linux-kernel - Re: [linux-pm] Fundamental flaw in system suspend, exposed by freezer removal

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Date:	Mon, 3 Mar 2008 18:12:31 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Alexey Starikovskiy <astarikovskiy@...e.de>
Subject: Re: [linux-pm] Fundamental flaw in system suspend, exposed by freezer
 removal

On Mon, 3 Mar 2008, Rafael J. Wysocki wrote:

> > > Perhaps it's better to include dpm_sysfs_add() into device_pm_add(), since we
> > > are going the make the return a result anyway?
> > 
> > Yes.
> 
> Okay, I'll prepare a patch for that, on top of the one introducing the
> 'sleeping' field into 'struct dev_pm_info' (posting in a while).

While you're at it, could you add a field to indicate whether 
begin_sleep() has been called?  It would help prevent multiple calls to 
that method when a race does occur, and it could be useful for drivers 
as well.

> The question remains what we're going to do with the drivers without pm_ops
> pointers in the long run (in the short run we will use the legacy callbacks in
> that cases, if defined).

One possibility is to unbind those drivers at the start of a sleep
transition and reprobe them at the end.  Another possibility is to
ignore the lack of PM support and hope it doesn't cause any problems.

Alan Stern

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