linux-kernel - RE: [PATCH v2 15/45] rcu: Use get/put_online_cpus

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Date:	Wed, 26 Jun 2013 15:29:40 +0100
From:	"David Laight" <David.Laight@...LAB.COM>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	<paulmck@...ux.vnet.ibm.com>
Cc:	<peterz@...radead.org>, <fweisbec@...il.com>,
	<linux-kernel@...r.kernel.org>, <walken@...gle.com>,
	<mingo@...nel.org>, <linux-arch@...r.kernel.org>,
	<vincent.guittot@...aro.org>, <xiaoguangrong@...ux.vnet.ibm.com>,
	<wangyun@...ux.vnet.ibm.com>, <nikunj@...ux.vnet.ibm.com>,
	<linux-pm@...r.kernel.org>, <rusty@...tcorp.com.au>,
	<rostedt@...dmis.org>, <namhyung@...nel.org>, <tglx@...utronix.de>,
	<laijs@...fujitsu.com>, <zhong@...ux.vnet.ibm.com>,
	<netdev@...r.kernel.org>, <oleg@...hat.com>, <sbw@....edu>,
	<tj@...nel.org>, <akpm@...ux-foundation.org>,
	<linuxppc-dev@...ts.ozlabs.org>
Subject: RE: [PATCH v2 15/45] rcu: Use get/put_online_cpus_atomic() to prevent CPU offline

> Once stop_machine() is gone from the CPU offline path, we won't be able
> to depend on disabling preemption to prevent CPUs from going offline
> from under us.

Could you use an rcu-like sequence so that disabling pre-emption
would be enough?

Something like rebuilding the cpu list, then forcing yourself
to run on all the cpu.

That would be far less intrusive.

	David



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