[osg-users] Multithreading crashduetoosgDb::Registry::instance()

[I-Nixon, Anthony D]

I'll have a crack at it, unless someone else is already doing it.  I've got an environment here that exercises the issue consistently.
 
Anthony


________________________________

	From: Robert Osfield [mailto:robert.osfield at gmail.com] 
	Sent: Tuesday, 17 March 2009 8:22 PM
	To: OpenSceneGraph Users
	Subject: Re: [osg-users] Multithreading crashduetoosgDb::Registry::instance()
	
	
	HI Richard + Paul,
	
	Thanks for explanation.  Feel free to dive in an code up such a solution.
	
	Robert.
	
	
	On Tue, Mar 17, 2009 at 10:17 AM, Schmidt, Richard <Richard.Schmidt at eads.com> wrote:
	

		The document is about a design pattern called double locking, which is especially suitable for singleton objects in multithreaded environments.
		
		The pattern is essentially this:
		

		static Singleton *instance (void)
		{
		// First check
		if (instance_ == 0)
		{
		// Ensure serialization (guard
		// constructor acquires lock_).
		Guard<Mutex> guard (lock_);
		// Double check.
		if (instance_ == 0)
		instance_ = new Singleton;
		}
		return instance_;
		// guard destructor releases lock_.
		}
		
		
		The guard mutex is only accessed in the initialization phase of the singleton. Once instance_ is set the guard does not need to be queried anymore.
		

		Richard
		_______________________________________
		Von: osg-users-bounces at lists.openscenegraph.org [mailto:osg-users-bounces at lists.openscenegraph.org] Im Auftrag von Robert Osfield
		
		Gesendet: Dienstag, 17. März 2009 11:07
		
		An: OpenSceneGraph Users
		Betreff: Re: [osg-users] Multithreading crash duetoosgDb::Registry::instance()
		
		
		2009/3/17 Schmidt, Richard <Richard.Schmidt at eads.com>
		http://www.cs.wustl.edu/~schmidt/PDF/DC-Locking.pdf <http://www.cs.wustl.edu/%7Eschmidt/PDF/DC-Locking.pdf> 
		
		Could you explain what the above document is all about...
		
		Robert.
		
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