linux-kernel - Re: [RFC][PATCH 4/4] Rename lock_cpu_hotplug/unlock_cpu

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Message-Id: <20060830105434.d00ae4dc.pj@sgi.com>
Date:	Wed, 30 Aug 2006 10:54:34 -0700
From:	Paul Jackson <pj@....com>
To:	paulmck@...ibm.com
Cc:	ego@...ibm.com, mingo@...e.hu, nickpiggin@...oo.com.au,
	arjan@...radead.org, rusty@...tcorp.com.au, torvalds@...l.org,
	akpm@...l.org, linux-kernel@...r.kernel.org, arjan@...el.linux.com,
	davej@...hat.com, dipankar@...ibm.com, vatsa@...ibm.com,
	ashok.raj@...el.com
Subject: Re: [RFC][PATCH 4/4] Rename lock_cpu_hotplug/unlock_cpu_hotplug

Paul E. McKenney wrote:
> Well, my next question was going to be whether cpuset readers really
> need to exclude the writers, or whether there can be a transition
> period while the mastodon makes the change as long as it avoids stomping
> the locusts.  ;-)

The mastodon's (aka mammoths ;) may make a batch of several related
changes to the cpuset configuration.  What's important is that the
locusts see either none or all of the changes in a given batch, not
some intermediate inconsistent state, and that the locusts see the
change batches in the same order they were applied.

Off the top of my head, I doubt I care when the locusts see the
changes.  Some delay is ok, if that's your question.

But don't try too hard to fit any work you do to cpusets.  For now,
I don't plan to mess with cpuset locking anytime soon.  And when I
do next, it might be that all I need to do is to change the quick
lock held by the locusts from a mutex to an ordinary rwsem, so that
multiple readers (locusts) can access the cpuset configuration in
parallel.

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@....com> 1.925.600.0401
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