Index: vm_map.c
===================================================================
RCS file: /usr/repo/src/sys/vm/vm_map.c,v
retrieving revision 1.379
diff -u -p -r1.379 vm_map.c
--- vm_map.c	21 Oct 2006 21:02:04 -0000	1.379
+++ vm_map.c	3 Dec 2006 12:51:37 -0000
@@ -437,6 +437,16 @@ _vm_map_unlock(vm_map_t map, const char 
 		_sx_xunlock(&map->lock, file, line);
 }
 
+static int
+vm_map_locked(vm_map_t map)
+{
+
+	if (map->system_map)
+		return (mtx_owned(&map->system_mtx));
+	else
+		return (sx_xlocked(&map->lock));
+}
+
 void
 _vm_map_lock_read(vm_map_t map, const char *file, int line)
 {
@@ -2775,6 +2785,7 @@ vm_map_growstack(struct proc *p, vm_offs
 	size_t grow_amount, max_grow;
 	rlim_t stacklim, vmemlim;
 	int is_procstack, rv;
+	int unlock;
 
 Retry:
 	PROC_LOCK(p);
@@ -2782,11 +2793,17 @@ Retry:
 	vmemlim = lim_cur(p, RLIMIT_VMEM);
 	PROC_UNLOCK(p);
 
-	vm_map_lock_read(map);
+	if (vm_map_locked(map))
+		unlock = 0;
+	else {
+		vm_map_lock_read(map);
+		unlock = 1;
+	}
 
 	/* If addr is already in the entry range, no need to grow.*/
 	if (vm_map_lookup_entry(map, addr, &prev_entry)) {
-		vm_map_unlock_read(map);
+		if (unlock)
+			vm_map_unlock_read(map);
 		return (KERN_SUCCESS);
 	}
 
@@ -2799,7 +2816,8 @@ Retry:
 		 * never a growable entry, so it suffices to check the flags.
 		 */
 		if (!(next_entry->eflags & MAP_ENTRY_GROWS_DOWN)) {
-			vm_map_unlock_read(map);
+			if (unlock)
+				vm_map_unlock_read(map);
 			return (KERN_SUCCESS);
 		}
 		stack_entry = next_entry;
@@ -2840,7 +2858,8 @@ Retry:
 	}
 
 	if (grow_amount > stack_entry->avail_ssize) {
-		vm_map_unlock_read(map);
+		if (unlock)
+			vm_map_unlock_read(map);
 		return (KERN_NO_SPACE);
 	}
 
@@ -2854,12 +2873,13 @@ Retry:
 	 * intended by limiting the stack size.
 	 */
 	if (grow_amount > max_grow) {
-		if (vm_map_lock_upgrade(map))
+		if (unlock && vm_map_lock_upgrade(map))
 			goto Retry;
 
 		stack_entry->avail_ssize = max_grow;
 
-		vm_map_unlock(map);
+		if (unlock)
+			vm_map_unlock(map);
 		return (KERN_NO_SPACE);
 	}
 
@@ -2870,7 +2890,8 @@ Retry:
 	 * limit.
 	 */
 	if (is_procstack && (ctob(vm->vm_ssize) + grow_amount > stacklim)) {
-		vm_map_unlock_read(map);
+		if (unlock)
+			vm_map_unlock_read(map);
 		return (KERN_NO_SPACE);
 	}
 
@@ -2884,11 +2905,12 @@ Retry:
 
 	/* If we would blow our VMEM resource limit, no go */
 	if (map->size + grow_amount > vmemlim) {
-		vm_map_unlock_read(map);
+		if (unlock)
+			vm_map_unlock_read(map);
 		return (KERN_NO_SPACE);
 	}
 
-	if (vm_map_lock_upgrade(map))
+	if (unlock && vm_map_lock_upgrade(map))
 		goto Retry;
 
 	if (stack_entry == next_entry) {
@@ -2963,7 +2985,8 @@ Retry:
 	if (rv == KERN_SUCCESS && is_procstack)
 		vm->vm_ssize += btoc(grow_amount);
 
-	vm_map_unlock(map);
+	if (unlock)
+		vm_map_unlock(map);
 
 	/*
 	 * Heed the MAP_WIREFUTURE flag if it was set for this process.
@@ -3064,16 +3087,23 @@ vm_map_lookup(vm_map_t *var_map,		/* IN/
 	vm_map_t map = *var_map;
 	vm_prot_t prot;
 	vm_prot_t fault_type = fault_typea;
+	int unlock;
 
 RetryLookup:;
 	/*
 	 * Lookup the faulting address.
 	 */
 
-	vm_map_lock_read(map);
+	if (vm_map_locked(map))
+		unlock = 0;
+	else {
+		vm_map_lock_read(map);
+		unlock = 1;
+	}
 #define	RETURN(why) \
 		{ \
-		vm_map_unlock_read(map); \
+		if (unlock) \
+			vm_map_unlock_read(map); \
 		return (why); \
 		}
 
@@ -3102,7 +3132,8 @@ RetryLookup:;
 		vm_map_t old_map = map;
 
 		*var_map = map = entry->object.sub_map;
-		vm_map_unlock_read(old_map);
+		if (unlock)
+			vm_map_unlock_read(old_map);
 		goto RetryLookup;
 	}