ACE_Barrier Class Reference

Implements "barrier synchronization". More...

#include <Barrier.h>

Inheritance diagram for ACE_Barrier:

[legend]Collaboration diagram for ACE_Barrier:

[legend]List of all members.

Public Member Functions
	ACE_Barrier (unsigned int count, const ACE_TCHAR *name=0, void *arg=0)
	Initialize the barrier to synchronize count threads.
	~ACE_Barrier (void)
	Default dtor.
int	wait (void)
int	shutdown (void)
void	dump (void) const
	Dump the state of an object.
Public Attributes
	ACE_ALLOC_HOOK_DECLARE
	Declare the dynamic allocation hooks.
Protected Attributes
ACE_Thread_Mutex	lock_
	Serialize access to the barrier state.
int	current_generation_
int	count_
	Total number of threads that can be waiting at any one time.
ACE_Sub_Barrier	sub_barrier_1_
ACE_Sub_Barrier	sub_barrier_2_
ACE_Sub_Barrier *	sub_barrier_ [2]
Private Member Functions
void	operator= (const ACE_Barrier &)
	ACE_Barrier (const ACE_Barrier &)

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Detailed Description

Implements "barrier synchronization".

This class allows 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).

Definition at line 96 of file Barrier.h.

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Constructor & Destructor Documentation

ACE_Barrier::ACE_Barrier (  unsigned int  count, const ACE_TCHAR *  name = 0, void *  arg = 0 )

Initialize the barrier to synchronize count threads. Definition at line 68 of file Barrier.cpp. References ACE_TCHAR, ACE_TRACE, sub_barrier_, sub_barrier_1_, and sub_barrier_2_. : lock_ (name, (ACE_mutexattr_t *) arg), current_generation_ (0), count_ (count), sub_barrier_1_ (count, lock_, name, arg), sub_barrier_2_ (count, lock_, name, arg) { ACE_TRACE ("ACE_Barrier::ACE_Barrier"); this->sub_barrier_[0] = &this->sub_barrier_1_; this->sub_barrier_[1] = &this->sub_barrier_2_; }

ACE_INLINE ACE_Barrier::~ACE_Barrier (  void   )

Default dtor. Definition at line 13 of file Barrier.inl. { }

ACE_Barrier::ACE_Barrier (  const ACE_Barrier &   )  [private]

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Member Function Documentation

void ACE_Barrier::dump (  void   )  const

Dump the state of an object. Reimplemented in ACE_Thread_Barrier. Definition at line 53 of file Barrier.cpp. References ACE_BEGIN_DUMP, ACE_DEBUG, ACE_END_DUMP, ACE_LIB_TEXT, ACE_Sub_Barrier::dump(), ACE_Thread_Mutex::dump(), LM_DEBUG, lock_, sub_barrier_1_, and sub_barrier_2_. Referenced by ACE_Thread_Barrier::dump(). { #if defined (ACE_HAS_DUMP) // ACE_TRACE ("ACE_Barrier::dump"); ACE_DEBUG ((LM_DEBUG, ACE_BEGIN_DUMP, this)); this->lock_.dump (); ACE_DEBUG ((LM_DEBUG, ACE_LIB_TEXT ("current_generation_ = %d"), this->current_generation_)); ACE_DEBUG ((LM_DEBUG, ACE_LIB_TEXT ("\ncount_ = %d"), this->count_)); this->sub_barrier_1_.dump (); this->sub_barrier_2_.dump (); ACE_DEBUG ((LM_DEBUG, ACE_END_DUMP)); #endif /* ACE_HAS_DUMP */ }

void ACE_Barrier::operator= (  const ACE_Barrier &   )  [private]

