readwritesem.cpp

Pegasus is an open-source implementationof the DMTF CIM and WBEM standards. It is designed to be por

                              int milliseconds)
{
//-----------------------------------------------------------------
// Lock this object to maintain integrity while we decide
// exactly what to do next.
//-----------------------------------------------------------------
    // AutoPtr<IPCException> caught;
    // IPCException caught((ThreadType)0);
    // WaitFailed caughtWaitFailed((ThreadType)0);
    // TimeOut caughtTimeOut((ThreadType)0);
    // TooManyReaders caughtTooManyReaders((ThreadType)0);

    ThreadType zero;
    IPCException caught(zero);
    WaitFailed caughtWaitFailed(zero);
    TimeOut caughtTimeOut(zero);
    TooManyReaders caughtTooManyReaders(zero);

    // cleanup stack frame
    {
        // Threads::cleanup_push(extricate_read_write, this);

        try
        {
            if (milliseconds == 0)
                _rwlock._internal_lock.try_lock();
            else if (milliseconds == -1)
                _rwlock._internal_lock.lock();
            else
                _rwlock._internal_lock.timed_lock(milliseconds);
        }
        catch (const IPCException & e)
        {
            caught = e;
            goto throw_from_here;
        }

        if (mode == PEG_SEM_WRITE)
        {
//-----------------------------------------------------------------
// Write Lock Step 1: lock the object and allow all the readers to exit
//-----------------------------------------------------------------


            if (milliseconds == 0)      // fast wait
            {
                if (_readers.get() > 0)
                {
                    _rwlock._internal_lock.unlock();
                    // caught.reset(new WaitFailed(Threads::self()));
                    caughtWaitFailed = WaitFailed(Threads::self());
                    goto throw_from_here;
                }
            }
            else if (milliseconds == -1)        // infinite wait
            {
                while (_readers.get() > 0)
                    Threads::yield();
            }
            else                // timed wait
            {
                struct timeval start, now;
                Time::gettimeofday(&start);
                start.tv_usec += (1000 * milliseconds);
                while (_readers.get() > 0)
                {
                    Time::gettimeofday(&now);
                    if ((now.tv_usec > start.tv_usec) ||
                        now.tv_sec > start.tv_sec)
                    {
                        _rwlock._internal_lock.unlock();
                        // caught.reset(new TimeOut(Threads::self()));
                        caughtTimeOut = TimeOut(Threads::self());
                        goto throw_from_here;
                    }
                    Threads::yield();
                }
            }
//-----------------------------------------------------------------
// Write Lock Step 2: Obtain the Write Mutex
//  Although there are no readers, there may be a writer
//-----------------------------------------------------------------
            if (milliseconds == 0)      // fast wait
            {
                try
                {
                    _rwlock._wlock.try_lock();
                }
                catch (IPCException & e)
                {
                    _rwlock._internal_lock.unlock();
                    caught = e;
                    goto throw_from_here;
                }
            }
            else if (milliseconds == -1)        // infinite wait
            {
                try
                {
                    _rwlock._wlock.lock();
                }
                catch (const IPCException & e)
                {
                    _rwlock._internal_lock.unlock();
                    caught = e;
                    goto throw_from_here;
                }
            }
            else                // timed wait
            {
                try
                {
                    _rwlock._wlock.timed_lock(milliseconds);
                }
                catch (const IPCException & e)
                {
                    _rwlock._internal_lock.unlock();
                    caught = e;
                    goto throw_from_here;
                }
            }

