linux-kernel - Re: [PATCH V2 0/4] introduce device async actions mechanism

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Date:	Wed, 12 Aug 2009 10:03:21 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	Zhang Rui <rui.zhang@...el.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-pm <linux-pm@...ts.linux-foundation.org>,
	linux-acpi <linux-acpi@...r.kernel.org>,
	Pavel Machek <pavel@....cz>, Len Brown <lenb@...nel.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	"dtor@...l.ru" <dtor@...l.ru>
Subject: Re: [PATCH V2 0/4] introduce device async actions mechanism

On Wed, 12 Aug 2009, Rafael J. Wysocki wrote:

> That looks quite complicated at first sight, but asynchronous resume with
> completions can be done in a relatively simple patch.  I've got one, so
> tomorow I'll post it for further discussion.

Okay.  I would think that managing the threads would account for most 
of the complexity in either implementation, but I'll wait to see how 
your approach works out.

> Thanks,
> Rafael
> 
> 
> PS
> Did you have a chance to look at rev. 15 of the runtime PM patch
> (http://patchwork.kernel.org/patch/40306/)?

Yes, sorry for not getting back to you.  It looks okay.

The one thing I'm not sure of is the pm_runtime_put_noidle calls in 
driver_probe_device and __device_release_driver.  It seems that we 
should always call pm_runtime_put regardless of whether the probe 
succeeds or not.

For example, the USB stack is set up to suspend devices that don't have
a driver (this is handled at the bus subsystem level).  But if probing
failed, there wouldn't be any idle callback and so the suspend wouldn't
take place.

Alan Stern

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