Re: Broken kernel compile on 5.1-RELEASE / 5-CURRENT (SMP, PAE & scsi)

On Tue, 19 Aug 2003, Mark Sergeant wrote:

> There are no other errors apart from those listed so I may try compiling
> as a module that gets loaded on boot. Just one problem, I succesfully
> build an SMP kernel without PAE and then rebooted and the server is no
> longer responding, it seems it crashed just after coming up as I was
> able to ping it 5 or 6 times and then it went away again. If I've got a
> crash dump I'll post it. 

Can't speak to the specifics of this, but you want to be very careful not
to use kernel modules with PAE: modules are currently without the context
of the kernel configuration file, and PAE introduces possible binary
incompatibility with modules that dig into VM (which many drivers do). The
only supported configuration is to not use modules, but link the driver
directly into the kernel when running PAE.  This is why the PAE kernel has
no_modules defined in the sample PAE configuration file.  Various
conversations have happened regarding how to address this problem, and I'm
not sure we've come up with the right answer yet.  There seem to be two
conflicting directions: build modules in the context of a kernel module
(and get conditionally compiled type/structure/code/... pieces), and try
to make the module build entirely independent of a kernel configuration. 
As someone who uses conditionally compiled components in modules, I tend
to fall into the first camp, and no doubt we'll figure out the right
answer in due course.

The above crash sounds unfortunate too, but quite possibly a separate
failure mode :-).

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert_at_fledge.watson.org      Network Associates Laboratories