2 files changed, 64 insertions, 0 deletions

diff --git a/lib/libsys/Makefile.sys b/lib/libsys/Makefile.sys
index e31a30d731bb..ef800e4d2445 100644
--- a/lib/libsys/Makefile.sys
+++ b/lib/libsys/Makefile.sys
@@ -32,6 +32,7 @@ PSEUDO+= _clock_gettime.o _gettimeofday.o
 # Sources common to both syscall interfaces:
 SRCS+=	\
 	__error.c \
+	_once_stub.c \
 	interposing_table.c
 
 SRCS+= getdents.c lstat.c mknod.c stat.c
diff --git a/lib/libsys/_once_stub.c b/lib/libsys/_once_stub.c
new file mode 100644
index 000000000000..518072cbd28f
--- /dev/null
+++ b/lib/libsys/_once_stub.c
@@ -0,0 +1,63 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2009 Hudson River Trading LLC
+ * Written by: John H. Baldwin <jhb@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "namespace.h"
+#include <pthread.h>
+#include "un-namespace.h"
+#include "libc_private.h"
+
+/* This implements pthread_once() for the single-threaded case. */
+static int
+_libc_once(pthread_once_t *once_control, void (*init_routine)(void))
+{
+
+	if (once_control->state == PTHREAD_DONE_INIT)
+		return (0);
+	init_routine();
+	once_control->state = PTHREAD_DONE_INIT;
+	return (0);
+}
+
+/*
+ * This is the internal interface provided to libc.  It will use
+ * pthread_once() from the threading library in a multi-threaded
+ * process and _libc_once() for a single-threaded library.  Because
+ * _libc_once() uses the same ABI for the values in the pthread_once_t
+ * structure as the threading library, it is safe for a process to
+ * switch from _libc_once() to pthread_once() when threading is
+ * enabled.
+ */
+int
+_once(pthread_once_t *once_control, void (*init_routine)(void))
+{
+
+	if (__isthreaded)
+		return (_pthread_once(once_control, init_routine));
+	return (_libc_once(once_control, init_routine));
+}