diff --git a/sys/kern/kern_switch.c b/sys/kern/kern_switch.c
index 68b6bc230081..b337e9da7dad 100644
--- a/sys/kern/kern_switch.c
+++ b/sys/kern/kern_switch.c
@@ -584,6 +584,10 @@ critical_exit(void)
 	KASSERT(td->td_critnest != 0,
 	    ("critical_exit: td_critnest == 0"));
 	if (td->td_critnest == 1) {
+		if (td->td_pflags & TDP_WAKEPROC0) {
+			td->td_pflags &= ~TDP_WAKEPROC0;
+			wakeup(&proc0);
+		}
 #ifdef PREEMPTION
 		mtx_assert(&sched_lock, MA_NOTOWNED);
 		if (td->td_pflags & TDP_OWEPREEMPT) {
diff --git a/sys/kern/kern_synch.c b/sys/kern/kern_synch.c
index d67887a2f56f..690dc9a2962a 100644
--- a/sys/kern/kern_synch.c
+++ b/sys/kern/kern_synch.c
@@ -391,13 +391,13 @@ setrunnable(struct thread *td)
 	if ((p->p_sflag & PS_INMEM) == 0) {
 		if ((p->p_sflag & PS_SWAPPINGIN) == 0) {
 			p->p_sflag |= PS_SWAPINREQ;
-#ifndef SMP
 			/*
-			 * XXX: Disabled on SMP due to a LOR between
-			 * sched_lock and the sleepqueue chain locks.
+			 * due to a LOR between sched_lock and
+			 * the sleepqueue chain locks, delay
+			 * wakeup proc0 until thread leaves
+			 * critical region.
 			 */
-			wakeup(&proc0);
-#endif
+			curthread->td_pflags |= TDP_WAKEPROC0;
 		}
 	} else
 		sched_wakeup(td);
diff --git a/sys/sys/proc.h b/sys/sys/proc.h
index cd00c20e7e83..25d33c9d40cc 100644
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -369,7 +369,7 @@ struct thread {
 #define	TDP_SA		0x00000080 /* A scheduler activation based thread. */
 #define	TDP_OWEPREEMPT	0x00000100 /* Thread has a pending preemption. */
 #define	TDP_OWEUPC	0x00000200 /* Call addupc() at next AST. */
-#define	TDP_UNUSED10	0x00000400 /* -- available-- */
+#define	TDP_WAKEPROC0	0x00000400 /* Wants caller to wakeup(&proc0) */
 #define	TDP_CAN_UNBIND	0x00000800 /* Only temporarily bound. */
 #define	TDP_SCHED1	0x00001000 /* Reserved for scheduler private use */
 #define	TDP_SCHED2	0x00002000 /* Reserved for scheduler private use */