From: Arnd Bergmann <arnd@arndb.de>
To: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: Christian Krafft <krafft@de.ibm.com>, linux-kernel@vger.kernel.org
Subject: Re: [patch] nfs: fix locking in nfs/inode.c in nfs_free_open_context
Date: Thu, 26 Jul 2007 13:23:37 +0200 [thread overview]
Message-ID: <200707261323.38310.arnd@arndb.de> (raw)
In-Reply-To: <1185384502.6585.97.camel@localhost>
On Wednesday 25 July 2007, Trond Myklebust wrote:
>
> On Wed, 2007-07-25 at 17:08 +0200, Christian Krafft wrote:
>
> > Obviously the locking code in nfs_free_open_context is wrong.
> > Checking the list for entries and removing the entry should be an atomic operation.
>
> Wrong. It is quite safe to test the structure member ctx->list for
> emptiness outside the spinlock because we have an explicit guarantee
> that nobody else has a reference to this structure, plus the
> atomic_dec_and_test() in kref_put() has acted as a memory barrier for
> us.
Well, the real question then is how the ctx can still be present in the
nfsi->open_files list. Since we are in nfs_free_open_context(), there
must not be any pointer to the ctx anywhere, but still we have this other
thread calling get_nfs_open_context() on it.
Arnd <><
next prev parent reply other threads:[~2007-07-26 11:24 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-07-25 15:08 [patch] nfs: fix locking in nfs/inode.c in nfs_free_open_context Christian Krafft
2007-07-25 17:28 ` Trond Myklebust
2007-07-26 11:23 ` Arnd Bergmann [this message]
2007-07-26 12:37 ` Trond Myklebust
2007-07-26 12:44 ` Christian Krafft
2007-07-26 13:23 ` Trond Myklebust
2007-07-26 15:13 ` Arnd Bergmann
2007-07-26 16:08 ` Trond Myklebust
2007-07-26 18:00 ` Christian Krafft
2007-07-27 10:02 ` Christian Krafft
2007-07-27 9:44 ` Arnd Bergmann
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