linux-kernel - Re: [PATCH 1/3] futex_find_get_task: remove an obscure EXIT

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Date:	Tue, 22 Aug 2006 15:03:20 -0700
From:	Bill Huey (hui) <billh@...ppy.monkey.org>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	Andrew Morton <akpm@...l.org>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	linux-kernel@...r.kernel.org, Joe Taylor <joe@...silica.com>
Subject: Re: [PATCH 1/3] futex_find_get_task: remove an obscure EXIT_ZOMBIE check

On Tue, Aug 22, 2006 at 10:34:31PM +0400, Oleg Nesterov wrote:
> On 08/21, Bill Huey wrote:
> > On Mon, Aug 21, 2006 at 09:06:04PM +0400, Oleg Nesterov wrote:
> > > (Compile tested).
> > > 
> > > futex_find_get_task:
> > > 
> > > 	if (p->state == EXIT_ZOMBIE || p->exit_state == EXIT_ZOMBIE)
> > > 		return NULL;
> > > 
> > > I can't understand this. First, p->state can't be EXIT_ZOMBIE. The ->exit_state
> > > check looks strange too. Sub-threads or tasks whose ->parent ignores SIGCHLD go
> > > directly to EXIT_DEAD state (I am ignoring a ptrace case). Why EXIT_DEAD tasks
> > > should be ok? Yes, EXIT_ZOMBIE is more important (a task may stay zombie for a
> > > long time), but this doesn't mean we should explicitely ignore other EXIT_XXX
> > > states.
> > 
> > The p->state variable for EXIT_ZOMBIE is only live for some mystery architecture
> > in arch/xtensa/kernel/ptrace.c
> 
> Thanks. This
> 
> 	case PTRACE_KILL:
> 		ret = 0;
> 		if (child->state == EXIT_ZOMBIE)	/* already dead */
> 			break;
> 
> is an obvious bug, I beleive. May I suggest you to make a patch?

Oleg,

Here is it. Maintainers CCed...

bill


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