Index: sys/vm/vm_radix.c
===================================================================
--- sys/vm/vm_radix.c	(revisione 235178)
+++ sys/vm/vm_radix.c	(copia locale)
@@ -97,6 +97,7 @@
 CTASSERT(sizeof(struct vm_radix_node) < PAGE_SIZE);
 
 static uma_zone_t vm_radix_node_zone;
+static u_long allocfail;
 
 #ifndef UMA_MD_SMALL_ALLOC
 static vm_map_t rnode_map;
@@ -192,6 +193,10 @@
 vm_radix_node_get(void)
 {
 
+	if (++allocfail == 100000000) {
+		allocfail = 0;
+		return (NULL);
+	}
 	return (uma_zalloc(vm_radix_node_zone, M_NOWAIT | M_ZERO));
 }
 
@@ -280,11 +285,11 @@
 	rtree->rt_root = root;
 }
 
-static inline void
-vm_radix_unwind_heightup(struct vm_radix *rtree, struct vm_radix_node *root,
-    struct vm_radix_node *iroot, int ilevel)
+static void
+vm_radix_unwind_heightup(struct vm_radix *rtree, volatile struct vm_radix_node *root,
+    volatile struct vm_radix_node *iroot, int ilevel)
 {
-	struct vm_radix_node *rnode;
+	volatile struct vm_radix_node *rnode;
 
 	CTR4(KTR_VM, "unwind: tree %p, root %p, iroot %p, ilevel %d",
 	    rtree, root, iroot, ilevel);
@@ -293,9 +298,9 @@
 		MPASS(rnode->rn_count == 0 || rnode->rn_count == 1);
 		rnode->rn_count = 0;
 		root = rnode->rn_child[0];
-		vm_radix_node_put(rnode);
+		vm_radix_node_put(__DEVOLATILE(struct vm_radix_node *, rnode));
 	}
-	vm_radix_setroot(rtree, iroot, ilevel);
+	vm_radix_setroot(rtree, __DEVOLATILE(struct vm_radix_node *, iroot), ilevel);
 }
 
 static inline void *
@@ -349,15 +354,15 @@
 int
 vm_radix_insert(struct vm_radix *rtree, vm_pindex_t index, void *val)
 {
-	struct vm_radix_node *iroot, *rnode, *root;
-	u_int allocmsk;
-	int clev, ilevel, level, slot;
+	volatile struct vm_radix_node *iroot, *rnode, *root;
+	volatile u_int allocmsk;
+	volatile int clev, ilevel, level, slot;
 
 	CTR3(KTR_VM,
 	    "insert: tree %p, index %ju, val %p", rtree, (uintmax_t)index, val);
 	if (index == -1)
 		panic("vm_radix_insert: -1 is not a valid index.\n");
-	level = vm_radix_height(rtree, &root);
+	level = vm_radix_height(rtree, __DEVOLATILE(struct vm_radix_node **, &root));
 	/*
 	 * Increase the height by adding nodes at the root until
 	 * there is sufficient space.
@@ -395,7 +400,7 @@
 			}
 			root = rnode;
 		}
-		vm_radix_setroot(rtree, root, level);
+		vm_radix_setroot(rtree, __DEVOLATILE(struct vm_radix_node *, root), level);
 	}
 
 	/* Now that the tree is tall enough, fill in the path to the index. */