Re: [PATCH] x86: sysctl to allow panic on IOCK NMI error

Ingo Molnar
2009-07-02T07:53:29Z

* Maciej W. Rozycki <macro@linux-mips.org> wrote:

> On Wed, 1 Jul 2009, Ingo Molnar wrote:
>
> > > ENOTIME, sorry. Next year perhaps. Or a homework project
> > > for one of the newbies. ;)
> >
> > You know that this project would kill a newbie, right? :)
>
> Well, that's just a fast track to become a veteran, isn't it? ;)

No, that's just a fast track to quickly make it into the list of our
Fallen Heroes :-/ The fast track to become a kernel veteran is to,
if possible, not challenge a tank with a hand-grenade. But i
digress.

> > We have no real southbridge drivers on x86 - but we should
> > certainly add some. Also, walking the PCI device tree from NMI
> > context is tricky as the lists there are not NMI safe - we could
> > crash if we happen to get a #IOCK while loading/unloading
> > drivers (which is rare but could happen).
>
> That shouldn't be a problem if we were about to panic(). For a
> more sophisticated attempt of recovery -- yes, that would have to
> be addressed.

We are only panic-ing if the sysctl is set. The diagnostics would be
useful anyway. The proper approach would be to defer it a bit in the
non-panic case an read it out from some friendlier context - such as
the EDAC core.

Ingo