From 8d3549ebb0d72fdce64595ca1c7a02e3b6bfefd1 Mon Sep 17 00:00:00 2001
From: yamt <yamt@NetBSD.org>
Date: Sat, 29 Oct 2005 11:13:21 +0000
Subject: [PATCH] add something like pthread_once().

---
 sys/kern/subr_once.c | 58 ++++++++++++++++++++++++++++++++++++++++++++
 sys/sys/once.h       | 56 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 114 insertions(+)
 create mode 100644 sys/kern/subr_once.c
 create mode 100644 sys/sys/once.h

diff --git a/sys/kern/subr_once.c b/sys/kern/subr_once.c
new file mode 100644
index 000000000000..09c2ff8d2fd1
--- /dev/null
+++ b/sys/kern/subr_once.c
@@ -0,0 +1,58 @@
+/*	$NetBSD: subr_once.c,v 1.1 2005/10/29 11:13:21 yamt Exp $	*/
+
+/*-
+ * Copyright (c)2005 YAMAMOTO Takashi,
+ * 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 <sys/cdefs.h>
+__KERNEL_RCSID(0, "$NetBSD: subr_once.c,v 1.1 2005/10/29 11:13:21 yamt Exp $");
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/proc.h>
+#include <sys/once.h>
+
+void
+_run_once(once_t *o, void (*fn)(void))
+{
+
+	simple_lock(&o->o_lock);
+	while ((o->o_flags & ONCE_RUNNING) != 0) {
+		ltsleep(o, PUSER, "runonce", 0, &o->o_lock);
+	}
+	if (o->o_flags & ONCE_DONE) {
+		goto done;
+	}
+	o->o_flags |= ONCE_RUNNING;
+	simple_unlock(&o->o_lock);
+
+	(*fn)();
+
+	simple_lock(&o->o_lock);
+	o->o_flags = ONCE_DONE;
+	wakeup(o);
+done:
+	simple_unlock(&o->o_lock);
+}
diff --git a/sys/sys/once.h b/sys/sys/once.h
new file mode 100644
index 000000000000..a4f71790b5df
--- /dev/null
+++ b/sys/sys/once.h
@@ -0,0 +1,56 @@
+/*	$NetBSD: once.h,v 1.1 2005/10/29 11:13:21 yamt Exp $	*/
+
+/*-
+ * Copyright (c)2005 YAMAMOTO Takashi,
+ * 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.
+ */
+
+#if !defined(_SYS_ONCE_H_)
+#define	_SYS_ONCE_H_
+
+#include <sys/lock.h>
+
+typedef struct {
+	struct simplelock o_lock;
+	int o_flags;
+#define	ONCE_RUNNING	1
+#define	ONCE_DONE	2
+} once_t;
+
+void _run_once(once_t *, void (*)(void));
+
+#define	ONCE_DECL(o) \
+	once_t (o) = { \
+		.o_lock = SIMPLELOCK_INITIALIZER, \
+		.o_flags = 0, \
+	};
+
+#define	RUN_ONCE(o, fn) \
+	do { \
+		if (__predict_false(((o)->o_flags & ONCE_DONE) == 0)) { \
+			_run_once((o), (fn)); \
+		} \
+	} while (0 /* CONSTCOND */)
+
+#endif /* !defined(_SYS_ONCE_H_) */