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From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Nigel Cunningham <nigel@nigelcunningham.com.au>
Cc: Tejun Heo <tj@kernel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Jens Axboe <axboe@kernel.dk>, tomaz.solc@tablix.org,
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        Oleg Nesterov <oleg@redhat.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Fengguang Wu <fengguang.wu@intel.com>
Subject: Re: [PATCH] libata, freezer: avoid block device removal while system is frozen
Date: Tue, 17 Dec 2013 03:35:14 +0100
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On Sunday, December 15, 2013 08:21:36 AM Nigel Cunningham wrote:
> Hi.
> 
> On 15/12/13 07:36, Tejun Heo wrote:
> > On Sat, Dec 14, 2013 at 03:31:21PM -0500, Tejun Heo wrote:
> >> So, all this is about hibernation?  Does that mean that it's safe to
> >> unfreeze before invoking resume?  ie. we currently do,
> >>
> >> 	freeze
> >> 	suspend devs
> >> 	resume devs
> >> 	unfreeze
> >>
> >> If we can just do,
> >>
> >> 	freeze
> >> 	suspend devs
> >> 	unfreeze
> >> 	resume devs
> > Ummm... even better, does that mean, in the long term, we can decouple
> > freezing and device pm operations?  If this is just about hibernation,
> > there's no reason to wrap device driver pm ops with freezer, right?
> >
> > Thanks.
> >
> Rafael has spent far more time than me thinking about the semantics 
> here, so I'd like to defer to him. Rafael?...

Please see my reply to Tejun.

Thanks,
Rafael