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fthreads Mutexs

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fthreads Mutexs

This page discusses fthreads mutexs. A list of links is provided below.

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Introduction

A mutex is a synchronization object. A mutex may be locked or unlocked. If a mutex is locked by a thread, no other thread may lock it. A mutex may be used to allow only one thread at a time to execute a piece of code, for example, updating a global variable. The code which must be executed by one thread at a time is placed between calls to mutex_lock() and mutex_unlock(). A mutex is initialized by declaring a variable of type mutex_t and passing it to mutex_init(). Type mutex_t is defined in module fthreads.

A mutex's statistics may be gathered by mutex_status(). A mutex has a mutex id, which is a unique integer between one and the number passed to fthread_init(). The mutex id may be returned by calling mutex_id().

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Mutex Routines

mutex_init()

The mutex_init() routine initializes a new mutex synchronization object.

interface
   subroutine mutex_init( m, tm, name, &
              trace_v, flag)
      type( mutex_t), intent( out) :: m
      type( team_t), optional, &
            intent( in) :: tm
      character( len= *), optional, &
            intent( in) :: name
      type( trace_t), optional, &
            intent( inout) :: trace_v
      integer, optional, &
               intent( out) :: flag
   end subroutine mutex_init
end interface
			

The mutex_init() routine returns a type mutex_t variable m. The mutex is visible to members of optional type team_t variable tm, or the team of all worker threads. The optional character variable provides a mutex name. The optional type trace_tvariable trace_v and the optional integer variable flag provide tracing and feedback.

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mutex_del()

The mutex_del() routine deletes a mutex synchronization object.

interface
   subroutine mutex_del( m, trace_v, flag)
      type( mutex_t), intent( out) :: m
      type( trace_t), optional, &
            intent( inout) :: trace_v
      integer, optional, &
               intent( out) :: flag
   end subroutine mutex_del
end interface
			

The mutex_del() routine deletes a type mutex_t mutex variable m. The optional type trace_t variable trace_v and the optional integer variable flag provide tracing and feedback.

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mutex_lock()

The mutex_lock() routine waits until the mutex is unlocked, and then locks the mutex.

interface
   subroutine mutex_lock( m, th, &
            trace_v, flag)
      type( mutex_t), intent( out) :: m
      type( thread_t), optional, &
            intent( in) :: th
      type( trace_t), optional, &
            intent( inout) :: trace_v
      integer, optional, &
               intent( out) :: flag
   end subroutine mutex_lock
end interface
			

The mutex_lock() routine locks a type mutex_t mutex variable m. The calling thread waits until the mutex is unlocked before locking it. If the optional type thread_t variable th is present, the thread is checked for membership in the mutex's team. The optional type trace_t variable trace_v and the optional integer variable flag provide tracing and feedback.

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mutex_try()

The mutex_try() routine attempts to lock the mutex, and returns immediately whether locked or not.

interface
   logical function mutex_try( m, th, &
           trace_v, flag)
      type( mutex_t), intent( out) :: m
      type( thread_t), optional, &
            intent( in) :: th
      type( trace_t), optional, &
            intent( inout) :: trace_v
      integer, optional, &
               intent( out) :: flag
   end function mutex_try
end interface
			

The mutex_try() routine attempts to lock the mutex indicated by the type mutex_t mutex variable m, and returns immediately. The function returns true if the mutex is locked, and false if not. If the optional type thread_t thread variable th is present, the thread is checked for membership in the mutex's team. The optional type trace_t trace variable trace_v and the optional integer variable flag provide tracing and feedback.

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mutex_unlock()

The mutex_unlock() routine unlocks the mutex.

interface
   subroutine mutex_unlock( m, th, &
              trace_v, flag)
      type( mutex_t), intent( out) :: m
      type( thread_t), optional, &
            intent( in) :: th
      type( trace_t), optional, &
            intent( inout) :: trace_v
      integer, optional, &
               intent( out) :: flag
   end subroutine mutex_unlock
end interface
			

The mutex_unlock() routine unlocks a type mutex_t mutex variable m. If the optional type thread_t thread variable th is present, the thread is checked for membership in the mutex's team. The optional type trace_t trace variable trace_v and the optional integer variable flag provide tracing and feedback.

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mutex_id()

The mutex_id() return the mutex id.

interface
   integer function mutex_id( m)
      type( mutex_t), intent( in) :: m
   end function mutex_id
end interface
			

The integer function mutex_id() returns the mutex id. The mutex id is a unique positive integer from one through the number of mutexs.

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mutex_status()

The mutex_status() routine returns a mutex's statistics.

interface
   subroutine mutex_status( m, name, &
              locked, unlocked, &
              trace_v, flag)
      type( mutex_t), intent( in) :: m
      character( len= *), optional, &
                 intent( out) :: name
      integer, optional, &
               intent( out) :: locked
      integer, optional, &
               intent( out) :: unlocked
      type( trace_t), optional, &
            intent( inout) :: trace_v
      integer, optional, &
               intent( out) :: flag
   end subroutine event_status
end interface
			

The mutex_status() routine returns the mutex statistics of the mutex indicated by the type mutex_t mutex variable m. The optional character variable name returns the mutex's name. The optional integer variable locked returns the number of times a thread has locked the mutex. The optional integer unlocked returns the number of times a thread has unlocked the mutex. The optional type trace_t trace variable trace_v and the optional integer variable flag provide tracing and feedback.

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