diff --git a/sys/vm/vm_map.c b/sys/vm/vm_map.c
index 6bcebd543096..bb38d121a2ff 100644
--- a/sys/vm/vm_map.c
+++ b/sys/vm/vm_map.c
@@ -1655,6 +1655,7 @@ _vm_map_clip_start(vm_map_t map, vm_map_entry_t entry, vm_offset_t start)
 	vm_map_entry_t new_entry;
 
 	VM_MAP_ASSERT_LOCKED(map);
+	KASSERT(entry->end > start, ("invalid clip of entry %p", entry));
 
 	/*
 	 * Split off the front portion -- note that we must insert the new
@@ -1739,6 +1740,7 @@ _vm_map_clip_end(vm_map_t map, vm_map_entry_t entry, vm_offset_t end)
 	vm_map_entry_t new_entry;
 
 	VM_MAP_ASSERT_LOCKED(map);
+	KASSERT(entry->start < end, ("invalid clip of entry %p", entry));
 
 	/*
 	 * If there is no object backing this entry, we might as well create
@@ -1954,7 +1956,9 @@ vm_map_protect(vm_map_t map, vm_offset_t start, vm_offset_t end,
 	vm_map_entry_t current, entry;
 	vm_object_t obj;
 	struct ucred *cred;
+	vm_offset_t saved_start;
 	vm_prot_t old_prot;
+	u_int last_timestamp;
 
 	if (start == end)
 		return (KERN_SUCCESS);
@@ -1972,8 +1976,8 @@ vm_map_protect(vm_map_t map, vm_offset_t start, vm_offset_t end,
 	/*
 	 * Make a first pass to check for protection violations.
 	 */
-	current = entry;
-	while ((current != &map->header) && (current->start < end)) {
+	for (current = entry; current != &map->header && current->start < end;
+	    current = current->next) {
 		if (current->eflags & MAP_ENTRY_IS_SUB_MAP) {
 			vm_map_unlock(map);
 			return (KERN_INVALID_ARGUMENT);
@@ -1982,17 +1986,15 @@ vm_map_protect(vm_map_t map, vm_offset_t start, vm_offset_t end,
 			vm_map_unlock(map);
 			return (KERN_PROTECTION_FAILURE);
 		}
-		current = current->next;
 	}
 
-
 	/*
 	 * Do an accounting pass for private read-only mappings that
 	 * now will do cow due to allowed write (e.g. debugger sets
 	 * breakpoint on text segment)
 	 */
-	for (current = entry; (current != &map->header) &&
-	     (current->start < end); current = current->next) {
+	for (current = entry; current != &map->header && current->start < end;
+	    current = current->next) {
 
 		vm_map_clip_end(map, current, end);
 
@@ -2042,19 +2044,22 @@ vm_map_protect(vm_map_t map, vm_offset_t start, vm_offset_t end,
 	}
 
 	/*
-	 * Go back and fix up protections. [Note that clipping is not
-	 * necessary the second time.]
+	 * Go back and fix up protections.
 	 */
 	current = entry;
-	while ((current != &map->header) && (current->start < end)) {
+restart:
+	for (; current != &map->header && current->start < end;
+	    current = current->next) {
 		old_prot = current->protection;
 
-		if (set_max)
-			current->protection =
-			    (current->max_protection = new_prot) &
-			    old_prot;
-		else
-			current->protection = new_prot;
+		if ((current->eflags & MAP_ENTRY_IN_TRANSITION) == 0) {
+			if (set_max)
+				current->protection =
+				    (current->max_protection = new_prot) &
+				    old_prot;
+			else
+				current->protection = new_prot;
+		}
 
 		/*
 		 * For user wired map entries, the normal lazy evaluation of
@@ -2062,10 +2067,33 @@ vm_map_protect(vm_map_t map, vm_offset_t start, vm_offset_t end,
 		 * undesirable.  Instead, immediately copy any pages that are
 		 * copy-on-write and enable write access in the physical map.
 		 */
-		if ((current->eflags & MAP_ENTRY_USER_WIRED) != 0 &&
+		if ((current->eflags & (MAP_ENTRY_USER_WIRED |
+		     MAP_ENTRY_IN_TRANSITION)) != 0 &&
 		    (current->protection & VM_PROT_WRITE) != 0 &&
-		    (old_prot & VM_PROT_WRITE) == 0)
-			vm_fault_copy_entry(map, map, current, current, NULL);
+		    (old_prot & VM_PROT_WRITE) == 0) {
+			if ((current->eflags & MAP_ENTRY_IN_TRANSITION) != 0) {
+				current->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
+				last_timestamp = map->timestamp;
+				saved_start = current->start;
+				(void)vm_map_unlock_and_wait(map, 0);
+				vm_map_lock(map);
+				if (last_timestamp + 1 != map->timestamp) {
+					if (!vm_map_lookup_entry(map,
+					    saved_start, &current))
+						current = current->next;
+					else
+						vm_map_clip_start(map, current,
+						    saved_start);
+					if (current->start < end)
+						vm_map_clip_end(map, current,
+						    end);
+					goto restart;
+				}
+			}
+			if ((current->eflags & MAP_ENTRY_USER_WIRED) != 0)
+				vm_fault_copy_entry(map, map, current, current,
+				    NULL);
+		}
 
 		/*
 		 * When restricting access, update the physical map.  Worry
@@ -2080,7 +2108,6 @@ vm_map_protect(vm_map_t map, vm_offset_t start, vm_offset_t end,
 #undef	MASK
 		}
 		vm_map_simplify_entry(map, current);
-		current = current->next;
 	}
 	vm_map_unlock(map);
 	return (KERN_SUCCESS);