Kernel threads inherit CPU affinity from random sibling

[Attilio Rao]

2012/1/28 Attilio Rao <attilio at freebsd.org>:
> 2012/1/28 Ryan Stone <rysto32 at gmail.com>:
>> On Fri, Jan 27, 2012 at 10:41 PM, Attilio Rao <attilio at freebsd.org> wrote:
>>> I think what you found out is very sensitive.
>>> However, the patch is not correct as you cannot call
>>> cpuset_setthread() with thread_lock held.
>>
>> Whoops!  I actually discovered that for myself and had already fixed
>> it, but apparently I included an old version of the patch in the
>> email.
>>
>>> Hence this is my fix:
>>> http://www.freebsd.org/~attilio/cpuset_root.patch
>>
>> Oh, I do like this better.  I tried something similar myself but
>> abandoned it because I misread how sched_affinity() was implemented by
>> 4BSD(I had gotten the impression that once TSF_AFFINITY is set it
>> could never be cleared).
>
> Do you have a pathological test-case for it? Are you going to test the patch?

BTW, I've just now updated the patch in order to remove an added white
line and s/priority/affinity in comments.

Thanks,
Attilio


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