linux-kernel - Re: locking design for task_subsys

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Message-ID: <6599ad831001251808k143c03fal14fe6bf5f19e0e5e@mail.gmail.com>
Date:	Mon, 25 Jan 2010 18:08:51 -0800
From:	Paul Menage <menage@...gle.com>
To:	paulmck@...ux.vnet.ibm.com
Cc:	linux-kernel@...r.kernel.org
Subject: Re: locking design for task_subsys_state()?

On Sun, Jan 24, 2010 at 3:25 PM, Paul E. McKenney
<paulmck@...ux.vnet.ibm.com> wrote:
>
> Is there some flag in the task structure that I should check in order to
> suppress this splat, and, more important, to document the locking
> design?  Here is what I currently have in my local tree:

Nothing cgroup-specific as far as I know - I guess it's just assumed
that since nothing else can be accessing the task_struct at that point
as it's not linked into any lists (is that correct?) then there's no
locking needed. If there's no generic task flag that indicates that
the task has never been exposed to any other thread via a list, etc,
it could be added? I imagine that some other subsystems are likely to
have similar problems. Alternatively, adding an RCU read-lock pair
around the relevant code is probably possible too, even if not
technically necessary.

Paul
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