Index: sys/kern/subr_autoconf.c
===================================================================
--- sys/kern/subr_autoconf.c
+++ sys/kern/subr_autoconf.c
@@ -138,6 +138,7 @@
 	while (next_to_notify != NULL) {
 		hook_entry = next_to_notify;
 		next_to_notify = STAILQ_NEXT(hook_entry, ich_links);
+		hook_entry->ich_flags |= ICHF_RUNNING;
 		mtx_unlock(&intr_config_hook_lock);
 		(*hook_entry->ich_func)(hook_entry->ich_arg);
 		mtx_lock(&intr_config_hook_lock);
@@ -226,12 +227,11 @@
 	config_intrhook_establish(&ohook->och_hook);
 }
 
-void
-config_intrhook_disestablish(struct intr_config_hook *hook)
+static void
+config_intrhook_disestablish_locked(struct intr_config_hook *hook)
 {
 	struct intr_config_hook *hook_entry;
 
-	mtx_lock(&intr_config_hook_lock);
 	STAILQ_FOREACH(hook_entry, &intr_config_hook_list, ich_links)
 		if (hook_entry == hook)
 			break;
@@ -245,7 +245,40 @@
 	TSRELEASE("config hooks");
 
 	/* Wakeup anyone watching the list */
+	hook->ich_flags &= ~ICHF_RUNNING;
 	wakeup(&intr_config_hook_list);
+}
+
+void
+config_intrhook_disestablish(struct intr_config_hook *hook)
+{
+	mtx_lock(&intr_config_hook_lock);
+	config_intrhook_disestablish_locked(hook);
+	mtx_unlock(&intr_config_hook_lock);
+}
+
+void
+config_intrhook_drain(struct intr_config_hook *hook)
+{
+	mtx_lock(&intr_config_hook_lock);
+	/*
+	 * The config hook is not running, so just call disestablish
+	 */
+	if ((hook->ich_flags & ICHF_RUNNING) == 0) {
+		config_intrhook_disestablish_locked(hook);
+		mtx_unlock(&intr_config_hook_lock);
+		return;
+	}
+
+	/*
+	 * The config hook is running, so wait for it to complete and return.
+	 */
+	while (hook->ich_flags & ICHF_RUNNING) {
+		if (msleep(&intr_config_hook_list, &intr_config_hook_lock,
+		    0, "confhd", hz) == EWOULDBLOCK) {
+			// XXX do I whine?
+		}
+	}
 	mtx_unlock(&intr_config_hook_lock);
 }
 
Index: sys/sys/kernel.h
===================================================================
--- sys/sys/kernel.h
+++ sys/sys/kernel.h
@@ -475,6 +475,7 @@
 
 int	config_intrhook_establish(struct intr_config_hook *hook);
 void	config_intrhook_disestablish(struct intr_config_hook *hook);
+void	config_intrhook_drain(struct intr_config_hook *hook);
 void	config_intrhook_oneshot(ich_func_t _func, void *_arg);
 
 #endif /* !_SYS_KERNEL_H_*/