linux-kernel - Re: [PATCH 0/6] sched/cpusets fixes, more changes are needed

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Message-ID: <20100325191554.GA19830@redhat.com>
Date:	Thu, 25 Mar 2010 20:15:54 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Ben Blum <bblum@...gle.com>,
	Jiri Slaby <jirislaby@...il.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Li Zefan <lizf@...fujitsu.com>,
	Miao Xie <miaox@...fujitsu.com>,
	Paul Menage <menage@...gle.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Tejun Heo <tj@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/6] sched/cpusets fixes, more changes are needed

On 03/25, Peter Zijlstra wrote:
>
> Yeah, such a smaller patch might work too, but I was trying to remove
> some more of the complexity we grown.
>
> Being able to fully remove that TASK_WAKING check from task_rq_lock()
> and only have it in set_cpus_allowed_ptr() would reduce some fast-path
> logic.

OK. Agreed.

> You patch add a memory barrier and an unlock_wait(), which, while
> seemingly correct, are harder to parse than the modified locking.

Yes, lock + set WAKING + unlock is simpler and cleaner, but this
doesn't matter.

I think your patch should address all problems.

Oleg.

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