Improvements to fork handling (2/5)

[Christopher Faylor]

On Wed, May 11, 2011 at 02:31:37PM -0400, Ryan Johnson wrote:
>Hi all,
>
>This patch has the parent sort its dll list topologically by 
>dependencies. Previously, attempts to load a DLL_LOAD dll risked pulling 
>in dependencies automatically, and the latter would then not benefit 
>from the code which "encourages" them to land in the right places.  The 
>dependency tracking is achieved using a simple class which allows to 
>introspect a mapped dll image and pull out the dependencies it lists. 
>The code currently rebuilds the dependency list at every fork rather 
>than attempt to update it properly as modules are loaded and unloaded. 
>Note that the topsort optimization affects only cygwin dlls, so any 
>windows dlls which are pulled in dynamically (directly or indirectly) 
>will still impose the usual risk of address space clobbers.

This seems CPU and memory intensive during a time for which we already
know is very slow.  Is the benefit really worth it?  How much more robust
does it make forking?

cgf