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diff --git a/libcilkrts/runtime/spin_mutex.h b/libcilkrts/runtime/spin_mutex.h
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+/* spin_mutex.h                  -*-C++-*-
+ *
+ *************************************************************************
+ *
+ *  @copyright
+ *  Copyright (C) 2009-2013, Intel Corporation
+ *  All rights reserved.
+ *  
+ *  @copyright
+ *  Redistribution and use in source and binary forms, with or without
+ *  modification, are permitted provided that the following conditions
+ *  are met:
+ *  
+ *    * Redistributions of source code must retain the above copyright
+ *      notice, this list of conditions and the following disclaimer.
+ *    * 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.
+ *    * Neither the name of Intel Corporation nor the names of its
+ *      contributors may be used to endorse or promote products derived
+ *      from this software without specific prior written permission.
+ *  
+ *  @copyright
+ *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT
+ *  HOLDER 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.
+ **************************************************************************/
+
+/**
+ * @file spin_mutex.h
+ *
+ * @brief Support for Cilk runtime mutexes.
+ *
+ * Cilk runtime mutexes are implemented as simple spin loops.
+ *
+ * This file is similar to a worker_mutex, except it does not have an
+ * owner field.
+ *
+ * TBD: This class, worker_mutex, and os_mutex overlap quite a bit in
+ * functionality.  Can we unify these mutexes somehow?
+ */
+#ifndef INCLUDED_SPIN_MUTEX_DOT_H
+#define INCLUDED_SPIN_MUTEX_DOT_H
+
+#include <cilk/common.h>
+#include "rts-common.h"
+#include "cilk_malloc.h"
+
+__CILKRTS_BEGIN_EXTERN_C
+
+/**
+ * Mutexes are treated as an abstract data type within the Cilk
+ * runtime system.  They are implemented as simple spin loops.
+ */
+typedef struct spin_mutex {
+    /** Mutex spin loop variable. 0 if unowned, 1 if owned. */
+    volatile int lock;
+
+    /** Padding so the mutex takes up a cache line. */
+    char pad[64/sizeof(int) - 1];
+} spin_mutex;
+
+
+/**
+ * @brief Create a new Cilk spin_mutex.
+ *
+ * @return Returns an initialized spin mutex.  
+ */
+COMMON_PORTABLE
+spin_mutex* spin_mutex_create();
+
+/**
+ * @brief Initialize a Cilk spin_mutex.
+ *
+ * @param m Spin_Mutex to be initialized.
+ */
+COMMON_PORTABLE
+void spin_mutex_init(spin_mutex *m);
+
+/**
+ * @brief Acquire a Cilk spin_mutex.
+ *
+ * If statistics are being gathered, the time spent
+ * acquiring the spin_mutex will be attributed to the specified worker.
+ *
+ * @param m Spin_Mutex to be initialized.
+ */
+COMMON_PORTABLE
+void spin_mutex_lock(struct spin_mutex *m);
+/**
+ * @brief Attempt to lock a Cilk spin_mutex and fail if it isn't available.
+ *
+ * @param m Spin_Mutex to be acquired.
+ *
+ * @return 1 if the spin_mutex was acquired.
+ * @return 0 if the spin_mutex was not acquired.
+ */
+COMMON_PORTABLE
+int spin_mutex_trylock(struct spin_mutex *m);
+
+/**
+ * @brief Release a Cilk spin_mutex.
+ *
+ * @param m Spin_Mutex to be released.
+ */
+COMMON_PORTABLE
+void spin_mutex_unlock(struct spin_mutex *m);
+
+/**
+ * @brief Deallocate a Cilk spin_mutex.  Currently does nothing.
+ *
+ * @param m Spin_Mutex to be deallocated.
+ */
+COMMON_PORTABLE
+void spin_mutex_destroy(struct spin_mutex *m);
+
+__CILKRTS_END_EXTERN_C
+
+#endif // ! defined(INCLUDED_SPIN_MUTEX_DOT_H)