Hi, I try to catch up on things past an other busy week.
On Thursday, March 29, 2012 00:22:46 ThorstenB wrote: > Mathias, maybe you can have a look at the simgear changes. Maybe you see > a way to improve this even further - i.e. do we still need all these > cache maps? Or could we simply rely on some OSG cache in some places? Just looking quick over what you checked in, I think that this needs some improovements: The change just returns pointers to objects you get from the observer_ptr. In general, this is not exactly thread safe. I do not see currently if you can ensure from a higher level that this is not a problem or not. In general consider the following situation: Thread 1 has an observer_ptr to A. Thread 2 owns the last reference to A. Thread 1 gets the still valid raw pointer to A from the observer_ptr. Thread 2 releases the last reference to A and deletes it. Thread 1 assigns the raw pointer to a ref_ptr. This probably ends in a segfault. If you work with weak pointers/observer_ptr you need to use the lock method. That one gives you a atomically a dead or alive ref_ptr to A. If you have this ref_ptr in our hands, you own a thread safe reference which makes sure that nobody deletes the object. If your ref_ptr is invalid. An other one was faster on unreferencing. In effect this groups step 3 and 5 into an atomic operation which can not be intercepted by step 4 in the example above. So, if you use this kind of weak stuff, you need to ensure that all the call chain from getting the ref_ptr from any cache down to adding this object to the scenegraph does not use raw pointers. Also the initial ref_ptr in this chain must be gained by observer_ptr::lock(). Regarding the effects, I don't think we can rely on any caching in osg since we do not currently use any osg based loader mechanism to gain these objects. At least nothing that I know of. Greetings Mathias ------------------------------------------------------------------------------ This SF email is sponsosred by: Try Windows Azure free for 90 days Click Here http://p.sf.net/sfu/sfd2d-msazure _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
