linux-kernel - Re: [RFC PATCH v3 1/9] CPU hotplug: Provide APIs to prevent CPU offline from atomic context

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Message-ID: <20121209202234.GA5793@redhat.com>
Date:	Sun, 9 Dec 2012 21:22:34 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Cc:	tglx@...utronix.de, peterz@...radead.org,
	paulmck@...ux.vnet.ibm.com, rusty@...tcorp.com.au,
	mingo@...nel.org, akpm@...ux-foundation.org, namhyung@...nel.org,
	vincent.guittot@...aro.org, tj@...nel.org, sbw@....edu,
	amit.kucheria@...aro.org, rostedt@...dmis.org, rjw@...k.pl,
	wangyun@...ux.vnet.ibm.com, xiaoguangrong@...ux.vnet.ibm.com,
	nikunj@...ux.vnet.ibm.com, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v3 1/9] CPU hotplug: Provide APIs to prevent CPU
	offline from atomic context

On 12/10, Srivatsa S. Bhat wrote:
>
> On 12/10/2012 12:44 AM, Oleg Nesterov wrote:
>
> > But yes, it is easy to blame somebody else's code ;) And I can't suggest
> > something better at least right now. If I understand correctly, we can not
> > use, say, synchronize_sched() in _cpu_down() path
>
> We can't sleep in that code.. so that's a no-go.

But we can?

Note that I meant _cpu_down(), not get_online_cpus_atomic() or take_cpu_down().

Oleg.

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