Index: head/sys/kern/kern_timeout.c
===================================================================
--- head/sys/kern/kern_timeout.c
+++ head/sys/kern/kern_timeout.c
@@ -1155,14 +1155,14 @@
 }
 
 int
-_callout_stop_safe(struct callout *c, int safe, void (*drain)(void *))
+_callout_stop_safe(struct callout *c, int flags, void (*drain)(void *))
 {
 	struct callout_cpu *cc, *old_cc;
 	struct lock_class *class;
 	int direct, sq_locked, use_lock;
 	int not_on_a_list;
 
-	if (safe)
+	if ((flags & CS_DRAIN) != 0)
 		WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, c->c_lock,
 		    "calling %s", __func__);
 
@@ -1170,7 +1170,7 @@
 	 * Some old subsystems don't hold Giant while running a callout_stop(),
 	 * so just discard this check for the moment.
 	 */
-	if (!safe && c->c_lock != NULL) {
+	if ((flags & CS_DRAIN) == 0 && c->c_lock != NULL) {
 		if (c->c_lock == &Giant.lock_object)
 			use_lock = mtx_owned(&Giant);
 		else {
@@ -1253,7 +1253,7 @@
 			return (-1);
 		}
 
-		if (safe) {
+		if ((flags & CS_DRAIN) != 0) {
 			/*
 			 * The current callout is running (or just
 			 * about to run) and blocking is allowed, so
@@ -1370,7 +1370,7 @@
 				cc_exec_drain(cc, direct) = drain;
 			}
 			CC_UNLOCK(cc);
-			return (0);
+			return ((flags & CS_MIGRBLOCK) != 0);
 		}
 		CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
 		    c, c->c_func, c->c_arg);
Index: head/sys/kern/subr_sleepqueue.c
===================================================================
--- head/sys/kern/subr_sleepqueue.c
+++ head/sys/kern/subr_sleepqueue.c
@@ -586,7 +586,8 @@
 	 * another CPU, so synchronize with it to avoid having it
 	 * accidentally wake up a subsequent sleep.
 	 */
-	else if (callout_stop(&td->td_slpcallout) == 0) {
+	else if (_callout_stop_safe(&td->td_slpcallout, CS_MIGRBLOCK, NULL)
+	    == 0) {
 		td->td_flags |= TDF_TIMEOUT;
 		TD_SET_SLEEPING(td);
 		mi_switch(SW_INVOL | SWT_SLEEPQTIMO, NULL);
Index: head/sys/sys/callout.h
===================================================================
--- head/sys/sys/callout.h
+++ head/sys/sys/callout.h
@@ -62,6 +62,12 @@
 	struct callout *callout;
 };
 
+/* Flags for callout_stop_safe() */
+#define	CS_DRAIN		0x0001 /* callout_drain(), wait allowed */
+#define	CS_MIGRBLOCK		0x0002 /* Block migration, return value
+					  indicates that the callout was
+				          executing */
+
 #ifdef _KERNEL
 /* 
  * Note the flags field is actually *two* fields. The c_flags
@@ -81,7 +87,7 @@
  */
 #define	callout_active(c)	((c)->c_flags & CALLOUT_ACTIVE)
 #define	callout_deactivate(c)	((c)->c_flags &= ~CALLOUT_ACTIVE)
-#define	callout_drain(c)	_callout_stop_safe(c, 1, NULL)
+#define	callout_drain(c)	_callout_stop_safe(c, CS_DRAIN, NULL)
 void	callout_init(struct callout *, int);
 void	_callout_init_lock(struct callout *, struct lock_object *, int);
 #define	callout_init_mtx(c, mtx, flags)					\