linux-kernel - Re: [PATCH 2/7] revoke: add f

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Message-ID: <84144f020703090243j6fd49b5eoa23f4cc12866725a@mail.gmail.com>
Date:	Fri, 9 Mar 2007 12:43:36 +0200
From:	"Pekka Enberg" <penberg@...helsinki.fi>
To:	"Eric Dumazet" <dada1@...mosbay.com>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	hch@...radead.org, alan@...rguk.ukuu.org.uk, serue@...ibm.com
Subject: Re: [PATCH 2/7] revoke: add f_light flag for struct file

On 3/9/07, Eric Dumazet <dada1@...mosbay.com> wrote:
> Cannot we use a flag in 'struct files_struct', set to one when the task is
> mono-thread (at task creation in fact), and set to 0 when it creates a new
> thread  (or when someone remotely access to this "struct files_struct"
> in /proc/pid/fd/... )

How does that work? fget_light() has a built-in assumption that as
long as you don't share files_struct, it's okay not to take an extra
reference as current is only one doing close(2) and revoke(2) changes
that. So it's not really about being single-threaded or not.

On 3/9/07, Eric Dumazet <dada1@...mosbay.com> wrote:
> Also, the thing is racy.

Aah, fget_light() indeed has a race window between fcheck_files() and
set_f_light().
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