linux-kernel - Re: [PATCH 44/62] sysfs: Use one lockdep class per sysfs attribute.

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Date:	Wed, 03 Mar 2010 10:41:11 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Greg Kroah-Hartman <gregkh@...e.de>
CC:	linux-kernel@...r.kernel.org,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH 44/62] sysfs: Use one lockdep class per sysfs attribute.

On 03/03/2010 08:28 AM, Greg Kroah-Hartman wrote:
> From: Eric W. Biederman <ebiederm@...ssion.com>
> 
> Acknowledge that the logical sysfs rwsem has one instance per
> sysfs attribute with different locking depencencies for different
> attributes.
> 
> There is a sysfs idiom where writing to one sysfs file causes the
> addition or removal of other sysfs files.   Lumping all of the
> sysfs attributes together in one lock class causes lockdep to
> generate lots of false positives.
> 
> This introduces the requirement that non-static sysfs attributes
> need to be initialized with sysfs_attr_init or sysfs_bin_attr_init.
> Strictly speaking this requirement only exists when lockdep is
> enabled, and when lockdep is enabled we get a bit fat warning
> if this requirement is not met.
> 
> Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com>
> Acked-by: WANG Cong <xiyou.wangcong@...il.com>
> Cc: Tejun Heo <tj@...nel.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

Acked-by: Tejun Heo <tj@...nel.org> but it would be nice if when and
how attr->key is set for each case and how it's supposed to trigger
big fat warning in the code.  It's a bit difficult to follow
currently.

-- 
tejun
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