linux-kernel - Re: [Resend][PATCH] PM: Move disabling/enabling runtime PM to late suspend/early resume

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Date:	Sun, 16 Dec 2012 10:29:47 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	Jiri Kosina <jkosina@...e.cz>,
	Linux PM list <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Jan-Matthias Braun <jan_braun@....net>
Subject: Re: [Resend][PATCH] PM: Move disabling/enabling runtime PM to late
 suspend/early resume

On Sun, 16 Dec 2012, Rafael J. Wysocki wrote:

> On Saturday, December 15, 2012 10:16:29 PM Jiri Kosina wrote:
> > On Sat, 15 Dec 2012, Rafael J. Wysocki wrote:
> > 
> > > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > 
> > > Currently, the PM core disables runtime PM for all devices right
> > > after executing subsystem/driver .suspend() callbacks for them
> > > and re-enables it right before executing subsystem/driver .resume()
> > > callbacks for them.  This may lead to problems when there are
> > > two devices such that the .suspend() callback executed for one of
> > > them depends on runtime PM working for the other.  In that case,
> > > if runtime PM has already been disabled for the second device,
> > > the first one's .suspend() won't work correctly (and analogously
> > > for resume).
> > > 
> > > To make those issues go away, make the PM core disable runtime PM
> > > for devices right before executing subsystem/driver .suspend_late()
> > > callbacks for them and enable runtime PM for them right after
> > > executing subsystem/driver .resume_early() callbacks for them.  This
> > > way the potential conflitcs between .suspend_late()/.resume_early()
> > > and their runtime PM counterparts are still prevented from happening,
> > > but the subtle ordering issues related to disabling/enabling runtime
> > > PM for devices during system suspend/resume are much easier to avoid.
> > > 
> > > Reported-and-tested-by: Jan-Matthias Braun <jan_braun@....net>
> > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > 
> > Hi Rafael,
> > 
> > just curious what is the reason for resend? Do you want to gather more 
> > Acks before pushing this upstream?
> 
> Well, I thought that some people might actually look at it when they found it
> again in their mailboxes. :-)

I did look at it the first time it appeared.  It seemed to be okay, but 
I haven't tried any testing.

Alan Stern

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