From: Al Viro <viro@ZenIV.linux.org.uk>
To: Jonathan Corbet <corbet@lwn.net>
Cc: LKML <linux-kernel@vger.kernel.org>,
Andi Kleen <andi@firstfloor.org>,
Alan Cox <alan@lxorguk.ukuu.org.uk>,
Oleg Nesterov <oleg@redhat.com>,
bfields@fieldses.org, xfs-masters@oss.sgi.com
Subject: Re: RFC: Fix f_flags races without the BKL
Date: Fri, 2 Jan 2009 18:42:32 +0000 [thread overview]
Message-ID: <20090102184232.GH28946@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20081229041352.6bbdf57c@tpl>
On Mon, Dec 29, 2008 at 04:13:52AM -0700, Jonathan Corbet wrote:
> Accesses to the f_flags field have always involved a read-modify-write
> operation, and have always been racy in the absence of the BKL. The recent
> BKL-removal work made this problem worse, but it has been there for a very
> long time. The race is quite small, and, arguably, has never affected
> anybody, but it's still worth fixing.
>
> After pondering for a while, I couldn't come up with anything better than a
> global file->f_flags mutex. There's no point in bloating struct file with
> a mutex just for this purpose; it's hard to imagine that there will be any
> real contention for this lock.
Bloating with mutex is over the top, indeed, but why can't we simply keep
a pointer to fasync_struct in there? Do we ever have a struct file with
several fasync_struct? They'd have to be on different queues and I don't
see any cases where that would happen...
next prev parent reply other threads:[~2009-01-02 18:42 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-12-29 11:13 RFC: Fix f_flags races without the BKL Jonathan Corbet
2008-12-29 11:57 ` Sam Ravnborg
2008-12-30 12:49 ` Jonathan Corbet
2008-12-29 12:41 ` Oleg Nesterov
2008-12-29 15:27 ` Andi Kleen
2008-12-30 12:59 ` Jonathan Corbet
2008-12-30 13:04 ` [xfs-masters] " Christoph Hellwig
2008-12-30 13:37 ` Andi Kleen
2008-12-30 14:48 ` Christoph Hellwig
2008-12-31 9:52 ` Jonathan Corbet
2008-12-30 14:55 ` Andi Kleen
2009-01-08 23:28 ` Jonathan Corbet
2009-01-09 10:08 ` Oleg Nesterov
2009-01-09 13:18 ` Jonathan Corbet
2009-01-09 14:03 ` Oleg Nesterov
2009-01-09 15:09 ` Andi Kleen
2008-12-29 12:50 ` [xfs-masters] " Christoph Hellwig
2008-12-29 15:15 ` Andi Kleen
2009-01-02 18:29 ` Al Viro
2009-01-02 18:27 ` Al Viro
2009-01-02 18:42 ` Al Viro [this message]
2009-01-02 19:09 ` Oleg Nesterov
2009-01-02 19:54 ` Al Viro
2009-01-03 16:45 ` Oleg Nesterov
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