Re: [RFC][PATCH 0/3] configfs: Make nested default groups lockdep-friendly

From: Louis Rilling
Date: Tue May 20 2008 - 13:09:30 EST

Arjan van de Ven a écrit :
> On Tue, 20 May 2008 18:33:20 +0200
> Louis Rilling <Louis.Rilling@xxxxxxxxxxx> wrote:
>> Hi all,
>> The following patches fix lockdep warnings resulting from (correct)
>> recursive locking in configfs.
>> Current lockdep annotations for inode mutexes in configfs are
>> lockdep-friendly provided that:
>> 1/ config_groups have at most one level of default groups (see
>> configfs_attach_group()),
>> 2/ config_groups having default groups are never removed (see
>> configfs_detach_prep()).
>> Since lockdep does not handle such correct recursion, the idea is to
>> insert lockdep_off()/lockdep_on() for inode mutexes as soon as the
>> level of recursion of the I_MUTEX_PARENT -> I_MUTEX_CHILD dependency
>> pattern increases.
> I'm... not entirely happy with such a solution ;(
> there must be a better one.

Hmm, to me there are three solutions:

1/ keep lockdep and configfs like they are, and use this patchset

2/ enhance lockdep to handle wariable-depth but correct recursion:
seems uncertain...

3/ remove this recursive locking from configfs:
unfortunately, it seems that there are a good reasons for doing
recursive inode locking, at least when removing a config_group with
default groups. So, seems uncertain too...

Other ideas?

Dr Louis Rilling Kerlabs
Skype: louis.rilling Batiment Germanium
Phone: (+33|0) 6 80 89 08 23 80 avenue des Buttes de Coesmes 35700 Rennes
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