Index: sys/kern/subr_unit.c
===================================================================
--- sys/kern/subr_unit.c
+++ sys/kern/subr_unit.c
@@ -98,6 +98,19 @@
 
 MTX_SYSINIT(unit, &unitmtx, "unit# allocation", MTX_DEF);
 
+#ifdef UNR64_LOCKED
+uint64_t
+alloc_unr64(struct unrhdr64 *unr64)
+{
+	uint64_t item;
+
+	mtx_lock(&unitmtx);
+	item = unr64->counter++;
+	mtx_unlock(&unitmtx);
+	return (item);
+}
+#endif
+
 #else /* ...USERLAND */
 
 #include <bitstring.h>
Index: sys/kern/sys_pipe.c
===================================================================
--- sys/kern/sys_pipe.c
+++ sys/kern/sys_pipe.c
@@ -244,7 +244,7 @@
 static void	pipe_zone_fini(void *mem, int size);
 
 static uma_zone_t pipe_zone;
-static struct unrhdr *pipeino_unr;
+static struct unrhdr64 pipeino_unr;
 static dev_t pipedev_ino;
 
 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, pipeinit, NULL);
@@ -257,8 +257,7 @@
 	    pipe_zone_ctor, NULL, pipe_zone_init, pipe_zone_fini,
 	    UMA_ALIGN_PTR, 0);
 	KASSERT(pipe_zone != NULL, ("pipe_zone not initialized"));
-	pipeino_unr = new_unrhdr(1, INT32_MAX, NULL);
-	KASSERT(pipeino_unr != NULL, ("pipe fake inodes not initialized"));
+	new_unrhdr64(&pipeino_unr, 1);
 	pipedev_ino = devfs_alloc_cdp_inode();
 	KASSERT(pipedev_ino > 0, ("pipe dev inode not initialized"));
 }
@@ -390,8 +389,6 @@
 		funsetown(&peer->pipe_sigio);
 		pipeclose(peer);
 	}
-	if (ino != 0 && ino != (ino_t)-1)
-		free_unr(pipeino_unr, ino);
 }
 
 /*
@@ -639,7 +636,7 @@
 			(void)pipespace_new(pipe, PIPE_SIZE);
 	}
 
-	pipe->pipe_ino = -1;
+	pipe->pipe_ino = alloc_unr64(&pipeino_unr);
 }
 
 /* ARGSUSED */
@@ -1461,7 +1458,6 @@
     struct thread *td)
 {
 	struct pipe *pipe;
-	int new_unr;
 #ifdef MAC
 	int error;
 #endif
@@ -1482,23 +1478,6 @@
 		return (vnops.fo_stat(fp, ub, active_cred, td));
 	}
 
-	/*
-	 * Lazily allocate an inode number for the pipe.  Most pipe
-	 * users do not call fstat(2) on the pipe, which means that
-	 * postponing the inode allocation until it is must be
-	 * returned to userland is useful.  If alloc_unr failed,
-	 * assign st_ino zero instead of returning an error.
-	 * Special pipe_ino values:
-	 *  -1 - not yet initialized;
-	 *  0  - alloc_unr failed, return 0 as st_ino forever.
-	 */
-	if (pipe->pipe_ino == (ino_t)-1) {
-		new_unr = alloc_unr(pipeino_unr);
-		if (new_unr != -1)
-			pipe->pipe_ino = new_unr;
-		else
-			pipe->pipe_ino = 0;
-	}
 	PIPE_UNLOCK(pipe);
 
 	bzero(ub, sizeof(*ub));
Index: sys/sys/systm.h
===================================================================
--- sys/sys/systm.h
+++ sys/sys/systm.h
@@ -523,6 +523,32 @@
 int alloc_unrl(struct unrhdr *uh);
 void free_unr(struct unrhdr *uh, u_int item);
 
+#if defined(__mips__) || defined(__powerpc__)
+#define UNR64_LOCKED
+#endif
+
+struct unrhdr64 {
+        uint64_t	counter;
+};
+
+static __inline void
+new_unrhdr64(struct unrhdr64 *unr64, uint64_t low)
+{
+
+	unr64->counter = low;
+}
+
+#ifdef UNR64_LOCKED
+uint64_t alloc_unr64(struct unrhdr64 *);
+#else
+static __inline uint64_t
+alloc_unr64(struct unrhdr64 *unr64)
+{
+
+	return (atomic_fetchadd_64(&unr64->counter, 1));
+}
+#endif
+
 void	intr_prof_stack_use(struct thread *td, struct trapframe *frame);
 
 void counted_warning(unsigned *counter, const char *msg);