Re: CPU Hotplug: Hotplug Script And SIGPWR

Nick Piggin
2004-01-20T07:23:22Z

Tim Hockin wrote:

>On Tue, Jan 20, 2004 at 05:43:59PM +1100, Nick Piggin wrote:
>
>>>I think the sanest thing for a CPU removal is to migrate everything off the
>>>processor in question, move unrunnable tasks into TASK_UNRUNNABLE state,
>>>then notify /sbin/hotplug. The hotplug script can then find and handle the
>>>unrunnable tasks. No SIGPWR grossness needed.
>>>
>>>Code against 2.4 at http://www.hockin.org/~thockin/procstate - it was
>>>heavily tested and I *think* it is all correct (for that kernel snapshot).
>>>
>>Seems less robust and more ad hoc than SIGPWR, however.
>>
>
>Disagree. SIGPWR will kill any process that doesn't catch it. That's
>policy. It seems more robust to let the hotplug script decide what to do.
>If it wants to kill each unrunnable task with SIGPWR, it can. But if it
>wants to let them live, it can.
>

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 dropped lhcs-devel@lists.sourceforge.net because its moderated)