Collaboration diagram for osgEarth::Threading::ReadWriteMutex:

Public Member Functions
	ReadWriteMutex ()
void	readLock ()
void	readUnlock ()
void	writeLock ()
void	writeUnlock ()
Protected Member Functions
void	incrementReaderCount ()
void	decrementReaderCount ()
Private Attributes
int	_readerCount
OpenThreads::Mutex	_lockWriterMutex
OpenThreads::Mutex	_readerCountMutex
Event	_noWriterEvent
Event	_noReadersEvent

Detailed Description

Custom read/write lock. The read/write lock in OSG can unlock mutexes from a different thread than the one that locked them - this can hang the thread in Windows.

Adapted from: http://www.codeproject.com/KB/threads/ReadWriteLock.aspx

Definition at line 156 of file ThreadingUtils.

Constructor & Destructor Documentation

osgEarth::Threading::ReadWriteMutex::ReadWriteMutex ( ) [inline]

Definition at line 165 of file ThreadingUtils.

                         :
          _readerCount(0)
        { 
            _noWriterEvent.set();
            _noReadersEvent.set();
        }

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Member Function Documentation

void osgEarth::Threading::ReadWriteMutex::decrementReaderCount ( ) [inline, protected]

Definition at line 255 of file ThreadingUtils.

        {
            OpenThreads::ScopedLock<OpenThreads::Mutex> lock( _readerCountMutex );
            _readerCount--;               // remove a reader
            if ( _readerCount <= 0 )      // if that was the last one, signal that writers are now allowed
                _noReadersEvent.set();
        }

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void osgEarth::Threading::ReadWriteMutex::incrementReaderCount ( ) [inline, protected]

Definition at line 248 of file ThreadingUtils.

        {
            OpenThreads::ScopedLock<OpenThreads::Mutex> lock( _readerCountMutex );
            _readerCount++;            // add a reader
            _noReadersEvent.reset();   // there's at least one reader now so clear the flag
        }

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void osgEarth::Threading::ReadWriteMutex::readLock ( ) [inline]

Definition at line 172 of file ThreadingUtils.

        {

#ifdef TRACE_THREADS
            {
                OpenThreads::ScopedLock<OpenThreads::Mutex> ttLock(_traceMutex);
                if( _trace.find(OpenThreads::Thread::CurrentThread()) != _trace.end() )
                    OE_WARN << "TRACE: tried to double-lock" << std::endl;
            }
#endif
            for( ; ; )
            {
                _noWriterEvent.wait();             // wait for a writer to quit if there is one
                incrementReaderCount();            // register this reader
                if ( !_noWriterEvent.isSet() )     // double lock check, in case a writer snuck in while inrementing
                    decrementReaderCount();        // if it did, undo the registration and try again
                else
                    break;                         // otherwise, we're in
            }

#ifdef TRACE_THREADS
            {
                OpenThreads::ScopedLock<OpenThreads::Mutex> ttLock(_traceMutex);
                _trace.insert(OpenThreads::Thread::CurrentThread());
            }
#endif
        }

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void osgEarth::Threading::ReadWriteMutex::readUnlock ( ) [inline]

Definition at line 200 of file ThreadingUtils.

        {
            decrementReaderCount();                // unregister this reader
            
#ifdef TRACE_THREADS
            {
                OpenThreads::ScopedLock<OpenThreads::Mutex> ttLock(_traceMutex);
                _trace.erase(OpenThreads::Thread::CurrentThread());
            }
#endif
        }

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void osgEarth::Threading::ReadWriteMutex::writeLock ( ) [inline]

Definition at line 212 of file ThreadingUtils.

        {
#ifdef TRACE_THREADS
            {
                OpenThreads::ScopedLock<OpenThreads::Mutex> ttLock(_traceMutex);
                if( _trace.find(OpenThreads::Thread::CurrentThread()) != _trace.end() )
                    OE_WARN << "TRACE: tried to double-lock" << std::endl;
            }
#endif
            OpenThreads::ScopedLock<OpenThreads::Mutex> lock( _lockWriterMutex ); // one at a time please
            _noWriterEvent.wait();    // wait for a writer to quit if there is one
            _noWriterEvent.reset();   // prevent further writers from joining
            _noReadersEvent.wait();   // wait for all readers to quit

#ifdef TRACE_THREADS
            {
                OpenThreads::ScopedLock<OpenThreads::Mutex> ttLock(_traceMutex);
                _trace.insert(OpenThreads::Thread::CurrentThread());
            }
#endif
        }

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void osgEarth::Threading::ReadWriteMutex::writeUnlock ( ) [inline]

Definition at line 234 of file ThreadingUtils.

        {
            _noWriterEvent.set();

#ifdef TRACE_THREADS
            {
                OpenThreads::ScopedLock<OpenThreads::Mutex> ttLock(_traceMutex);
                _trace.erase(OpenThreads::Thread::CurrentThread());
            }
#endif
        }

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