Index: sys/kern/kern_shutdown.c
===================================================================
--- sys/kern/kern_shutdown.c	(revision 206800)
+++ sys/kern/kern_shutdown.c	(working copy)
@@ -62,7 +62,7 @@
 #include <sys/reboot.h>
 #include <sys/resourcevar.h>
 #include <sys/sched.h>
-#include <sys/smp.h>		/* smp_active */
+#include <sys/smp.h>
 #include <sys/sysctl.h>
 #include <sys/sysproto.h>
 
@@ -485,15 +485,17 @@
 shutdown_reset(void *junk, int howto)
 {
 
+	printf("Rebooting...\n");
+	DELAY(1000000);	/* wait 1 sec for printf's to complete and be read */
+
 	/*
-	 * Disable interrupts on CPU0 in order to avoid fast handlers
-	 * to preempt the stopping process and to deadlock against other
-	 * CPUs.
+	 * Acquiring smp_ipi_mtx here has a double effect:
+	 * it disables interrupts avoiding CPU0 preemption
+	 * by fast handlers (thus deadlocking  against other CPUs) and,
+	 * secondly, avoids deadlocks against smp_tlb_shootdown() and
+	 * smp_rendezvous().
 	 */
-	spinlock_enter();
-
-	printf("Rebooting...\n");
-	DELAY(1000000);	/* wait 1 sec for printf's to complete and be read */
+	mtx_lock_spin(&smp_ipi_mtx);
 	/* cpu_boot(howto); */ /* doesn't do anything at the moment */
 	cpu_reset();
 	/* NOTREACHED */ /* assuming reset worked */