Re: panic! panic! panic! sigh.. panic!

[David Laight <david%l8s.co.uk@localhost>]

On Mon, Sep 22, 2008 at 09:46:07PM +0200, Vincent wrote:
> Greg Troxel a ?crit :
> >  The kernel doesn't save any of these registers on entry into the kernel
> >  (via an interrupt or system call) and doesn't restore them on exit. It
> >  also doesn't save and restore them on internal scheduling. If you
> >  compile the kernel with MMX or SSE<n> enabled the kernel will sooner
> >  or later globber some state and you get a panic.
> 
> Since eons I've had "-msse2 -mfpmath=sse -march=pentium4" in my 
> /etc/mk.conf, resulting in my i386 kernel being built with those 
> options. I've never seen a crash likely caused by these superfluous 
> flags. I'm dubious if, anyhow, SIMD integer operations could be of a 
> significant help in kernel operations.

Beware, the compile might decide to use the sse (ie fp) registers
for operations that don't involve fp.

        David

-- 
David Laight: david%l8s.co.uk@localhost