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

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Date:	Tue, 30 Dec 2008 05:59:56 -0700
From:	Jonathan Corbet <corbet@....net>
To:	Andi Kleen <andi@...stfloor.org>
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,
	xfs-masters@....sgi.com
Subject: Re: RFC: Fix f_flags races without the BKL

On Mon, 29 Dec 2008 16:27:32 +0100
Andi Kleen <andi@...stfloor.org> wrote:

> I would prefer O_LOCK_FLAGS bit too. The global lock is not very nice
> and I don't doubt someone will come up with a workload which
> pounds on it.

Seems hard to imagine that it would be worse than the longstanding BKL
situation.  That said, the global lock is clearly an unsubtle approach,
and people don't like it.  I'd hoped to slip something quick through
the merge window, but that seems unlikely, especially, since I'm
allegedly on vacation.  I'll forget this patch for now and revisit it
next week.

(Unless, of course, somebody wants to just send in the O_LOCK_FLAGS
patch and be done with it.  I hate to invent a new and different
locking scheme for such a trivial purpose, but it's not *that* bad...)

Otherwise, maybe it's worth thinking for a bit on whether it might be
possible to do away with >fasync() altogether; that would make most of
the problem go away.  Will ponder later.

jon
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