linux-kernel - Re: deferring _

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Message-ID: <20120624153310.GB24596@redhat.com>
Date:	Sun, 24 Jun 2012 17:33:10 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	". James Morris" <jmorris@...ei.org>,
	linux-security-module@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: deferring __fput()

On 06/24, Al Viro wrote:
>
> BTW, I suspect that we really want to move exit_task_work() down past the
> calls of exit_mm()/exit_files()

Yes, probably. But I do not know how far we should move it.

> (and lose the PF_EXITING check in
> task_work_add(), making that ordering responsibility of callers).

No, we can't do this?

OK, perhaps we can check something else instead of PF_EXITING.
But somehow we should ensuree that if task_work_add(twork) succeeds,
then twork->func() will be called. IOW, if task_work_add() races with
the exiting task, it should not succeed after exit_task_work().

> I'm not 100% sure about that one - if you have planned task_work users
> relying on e.g. task->mm still being there when callback runs,

No, I didn't.

Oleg.

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