linux-kernel - Re: [PATCH] ptrace: use safer wake up on ptrace

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Date:	Tue, 1 Feb 2011 14:40:37 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Roland McGrath <roland@...hat.com>, jan.kratochvil@...hat.com,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org
Subject: Re: [PATCH] ptrace: use safer wake up on ptrace_detach()

On 02/01, Tejun Heo wrote:
>
> --- work.orig/kernel/ptrace.c
> +++ work/kernel/ptrace.c
> @@ -313,7 +313,7 @@ int ptrace_detach(struct task_struct *ch
>  		child->exit_code = data;
>  		dead = __ptrace_detach(current, child);
>  		if (!child->exit_state)
> -			wake_up_process(child);
> +			wake_up_state(child, TASK_TRACED | TASK_STOPPED);

Well, it can't be TASK_TRACED at this point. And of course this still
contradicts to __set_task_state(child, TASK_STOPPED) in ptrace_untrace().
IOW, to me the previous patch makes more sense.

But OK, I understand Roland's concerns. And, at least this change
fixes the bug mentioned in 95a3540d.

Acked-by: Oleg Nesterov <oleg@...hat.com>

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