Re: Perhaps a side effect regarding NMI returns

[Linus Torvalds]

On Tue, Nov 29, 2011 at 12:09 PM, Andi Kleen <andi@xxxxxxxxxxxxxx> wrote:
>
> Not sure what problem Steven thinks is there. Once you
> switched the stack any nesting is fine.

The problem is that NMI's are blocked!

We're potentially switching to another process, there is no guarantee
there will be an "iret" *anywhere* in any patch for a long time. So
any subsequent NMI's will not be able to come in.

> The reason I added them originally is to prevent the race of remote
> kernel events being delayed for a long time. With Frederic's nohz work
> this will be more important in the future. Today it would be eventually
> picked up by the regular timer interrupts.

You're just delaying another kind of event: the next NMI.

And NMI's really shouldn't be triggering any scheduling-related events afaik.

                Linus
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