diff -r 45981aefbe48 xen/arch/x86/nmi.c
--- a/xen/arch/x86/nmi.c	Fri Jul 17 12:25:06 2009 +0100
+++ b/xen/arch/x86/nmi.c	Fri Jul 17 12:51:43 2009 +0100
@@ -383,10 +383,38 @@
     }
 }
 
+static atomic_t all_panic = ATOMIC_INIT(0);
+static DEFINE_SPINLOCK(panic_lock);
+
+static void do_nmi_trigger_cpu(int cpu)
+{
+    u32 id = cpu_physical_id(cpu);
+
+    printk("Triggering NMI on APIC ID %x\n", id);
+    debugtrace_dump();
+
+    local_irq_disable();
+    apic_wait_icr_idle();
+    apic_icr_write(APIC_DM_NMI | APIC_DEST_PHYSICAL, id);
+    local_irq_enable();
+}
+
 void nmi_watchdog_tick(struct cpu_user_regs * regs)
 {
     unsigned int sum = this_cpu(nmi_timer_ticks);
 
+    if ( atomic_read(&all_panic) )
+    {
+        spin_lock(&panic_lock);
+        console_force_unlock();
+        printk("Sibling watchdog timer fired! Printing state for CPU%d\n",
+               smp_processor_id());
+        show_execution_state(regs);
+        debugtrace_dump();
+        spin_unlock(&panic_lock);
+        while(1);
+    }
+
     if ( (this_cpu(last_irq_sums) == sum) &&
          !atomic_read(&watchdog_disable_count) )
     {
@@ -400,7 +428,22 @@
             console_force_unlock();
             printk("Watchdog timer detects that CPU%d is stuck!\n",
                    smp_processor_id());
-            fatal_trap(TRAP_nmi, regs);
+            show_execution_state(regs);
+            debugtrace_dump();
+            atomic_inc(&all_panic);
+            {
+                int cpu;
+                spin_lock(&panic_lock);
+                for_each_cpu(cpu)
+                {
+                    if ( cpu == smp_processor_id())
+                        continue;
+                    do_nmi_trigger_cpu(cpu);
+                }
+                spin_unlock(&panic_lock);
+            }
+            while(1);
+            //fatal_trap(TRAP_nmi, regs);
         }
     } 
     else