linux-kernel - Re: main thread pthread_exit/sys

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Message-ID: <20090205232223.GB10345@redhat.com>
Date:	Fri, 6 Feb 2009 00:22:23 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Roland McGrath <roland@...hat.com>
Cc:	Kaz Kylheku <kkylheku@...il.com>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ulrich Drepper <drepper@...hat.com>
Subject: Re: main thread pthread_exit/sys_exit bug!

On 02/05, Roland McGrath wrote:
>
> I wrote this test case for it.  Is there any problem other than this one?

I don't know about other problems with the zombie leaders.

Except, I am worried whether the fix I have in mind is correct ;)
It is simple, wait_task_stopped() should do

	if we tracer:

		check ->state, eat ->exit_code

	else:
		check SIGNAL_STOP_STOPPED, use ->group_exit_code

This looks logical, and should fix the problem. But this is
the user-visible change. For example,

	$ sleep 100
	^Z
	[1]+  Stopped                 sleep 100
	$ strace -p `pidof sleep`
	Process 11442 attached - interrupt to quit

strace hangs in do_wait(). But after the fix strace will happily
proceed. I can't know whether this behaviour change is bad or not.

Oleg.

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