Re: lua-ev vs. fork

[Brian Maher <brimworks@...>]

You've got me convinced ;-).

http://github.com/brimworks/lua-ev/commit/c3b08a1cdf887cfa7e9f47646484a3bd7eb452f2

Now, you just need to call loop:fork() if you want to use an event
loop in the child process after a fork.  No more ugly pthread
dependency.

Cheers,
-Brian

On Fri, Apr 23, 2010 at 5:30 PM, Alexander Gladysh <agladysh@gmail.com> wrote:
>>>> Consider exposing ev.at_fork() callback to user and creating a
>>>> separate, auxiliary Lua module which exposes pthread_atfork to Lua.
>
>>>> This way users, who do not need forking, would not have to pay for it. :-)
>
>>> I think the "cost" is very minimal.  The only real "cost" (in my mind)
>>> is the currently required dependency on pthreads (the ev_default_fork
>>> function simply sets two variables).  Ideally, at build time we would
>>> give people the option to build without pthreads in which case we
>>> print a loud warning that if you try to use the default event loop in
>>> a child process things may be messed up unless they call loop:fork().
>
>> Well, the cost is in build compexity as well.
>
>> For example, I do not think that you'll be able to build such option
>> into a rockspec file.
>
> Note also that Lua executable is not linked with pthreads. And some
> tools (like gdb) do not like when program suddenly becomes
> multithreaded.
>
> See this discussion for example:
>
> http://thread.gmane.org/gmane.comp.gdb.devel/24205
>
> And this post in particular:
>
> http://thread.gmane.org/gmane.comp.gdb.devel/24198/focus=24209
>
> I'm actually bitten by this problem, my gdb refuses to debug lua
> executable after I do 'require "ev"':
>
> http://stackoverflow.com/questions/2702628/gdb-cannot-find-new-threads-generic-error
>
> And really want to report you a bug with hidden SIGSEGV that I observe. :-)
>
> (Note that I need to be able to fork() properly to reproduce this bug,
> so simply hacking out pthreads is not a solution — an at_fork()
> callback is still needed.)
>
> Alexander.
>



-- 
Brian Maher >> Glory to God <<