linux-kernel - Re: [RFC][PATCH 0/3] PM: Asynchronous suspend and resume

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Message-ID: <Pine.LNX.4.44L0.0908121702520.23954-100000@iolanthe.rowland.org>
Date:	Wed, 12 Aug 2009 17:12:09 -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>,
	linux-acpi <linux-acpi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Zhang Rui <rui.zhang@...el.com>, Len Brown <lenb@...nel.org>,
	Arjan van de Ven <arjan@...ux.intel.com>
Subject: Re: [RFC][PATCH 0/3] PM: Asynchronous suspend and resume

On Wed, 12 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 [1/1] patch
> message.
> 
> Comments welcome.

I get the idea.  Not bad.  Have you tried it in a serious way?  For 
example, turning on the async_suspend flag for every device?

In one way it isn't as efficient as it could be.  You fire off a bunch
of async threads and then make many of them wait for parent or child
devices.  They could be doing useful work instead.

It would be interesting to invent a way of representing explicitly the 
non-tree dependencies -- assuming there aren't too many of them!  (I 
can just hear the TI guys hollering about power and timer domains...)

Alan Stern

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