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SubjectRe: small migration thread fix
On Friday 10 January 2003 14:11, William Lee Irwin III wrote:
>> I'm not mingo, but I can say this looks sane. My only question is
>> whether there are more codepaths that need this kind of check, for
>> instance, what happens if someone does set_cpus_allowed() to a cpumask
>> with !(task->cpumask & cpu_online_map) ?

On Fri, Jan 10, 2003 at 03:29:33PM +0100, Erich Focht wrote:
> The piece of code below was intended for that. I agree with Rusty's
> comment, BUG() is too strong for that case.
> #if 0 /* FIXME: Grab cpu_lock, return error on this case. --RR */
> new_mask &= cpu_online_map;
> if (!new_mask)
> BUG();
> #endif
> Anyhow, changing the new_mask in this way is BAD, because the masks
> are inherited. So when more CPUs come online, they remain excluded
> from the mask of the process and it's children.
> The fix suggested in the comments still has to be done...

I don't have much to add but another ack and a "hmm, maybe something
could be done". My prior comments stand. I'd be very much obliged if
you provide a fix for the set_cpus_allowed() issue. I very much rely
upon you now to provide scheduler fixes and optimizations for large
scale and/or NUMA machines these days.

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