linux-kernel - Re: [PATCH 1/3] PM: Handle device registrations during suspend/resume

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Date:	Thu, 13 Mar 2008 09:37:13 +0100
From:	Pavel Machek <pavel@....cz>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Greg KH <greg@...ah.com>, Alan Stern <stern@...land.harvard.edu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Brownell <david-b@...bell.net>,
	LKML <linux-kernel@...r.kernel.org>,
	pm list <linux-pm@...ts.linux-foundation.org>
Subject: Re: [PATCH 1/3] PM: Handle device registrations during
	suspend/resume

On Wed 2008-03-12 00:57:22, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rjw@...k.pl>
> 
> Modify the PM core to protect its data structures, specifically the
> dpm_active list, from being corrupted if a child of the currently
> suspending device is registered concurrently with its ->suspend()
> callback.  In that case, since the new device (the child) is added
> to dpm_active after its parent, the PM core will attempt to
> suspend it after the parent, which is wrong.
> 
> Introduce a new member of struct dev_pm_info, called 'sleeping',
> and use it to check if the parent of the device being added to
> dpm_active has been suspended, in which case the device registration
> fails.  Also, use 'sleeping' for checking if the ordering of devices
> on dpm_active is correct.
> 
> Introduce variable 'all_sleeping' that will be set to 'true' once all
> devices have been suspended and make new device registrations fail
> until 'all_sleeping' is reset to 'false', in order to avoid having
> unsuspended devices around while the system is going into a sleep state.
> 
> Remove pm_sleep_rwsem which is not necessary any more.
> 
> Special thanks to Alan Stern for discussions and suggestions that
> lead to the creation of this patch.
> 
> Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>

ACK.

-- 
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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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