linux-kernel - Re: [PATCH] w1: Introduce a slave mutex for serializing IO.

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Message-ID: <20120515012634.GF25482@ioremap.net>
Date:	Tue, 15 May 2012 05:26:34 +0400
From:	Evgeniy Polyakov <zbr@...emap.net>
To:	NeilBrown <neilb@...e.de>
Cc:	linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] w1: Introduce a slave mutex for serializing IO.

On Wed, May 09, 2012 at 11:43:49AM +1000, NeilBrown (neilb@...e.de) wrote:
> However lockdep didn't like it.  There are ordering problems between this
> mutex and and sysfs's s_active.
> 
> When you access battery properies via sysfs, the sysfs lock is taken first,
> then the master->mutex.
> When w1_reconnect_slaves calls through to device_del and sys_addrm_finish,
> the mutex is held while the sysfs lock is wanted.

I only came to idea of not allowing sysfs in ->probe() and instead
introduce new callback, which will initialize 'external' to w1 core
parts without holding master's mutex

-- 
	Evgeniy Polyakov
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