linux-kernel - Re: [PATCH 0/6] PM: Asynchronous suspend and resume of devices

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Message-ID: <Pine.LNX.4.44L0.0908271637480.25639-100000@iolanthe.rowland.org>
Date:	Thu, 27 Aug 2009 16:46:08 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	linux-pm <linux-pm@...ts.linux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>, Len Brown <lenb@...nel.org>,
	Pavel Machek <pavel@....cz>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Zhang Rui <rui.zhang@...el.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Linux PCI <linux-pci@...r.kernel.org>
Subject: Re: [PATCH 0/6] PM: Asynchronous suspend and resume of devices

On Wed, 26 Aug 2009, Rafael J. Wysocki wrote:

> Hi,
> 
> The following patches introduce a mechanism allowing us to execute device
> drivers' suspend and resume callbacks asynchronously during system sleep
> transitions, such as suspend to RAM.
> 
> The idea is explained in the changelogs of the first two patches.
> 
> Comments welcome.

I've been terribly busy and haven't had a chance to look at this.  The
earlier version seemed to have a bunch of mutual-exclusion issues; are
they resolved now?  There were also some problems involving unsafe
iteration over the dpm_list -- remember that devices can be
unregistered at any time, not just while they are suspending or
resuming.

When a device finishes, instead of having the async thread look for 
another device to work on, I think it would be better to have the 
thread check the dependents of the current device.  Those which are 
now ready can be added to a "device-ready" list, which is used to 
direct the actions of new async threads.

Alan Stern

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