Date: Fri, 25 Nov 2005 06:12:32 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Oleg Nesterov <oleg@tv-sign.ru>
Cc: linux-kernel@vger.kernel.org, Linus Torvalds <torvalds@osdl.org>,
       Andrew Morton <akpm@osdl.org>
Subject: Re: [PATCH 1/2] PF_DEAD: cleanup usage
Message-ID: <20051125051232.GB22230@elte.hu>
References: <4385E3FF.C99DBCF5@tv-sign.ru>
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* Oleg Nesterov <oleg@tv-sign.ru> wrote:

> schedule() checks PF_DEAD on every context switch, and sets ->state = 
> EXIT_DEAD to ensure that exited task will be deactivated.
> 
> I think it is better to set EXIT_DEAD in do_exit(), along with PF_DEAD 
> flag.

nice idea - your patch looks good to me.

> It is safe to do without task_rq() locking, because concurrent 
> try_to_wake_up() can't change task's ->state: the 'state' argument of 
> try_to_wake_up() can't have EXIT_DEAD bit. And in case when 
> try_to_wake_up() sees stale value of ->state == TASK_RUNNING it will 
> do nothing.

we should really not be getting concurrent wakeups in this situation 
anyway - and you are right that even if we got, it should have no effect 
neither in the EXIT_DEAD nor in the TASK_RUNNING case.

Acked-by: Ingo Molnar <mingo@elte.hu>

	Ingo
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