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Date: Thu, 26 Apr 2012 15:17:53 -0700 From: Tejun Heo <tj@...nel.org> To: Alan Stern <stern@...land.harvard.edu> Cc: "Eric W. Biederman" <ebiederm@...ssion.com>, Peter Zijlstra <peterz@...radead.org>, Kernel development list <linux-kernel@...r.kernel.org> Subject: Re: Lockdep false positive in sysfs 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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