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

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Date:	Mon, 13 Aug 2012 17:39:27 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
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 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.)

Alan Stern

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