linux-kernel - Re: [RESEND] [PATCH] VFS: make file->f

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Message-ID: <20081007102942.GE20740@one.firstfloor.org>
Date:	Tue, 7 Oct 2008 12:29:42 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Hisashi Hifumi <hifumi.hisashi@....ntt.co.jp>
Cc:	Andi Kleen <andi@...stfloor.org>, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [RESEND] [PATCH] VFS: make file->f_pos access atomic on 32bit arch

> Maybe cmpxchg8b is good for i486 or later x86, but i386 or other architectures
> that do not have similar instruction needs some locking primitive. I think lazy

We have a cmpxchg emulation on 386. That works because only UP 386s are 
supported, so it can be done in software.

> seqlock is one option for making file->f_pos access atomic.

The question is if it's the right option. At least all the common
operations on fds (read/write) are all writers, not readers.

-Andi

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