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// -*- C++ -*-
//==========================================================================
/**
* @file Barrier.h
*
* $Id$
*
* Moved from Synch.h.
*
* @author Douglas C. Schmidt <schmidt@cs.wustl.edu>
*/
//==========================================================================
#ifndef ACE_BARRIER_H
#define ACE_BARRIER_H
#include /**/ "ace/pre.h"
#include /**/ "ace/ACE_export.h"
#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */
#include /**/ "ace/config-all.h"
// ACE platform supports some form of threading.
#if !defined (ACE_HAS_THREADS)
#include "ace/OS_NS_errno.h"
ACE_BEGIN_VERSIONED_NAMESPACE_DECL
/**
* @class ACE_Barrier
*
* @brief This is a no-op to make ACE "syntactically consistent."
*/
class ACE_Export ACE_Barrier
{
public:
ACE_Barrier (unsigned int, const ACE_TCHAR * = 0, void * = 0) {}
~ACE_Barrier (void) {}
int wait (void) { ACE_NOTSUP_RETURN (-1); }
void dump (void) const {}
};
ACE_END_VERSIONED_NAMESPACE_DECL
#else /* ACE_HAS_THREADS */
#include "ace/Condition_Thread_Mutex.h"
ACE_BEGIN_VERSIONED_NAMESPACE_DECL
struct ACE_Export ACE_Sub_Barrier
{
// = Initialization.
ACE_Sub_Barrier (unsigned int count,
ACE_Thread_Mutex &lock,
const ACE_TCHAR *name = 0,
void *arg = 0);
~ACE_Sub_Barrier (void);
/// True if this generation of the barrier is done.
ACE_Condition_Thread_Mutex barrier_finished_;
/// Number of threads that are still running.
int running_threads_;
/// Dump the state of an object.
void dump (void) const;
/// Declare the dynamic allocation hooks.
ACE_ALLOC_HOOK_DECLARE;
};
/**
* @class ACE_Barrier
*
* @brief Implements "barrier synchronization".
*
* This class allows <count> number of threads to synchronize
* their completion of (one round of) a task, which is known as
* "barrier synchronization". After all the threads call <wait()>
* on the barrier they are all atomically released and can begin a new
* round.
*
* This implementation uses a "sub-barrier generation numbering"
* scheme to avoid overhead and to ensure that all threads wait to
* leave the barrier correct. This code is based on an article from
* SunOpsis Vol. 4, No. 1 by Richard Marejka
* (Richard.Marejka@canada.sun.com).
*/
class ACE_Export ACE_Barrier
{
public:
/// Initialize the barrier to synchronize @a count threads.
ACE_Barrier (unsigned int count,
const ACE_TCHAR *name = 0,
void *arg = 0);
/// Default destructor.
~ACE_Barrier (void);
/// Block the caller until all @c count threads have called @c wait and
/// then allow all the caller threads to continue in parallel.
///
/// @retval 0 after successfully waiting for all threads to wait.
/// @retval -1 if an error occurs or the barrier is shut
/// down (@sa shutdown ()).
int wait (void);
/// Shut the barrier down, aborting the wait of all waiting threads.
/// Any threads waiting on the barrier when it is shut down will return with
/// value -1, errno ESHUTDOWN.
///
/// @retval 0 for success, -1 if already shut down.
///
/// @since ACE beta 5.4.9.
int shutdown (void);
/// Dump the state of an object.
void dump (void) const;
/// Declare the dynamic allocation hooks.
ACE_ALLOC_HOOK_DECLARE;
protected:
/// Serialize access to the barrier state.
ACE_Thread_Mutex lock_;
/// Either 0 or 1, depending on whether we are the first generation
/// of waiters or the next generation of waiters.
int current_generation_;
/// Total number of threads that can be waiting at any one time.
int count_;
/**
* We keep two @c sub_barriers, one for the first "generation" of
* waiters, and one for the next "generation" of waiters. This
* efficiently solves the problem of what to do if all the first
* generation waiters don't leave the barrier before one of the
* threads calls wait() again (i.e., starts up the next generation
* barrier).
*/
ACE_Sub_Barrier sub_barrier_1_;
ACE_Sub_Barrier sub_barrier_2_;
ACE_Sub_Barrier *sub_barrier_[2];
private:
// = Prevent assignment and initialization.
void operator= (const ACE_Barrier &);
ACE_Barrier (const ACE_Barrier &);
};
/**
* @class ACE_Thread_Barrier
*
* @brief Implements "barrier synchronization" using ACE_Thread_Mutexes!
*
* This class is just a simple wrapper for ACE_Barrier that
* selects the USYNC_THREAD variant for the locks.
*/
class ACE_Export ACE_Thread_Barrier : public ACE_Barrier
{
public:
/// Create a Thread_Barrier, passing in the optional @a name.
ACE_Thread_Barrier (unsigned int count, const ACE_TCHAR *name = 0);
/// Default destructor.
~ACE_Thread_Barrier (void);
/// Dump the state of an object.
void dump (void) const;
/// Declare the dynamic allocation hooks.
ACE_ALLOC_HOOK_DECLARE;
};
ACE_END_VERSIONED_NAMESPACE_DECL
#if defined (__ACE_INLINE__)
#include "ace/Barrier.inl"
#endif /* __ACE_INLINE__ */
#endif /* !ACE_HAS_THREADS */
#include /**/ "ace/post.h"
#endif /* ACE_BARRIER_H */
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