linux-kernel - Re: [RFC][PATCH 3/7] exit: Desl with nested sleeps

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Message-ID: <20140804185336.GA21619@redhat.com>
Date:	Mon, 4 Aug 2014 20:53:36 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	mingo@...nel.org, torvalds@...ux-foundation.org,
	tglx@...utronix.de, ilya.dryomov@...tank.com,
	umgwanakikbuti@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH 3/7] exit: Desl with nested sleeps

On 08/04, Peter Zijlstra wrote:
>
> Not strictly a bug in the current form,

Yes, this is the false positive.

> but clean it up to enable
> debugging infrastructure and avoid it becoming a bug.

OK, but

> @@ -991,6 +991,8 @@ static int wait_task_zombie(struct wait_
>
>  		get_task_struct(p);
>  		read_unlock(&tasklist_lock);
> +		__set_current_state(TASK_RUNNING);
> +

without a comment it is not clear why do we bother to set RUNNING here.

Perhaps we can add another helper which sets current->state = RUNNING?
Just to self-document the usage.

We can even make it depend on CONFIG_DEBUG_ATOMIC_SLEEP (not sure this
makes sense). But in this case it should set ->task_state_change = 0
and __might_sleep() should take !task_state_change into account.

Oleg.

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