int ACE_Barrier::shutdown (  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. Return values: 0  for success, -1 if already shut down. Since: ACE beta 5.4.9. Definition at line 132 of file Barrier.cpp. References ACE_GUARD_RETURN, ACE_TRACE, ACE_Sub_Barrier::barrier_finished_, ACE_Condition_Thread_Mutex::broadcast(), count_, current_generation_, ESHUTDOWN, ACE_Sub_Barrier::running_threads_, and sub_barrier_. { ACE_TRACE ("ACE_Barrier::shutdown"); ACE_GUARD_RETURN (ACE_Thread_Mutex, ace_mon, this->lock_, -1); ACE_Sub_Barrier *sbp = this->sub_barrier_[this->current_generation_]; // Check for shutdown... if (sbp == 0) { errno = ESHUTDOWN; return -1; } // Flag the shutdown this->sub_barrier_[0] = 0; this->sub_barrier_[1] = 0; // Tell all the threads waiting on the barrier to continue on their way. sbp->running_threads_ = this->count_; sbp->barrier_finished_.broadcast (); return 0; }

int ACE_Barrier::wait (  void   )

Block the caller until all count threads have called wait and then allow all the caller threads to continue in parallel. Return values: 0  after successfully waiting for all threads to wait. -1 if an error occurs or the barrier is shut down ( See also: shutdown ()). Definition at line 83 of file Barrier.cpp. References ACE_GUARD_RETURN, ACE_TRACE, ACE_Sub_Barrier::barrier_finished_, ACE_Condition_Thread_Mutex::broadcast(), count_, current_generation_, ESHUTDOWN, ACE_Sub_Barrier::running_threads_, sub_barrier_, and ACE_Condition_Thread_Mutex::wait(). { ACE_TRACE ("ACE_Barrier::wait"); ACE_GUARD_RETURN (ACE_Thread_Mutex, ace_mon, this->lock_, -1); ACE_Sub_Barrier *sbp = this->sub_barrier_[this->current_generation_]; // Check for shutdown... if (sbp == 0) { errno = ESHUTDOWN; return -1; } int retval = 0; if (sbp->running_threads_ == 1) { // We're the last running thread, so swap generations and tell // all the threads waiting on the barrier to continue on their // way. sbp->running_threads_ = this->count_; // Swap generations. this->current_generation_ = 1 - this->current_generation_; sbp->barrier_finished_.broadcast (); } else { --sbp->running_threads_; // Block until all the other threads wait(). while (sbp->running_threads_ != this->count_) sbp->barrier_finished_.wait (); // We're awake and the count has completed. See if it completed // because all threads hit the barrier, or because the barrier // was shut down. if (this->sub_barrier_[this->current_generation_] == 0) { errno = ESHUTDOWN; retval = -1; } } return retval; }

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Member Data Documentation

ACE_Barrier::ACE_ALLOC_HOOK_DECLARE

Declare the dynamic allocation hooks. Reimplemented in ACE_Thread_Barrier. Definition at line 127 of file Barrier.h.

int ACE_Barrier::count_ [protected]

Total number of threads that can be waiting at any one time. Definition at line 138 of file Barrier.h. Referenced by shutdown(), and wait().

int ACE_Barrier::current_generation_ [protected]

Either 0 or 1, depending on whether we are the first generation of waiters or the next generation of waiters. Definition at line 135 of file Barrier.h. Referenced by shutdown(), and wait().

ACE_Thread_Mutex ACE_Barrier::lock_ [protected]

Serialize access to the barrier state. Definition at line 131 of file Barrier.h. Referenced by dump().

ACE_Sub_Barrier* ACE_Barrier::sub_barrier_[2] [protected]

Definition at line 150 of file Barrier.h. Referenced by ACE_Barrier(), shutdown(), and wait().

ACE_Sub_Barrier ACE_Barrier::sub_barrier_1_ [protected]

We keep two 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). Definition at line 148 of file Barrier.h. Referenced by ACE_Barrier(), and dump().

ACE_Sub_Barrier ACE_Barrier::sub_barrier_2_ [protected]

Definition at line 149 of file Barrier.h. Referenced by ACE_Barrier(), and dump().

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The documentation for this class was generated from the following files:

• Barrier.h
• Barrier.cpp
• Barrier.inl

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