//-----------------------------------------------------------------
// Write Lock Step 3: set the writer count to one, unlock the object
//   There are no readers and we are the only writer !
//-----------------------------------------------------------------
            _writers = 1;
            // set the owner
            _rwlock._owner = Threads::self();
            // unlock the object
            _rwlock._internal_lock.unlock();
        }                       // PEG_SEM_WRITE
        else
        {
//-----------------------------------------------------------------
// Read Lock Step 1: Wait for the existing writer (if any) to clear
//-----------------------------------------------------------------
            if (milliseconds == 0)      // fast wait
            {
                if (_writers.get() > 0)
                {
                    _rwlock._internal_lock.unlock();
                    // caught.reset(new WaitFailed(Threads::self()));
                    caughtWaitFailed = WaitFailed(Threads::self());
                    goto throw_from_here;
                }
            }
            else if (milliseconds == -1)        // infinite wait
            {
                while (_writers.get() > 0)
                    Threads::yield();
            }
            else                // timed wait
            {
                struct timeval start, now;
                Time::gettimeofday(&start);
                start.tv_usec += (milliseconds * 1000);

                while (_writers.get() > 0)
                {
                    Time::gettimeofday(&now);
                    if ((now.tv_usec > start.tv_usec) ||
                        (now.tv_sec > start.tv_sec))
                    {
                        _rwlock._internal_lock.unlock();
                        // caught.reset(new TimeOut(Threads::self()));
                        caughtTimeOut = TimeOut(Threads::self());
                        goto throw_from_here;
                    }
                    Threads::yield();
                    Time::gettimeofday(&now);
                }
            }

//-----------------------------------------------------------------
// Read Lock Step 2: wait for a reader slot to open up, then return
//  At this point there are no writers, but there may be too many
//  readers.
//-----------------------------------------------------------------
            if (milliseconds == 0)      // fast wait
            {
                try
                {
                    _rwlock._rlock.try_wait();
                }
                catch (const IPCException &)
                {
                    // the wait failed, there must be too many readers
                    // already.
                    // unlock the object
                    caughtTooManyReaders = TooManyReaders(Threads::self());
                    _rwlock._internal_lock.unlock();
                    // caught.reset(new TooManyReaders(Threads::self()));
                }
            }
            else if (milliseconds == -1)        // infinite wait
            {
                try
                {
                    _rwlock._rlock.wait();
                }
                catch (const IPCException & e)
                {
                    _rwlock._internal_lock.unlock();
                    caught = e;
                    goto throw_from_here;
                }
            }
            else                // timed wait
            {
                try
                {
                    _rwlock._rlock.time_wait(milliseconds);
                }
                catch (const IPCException & e)
                {
                    _rwlock._internal_lock.unlock();
                    caught = e;
                    goto throw_from_here;
                }
            }

//-----------------------------------------------------------------
// Read Lock Step 3: increment the number of readers, unlock the object,
// return
//-----------------------------------------------------------------
            _readers++;
            _rwlock._internal_lock.unlock();
        }
      throw_from_here:
        // ATTN:
        Threads::cleanup_pop(0);
    }

    if (!Threads::null(caught.get_owner()))
        throw caught;
    if (!Threads::null(caughtWaitFailed.get_owner()))
        throw caughtWaitFailed;
    if (!Threads::null(caughtTimeOut.get_owner()))
        throw caughtTimeOut;
    if (!Threads::null(caughtTooManyReaders.get_owner()))

        throw caughtTooManyReaders;
    return;
}

//---------------------------------------------------------------------
void ReadWriteSem::wait(Uint32 mode, ThreadType caller)
{
    timed_wait(mode, caller, -1);
}

void ReadWriteSem::try_wait(Uint32 mode, ThreadType caller)
{
    timed_wait(mode, caller, 0);
}


void ReadWriteSem::unlock(Uint32 mode, ThreadType caller)
{
    if (mode == PEG_SEM_WRITE && _writers.get() != 0)
    {
        _writers = 0;
        _rwlock._wlock.unlock();
    }
    else if (_readers.get() != 0)
    {
        _readers--;
        _rwlock._rlock.signal();
    }
}

int ReadWriteSem::read_count() const
{
    return _readers.get();
}

int ReadWriteSem::write_count() const
{
    return _writers.get();
}

#endif /* !PEGASUS_USE_SEMAPHORE_RWLOCK */

PEGASUS_NAMESPACE_END