linux-kernel - Re: [linux-pm] Re: Hibernation considerations

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Message-ID: <Pine.LNX.4.44L0.0707201608120.2546-100000@iolanthe.rowland.org>
Date:	Fri, 20 Jul 2007 16:12:31 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Oliver Neukum <oliver@...kum.org>
cc:	Milton Miller <miltonm@....com>, Ying Huang <ying.huang@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, David Lang <david@...g.hm>,
	linux-pm <linux-pm@...ts.linux-foundation.org>,
	Jeremy Maitin-Shepard <jbms@....edu>
Subject: Re: [linux-pm] Re: Hibernation considerations

On Fri, 20 Jul 2007, Oliver Neukum wrote:

> Am Freitag 20 Juli 2007 schrieb Alan Stern:
> > Some drivers need the ability to schedule.  Some will need the ability 
> > to allocate memory (although GFP_ATOMIC is probably sufficient).  Some 
> > will need timers to run.
> 
> Some will have to request firmware. It can add up to some megabytes.
> In addition, if we don't freeze, some drivers, eg. video drivers, can
> do allocations in the megabyte range.
> 
> It seems to me that without the freezer we will end up with many drivers
> needing a two step notification process. Furthermore there are requirements
> on the order of shutting down system facilities, eg. device addition must
> be stopped before drivers allocate firmware.

These are really separate issues, since they refer to things that have 
to happen well before the memory snapshot is captured.

We already have a pre-suspend notification available for drivers that 
need to allocate large amounts of memory.

You are correct about the need to delay/stop device addition.  I don't
know how this can be done in general; each code path calling
device_add() may have to be treated individually.

Alan Stern

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