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Date: Tue, 24 Apr 2007 19:53:32 +0400
From: Oleg Nesterov <oleg@tv-sign.ru>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
       Davide Libenzi <davidel@xmailserver.org>, Ingo Molnar <mingo@elte.hu>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       "Rafael J. Wysocki" <rjw@sisk.pl>, Roland McGrath <roland@redhat.com>,
       Rusty Russell <rusty@rustcorp.com.au>, linux-kernel@vger.kernel.org,
       linux-arch@vger.kernel.org
Subject: Re: [PATCH] kthread: Enhance kthread_stop to abort interruptible sleeps
Message-ID: <20070424155332.GA321@tv-sign.ru>
References: <20070413130236.GA173@tv-sign.ru> <m1zm5bmywm.fsf@ebiederm.dsl.xmission.com> <20070424030924.be44ebfa.akpm@linux-foundation.org> <m1r6qat681.fsf@ebiederm.dsl.xmission.com> <20070424150558.GA233@tv-sign.ru>
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On 04/24, Oleg Nesterov wrote:
>
> Hm, mm_release() clears ->vfork_done before complete().
> 
> 	mm_release:
> 
> 		struct completion *vfork_done = tsk->vfork_done;
> 
> 		if (vfork_done) {
> 			tsk->vfork_done = NULL;
> 			complete(vfork_done);
> 		}
> 
> 
> 	kthread_stop:
> 
> 		set_tsk_thread_flag(tsk, TIF_KTHREAD_STOP);
> 		signal_wake_up(tsk, 1);
> 
> 		// tsk exits, sets ->vfork_done == NULL
> 
> 		wait_for_completion(tsk->vfork_done);

Since the task_struct should be pinned anyway, I think kthread_stop()
should do:

	vfork_done = tsk->vfork_done;
	barrier();
	if (vfork_done)
		wait_for_completion(vfork_done);

Oleg.