Re: CPU Hotplug: Hotplug Script And SIGPWR

[Nick Piggin]

Tim Hockin wrote:

> On Tue, Jan 20, 2004 at 06:11:49PM +1100, Nick Piggin wrote:
>
> > I thought hotplug is allowed to fail? Thus you can have a hung system.
> > Or what if the hotplug script itself becomes TASK_UNRUNNABLE? What if the
> > process needs a guaranteed scheduling latency?
>
> I guess a hotplug script MAY fail.  I don't think it's a good idea to make
> your CPU hotplug script fail.  May and Misght are different.  It's up to the
> implementor whether the script can get into a failure condition.

Sorry bad wording. The script may fail to be executed.

> The hotplug script can only become unrunnable if you yank out all the CPUs
> on the system.  I'd assume it would have an affinity of 0xffffffff.

OK I guess thats not such a valid concern

> What if <which> process needs guaranteed scheduling latency?  Do we really
> _guarantee_ scheduling latency *anywhere*?

We do guarantee that a realtime task won't be blocked waiting for
a hotplug script to fault in and start it up again (which may not
happen). Not sure how important this issue is.


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