Re: CPU Hotplug: Hotplug Script And SIGPWR

Nick Piggin
2004-01-20T07:45:43Z

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.