xen-debug-hang.patch

diff --git a/xen/common/smp.c b/xen/common/smp.c
index 79f4ebd14502..155d6d52f655 100644
--- a/xen/common/smp.c
+++ b/xen/common/smp.c
@@ -51,6 +51,7 @@ void on_selected_cpus(
     int wait)
 {
     unsigned int nr_cpus;
+    unsigned long counter = 0;
 
     ASSERT(local_irq_is_enabled());
     ASSERT(cpumask_subset(selected, &cpu_online_map));
@@ -69,8 +70,15 @@ void on_selected_cpus(
 
     smp_send_call_function_mask(&call_data.selected);
 
-    while ( !cpumask_empty(&call_data.selected) )
+    while ( !cpumask_empty(&call_data.selected) ) {
+        if (counter > 100000) {
+            printk(XENLOG_WARNING "still waiting for %*pbl\n", CPUMASK_PR(&call_data.selected));
+            WARN();
+            counter = 0;
+        }
+        counter++;
         cpu_relax();
+    }
 
 out:
     spin_unlock(&call_lock);