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+/* $OpenBSD: mutex.h,v 1.6 2009/04/27 21:48:56 kettenis Exp $ */
+/*
+ * Copyright (c) 2004 Artur Grabowski <art@openbsd.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. The name of the author may not be used to endorse or promote products
+ * derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED ``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 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.
+ */
+/*
+ * Portions copyright (c) 2010, Intel Corporation
+ */
+
+#ifndef __MUTEX_H__
+#define __MUTEX_H__
+
+/*
+ * A mutex is:
+ * - owned by a cpu.
+ * - non-recursive.
+ * - spinning.
+ * - not providing mutual exclusion between processes, only cpus.
+ * - providing interrupt blocking when necessary.
+ *
+ * Different mutexes can be nested, but not interleaved. This is ok:
+ * "mtx_enter(foo); mtx_enter(bar); mtx_leave(bar); mtx_leave(foo);"
+ * This is _not_ ok:
+ * "mtx_enter(foo); mtx_enter(bar); mtx_leave(foo); mtx_leave(bar);"
+ */
+
+struct mutex {
+ __volatile__ uint64_t mtx_lock;
+};
+
+/*
+ * Some architectures need to do magic for the ipl, so they need a macro.
+ */
+void mtx_init(struct mutex *);
+void mtx_enter(struct mutex *);
+void mtx_leave(struct mutex *);
+
+#endif /* __MUTEX_H__ */