From: Keir Fraser <keir.fraser@eu.citrix.com>
References: bnc#638465

--- a/xen/common/page_alloc.c	Wed Sep 01 10:22:05 2010 +0100
+++ b/xen/common/page_alloc.c	Tue Sep 07 13:55:34 2010 +0100
@@ -378,8 +378,6 @@
     total_avail_pages -= request;
     ASSERT(total_avail_pages >= 0);
 
-    spin_unlock(&heap_lock);
-
     cpus_clear(mask);
 
     for ( i = 0; i < (1 << order); i++ )
@@ -400,6 +398,8 @@
         pg[i].u.inuse.type_info = 0;
         page_set_owner(&pg[i], NULL);
     }
+
+    spin_unlock(&heap_lock);
 
     if ( unlikely(!cpus_empty(mask)) )
     {
@@ -496,6 +496,8 @@
     ASSERT(order <= MAX_ORDER);
     ASSERT(node >= 0);
 
+    spin_lock(&heap_lock);
+
     for ( i = 0; i < (1 << order); i++ )
     {
         /*
@@ -522,8 +524,6 @@
         if ( pg[i].u.free.need_tlbflush )
             pg[i].tlbflush_timestamp = tlbflush_current_time();
     }
-
-    spin_lock(&heap_lock);
 
     avail[node][zone] += 1 << order;
     total_avail_pages += 1 << order;