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

From: Tejun Heo
Date: Tue Mar 02 2010 - 20:30:12 EST

On 03/03/2010 08:28 AM, Greg Kroah-Hartman wrote:
> From: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
> 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@xxxxxxxxxxxx>
> Acked-by: WANG Cong <xiyou.wangcong@xxxxxxxxx>
> Cc: Tejun Heo <tj@xxxxxxxxxx>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

Acked-by: Tejun Heo <tj@xxxxxxxxxx> 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

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