Index: head/sys/fs/nfs/nfsport.h
===================================================================
--- head/sys/fs/nfs/nfsport.h
+++ head/sys/fs/nfs/nfsport.h
@@ -692,8 +692,6 @@
 #define	NFSUNLOCKMNT(m)		mtx_unlock(&((m)->nm_mtx))
 #define	NFSLOCKREQUEST(r)	mtx_lock(&((r)->r_mtx))
 #define	NFSUNLOCKREQUEST(r)	mtx_unlock(&((r)->r_mtx))
-#define	NFSPROCLISTLOCK()	sx_slock(&allproc_lock)
-#define	NFSPROCLISTUNLOCK()	sx_sunlock(&allproc_lock)
 #define	NFSLOCKSOCKREQ(r)	mtx_lock(&((r)->nr_mtx))
 #define	NFSUNLOCKSOCKREQ(r)	mtx_unlock(&((r)->nr_mtx))
 #define	NFSLOCKDS(d)		mtx_lock(&((d)->nfsclds_mtx))
Index: head/sys/fs/nfsclient/nfs_clport.c
===================================================================
--- head/sys/fs/nfsclient/nfs_clport.c
+++ head/sys/fs/nfsclient/nfs_clport.c
@@ -1156,7 +1156,7 @@
 	tl.cval[2] = *own++;
 	tl.cval[3] = *own++;
 	pid = tl.lval;
-	p = pfind(pid);
+	p = pfind_any_locked(pid);
 	if (p == NULL)
 		return (1);
 	if (p->p_stats == NULL) {
Index: head/sys/fs/nfsclient/nfs_clstate.c
===================================================================
--- head/sys/fs/nfsclient/nfs_clstate.c
+++ head/sys/fs/nfsclient/nfs_clstate.c
@@ -1789,7 +1789,13 @@
 	struct nfscllockowner *lp, *nlp;
 	struct nfscldeleg *dp;
 
-	NFSPROCLISTLOCK();
+	/*
+	 * All the pidhash locks must be acquired, since they are sx locks
+	 * and must be acquired before the mutexes.  The pid(s) that will
+	 * be used aren't known yet, so all the locks need to be acquired.
+	 * Fortunately, this function is only performed once/sec.
+	 */
+	pidhash_slockall();
 	NFSLOCKCLSTATE();
 	LIST_FOREACH_SAFE(owp, &clp->nfsc_owner, nfsow_list, nowp) {
 		LIST_FOREACH(op, &owp->nfsow_open, nfso_list) {
@@ -1816,7 +1822,7 @@
 		}
 	}
 	NFSUNLOCKCLSTATE();
-	NFSPROCLISTUNLOCK();
+	pidhash_sunlockall();
 }
 
 /*
Index: head/sys/kern/kern_proc.c
===================================================================
--- head/sys/kern/kern_proc.c
+++ head/sys/kern/kern_proc.c
@@ -193,7 +193,7 @@
 	pidhashtbl_lock = malloc(sizeof(*pidhashtbl_lock) * (pidhashlock + 1),
 	    M_PROC, M_WAITOK | M_ZERO);
 	for (i = 0; i < pidhashlock + 1; i++)
-		sx_init(&pidhashtbl_lock[i], "pidhash");
+		sx_init_flags(&pidhashtbl_lock[i], "pidhash", SX_DUPOK);
 	pgrphashtbl = hashinit(maxproc / 4, M_PROC, &pgrphash);
 	proc_zone = uma_zcreate("PROC", sched_sizeof_proc(),
 	    proc_ctor, proc_dtor, proc_init, proc_fini,
@@ -365,6 +365,52 @@
 			return (0);
 	}
 	return (1);
+}
+
+/*
+ * Shared lock all the pid hash lists.
+ */
+void
+pidhash_slockall(void)
+{
+	u_long i;
+
+	for (i = 0; i < pidhashlock + 1; i++)
+		sx_slock(&pidhashtbl_lock[i]);
+}
+
+/*
+ * Shared unlock all the pid hash lists.
+ */
+void
+pidhash_sunlockall(void)
+{
+	u_long i;
+
+	for (i = 0; i < pidhashlock + 1; i++)
+		sx_sunlock(&pidhashtbl_lock[i]);
+}
+
+/*
+ * Similar to pfind_any(), this function finds zombies.
+ */
+struct proc *
+pfind_any_locked(pid_t pid)
+{
+	struct proc *p;
+
+	sx_assert(PIDHASHLOCK(pid), SX_LOCKED);
+	LIST_FOREACH(p, PIDHASH(pid), p_hash) {
+		if (p->p_pid == pid) {
+			PROC_LOCK(p);
+			if (p->p_state == PRS_NEW) {
+				PROC_UNLOCK(p);
+				p = NULL;
+			}
+			break;
+		}
+	}
+	return (p);
 }
 
 /*
Index: head/sys/sys/proc.h
===================================================================
--- head/sys/sys/proc.h
+++ head/sys/sys/proc.h
@@ -989,8 +989,11 @@
 
 struct	proc *pfind(pid_t);		/* Find process by id. */
 struct	proc *pfind_any(pid_t);		/* Find (zombie) process by id. */
+struct	proc *pfind_any_locked(pid_t pid); /* Find process by id, locked. */
 struct	pgrp *pgfind(pid_t);		/* Find process group by id. */
 struct	proc *zpfind(pid_t);		/* Find zombie process by id. */
+void	pidhash_slockall(void);		/* Shared lock all pid hash lists. */
+void	pidhash_sunlockall(void);	/* Shared unlock all pid hash lists. */
 
 struct	fork_req {
 	int		fr_flags;