Mutex.hpp

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/***************************************************************************
  tag: Peter Soetens  Thu Oct 10 16:16:57 CEST 2002  Mutex.hpp

                        Mutex.hpp -  description
                           -------------------
    begin                : Thu October 10 2002
    copyright            : (C) 2002 Peter Soetens
    email                : peter.soetens@mech.kuleuven.ac.be

 ***************************************************************************
 *   This library is free software; you can redistribute it and/or         *
 *   modify it under the terms of the GNU General Public                   *
 *   License as published by the Free Software Foundation;                 *
 *   version 2 of the License.                                             *
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 *   software library without restriction.  Specifically, if other files   *
 *   instantiate templates or use macros or inline functions from this     *
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 *   produce an executable, this file does not by itself cause the         *
 *   resulting executable to be covered by the GNU General Public          *
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 *   Lesser General Public License for more details.                       *
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#ifndef OS_MUTEX_HPP
#define OS_MUTEX_HPP

#include "fosi.h"
#include "../rtt-config.h"
#include "rtt-os-fwd.hpp"
#include "CAS.hpp"
#include "Semaphore.hpp"
#include "Time.hpp"

#include <cassert>

#ifdef ORO_OS_USE_BOOST_THREAD
// BOOST_DATE_TIME_POSIX_TIME_STD_CONFIG is defined in rtt-config.h
#include <boost/thread/mutex.hpp>
#include <boost/thread/recursive_mutex.hpp>
#include <boost/thread/shared_mutex.hpp>
#include <boost/date_time/posix_time/posix_time_types.hpp>
#endif

namespace RTT
{ namespace os {

    class RTT_API MutexInterface
    {
    public:
        virtual ~MutexInterface() {}
        virtual void lock() =0;
        virtual void unlock() =0;
        virtual bool trylock() = 0;
        virtual bool timedlock(Seconds) = 0;
        virtual void lock_shared() {}
        virtual void unlock_shared() {}
        virtual bool trylock_shared() { return false; }
        virtual bool timedlock_shared(Seconds) { return false; }
    };


    class RTT_API Mutex : public MutexInterface
    {
        friend class Condition;
#ifndef ORO_OS_USE_BOOST_THREAD
    protected:
        rt_mutex_t m;
    public:
        Mutex()
        {
            rtos_mutex_init( &m);
        }

        virtual ~Mutex()
        {
            if ( trylock() ) {
                unlock();
                rtos_mutex_destroy( &m );
            }
        }

        virtual void lock ()
        {
            rtos_mutex_lock( &m );
        }

        virtual void unlock()
        {
            rtos_mutex_unlock( &m );
        }

        virtual bool trylock()
        {
            if ( rtos_mutex_trylock( &m ) == 0 )
                return true;
            return false;
        }

        virtual bool timedlock(Seconds s)
        {
            if ( rtos_mutex_trylock_for( &m, Seconds_to_nsecs(s) ) == 0 )
                return true;
            return false;
        }
#else
    protected:
        boost::timed_mutex m;
    public:
        Mutex()
        {
        }

        virtual ~Mutex()
        {
        }

        virtual void lock ()
        {
            m.lock();
        }

        virtual void unlock()
        {
            m.unlock();
        }

        virtual bool trylock()
        {
            return m.try_lock();
        }

        virtual bool timedlock(Seconds s)
        {
            return m.timed_lock( boost::posix_time::microseconds(Seconds_to_nsecs(s)/1000) );
        }
#endif

    };

    class RTT_API MutexRecursive : public MutexInterface
    {
#ifndef ORO_OS_USE_BOOST_THREAD
    protected:
        rt_rec_mutex_t recm;
    public:
        MutexRecursive()
        {
            rtos_mutex_rec_init( &recm );
        }

        virtual ~MutexRecursive()
        {
            if ( trylock() ) {
                unlock();
                rtos_mutex_rec_destroy( &recm );
            }
        }

        void lock ()
        {
            rtos_mutex_rec_lock( &recm );
        }

        virtual void unlock()
        {
            rtos_mutex_rec_unlock( &recm );
        }

        virtual bool trylock()
        {
            if ( rtos_mutex_rec_trylock( &recm ) == 0 )
                return true;
            return false;
        }

