linux-kernel - Re: [linux-pm] [GIT PULL] One more power management fix for 2.6.37

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Message-ID: <20101103211855.GA29721@isilmar-3.linta.de>
Date:	Wed, 3 Nov 2010 22:18:55 +0100
From:	Dominik Brodowski <linux@...inikbrodowski.net>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [linux-pm] [GIT PULL] One more power management fix for 2.6.37

> There's apparently an ordering problem with dpm_list_mtx and
> socket->skt_mutex. Lockdep details appended.
> 
> Dominik, Rafael? What's the proper locking order here, and
> how do we fix this?

Thanks for noting this; let's see:

- We add a PCMCIA device holding skt_mutex, therefore we have the ordering
  (1) skt_mutex -> (2) dpm_list_mtx

- If we're suspending, dpm_list_mtx is held, but we need to acquire
  skt_mutex as we modify some data being protected by skt_mutex
  (1) dpm_list_mtx -> (2) skt_mutex

Rafael, any idea on how to solve this? How do other subsystems handle such
an issue? Do they call device_add() with no locks held at all?

Best,
	Dominik
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