Re: CVS commit: src/sys

[Mindaugas Rasiukevicius <rmind%netbsd.org@localhost>]

Alex,

Alexander Nasonov <alnsn%yandex.ru@localhost> wrote:
> Lourival Pereira Vieira Neto wrote:
> > Module Name:        src
> > Committed By:       lneto
> > Date:               Sat Jul 19 17:13:22 UTC 2014
> > 
> > Modified Files:
> >     src/sys/modules/lua: lua.c
> >     src/sys/sys: lua.h
> > 
> > Log Message:
> > lua(4): added support for running Lua scripts in intr context
> 
> Please revert this. You can't make a mechanical change
> (s/kmem_/kmem_intr_/g and so on) to enable lua in softintr
> context. You need to design it.
> 
> What if GC kicks-in in softintr? What if the code tries to
> load a chunk of new code in softintr? And there are other
> questions.

I have explained to Lourival that softint context is a very constrained
environment and he should seek for a better design, e.g. have per-CPU
Lua state while keeping such Lua programs mostly stateless and sharing no
global state.  Ideally, we should have deterministic behaviour and memory
pre-allocation with such programs (whether it is Lua or not).

This is tricky with Lua, but I think he understands the implications and
issues.  The change is more of an initial step to (inefficiently) support
the capability.  Meanwhile, those interested can research and experiment
with NPF+Lua.  Such use of Lua is not really meant to be production-ready
at this point.

-- 
Mindaugas