Messages in this thread | | | Date | Sat, 23 Apr 2005 13:22:27 -0500 | From | Nathan Lynch <> | Subject | Re: Hotplug CPU and setaffinity? |
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Dr. David Alan Gilbert wrote: > > I got to wondering how Hotplug CPU and sched_setaffinity interact; > if I have a process that has its affinity set to one CPU and some > nasty person comes along and unplugs it what happens to that process- > does it get scheduled onto another cpu, just not get any time or > die ?
The affinity of the process is reset to the default and it is migrated to another cpu, for better or worse. The kernel assumes the admin know what he/she is doing.
> > In particular I was thinking of the cases where a thread has a > functional reason for remaining on one particular CPU (e.g. if you > had calibrated for some feature of that CPU say its time stamp > counter skew/speed). Another case would be a set of threads which > had set their affinity to the same CPU and then made memory > consistency or locking assumptions that wouldn't be valid > if they got rescheduled onto different CPUs.
Yeah. But I don't think this is an issue to be solved in the kernel. Applications that are this sensitive to cpu hotplugging need to arrange to be notified before the hotplug occurs, which I think would be best done with dbus or some other IPC.
Nathan
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