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SubjectRe: Recoverable MCA interrupts from NMI handlers? IPMI and RCU?
On Fri, Jun 06, 2008 at 03:53:00PM -0500, Corey Minyard wrote:
> Paul E. McKenney wrote:
> >Hello!
> >
> >A couple of questions about the x86 architecture...
> >
> >1. Can recoverable machine-check exceptions occur from within
> > NMI handlers? If so, there is a bug in preemptable RCU's
> > CONFIG_NO_HZ handling that could be fixed by a patch something
> > like the one shown below (untested, probably does not even
> > compile).
> >
> >2. Does the IPMI subsystem make use of RCU read-side primitives
> > from within SMI handlers? If so, we need the SMI handlers to
> > invoke rcu_irq_enter() upon entry and rcu_irq_exit() upon exit
> > when they are invoked from dynticks idle state. Or something
> > similar, depending on restrictions on code within SMI handlers.
> >
> If you mean the IPMI driver, it does not tie into any SMI. It
> theoretically could since there's a bit for that in the watchdog timer,
> but there's been no demand and I haven't looked at it. I guess it would
> be better than an NMI.
>
> If it did tie in, it would most likely just panic to get useful
> information out before the watchdog reset the system.

Thanks for the info! I will stop worrying about SMIs and RCU, then.

Thanx, Paul


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