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- Subject: Re: Lua and multi-threaded FastCGI servers
- From: Peter Colson <pcolson@...>
- Date: Wed, 9 Mar 2005 16:09:11 +1100
On 04/03/2005, at 7:24 PM, Wim Couwenberg wrote:
- Is LuaThreads a separate package or is it the coroutines facility
Lua for doing non-pre-emptive threading in a Lua script? Does it sit
of Posix threads (saw references to LuaThreads on top of eCos threads
I'm not knowledgable on LuaThreads (I'm sure Diego will answer your
question). However, from my own experience and what I read on this
list, it is probably not a good idea to run several pre-emptive
threads on one and the same Lua state. The locking overhead can be
quite high. I'd stick with a Lua state per thread and handle
marshalling of any data yourself.
Yes agree with this - it feels safer to me too.
- I can see a lua_newthread() API that can be called from C - is this
alternative to creating my own Posix thread and then lua_open()'ing a
Lua VM within that thread (which was what I was trying to do now)?
No. lua_newthread is for coroutine support. It creates a "Lua
thread" (essentially a separate call stack) as a data structure in a
Lua state. It does not offer or support pre-emptive threading
automatically (i.e. you still need some extension). There are endless
discussions about coroutines on this list and they are explained in
the manual and in PIL.
OK, at this point I think the threading infrastructure will remain
outside of Lua anyway due to pre-existing FastCGI code in C.
- lua_set/gettable(L, LUA_GLOBALSINDEX) vs. lua_set/getglobal(L,
as a way of setting/getting globals in a Lua VM. Are these equivalent
have I confused two concepts?
Equivalent. The _global versions save you an additional push call.
OK, and this is working nicely for me now.
- Also, lua_pcall vs. lua_cpcall. lua_cpcall seems to be the
for invoking a Lua script and not having the calling program
terminate if an
error occurs since the C function passed to lua_cpcall will return to
function calling lua_cpcall in the event of an error?
Depends on your situation. To safely call a function on the Lua stack
lua_pcall is just what you'll need.
Shall stick with pcall then, it's working fine at the moment.