linux-kernel - Re: [PATCH 1/7] Freezer: Read PF_BORROWED

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Message-ID: <20070512142558.GB98@tv-sign.ru>
Date:	Sat, 12 May 2007 18:25:58 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	ego@...ibm.com, Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>, Pavel Machek <pavel@....cz>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH 1/7] Freezer: Read PF_BORROWED_MM in a nonracy way

On 05/12, Rafael J. Wysocki wrote:
>
> Hmm, I'm not sure if the task can call try_to_freeze() after doing exit().
> May it happen?

It can, note the do_exit()->ptrace_notify(). But this doesn't matter, I think.
>From the freezer POV an exiting task has 2 "interesting" events

	exit_mm()	->mm becomes NULL

	exit_notify()   ->exit_state != 0, and perhaps the task disappears
	                  from global process list

> Or, perhaps, it's better to clear TIF_FREEZE (unconditionally) in exit_mm(),
> after we've done tsk->mm = NULL?  Oleg, what do you think?

Please see another message.

Oleg.

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