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

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Message-ID: <20090109150911.GC26290@one.firstfloor.org>
Date:	Fri, 9 Jan 2009 16:09:11 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Jonathan Corbet <corbet@....net>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	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

> > 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 presume it could be a problem on a program that uses asynchronous sockets
multi threaded. At some point that used to be a common pattern for
network servers like squid (not saying that it's necessarily contended
in squid itself)

-andi

-- 
ak@...ux.intel.com
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