linux-kernel - Re: RFC: Fix f_flags races without the BKL

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Message-ID: <20090109140354.GA6018@redhat.com>
Date:	Fri, 9 Jan 2009 15:03:54 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Jonathan Corbet <corbet@....net>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andi Kleen <andi@...stfloor.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Al Viro <viro@...IV.linux.org.uk>, bfields@...ldses.org
Subject: Re: RFC: Fix f_flags races without the BKL

On 01/09, Jonathan Corbet wrote:
>
> On Fri, 9 Jan 2009 11:08:21 +0100
> Oleg Nesterov <oleg@...hat.com> wrote:
>
> > and then we change f_flags again, including F_ASYNC bit.
> >
> > This is racy?
>
> No, I took FASYNC out of SETFL_MASK, so it isn't changed here.

Ah yes, I missed the change in SETFL_MASK. Thanks.

> > Now we have the global mutex for ->fasync... Well, not very
> > good but fasync_helper() takes fasync_lock anyway.
>
> Not very good, but does anybody know of a workload which would result in
> that mutex being contended ever?

I don't.

Actually, I personally dislike the global file_flags_lock more.
But don't get me wrong, I do not think O_LOCK_FLAGS is better
or cleaner.

Oleg.

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