linux-kernel - Re: [PATCH v2 1/3] PM suspend/hibernate: Call notifier after freezing processes

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Message-ID: <20150722080827.5adcf5f1@noble>
Date:	Wed, 22 Jul 2015 08:08:27 +1000
From:	NeilBrown <neilb@...e.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Pali Rohár <pali.rohar@...il.com>,
	Alasdair Kergon <agk@...hat.com>,
	Mike Snitzer <snitzer@...hat.com>, Neil Brown <neilb@...e.de>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	dm-devel@...hat.com, linux-raid@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH v2 1/3] PM suspend/hibernate: Call notifier after
 freezing processes

On Mon, 20 Jul 2015 23:46:32 +0200 "Rafael J. Wysocki"
<rjw@...ysocki.net> wrote:

> On Monday, July 20, 2015 09:32:26 AM Pali Rohár wrote:
> > On Saturday 18 July 2015 01:27:15 Rafael J. Wysocki wrote:
> > > On Thursday, July 16, 2015 09:33:02 AM Pali Rohár wrote:
> > > > On Thursday 16 July 2015 03:02:03 Rafael J. Wysocki wrote:
> > > > > Also, if you're adding AFTER_FREEZE, it would be good to add BEFORE_THAW too
> > > > > for symmetry.
> > > > > 
> > > > 
> > > > But there is no use case for BEFORE_THAW. At least it is not needed for now.
> > > 
> > > For your use case, a single function pointer would be sufficient too.
> > > 
> > 
> > What do you mean by single function pointer? kernel/power is part of
> > kernel image and dm-crypt is external kernel module.
> 
> Well, if there is a function pointer in the core suspend code initially set to
> NULL and exported to modules such that the dm-crypt code can set it to
> something else, that should be sufficient, shouldn't it?

As long as the dm-crypt module is never unloaded.  And as long as no
other module could very possible want functionality like this. Ever.

If a module wants to be notified - the providing a notifier chain
really seems like the right thing to do...

NeilBrown


> 
> So if you're adding new PM notifier events, that's already more than *you* need.
> 
> Anyway, I guess the "post freeze" new one should be enough for now, but please
> change the name to POST_FREEZE.
> 
> Also I think we don't need separate "post freeze" events for suspend and
> hibernation.
> 
> Thanks,
> Rafael

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