linux-kernel - Re: [PATCH] PM: Prevent waiting forever on asynchronous resume after abort

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Date:	Thu, 2 Sep 2010 23:06:43 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Colin Cross <ccross@...roid.com>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	linux-kernel@...r.kernel.org, linux-pm@...ts.linux-foundation.org,
	Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
	"Greg Kroah-Hartman" <gregkh@...e.de>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] PM: Prevent waiting forever on asynchronous resume after abort

On Thursday, September 02, 2010, Colin Cross wrote:
> On Thu, Sep 2, 2010 at 1:45 PM, Alan Stern <stern@...land.harvard.edu> wrote:
> > On Thu, 2 Sep 2010, Colin Cross wrote:
> >
> >> >> I think it would be better to change device_pm_init() and add a
> >> >> complete_all().
> >> >
> >> > I agree.
> >> That would work, and was my first solution, but it increases the
> >> reliance on the completion variable being left completed between state
> >> transitions, which is undocumented and unnecessary.  It seems more
> >> straightforward to me to only wait on the parent if the parent is
> >> suspended.
> >
> > How about calling complete_all() from within dpm_prepare() as well?
> > Then it will get initialized properly at the beginning of every sleep
> > transition.
> That would work, but I still don't see why it's better.  With either
> of your changes, the power.completion variable is storing state, and
> not just used for notification.  However, the exact meaning of that
> state is unclear, especially during the transition from an aborted
> suspend to resume, and the state is duplicating power.status.  Setting
> it to complete in dpm_prepare is especially confusing, because at that
> point nothing is completed, it hasn't even been started.

It just sets the initial value.  But I agree it would be cleaner to do that
during the initialization.

Thanks,
Rafael
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