        virtual bool timedlock(Seconds s)
        {
            if ( rtos_mutex_rec_trylock_for( &recm, Seconds_to_nsecs(s) ) == 0 )
                return true;
            return false;
        }
#else
    protected:
        boost::recursive_timed_mutex recm;
    public:
        MutexRecursive()
        {
        }

        virtual ~MutexRecursive()
        {
        }

        void lock ()
        {
            recm.lock();
        }

        virtual void unlock()
        {
            recm.unlock();
        }

        virtual bool trylock()
        {
            return recm.try_lock();
        }

        virtual bool timedlock(Seconds s)
        {
            return recm.timed_lock( boost::posix_time::microseconds( Seconds_to_nsecs(s)/1000 ) );
        }
#endif
    };

    class RTT_API SharedMutex : public MutexInterface
    {
    protected:
        typedef unsigned int Status;
        oro_atomic_t status;
        Semaphore read_semaphore;
        Semaphore write_semaphore;

        static const Status one_reader       = (1 << 0);
        static const Status one_wait_to_read = (1 << 10);
        static const Status one_writer       = (1 << 20);
        static const Status status_mask      = (1 << 10) - 1;

        static inline unsigned int readers(Status status) {
            return (status & status_mask);
        }
        static inline unsigned int waitToRead(Status status) {
            return ((status >> 10) & status_mask);
        }
        static inline unsigned int writers(Status status) {
            return ((status >> 20) & status_mask);
        }

    public:
        SharedMutex()
            : read_semaphore(0)
            , write_semaphore(0)
        {
            ORO_ATOMIC_SETUP( &status, 0 );
        }

        virtual ~SharedMutex()
        {
            ORO_ATOMIC_CLEANUP( &status );
        }

        virtual void lock ()
        {
            Status old_status, new_status;
            do {
                new_status = old_status = (Status) oro_atomic_read( &status );
                new_status += one_writer;
                assert(writers(new_status) > 0);  // overflow?
            } while(!CAS(&status, (int) old_status, (int) new_status));

            if (readers(old_status) > 0 || writers(old_status) > 0) {
                write_semaphore.wait();
            }
        }

        virtual void unlock()
        {
            Status old_status, new_status;
            unsigned int wait_to_read = 0;
            do {
                new_status = old_status = (Status) oro_atomic_read( &status );
                assert(readers(old_status) == 0);
                assert(writers(old_status) > 0);
                new_status -= one_writer;
                wait_to_read = waitToRead(old_status);
                if (wait_to_read > 0) {
                    // all waiting threads can be unblocked
                    new_status = (new_status & (status_mask << 20)) | wait_to_read;
                }
            } while(!CAS(&status, (int) old_status, (int) new_status));

            // Signal threads that have been waiting for a read lock
            if (wait_to_read > 0) {
                for(unsigned int i = 0; i < wait_to_read; ++i) read_semaphore.signal();
            } else
            // ... or signal a thread that has been waiting for a write lock
            if (writers(old_status) > 1) {
                write_semaphore.signal();
            }
        }

        virtual bool trylock()
        {
            return false;
        }

        virtual bool timedlock(Seconds s)
        {
            (void) s;
            return false;
        }

        void lock_shared ()
        {
            Status old_status, new_status;
            do {
                new_status = old_status = (Status) oro_atomic_read( &status );
                if (writers(old_status) > 0) {
                    new_status += one_wait_to_read;
                    assert(waitToRead(new_status) > 0);  // overflow?
                } else {
                    new_status += one_reader;
                    assert(readers(new_status) > 0);  // overflow?
                }
            } while(!CAS(&status, (int) old_status, (int) new_status));

            // wait until all writers are finished
            if (writers(old_status) > 0) {
                read_semaphore.wait();
            }
        }

        virtual void unlock_shared()
        {
            Status old_status, new_status;
            do {
                new_status = old_status = (Status) oro_atomic_read( &status );
                assert(readers(old_status) > 0);
                new_status -= one_reader;
            } while(!CAS(&status, (int) old_status, (int) new_status));

            // one writer thread can be unblocked if there are no more readers
            if (readers(old_status) == 1 && writers(old_status) > 0) {
                write_semaphore.signal();
            }
        }

        virtual bool trylock_shared()
        {
            return false;
        }

        virtual bool timedlock_shared(Seconds s)
        {
            (void) s;
            return false;
        }
    };

}}

#endif