src/parsec/disk-image/parsec/parsec-benchmark/pkgs/libs/tbblib/src/src/tbb/queuing_mutex.cpp

/*
    Copyright 2005-2010 Intel Corporation.  All Rights Reserved.

    This file is part of Threading Building Blocks.

    Threading Building Blocks is free software; you can redistribute it
    and/or modify it under the terms of the GNU General Public License
    version 2 as published by the Free Software Foundation.

    Threading Building Blocks is distributed in the hope that it will be
    useful, but WITHOUT ANY WARRANTY; without even the implied warranty
    of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with Threading Building Blocks; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    As a special exception, you may use this file as part of a free software
    library without restriction.  Specifically, if other files instantiate
    templates or use macros or inline functions from this file, or you compile
    this file and link it with other files to produce an executable, this
    file does not by itself cause the resulting executable to be covered by
    the GNU General Public License.  This exception does not however
    invalidate any other reasons why the executable file might be covered by
    the GNU General Public License.
*/

#include "tbb/tbb_machine.h"
#include "tbb/tbb_stddef.h"
#include "tbb_misc.h"
#include "tbb/queuing_mutex.h"
#include "itt_notify.h"


namespace tbb {

using namespace internal;

//! A method to acquire queuing_mutex lock
void queuing_mutex::scoped_lock::acquire( queuing_mutex& m )
{
    __TBB_ASSERT( !this->mutex, "scoped_lock is already holding a mutex");

    // Must set all fields before the fetch_and_store, because once the
    // fetch_and_store executes, *this becomes accessible to other threads.
    mutex = &m;
    next  = NULL;
    going = 0;

    // The fetch_and_store must have release semantics, because we are
    // "sending" the fields initialized above to other processors.
    scoped_lock* pred = m.q_tail.fetch_and_store<tbb::release>(this);
    if( pred ) {
        ITT_NOTIFY(sync_prepare, mutex);
        __TBB_ASSERT( !pred->next, "the predecessor has another successor!");
        pred->next = this;
        spin_wait_while_eq( going, 0ul );
    }
    ITT_NOTIFY(sync_acquired, mutex);

    // Force acquire so that user's critical section receives correct values
    // from processor that was previously in the user's critical section.
    __TBB_load_with_acquire(going);
}

//! A method to acquire queuing_mutex if it is free
bool queuing_mutex::scoped_lock::try_acquire( queuing_mutex& m )
{
    __TBB_ASSERT( !this->mutex, "scoped_lock is already holding a mutex");

    // Must set all fields before the fetch_and_store, because once the
    // fetch_and_store executes, *this becomes accessible to other threads.
    next  = NULL;
    going = 0;

    if( m.q_tail ) return false;
    // The CAS must have release semantics, because we are
    // "sending" the fields initialized above to other processors.
    scoped_lock* pred = m.q_tail.compare_and_swap<tbb::release>(this, NULL);

    // Force acquire so that user's critical section receives correct values
    // from processor that was previously in the user's critical section.
    // try_acquire should always have acquire semantic, even if failed.
    __TBB_load_with_acquire(going);
    if( !pred ) {
        mutex = &m;
        ITT_NOTIFY(sync_acquired, mutex);
        return true;
    } else return false;
}

//! A method to release queuing_mutex lock
void queuing_mutex::scoped_lock::release( )
{
    __TBB_ASSERT(this->mutex!=NULL, "no lock acquired");

    ITT_NOTIFY(sync_releasing, mutex);
    if( !next ) {
        if( this == mutex->q_tail.compare_and_swap<tbb::release>(NULL, this) ) {
            // this was the only item in the queue, and the queue is now empty.
            goto done;
        }
        // Someone in the queue
        spin_wait_while_eq( next, (scoped_lock*)0 );
    }
    __TBB_ASSERT(next,NULL);
    __TBB_store_with_release(next->going, 1);
done:
    initialize();
}

void queuing_mutex::internal_construct() {
    ITT_SYNC_CREATE(this, _T("tbb::queuing_mutex"), _T(""));
}

} // namespace tbb