From 6830d0fc0de36e92552f8aee97d44750f49c6a62 Mon Sep 17 00:00:00 2001
From: Simon Schubert <corecode@dragonflybsd.org>
Date: Fri, 11 Dec 2009 23:25:09 +0100
Subject: [PATCH] condvar: add implementation

Add a small implementation of condition variables.  API design adopted
from FreeBSD.
---
 sys/conf/files          |  1 +
 sys/kern/kern_condvar.c | 56 +++++++++++++++++++++++++++++++++++++++++
 sys/sys/condvar.h       | 36 ++++++++++++++++++++++++++
 3 files changed, 93 insertions(+)
 create mode 100644 sys/kern/kern_condvar.c
 create mode 100644 sys/sys/condvar.h

diff --git a/sys/conf/files b/sys/conf/files
index 39793d0d1f..a5bc7b8ed8 100644
--- a/sys/conf/files
+++ b/sys/conf/files
@@ -649,6 +649,7 @@ kern/link_elf.c		standard
 kern/kern_acct.c	standard
 kern/kern_acl.c		standard
 kern/kern_clock.c	standard
+kern/kern_condvar.c	standard
 kern/kern_conf.c	standard
 kern/kern_debug.c	standard
 kern/kern_device.c	standard
diff --git a/sys/kern/kern_condvar.c b/sys/kern/kern_condvar.c
new file mode 100644
index 0000000000..06ec868c45
--- /dev/null
+++ b/sys/kern/kern_condvar.c
@@ -0,0 +1,56 @@
+#include <sys/condvar.h>
+#include <sys/spinlock2.h>
+#include <sys/systm.h>
+#include <sys/lock.h>
+
+void
+cv_init(struct cv *c, const char *desc)
+{
+	c->cv_desc = desc;
+	c->cv_waiters = 0;
+	spin_init(&c->cv_lock);
+}
+
+void
+cv_destroy(struct cv *c)
+{
+	spin_uninit(&c->cv_lock);
+}
+
+int
+_cv_timedwait(struct cv *c, struct lock *l, int timo, int wakesig)
+{
+	int flags = wakesig ? PCATCH : 0;
+	int error;
+
+	spin_lock_wr(&c->cv_lock);
+	tsleep_interlock(c, flags);
+	c->cv_waiters++;
+	spin_unlock_wr(&c->cv_lock);
+	if (l != NULL)
+		lockmgr(l, LK_RELEASE);
+	error = tsleep(c, flags, c->cv_desc, timo);
+	if (l != NULL)
+		lockmgr(l, LK_EXCLUSIVE);
+
+	return (error);
+}
+
+void
+_cv_signal(struct cv *c, int broadcast)
+{
+	spin_lock_wr(&c->cv_lock);
+	if (c->cv_waiters == 0)
+		goto out;
+
+	if (broadcast) {
+		c->cv_waiters = 0;
+		wakeup(c);
+	} else {
+		c->cv_waiters--;
+		wakeup_one(c);
+	}
+
+out:
+	spin_unlock_wr(&c->cv_lock);
+}
diff --git a/sys/sys/condvar.h b/sys/sys/condvar.h
new file mode 100644
index 0000000000..3acd3144a7
--- /dev/null
+++ b/sys/sys/condvar.h
@@ -0,0 +1,36 @@
+#ifndef	_SYS_CONDVAR_H_
+#define	_SYS_CONDVAR_H_
+
+#include <sys/spinlock.h>
+
+struct lock;
+
+struct cv {
+	struct spinlock cv_lock;
+	int		cv_waiters;
+	const char	*cv_desc;
+};
+
+void	cv_init(struct cv *, const char *desc);
+void	cv_destroy(struct cv *);
+
+int	_cv_timedwait(struct cv *, struct lock *, int timo, int wakesig);
+void	_cv_signal(struct cv *, int broadcast);
+
+#define	cv_wait(cv, lock)			\
+		_cv_timedwait((cv), (lock), 0, 0)
+#define	cv_wait_sig(cv, lock)			\
+		_cv_timedwait((cv), (lock), 0, 1)
+#define	cv_timedwait(cv, lock, timeo)		\
+		_cv_timedwait((cv), (lock), (timeo), 0)
+#define	cv_timedwait_sig(cv, lock, timeo)	\
+		_cv_timedwait((cv), (lock), (timeo), 1)
+
+#define	cv_signal(cv)				\
+		_cv_signal((cv), 0)
+#define	cv_broadcast(cv)			\
+		_cv_signal((cv), 1)
+#define	cv_broadcastpri(cv)			\
+		cv_broadcast((cv))
+
+#endif	/* _SYS_CONDVAR_H_ */
-- 
2.41.0