Re: [RFC][PATCH] avoid cpu hot remove of cpus which have specialRT tasks.

[Nick Piggin]

KAMEZAWA Hiroyuki wrote:
> On Sat, 17 Jun 2006 17:29:32 +1000
> Nick Piggin <nickpiggin@xxxxxxxxxxxx> wrote:
>
>
> > > As SIGSTOP/KILL patch I posted, the apps shouldn't do unexpected
> > > work, I think.
> >
> > I don't quite understand you here... the kernel doesn't need to enforce
> > anything but a dumb fallback policy where userspace is otherwise capable
> > of handling it themselves.
>
>
> If all things about apps are properly maintained/managed, it is reconfigured
> by the user/system admin *before* cpu hotremove.
>
> The case "the kernel have to move the task to other cpu which user doesn't want"
> means the application is already broken.
>
> So, I think "stop mis-configurated process" can be one way for handling  such apps.
>
> For example)
> After exchanging broken cpu, the application can continue its work with the
> same # of cpus.

OK I can see what you're trying to achieve, but I don't know that it is
worthwhile. Userspace is doing something wrong, and it isn't normally the
kernel's job to detect that.

When something like this comes up, sticking to the simplest semantics is
often best.

That said, it isn't a great deal of code to maintain, and not "incorrect"
as such. So if you convince Ingo to pick it up, I wouldn't complain.

--
SUSE Labs, Novell Inc.
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