Re: 2.7 thoughts

[William Lee Irwin III]

On Fri, Oct 10, 2003 at 10:48:37AM -0400, Mark Mielke wrote:
> Perhaps I've naive here, but - with hot-pluggable CPU machines, do you not
> de-activate the CPU through software first, before pulling the CPU out, at
> which point it is not in use?

Well, you deleted my reply, but never mind that.

This obviously can't work unless the kernel gets some kind of warning.
Userspace and kernel register state, once lost that way, can't be
recovered, and if tasks are automatically suspended (e.g. cpu dumps to
somewhere and a miracle occurs), you'll deadlock if the kernel was in
a non-preemptible critical section at the time.

What I suspect to be the case is some kind of warning is given to the
kernel, and it has to respond within a certain time. Apparently it
succeeds most of the time despite my naysaying if this actually works.


-- wli
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