diff --git a/lib/libc/stdio/fflush.c b/lib/libc/stdio/fflush.c
index e315a14fd06e..bd07b958ee21 100644
--- a/lib/libc/stdio/fflush.c
+++ b/lib/libc/stdio/fflush.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: fflush.c,v 1.9 1998/01/19 07:38:42 jtc Exp $	*/
+/*	$NetBSD: fflush.c,v 1.10 1998/01/22 08:21:45 jtc Exp $	*/
 
 /*-
  * Copyright (c) 1990, 1993
@@ -41,7 +41,7 @@
 #if 0
 static char sccsid[] = "@(#)fflush.c	8.1 (Berkeley) 6/4/93";
 #else
-__RCSID("$NetBSD: fflush.c,v 1.9 1998/01/19 07:38:42 jtc Exp $");
+__RCSID("$NetBSD: fflush.c,v 1.10 1998/01/22 08:21:45 jtc Exp $");
 #endif
 #endif /* LIBC_SCCS and not lint */
 
@@ -50,6 +50,10 @@ __RCSID("$NetBSD: fflush.c,v 1.9 1998/01/19 07:38:42 jtc Exp $");
 #include "local.h"
 #include "reentrant.h"
 
+#ifdef _REENT
+extern rwlock_t __sfp_lock;
+#endif
+
 /* Flush a single file, or (if fp is NULL) all files.  */
 int
 fflush(fp)
@@ -57,8 +61,12 @@ fflush(fp)
 {
 	int r;
 
-	if (fp == NULL)
-		return (_fwalk(__sflush));
+	if (fp == NULL) {
+		rwlock_rdlock(&__sfp_lock);
+		r = _fwalk(__sflush);
+		rwlock_unlock(&__sfp_lock);
+		return r;
+	}
 
 	FLOCKFILE(fp);
 	if ((fp->_flags & (__SWR | __SRW)) == 0) {
diff --git a/lib/libc/stdio/findfp.c b/lib/libc/stdio/findfp.c
index 5d477a21124b..acc93c81524c 100644
--- a/lib/libc/stdio/findfp.c
+++ b/lib/libc/stdio/findfp.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: findfp.c,v 1.7 1997/07/13 20:14:58 christos Exp $	*/
+/*	$NetBSD: findfp.c,v 1.8 1998/01/22 08:21:47 jtc Exp $	*/
 
 /*-
  * Copyright (c) 1990, 1993
@@ -41,7 +41,7 @@
 #if 0
 static char sccsid[] = "@(#)findfp.c	8.2 (Berkeley) 1/4/94";
 #else
-__RCSID("$NetBSD: findfp.c,v 1.7 1997/07/13 20:14:58 christos Exp $");
+__RCSID("$NetBSD: findfp.c,v 1.8 1998/01/22 08:21:47 jtc Exp $");
 #endif
 #endif /* LIBC_SCCS and not lint */
 
@@ -53,6 +53,7 @@ __RCSID("$NetBSD: findfp.c,v 1.7 1997/07/13 20:14:58 christos Exp $");
 #include <string.h>
 #include "local.h"
 #include "glue.h"
+#include "reentrant.h"
 
 int	__sdidinit;
 
@@ -76,6 +77,10 @@ struct glue __sglue = { &uglue, 3, __sF };
 static struct glue *moreglue __P((int));
 void f_prealloc __P((void));
 
+#ifdef _REENT
+rwlock_t __sfp_lock = RWLOCK_INITIALIZER;
+#endif
+
 static struct glue *
 moreglue(n)
 	register int n;
@@ -108,6 +113,8 @@ __sfp()
 
 	if (!__sdidinit)
 		__sinit();
+
+	rwlock_wrlock(&__sfp_lock);
 	for (g = &__sglue;; g = g->next) {
 		for (fp = g->iobs, n = g->niobs; --n >= 0; fp++)
 			if (fp->_flags == 0)
@@ -115,6 +122,7 @@ __sfp()
 		if (g->next == NULL && (g->next = moreglue(NDYNAMIC)) == NULL)
 			break;
 	}
+	rwlock_unlock(&__sfp_lock);
 	return (NULL);
 found:
 	fp->_flags = 1;		/* reserve this slot; caller sets real flags */
@@ -130,6 +138,7 @@ found:
 	fp->_ub._size = 0;
 	fp->_lb._base = NULL;	/* no line buffer */
 	fp->_lb._size = 0;
+	rwlock_unlock(&__sfp_lock);
 	return (fp);
 }
 
diff --git a/lib/libc/stdio/refill.c b/lib/libc/stdio/refill.c
index aeca280ad291..1e76eda64111 100644
--- a/lib/libc/stdio/refill.c
+++ b/lib/libc/stdio/refill.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: refill.c,v 1.7 1997/07/13 20:15:22 christos Exp $	*/
+/*	$NetBSD: refill.c,v 1.8 1998/01/22 08:21:48 jtc Exp $	*/
 
 /*-
  * Copyright (c) 1990, 1993
@@ -41,7 +41,7 @@
 #if 0
 static char sccsid[] = "@(#)refill.c	8.1 (Berkeley) 6/4/93";
 #else
-__RCSID("$NetBSD: refill.c,v 1.7 1997/07/13 20:15:22 christos Exp $");
+__RCSID("$NetBSD: refill.c,v 1.8 1998/01/22 08:21:48 jtc Exp $");
 #endif
 #endif /* LIBC_SCCS and not lint */
 
@@ -49,6 +49,11 @@ __RCSID("$NetBSD: refill.c,v 1.7 1997/07/13 20:15:22 christos Exp $");
 #include <stdio.h>
 #include <stdlib.h>
 #include "local.h"
+#include "reentrant.h"
+
+#ifdef _REENT
+extern rwlock_t __sfp_lock;
+#endif
 
 static int lflush __P((FILE *));
 
@@ -56,7 +61,6 @@ static int
 lflush(fp)
 	FILE *fp;
 {
-
 	if ((fp->_flags & (__SLBF|__SWR)) == (__SLBF|__SWR))
 		return (__sflush(fp));
 	return (0);
@@ -120,8 +124,11 @@ __srefill(fp)
 	 * flush all line buffered output files, per the ANSI C
 	 * standard.
 	 */
-	if (fp->_flags & (__SLBF|__SNBF))
+	if (fp->_flags & (__SLBF|__SNBF)) {
+		rwlock_rdlock(&__sfp_lock);
 		(void) _fwalk(lflush);
+		rwlock_unlock(&__sfp_lock);
+	}
 	fp->_p = fp->_bf._base;
 	fp->_r = (*fp->_read)(fp->_cookie, (char *)fp->_p, fp->_bf._size);
 	fp->_flags &= ~__SMOD;	/* buffer contents are again pristine */