Index: kern_prot.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/kern_prot.c,v
retrieving revision 1.59
diff -u -r1.59 kern_prot.c
--- kern_prot.c	2000/06/22 22:27:15	1.59
+++ kern_prot.c	2000/10/04 07:34:24
@@ -91,8 +91,20 @@
 	struct proc *p;
 	struct getppid_args *uap;
 {
+	struct proc *parent;
+	pid_t pid;
 
-	p->p_retval[0] = p->p_pptr->p_pid;
+	parent = p->p_pptr;
+	pid = parent->p_pid;
+	for (;;) {
+		__asm __volatile("" : : : "memory");	/* a gcc mb(); */
+		if (parent == p->p_pptr)
+			break;
+		/* else we lost a race and got reparented */
+		parent = p->p_pptr;
+		pid = parent->p_pid;
+	}
+	p->p_retval[0] = (register_t)pid;
 	return (0);
 }