[fpc-devel] TAVLTree(avl_tree.pp) thread safety, fcl-xml(DOM) is also concerned.

[Mattias Gaertner]

On Wed, 6 Aug 2008 19:41:27 +0100
"Inoussa OUEDRAOGO" <inoussa12 at gmail.com> 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.

Maybe move NodeMemManager to the interface, so that a user can replace
it with a threadsafe one?

Mattias