linux-kernel - Re: [PATCH 7/7] driver-core : convert semaphore to mutex in struct class

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Date:	Thu, 17 Jan 2008 23:02:36 +0100
From:	Jarek Poplawski <jarkao2@...il.com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Dave Young <hidave.darkstar@...il.com>, Greg KH <gregkh@...e.de>,
	stefanr@...6.in-berlin.de, David Brownell <david-b@...bell.net>,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 7/7] driver-core : convert semaphore to mutex in struct
	class

On Thu, Jan 17, 2008 at 09:31:55PM +0100, Jarek Poplawski wrote:
> On Thu, Jan 17, 2008 at 02:57:36PM -0500, Alan Stern wrote:
...
> > If I recall correctly the nature of the warning was that a method
> > routine for one class (called with the class's mutex held) was creating
> > a second class and locking that class's mutex.  In principle this is
> > perfectly legal and should be allowed for arbitrary depths of nesting,
> > even though it is the sort of thing lockdep is currently unable to
> > handle.

BTW, Dave, if it's only about one such "second class" here, then it
shouldn't be so hard to try this one more level of nesting. I think,
the real problem for lockdep starts when there are more such "second
classes", but it's probably in another place.

You could also have a look at e.g. enum_inode_i_mutex_lock_class in
include/linux/fs.h and fh_lock_nested() in include/linux/nfsd/nfsfh.h,
and maybe define similar enum for this.

Jarek P.
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