2008/8/6 Mattias Gaertner <[EMAIL PROTECTED]>: > On Wed, 6 Aug 2008 19:41:27 +0100 > "Inoussa OUEDRAOGO" <[EMAIL PROTECTED]> wrote: > >> Hi, >> >> TAVLTree in avl_tree.pp is not thread safe due to the node >> allocation and de-allocation done through the global >> declared "NodeMemManager" variable. TAVLTreeNodeMemManager >> implementation is cleary not thread safe, which btw IMHO >> is a good thing ( for performance reason). >> >> Proposition : >> >> (a) TAVLTree should allow, at construct time, to >> specify a Node memory manager which will be kept and used. >> If not specified the global one will be used. >> >> (b) "NodeMemManager" should be declared as "ThreadVar". >> >> This changes does not break the API while making the >> implementation thread safe. >> >> By the way note that the XML DOM's implementation >> ( TDOMNode_WithChildren ) uses TAVLTree, so every code that uses the >> fcl-xml package mainly the DOM unit, is not thread safe. If this >> proposition is accepted it will be nice to have it introduced in the >> soon to be release fpc 2.2.2, in the case that is still possible, >> mainly for server programming. >> >> Attached is a patch that demonstrate the above proposition. > > Providing a local node mem manager does not repair xml dom.
A "threadvar" declared variable is local to the calling thread. But if object is modified in more than one thread, indeed there are still some problems ( for objects using the default manager ) : Thread A create a node n1 and the node is released in ThreadB . > Maybe move NodeMemManager to the interface, so that a user can replace > it with a threadsafe one? Good solution, but : if ThreadA create an avl object that is _exclusively_ used in ThreadA, why should ThreadA wait in a multithreaded node mem manager? That is when comes the constructor that takes a node mem manager. That way, ThreadA could provide a local node mem manager that is not multithreaded and thus not paying penalty of multithreaded node mem manager. -- Inoussa O. _______________________________________________ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
