> > * Multi-threading support (i.e. r/w locking for dl*() calls) is added.
>
> I think there are some problems with this.
>
>         1. We've been talking a lot about performance of the dynamic
>            linker lately.  The r/w locking is totally unnecessary for
>            non-threaded applications.  Making non-threaded applications
>            pay the penalty of using them seems to go against the spirit
>            of improving performance.

Had you bothered to *look* at the FreeBSD code, or *ask* how it works,
rather than simply tossing out another strawman, you would know that
the code does not actually introduce a significant penalty for
non-threaded apps.  It uses a callback (dllockinit()) to enable
locking.