/* spin_mutex.h                  -*-C++-*-
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/**
 * @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)