree.

Signed-off-by: Chris Lalancette <clalance@redhat.com>

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diff --git a/drivers/xen/fbfront/xenfb.c b/drivers/xen/fbfront/xenfb.c
--- a/drivers/xen/fbfront/xenfb.c
+++ b/drivers/xen/fbfront/xenfb.c
@@ -831,7 +831,7 @@ static void xenfb_backend_changed(struct
 				 "request-update", "%d", &val) < 0)
 			val = 0;
 
-		if (val){
+		if (val && !info->kthread) {
 			info->kthread = kthread_run(xenfb_thread, info,
 						    "xenfb thread");
 			if (IS_ERR(info->kthread)) {

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