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Date: Tue, 23 Apr 2002 10:41:35 -0700
From: Mike Kravetz <kravetz@us.ibm.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Robert Love <rml@tech9.net>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH][RFC] task cpu affinity syscalls for 2.4-O(1)
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On Tue, Apr 23, 2002 at 04:41:10PM +0200, Ingo Molnar wrote:
> 
> well, my goal was the following: the migration thread makes sure that the
> migrated thread will *not* run on that particular CPU. The only issue the
> migration thread is for is to 'push' the migrated thread from its current
> CPU.
> 
> so we first set the cpus_allowed mask, then we schedule the migration
> thread (which is a highest RT priority thread) if the thread is running on
> an invalid CPU.
> 
> load_balance() moving a process to another CPU is in fact makes this job
> easier, and causes no problems. It will pull a process only to allowed
> runqueues.
> 
> this way it can be guaranteed that after the set_cpus_allowed() call the
> thread is not running on an invalid CPU.
> 
> the affinity setting syscalls added by Robert's patch utilize this
> underlying mechanizm, but kernel threads call it directly as well. Eg. in
> the softirqd case it's of importance whether the thread is running on the
> right CPU or not, after calling set_cpus_allowed().
> 
> is there anything else unclear in this area?

Thanks,  I just needed to stare at the migration_thread code a bit 
more to convince myself that all the special cases were covered.

-- 
Mike
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