lunchbox::SpinLock Class Reference

A fast lock for uncontended memory access. More...

#include <spinLock.h>

Inheritance diagram for lunchbox::SpinLock:

Collaboration diagram for lunchbox::SpinLock:

Public Member Functions
	SpinLock ()
	Construct a new lock. More...
	~SpinLock ()
	Destruct the lock. More...
void	set ()
	Acquire the lock exclusively. More...
void	unset ()
	Release an exclusive lock. More...
bool	trySet ()
	Attempt to acquire the lock exclusively. More...
void	setRead ()
	Acquire the lock shared with other readers. More...
void	unsetRead ()
	Release a shared read lock. More...
bool	trySetRead ()
	Attempt to acquire the lock shared with other readers. More...
bool	isSet ()
	Test if the lock is set. More...
bool	isSetWrite ()
	Test if the lock is set exclusively. More...
bool	isSetRead ()
	Test if the lock is set shared. More...

Detailed Description

A fast lock for uncontended memory access.

If Thread::yield() does not work, priority inversion is possible. If used as a read-write lock, readers or writers will starve on high contention.

See also

ScopedMutex

Example:

/* Copyright (c) 2006-2016, Stefan Eilemann <eile@equalizergraphics.com>
 *
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License version 2.1 as published
 * by the Free Software Foundation.
 *
 * This library 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 Lesser General Public License for more
 * details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#define TEST_RUNTIME 600 // seconds, needed for NighlyMemoryCheck
#include <lunchbox/test.h>

#include <lunchbox/clock.h>
#include <lunchbox/debug.h>
#include <lunchbox/init.h>
#include <lunchbox/lock.h>
#include <lunchbox/spinLock.h>
#include <lunchbox/timedLock.h>

#include <iostream>

#define MAXTHREADS 256
#define TIME       500  // ms

lunchbox::Clock _clock;
bool _running = false;

template< class T > class Thread : public lunchbox::Thread
{
public:
    Thread() : lock( 0 ), ops( 0 ) {}

    T* lock;
    size_t ops;

    virtual void run()
    {
        ops = 0;
        while( LB_LIKELY( _running ))
        {
            lock->set();
            lock->unset();
            ++ops;
        }
    }
};

template< class T > void _test()
{
    const size_t nThreads = 16;

    T lock;
    lock.set();

    Thread< T > threads[MAXTHREADS];
    for( size_t i = 1; i <= nThreads; i = i << 1 )
    {
        _running = true;
        for( size_t j = 0; j < i; ++j )
        {
            threads[j].lock = &lock;
            TEST( threads[j].start( ));
        }
        lunchbox::sleep( 10 ); // let threads initialize

        _clock.reset();
        lock.unset();
        lunchbox::sleep( TIME ); // let threads run
        _running = false;

        for( size_t j = 0; j < i; ++j )
            TEST( threads[j].join( ));
        const float time = _clock.getTimef();

#ifndef NDEBUG
        TEST( !lock.isSet( ));
#endif
        lock.set();

        size_t ops = 0;
        for( size_t j = 0; j < nThreads; ++j )
            ops += threads[j].ops;

        std::cout << std::setw(20) << lunchbox::className( lock ) << ", "
                  << std::setw(12) << /*set, test, unset*/ 3 * ops / time
                  << ", " << std::setw(3) << i << std::endl;
    }
}

int main( int argc, char **argv )
{
    TEST( lunchbox::init( argc, argv ));

    std::cout << "               Class,       ops/ms, threads" << std::endl;
    _test< lunchbox::SpinLock >();
    std::cout << std::endl;

    _test< lunchbox::Lock >();
    std::cout << std::endl;

    _test< lunchbox::TimedLock >();
    TEST( lunchbox::exit( ));

    return EXIT_SUCCESS;
}

Definition at line 38 of file spinLock.h.

Constructor & Destructor Documentation

lunchbox::SpinLock::SpinLock

(

)

Construct a new lock.

Version

1.0

lunchbox::SpinLock::~SpinLock

(

)

Destruct the lock.

Version

1.0

Member Function Documentation

bool lunchbox::SpinLock::isSet

(

)

Test if the lock is set.

Returns

true if the lock is set, false if it is not set.

Version

1.0

bool lunchbox::SpinLock::isSetRead

(

)

Test if the lock is set shared.

Returns

true if the lock is set, false if it is not set.

Version

1.1.2

bool lunchbox::SpinLock::isSetWrite

(

)

Test if the lock is set exclusively.

Returns

true if the lock is set, false if it is not set.

Version

1.1.2

void lunchbox::SpinLock::set

(

)

Acquire the lock exclusively.

Version

1.0

void lunchbox::SpinLock::setRead

(

)

Acquire the lock shared with other readers.

Version

1.1.2

bool lunchbox::SpinLock::trySet

(

)

Attempt to acquire the lock exclusively.

Returns

true if the lock was set, false if it was not set.

Version

1.0

bool lunchbox::SpinLock::trySetRead

(

)

Attempt to acquire the lock shared with other readers.

Returns

true if the lock was set, false if it was not set.

Version

1.1.2

void lunchbox::SpinLock::unset

(

)

Release an exclusive lock.

Version

1.0

void lunchbox::SpinLock::unsetRead

(

)

Release a shared read lock.

Version

1.1.2

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

• spinLock.h