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Subject: Re: [PATCH]: In kernel hibernation, suspend to both
From: Bojan Smojver <bojan@rexursive.com>
Date: Sun, 13 May 2012 11:37:09 +1000
To: "Rafael J. Wysocki" <rjw@sisk.pl>
CC: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
        Linux PM list <linux-pm@vger.kernel.org>, linux-kernel@vger.kernel.org,
        bp@alien8.de
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"Rafael J. Wysocki" <rjw@sisk.pl> wrote:

>On Wednesday, May 09, 2012, Bojan Smojver wrote:
>> On Wed, 2012-05-09 at 13:40 +0530, Srivatsa S. Bhat wrote:
>> > > +             error = suspend_devices_and_enter(PM_SUSPEND_MEM);
>> > 
>> > 
>> > I can imagine running into a host of problems here, since the
>suspend
>> > sequence is not carried out fully, from the beginning.
>> > 
>> > For example, this will skip sending out the PM_SUSPEND_PREPARE and
>the
>> > PM_POST_SUSPEND notifiers. Worse, we actually send out the
>> > PM_HIBERNATION_PREPARE
>> > and PM_POST_HIBERNATION notifiers and then do a suspend instead,
>> > underneath!
>> > 
>> > (Similar cases for the rest of the notifiers sent during suspend vs
>> > hibernation).
>> > 
>> > Don't we need to handle such things properly, in order to make
>> > suspend-to-both
>> > work reliably? 
>> 
>> Honest answer - I have absolutely no idea. I've seen the code of
>> suspend-utils (i.e. user mode stuff) and it seems to me that it does
>> exactly this. Could be wrong of course, just like many times before.
>> 
>> Rafael?
>
>Sorry, that has fallen out of my radar somehow.
>
>Srivatsa is right, we should generally pay attention to those details.
>
>I think we should generally use a different "prepare" notification for
>the
>save-image-and-suspend case.
>
>Thanks,
>Rafael


OK, I will try to rework then, if that is the case.

What I don't understand is this: should the hibernation fail for some reason, we would get the same hibernation code unwind that failure, right? So, a suspend after the image write will be just one long "failure", after which hibernation code has to unwind again. No?

-- 
Bojan
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