2 files changed, 61 insertions, 1 deletions

diff --git a/sys/vm/vm_map.c b/sys/vm/vm_map.c
index 37bad54756b9..900c8d162343 100644
--- a/sys/vm/vm_map.c
+++ b/sys/vm/vm_map.c
@@ -561,6 +561,56 @@ vm_map_wakeup(vm_map_t map)
 	wakeup(&map->root);
 }
 
+void
+vm_map_busy(vm_map_t map)
+{
+
+#ifdef INVARIANTS
+	if (map->system_map) {
+		mtx_assert(&map->system_mtx, MA_OWNED);
+	} else
+		sx_assert(&map->lock, SX_XLOCKED);
+#endif
+	map->busy++;
+}
+
+void
+vm_map_unbusy(vm_map_t map)
+{
+
+#ifdef INVARIANTS
+	if (map->system_map) {
+		mtx_assert(&map->system_mtx, MA_OWNED);
+	} else
+		sx_assert(&map->lock, SX_XLOCKED);
+#endif
+	KASSERT(map->busy, ("vm_map_unbusy: not busy"));
+	if (--map->busy == 0 && (map->flags & MAP_BUSY_WAKEUP)) {
+		vm_map_modflags(map, 0, MAP_BUSY_WAKEUP);
+		wakeup(&map->busy);
+	}
+}
+
+void 
+vm_map_wait_busy(vm_map_t map)
+{
+
+#ifdef INVARIANTS
+	if (map->system_map) {
+		mtx_assert(&map->system_mtx, MA_OWNED);
+	} else
+		sx_assert(&map->lock, SX_XLOCKED);
+#endif
+	while (map->busy) {
+		vm_map_modflags(map, MAP_BUSY_WAKEUP, 0);
+		if (map->system_map)
+			msleep(&map->busy, &map->system_mtx, 0, "mbusy", 0);
+		else
+			sx_sleep(&map->busy, &map->lock, 0, "mbusy", 0);
+	}
+	map->timestamp++;
+}
+
 long
 vmspace_resident_count(struct vmspace *vmspace)
 {
@@ -609,6 +659,7 @@ _vm_map_init(vm_map_t map, vm_offset_t min, vm_offset_t max)
 	map->flags = 0;
 	map->root = NULL;
 	map->timestamp = 0;
+	map->busy = 0;
 }
 
 void
@@ -2070,12 +2121,14 @@ vm_map_wire(vm_map_t map, vm_offset_t start, vm_offset_t end,
 			    entry->object.vm_object->type == OBJT_SG);
 			/*
 			 * Release the map lock, relying on the in-transition
-			 * mark.
+			 * mark.  Mark the map busy for fork.
 			 */
+			vm_map_busy(map);
 			vm_map_unlock(map);
 			rv = vm_fault_wire(map, saved_start, saved_end,
 			    user_wire, fictitious);
 			vm_map_lock(map);
+			vm_map_unbusy(map);
 			if (last_timestamp + 1 != map->timestamp) {
 				/*
 				 * Look again for the entry because the map was
@@ -2605,6 +2658,8 @@ vmspace_fork(struct vmspace *vm1)
 	vm_object_t object;
 
 	vm_map_lock(old_map);
+	if (old_map->busy)
+		vm_map_wait_busy(old_map);
 
 	vm2 = vmspace_alloc(old_map->min_offset, old_map->max_offset);
 	if (vm2 == NULL)
diff --git a/sys/vm/vm_map.h b/sys/vm/vm_map.h
index 2421b2298b11..2fe9450194be 100644
--- a/sys/vm/vm_map.h
+++ b/sys/vm/vm_map.h
@@ -194,12 +194,14 @@ struct vm_map {
 	pmap_t pmap;			/* (c) Physical map */
 #define	min_offset	header.start	/* (c) */
 #define	max_offset	header.end	/* (c) */
+	int busy;
 };
 
 /*
  * vm_flags_t values
  */
 #define MAP_WIREFUTURE		0x01	/* wire all future pages */
+#define	MAP_BUSY_WAKEUP		0x02
 
 #ifdef	_KERNEL
 static __inline vm_offset_t
@@ -276,6 +278,9 @@ int _vm_map_lock_upgrade(vm_map_t map, const char *file, int line);
 void _vm_map_lock_downgrade(vm_map_t map, const char *file, int line);
 int vm_map_unlock_and_wait(vm_map_t map, boolean_t user_wait);
 void vm_map_wakeup(vm_map_t map);
+void vm_map_busy(vm_map_t map);
+void vm_map_unbusy(vm_map_t map);
+void vm_map_wait_busy(vm_map_t map);
 
 #define	vm_map_lock(map)	_vm_map_lock(map, LOCK_FILE, LOCK_LINE)
 #define	vm_map_unlock(map)	_vm_map_unlock(map, LOCK_FILE, LOCK_LINE)