From f07a4c844da9f0ecae5bbee1ab94be56505f26f7 Mon Sep 17 00:00:00 2001
From: Thomas Bushnell <thomas@gnu.org>
Date: Tue, 25 Feb 1997 21:28:37 +0000
Subject: Initial source

---
 kern/refcount.h | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100644 kern/refcount.h

(limited to 'kern/refcount.h')

diff --git a/kern/refcount.h b/kern/refcount.h
new file mode 100644
index 00000000..7fd6cdfb
--- /dev/null
+++ b/kern/refcount.h
@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 1993,1994 The University of Utah and
+ * the Computer Systems Laboratory (CSL).  All rights reserved.
+ *
+ * Permission to use, copy, modify and distribute this software and its
+ * documentation is hereby granted, provided that both the copyright
+ * notice and this permission notice appear in all copies of the
+ * software, derivative works or modified versions, and any portions
+ * thereof, and that both notices appear in supporting documentation.
+ *
+ * THE UNIVERSITY OF UTAH AND CSL ALLOW FREE USE OF THIS SOFTWARE IN ITS "AS
+ * IS" CONDITION.  THE UNIVERSITY OF UTAH AND CSL DISCLAIM ANY LIABILITY OF
+ * ANY KIND FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
+ *
+ * CSL requests users of this software to return to csl-dist@cs.utah.edu any
+ * improvements that they make and grant CSL redistribution rights.
+ *
+ *      Author: Bryan Ford, University of Utah CSL
+ */
+/*
+ *	File:	refcount.h
+ *
+ *	This defines the system-independent part of the atomic reference count data type.
+ *
+ */
+
+#ifndef	_KERN_REFCOUNT_H_
+#define _KERN_REFCOUNT_H_
+
+#include <kern/macro_help.h>
+
+#include "refcount.h" /*XXX*/
+
+/* Unless the above include file specified otherwise,
+   use the system-independent (unoptimized) atomic reference counter.  */
+#ifndef MACHINE_REFCOUNT
+
+#include <kern/lock.h>
+
+struct RefCount {
+	decl_simple_lock_data(,lock)	/* lock for reference count */
+	int		ref_count;	/* number of references */
+};
+typedef struct RefCount RefCount;
+
+#define refcount_init(refcount, refs)			\
+	MACRO_BEGIN					\
+		simple_lock_init(&(refcount)->lock);	\
+		((refcount)->ref_count = (refs));	\
+	MACRO_END
+
+#define refcount_take(refcount)				\
+	MACRO_BEGIN					\
+		simple_lock(&(refcount)->lock);		\
+		(refcount)->ref_count++;		\
+		simple_unlock(&(refcount)->lock);	\
+	MACRO_END
+
+#define refcount_drop(refcount, func)			\
+	MACRO_BEGIN					\
+		int new_value;				\
+		simple_lock(&(refcount)->lock);		\
+		new_value = --(refcount)->ref_count;	\
+		simple_unlock(&(refcount)->lock);	\
+		if (new_value == 0) { func; }		\
+	MACRO_END
+
+#endif
+
+#endif _KERN_REFCOUNT_H_
-- 
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