/* os_mutex.h                  -*-C++-*-
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/**
 * @file os_mutex.h
 *
 * @brief Portable interface to operating-system mutexes.
 *
 * Do not confuse os_mutex with Cilk runtime-specific spinlock mutexes.
 */

#ifndef INCLUDED_OS_MUTEX_DOT_H
#define INCLUDED_OS_MUTEX_DOT_H

#include <cilk/common.h>
#include "rts-common.h"

__CILKRTS_BEGIN_EXTERN_C

/// Opaque type
typedef struct os_mutex os_mutex;

/**
 * Allocate and initialize an os_mutex
 *
 * @return A pointer to the initialized os_mutex
 */
COMMON_SYSDEP os_mutex* __cilkrts_os_mutex_create(void);

/**
 * Acquire the os_mutex for exclusive use
 *
 * @param m The os_mutex that is to be acquired.
 */
COMMON_SYSDEP void __cilkrts_os_mutex_lock(os_mutex *m);

/**
 * Try to acquire the os_mutex.
 *
 * @param   m  The os_mutex to try to acquire
 * @return  0      if the lock acquire failed
 * @return nonzero if the lock was acquired
 */
COMMON_SYSDEP int __cilkrts_os_mutex_trylock(os_mutex *m);

/**
 * Release the os_mutex
 *
 * @param m The os_mutex that is to be released.
 */
COMMON_SYSDEP void __cilkrts_os_mutex_unlock(os_mutex *m);

/**
 * Release any resources and deallocate the os_mutex.
 *
 * @param m The os_mutex that is to be deallocated.
 */
COMMON_SYSDEP void __cilkrts_os_mutex_destroy(os_mutex *m);

/**
 * Acquire the global os_mutex for exclusive use.  The global os_mutex
 * will be initialized the first time this function is called in a
 * thread-safe manner.
 */
COMMON_SYSDEP void global_os_mutex_lock();

/**
 * Release the global os_mutex.  global_os_mutex_lock() must have been
 * called first.
 */
COMMON_SYSDEP void global_os_mutex_unlock();


#ifdef _MSC_VER

/**
 * @brief Create the global OS mutex - Windows only.
 *
 * On Windows we use DllMain() to create the global OS mutex when cilkrts20.dll
 * is loaded. As opposed to Linux/MacOS where we use pthread_once to implement
 * a singleton since there are no guarantees about constructor or destructor
 * ordering between shared objects.
 */
NON_COMMON void global_os_mutex_create();

/**
 * @brief Destroy the global OS mutex - Windows only
 *
 * On Windows we use DllMain() to destroy the global OS mutex when
 * cilkrts20.dll is unloaded.  As opposed to Linux/MacOS where we cannot
 * know when it's safe to destroy the global OS mutex since there are no
 * guarantees about constructor or destructor ordering.
 */
NON_COMMON void global_os_mutex_destroy();

#endif  // _MSC_VER

__CILKRTS_END_EXTERN_C

#endif // ! defined(INCLUDED_OS_MUTEX_DOT_H)
