From: Tejun Heo <tj@kernel.org>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
Peter Zijlstra <peterz@infradead.org>,
Kernel development list <linux-kernel@vger.kernel.org>
Subject: Re: Lockdep false positive in sysfs
Date: Thu, 26 Apr 2012 15:17:53 -0700 [thread overview]
Message-ID: <20120426221753.GF27486@google.com> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1204261153320.1530-100000@iolanthe.rowland.org>
On Thu, Apr 26, 2012 at 02:14:30PM -0400, Alan Stern wrote:
> > > Hmmm.... This happens because, by default, sysfs_dirents for the same
> > > attr share the same lockdep key. This happens from
> > > sysfs_dirent_init_lockdep(). Hmm.... we can,
> > >
> > > * Somehow assign different keys to sysfs_dirents for the specific
> > > attr. Use array of attrs indexed by bus depth?
> >
> > Possible with sysfs_attr_init but pretty ugly. Especially since it
> > sounds like this is a situation that does not presuppose a maximum
> > depth. I do remember that the lockdep keys must be statically allocated
> > which makes this a challenge.
The depth is limited by USB spec.
> I agree; this doesn't seem like a good approach.
It sure isn't pretty but probably best matches the situation in the
sense that lockdep would actually be able to know about the nesting
going on.
> Another idea is to have A's method temporarily drop the sysfs readlock.
> Of course that would put the onus on the USB core of guaranteeing that
> A cannot be removed while this happens, but we can handle that.
Yeah, that's an easier way out. Please make it a proper sysfs API
call tho so that people working on sysfs later can know of the special
case.
Thanks.
--
tejun
next prev parent reply other threads:[~2012-04-26 22:17 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-25 18:58 Lockdep false positive in sysfs Alan Stern
2012-04-25 21:59 ` Tejun Heo
2012-04-26 8:16 ` Eric W. Biederman
2012-04-26 18:14 ` Alan Stern
2012-04-26 22:17 ` Tejun Heo [this message]
2012-04-27 15:57 ` Alan Stern
2012-04-27 16:09 ` Tejun Heo
2012-05-03 21:30 ` Alan Stern
2012-05-04 16:52 ` Tejun Heo
2012-05-04 19:08 ` Alan Stern
2012-05-07 19:46 ` Tejun Heo
2012-05-07 21:51 ` Alan Stern
2012-05-07 21:55 ` Tejun Heo
2012-05-08 18:53 ` Alan Stern
2012-05-09 17:41 ` Tejun Heo
2012-05-09 17:47 ` Alan Stern
2012-05-09 17:48 ` Tejun Heo
2012-04-27 16:27 ` Eric W. Biederman
2012-04-27 18:27 ` Alan Stern
2012-04-27 20:17 ` Tejun Heo
2012-04-27 21:09 ` Eric W. Biederman
2012-04-27 21:16 ` Tejun Heo
2012-04-29 2:00 ` Alan Stern
2012-04-29 2:35 ` Eric W. Biederman
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