cvs commit: src/sys/kern kern_module.c

[John Baldwin]

On Friday 30 June 2006 01:58, Warner Losh wrote:
> From: John Baldwin <jhb at freebsd.org>
> Subject: Re: cvs commit: src/sys/kern kern_module.c
> Date: Tue, 27 Jun 2006 08:48:28 -0400
> 
> > On Monday 26 June 2006 19:41, Sam Leffler wrote:
> > > John Baldwin wrote:
> > > > jhb         2006-06-26 18:34:45 UTC
> > > > 
> > > >   FreeBSD src repository
> > > > 
> > > >   Modified files:
> > > >     sys/kern             kern_module.c 
> > > >   Log:
> > > >   Address a problem I missed in removing Giant from the kernel linker.  
Not
> > > >   all of the module event handlers are MP safe yet, so always acquire 
Giant
> > > >   for now when invoking module event handlers.  Eventually we can add 
an
> > > >   MPSAFE flag or some such and add appropriate locking to all module 
event
> > > >   handlers.
> > > 
> > > I suggest we should be marking things !MPSAFE rather than MPSAFE.
> > > 
> > > 	Sam
> > 
> > I would prefer that as well but that would require an exhaustive search of
> > all existing module event handlers to determine MPSAFE-ness up front.  
With
> > the mark as MPSAFE method (such as we've used for syscalls) we can mark 
things
> > MPSAFE (and/or add locking to make them MPSAFE) while doing the exhaustive
> > search and eventually when all are MPSAFE we can remove the flag (which 
I'm
> > in the process of doing now with the syscall flag) all the while having a
> > functioning system.
> 
> We have three cases right now:
> 
> 	(1) Unknown
> 	(2) MPSAFE
> 	(3) NEEDS GIANT
> 
> All the unknown ones need giant right now, or at least that's a
> reasonable guess.  Certainly all the device driver ones do since you
> need giant to do certain device tree activities.
> 
> Short of introducing a new API, I'm unsure how we'd be able to
> effectively and safely do NEEDS_GIANT marking in the interrum.

DECLARE_MODULE_MPSAFE() or some such is how one would do it, but for
now they are all in the (1) category.

-- 
John Baldwin