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From: Rusty Russell <rusty@rustcorp.com.au>
To: Thomas Gleixner <tglx@linutronix.de>,
        Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@elte.hu>,
        Peter Zijlstra <peterz@infradead.org>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>,
        "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
        Arjan van de Veen <arjan@infradead.org>, Paul Turner <pjt@google.com>,
        Richard Weinberger <rw@linutronix.de>,
        Magnus Damm <magnus.damm@gmail.com>
Subject: Re: [patch 00/40] CPU hotplug rework - episode I
In-Reply-To: <alpine.LFD.2.02.1302011128490.11905@ionos>
References: <20130131120348.372374706@linutronix.de> <20130131122342.31b28664.akpm@linux-foundation.org> <alpine.LFD.2.02.1301312233480.11905@ionos> <CA+55aFx=cv+HxKGx+oQk4iLnnTGO7P0u3+DnvuOWbYzM-wvEeQ@mail.gmail.com> <alpine.LFD.2.02.1301312302290.11905@ionos> <CA+55aFypNfzA1HZMmAiyFo48MhUTr+gt+1uvM7SHFzXh60-KQQ@mail.gmail.com> <alpine.LFD.2.02.1302011128490.11905@ionos>
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Date: Thu, 07 Feb 2013 14:31:04 +1030
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Thomas Gleixner <tglx@linutronix.de> writes:
> On Fri, 1 Feb 2013, Linus Torvalds wrote:
>> So for me it's the "expose these states" that I get worried about.. A
>> random driver should not necessarily even be able to *see* this, and
>> decide to be clever and take advantage of the ordering.
>> 
>> So I'd hope there would be some visibility restrictions. We currently
>> have drivers already being confused by DOWN_PREPARE vs DOWN_FAILED etc
>> etc random state transitions, and giving them even more flexibility to
>> pick random states sounds like a really bad idea. I'd like to make
>> sure that drivers and filesystems etc do not even *see* the states
>> that are meant for the scheduler or workqueues, for example).

Yeah, I assume Episode II is where we collapse each into sane states
as Thomas clarified.  That can be reviewed: I'd hate to try to do it
in one go.

Cheers,
Rusty.