Re: [PATCH v2 0/3] Freezer, CPU hotplug, x86 Microcode: Fix task freezing failures

[Borislav Petkov <bp@amd64.org>]

On Mon, Oct 10, 2011 at 01:30:34PM -0400, Srivatsa S. Bhat wrote:
> But I do agree that offlining and onlining CPUs while suspending might
> not seem all that useful or even wise, but like I said, it was designed to
> bring out such problematic race conditions.
> 
> So, in the interest of making the important components involved in
> suspend/resume call path (namely cpu hotplug) more robust and stable,
> I think it makes sense to fix any issue we hit (atleast when we
> practically hit it and it is proved that such a scenario is no longer
> hypothetical).
> 
> For that, we can either go with the simple one-line fix that I posted
> earlier (which has got another motivation now, thanks to Borislav) or
> with this elaborate solution, whichever seems better/worthwhile.
>
> If it is still strongly felt that this "bug" is not worth fixing with such
> mutual exclusion schemes, it will still get solved anyway by applying that
> one-line patch.

Well, this is easy: the oneliner is needed anyway for removing
unnecessary ucode reloading and since it fixes your test cases _and_ is
_simpler_, the whole deal is a no brainer.

And although Pavel had a valid concern there about suspending when low
on battery/failing UPSs and, AFAIUI, it might happen that the machine
automatically suspends while you offline one of your cores, I can't find
it in me to care about a case like that, sorry.

Thanks.

-- 
Regards/Gruss,
Boris.

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