linux-kernel - Re: [PATCH 2/2] cpusets: update tasks' cpus_allowed and mems

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Message-Id: <20080604142540.6fa2bcc3.pj@sgi.com>
Date:	Wed, 4 Jun 2008 14:25:40 -0500
From:	Paul Jackson <pj@....com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	menage@...gle.com, miaox@...fujitsu.com, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] cpusets: update tasks' cpus_allowed and
 mems_allowed after CPU/NODE offline/online

David wrote:
> That would only identify kthreads that have been created with a subsequent 
> call to set_cpus_allowed() or kthread_bind().
> 
> The PF_CPU_BOUND change targets only the latter since there are kthreads, 
> such as kstopmachine, that can continue to manipulate their cpus_allowed 
> during their lifetime.

Would your first sentence be more clearly written as:

> That would identify both kthreads that have been created with a subsequent 
> call to set_cpus_allowed() or kthread_bind().

Or do I misunderstand?

If I am reading you correctly, then would it work to have a check in the
cpuset code (rather than in the lower set_cpus_allowed() routine),
where that check refused to move tasks out of the root cpuset if they
were (1) kernel threads (mm NULL) and (2) had cpus_allowed that were a
strict subset of the root cpusets 'cpus' (the online cpus).

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@....com> 1.940.382.4214
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