Index: sys/kern/kern_exit.c
===================================================================
--- sys/kern/kern_exit.c
+++ sys/kern/kern_exit.c
@@ -108,8 +108,7 @@
 
 	sx_assert(&proctree_lock, SX_LOCKED);
 	if ((child->p_treeflag & P_TREE_ORPHANED) == 0) {
-		if (child->p_oppid == 0 ||
-		    child->p_pptr->p_pid == child->p_oppid)
+		if (child->p_pptr->p_pid == child->p_oppid)
 			parent = child->p_pptr;
 		else
 			parent = initproc;
@@ -854,7 +853,7 @@
 	 * If we got the child via a ptrace 'attach', we need to give it back
 	 * to the old parent.
 	 */
-	if (p->p_oppid != 0 && p->p_oppid != p->p_pptr->p_pid) {
+	if (p->p_oppid != p->p_pptr->p_pid) {
 		PROC_UNLOCK(p);
 		t = proc_realparent(p);
 		PROC_LOCK(t);
@@ -862,8 +861,7 @@
 		CTR2(KTR_PTRACE,
 		    "wait: traced child %d moved back to parent %d", p->p_pid,
 		    t->p_pid);
-		proc_reparent(p, t);
-		p->p_oppid = 0;
+		proc_reparent_ptrace(p, t);
 		PROC_UNLOCK(p);
 		pksignal(t, SIGCHLD, p->p_ksi);
 		wakeup(t);
@@ -872,7 +870,6 @@
 		sx_xunlock(&proctree_lock);
 		return;
 	}
-	p->p_oppid = 0;
 	PROC_UNLOCK(p);
 
 	/*
@@ -1334,8 +1331,8 @@
  * Make process 'parent' the new parent of process 'child'.
  * Must be called with an exclusive hold of proctree lock.
  */
-void
-proc_reparent(struct proc *child, struct proc *parent)
+static void
+proc_reparent_(struct proc *child, struct proc *parent, bool set_oppid)
 {
 
 	sx_assert(&proctree_lock, SX_XLOCKED);
@@ -1363,4 +1360,20 @@
 	}
 
 	child->p_pptr = parent;
+	if (set_oppid)
+		child->p_oppid = parent->p_pid;
+}
+
+void
+proc_reparent(struct proc *child, struct proc *parent)
+{
+
+	proc_reparent_(child, parent, true);
+}
+
+void
+proc_reparent_ptrace(struct proc *child, struct proc *parent)
+{
+
+	proc_reparent_(child, parent, false);
 }
Index: sys/kern/kern_fork.c
===================================================================
--- sys/kern/kern_fork.c
+++ sys/kern/kern_fork.c
@@ -645,6 +645,7 @@
 		pptr = p1;
 	}
 	p2->p_pptr = pptr;
+	p2->p_oppid = pptr->p_pid;
 	LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
 	LIST_INIT(&p2->p_reaplist);
 	LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling);
@@ -776,7 +777,7 @@
 			CTR2(KTR_PTRACE,
 			    "do_fork: attaching to new child pid %d: oppid %d",
 			    p2->p_pid, p2->p_oppid);
-			proc_reparent(p2, p1->p_pptr);
+			proc_reparent_ptrace(p2, p1->p_pptr);
 		}
 		PROC_UNLOCK(p2);
 		sx_xunlock(&proctree_lock);
Index: sys/kern/kern_proc.c
===================================================================
--- sys/kern/kern_proc.c
+++ sys/kern/kern_proc.c
@@ -920,8 +920,6 @@
 	struct sigacts *ps;
 	struct timeval boottime;
 
-	/* For proc_realparent. */
-	sx_assert(&proctree_lock, SX_LOCKED);
 	PROC_LOCK_ASSERT(p, MA_OWNED);
 	bzero(kp, sizeof(*kp));
 
