linux-kernel - Re: [PATCH] kthread: Enhance kthread_stop to abort interruptible sleeps

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Message-ID: <20070424155332.GA321@tv-sign.ru>
Date:	Tue, 24 Apr 2007 19:53:32 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Davide Libenzi <davidel@...ilserver.org>,
	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Roland McGrath <roland@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH] kthread: Enhance kthread_stop to abort interruptible sleeps

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.

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