linux-kernel - Re: [PATCH][Alternative][RFC] PM / Runtime: Introduce driver runtime PM work routine

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Date:	Tue, 14 Aug 2012 00:06:37 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Linux PM list <linux-pm@...r.kernel.org>,
	Ming Lei <tom.leiming@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
Subject: Re: [PATCH][Alternative][RFC] PM / Runtime: Introduce driver runtime PM work routine

On Monday, August 13, 2012, Alan Stern wrote:
> On Mon, 13 Aug 2012, Rafael J. Wysocki wrote:
> 
> > > I guess the best we can say is that if you call pm_runtime_barrier()  
> > > after updating the dev_pm_ops method pointers then after the barrier
> > > returns, the old method pointers will not be invoked and the old method
> > > routines will not be running.  So we need an equivalent guarantee with
> > > regard to the pm_runtime_work pointer.  (Yes, we could use a better 
> > > name for that pointer.)
> > > 
> > > Which means the code in the patch isn't quite right, because it saves 
> > > the pm_runtime_work pointer before calling rpm_resume().  Maybe we 
> > > should avoid looking at the pointer until rpm_resume() returns.
> > 
> > Yes, we can do that.
> > 
> > Alternatively, we can set power.work_in_progress before calling
> > rpm_resume(dev, 0) (i.e. regard the resume as a part of the work) to make
> > the barrier wait for all of it to complete.
> 
> Yep, that would work.  In fact, I did it that way in the proposed code 
> posted earlier in this thread.  (But that was just on general 
> principles, not because I had this particular race in mind.)

OK

I need to prepare a new patch now, but first I'll send a couple of (minor)
fixes for the core runtime PM code.

Thanks,
Rafael
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