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Date: Fri, 06 Jun 2008 09:12:44 -0700
From: "H. Peter Anvin" <hpa@...or.com>
To: paulmck@...ux.vnet.ibm.com
CC: linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
minyard@....org, dvhltc@...ibm.com, niv@...ibm.com
Subject: Re: Recoverable MCA interrupts from NMI handlers? IPMI and RCU?
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).
>
In theory, recoverable #MC's can occur anywhere. It's an exception.
> 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.
Not sure about that one. I clearly need to look carefully into this...
SMI is quite "special" in that it sets up an entirely new environment;
the concept of executing kernel code at SMI level makes me want to run
away and hide.
-hpa
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