linux-kernel - Re: Q. locking order of dcache_lru

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Message-ID: <20110411062703.GC21395@dastard>
Date:	Mon, 11 Apr 2011 16:27:03 +1000
From:	Dave Chinner <david@...morbit.com>
To:	"J. R. Okajima" <hooanon05@...oo.co.jp>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Christoph Hellwig <hch@...radead.org>,
	Nick Piggin <npiggin@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: Q. locking order of dcache_lru_lock

On Mon, Apr 11, 2011 at 02:09:31PM +0900, J. R. Okajima wrote:
> 
> Peter Zijlstra:
> > On Fri, 2011-04-08 at 22:20 +0900, J. R. Okajima wrote:
> > >=20
> > > When spin_trylock(&dentry->d_lock) successfully acquired d_lock, does
> > > the violation of locking order happen (or a deadlock, in worse case)?=20
> >
> > No, since a trylock never actually blocks a deadlock cannot occur.
> 
> Ah, exactly. I had to be sleeping when I wrote about deadlock.
> How about the locking order? Do you think d_lock after dcache_lru_lock
> is a problem?

>From fs/dcache.c:

 * Ordering:
 * dentry->d_inode->i_lock
 *   dentry->d_lock
 *     dcache_lru_lock
 *     dcache_hash_bucket lock
 *     s_anon lock

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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