@@ -1055,7 +1053,7 @@
 	kp->ki_acflag = p->p_acflag;
 	kp->ki_lock = p->p_lock;
 	if (p->p_pptr) {
-		kp->ki_ppid = proc_realparent(p)->p_pid;
+		kp->ki_ppid = p->p_oppid;
 		if (p->p_flag & P_TRACED)
 			kp->ki_tracer = p->p_pptr->p_pid;
 	}
@@ -1640,20 +1638,12 @@
 		error = sysctl_wire_old_buffer(req, 0);
 		if (error != 0)
 			return (error);
-		/*
-		 * This lock is only needed to safely grab the parent of a
-		 * traced process. Only grab it if we are producing any
-		 * data to begin with.
-		 */
-		sx_slock(&proctree_lock);
 	}
 	iterarg.flags = flags;
 	iterarg.oid_number = oid_number;
 	iterarg.req = req;
 	iterarg.name = name;
 	error = proc_iterate(sysctl_kern_proc_iterate, &iterarg);
-	if (req->oldptr != NULL)
-		sx_sunlock(&proctree_lock);
 	return (error);
 }
 
Index: sys/kern/kern_prot.c
===================================================================
--- sys/kern/kern_prot.c
+++ sys/kern/kern_prot.c
@@ -124,20 +124,9 @@
 kern_getppid(struct thread *td)
 {
 	struct proc *p = td->td_proc;
-	struct proc *pp;
 	int ppid;
 
-	PROC_LOCK(p);
-	if (!(p->p_flag & P_TRACED)) {
-		ppid = p->p_pptr->p_pid;
-		PROC_UNLOCK(p);
-	} else {
-		PROC_UNLOCK(p);
-		sx_slock(&proctree_lock);
-		pp = proc_realparent(p);
-		ppid = pp->p_pid;
-		sx_sunlock(&proctree_lock);
-	}
+	ppid = p->p_oppid;
 
 	return (ppid);
 }
Index: sys/kern/sys_process.c
===================================================================
--- sys/kern/sys_process.c
+++ sys/kern/sys_process.c
@@ -695,7 +695,6 @@
 	if (stop)
 		p->p_flag2 |= P2_PTRACE_FSTP;
 	p->p_ptevents = PTRACE_DEFAULT;
-	p->p_oppid = p->p_pptr->p_pid;
 }
 
 int
@@ -919,7 +918,7 @@
 		 */
 		proc_set_traced(p, true);
 		if (p->p_pptr != td->td_proc) {
-			proc_reparent(p, td->td_proc);
+			proc_reparent_ptrace(p, td->td_proc);
 		}
 		CTR2(KTR_PTRACE, "PT_ATTACH: pid %d, oppid %d", p->p_pid,
 		    p->p_oppid);
@@ -1113,7 +1112,7 @@
 				PROC_UNLOCK(p->p_pptr);
 
 				pp = proc_realparent(p);
-				proc_reparent(p, pp);
+				proc_reparent_ptrace(p, pp);
 				if (pp == initproc)
 					p->p_sigparent = SIGCHLD;
 				CTR3(KTR_PTRACE,
@@ -1122,7 +1121,6 @@
 			} else
 				CTR2(KTR_PTRACE, "PT_DETACH: pid %d, sig %d",
 				    p->p_pid, data);
-			p->p_oppid = 0;
 			p->p_ptevents = 0;
 			FOREACH_THREAD_IN_PROC(p, td3) {
 				if ((td3->td_dbgflags & TDB_FSTP) != 0) {
Index: sys/sys/proc.h
===================================================================
--- sys/sys/proc.h
+++ sys/sys/proc.h
@@ -594,8 +594,8 @@
 #define p_siglist	p_sigqueue.sq_signals
 
 /* The following fields are all zeroed upon creation in fork. */
-#define	p_startzero	p_oppid
 	pid_t		p_oppid;	/* (c + e) Save ppid in ptrace. XXX */
+#define	p_startzero	p_vmspace
 	struct vmspace	*p_vmspace;	/* (b) Address space. */
 	u_int		p_swtick;	/* (c) Tick when swapped in or out. */
 	u_int		p_cowgen;	/* (c) Generation of COW pointers. */
@@ -1053,6 +1053,7 @@
 struct proc *proc_realparent(struct proc *child);
 void	proc_reap(struct thread *td, struct proc *p, int *status, int options);
 void	proc_reparent(struct proc *child, struct proc *newparent);
+void	proc_reparent_ptrace(struct proc *child, struct proc *newparent);
 void	proc_set_traced(struct proc *p, bool stop);
 void	proc_wkilled(struct proc *p);
 struct	pstats *pstats_alloc(void);