linux-kernel - Re: 2.6.25-rc5-mm1: "consolechars" hangs on boot

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Message-ID: <20080314052606.GA226@tv-sign.ru>
Date:	Fri, 14 Mar 2008 08:26:06 +0300
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Laurent Riffard <laurent.riffard@...e.fr>,
	linux-kernel@...r.kernel.org, roland@...hat.com, mingo@...e.hu,
	xemul@...nvz.org
Subject: Re: 2.6.25-rc5-mm1: "consolechars" hangs on boot

On 03/13, Andrew Morton wrote:
>
> On Thu, 13 Mar 2008 23:07:30 +0100
> Laurent Riffard <laurent.riffard@...e.fr> wrote:
> 
> > Le 11.03.2008 09:14, Andrew Morton a __crit :
> > > ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.25-rc5/2.6.25-rc5-mm1/
> > > 
> > 
> > With 2.6.25-rc5-mm1, my system (Ubuntu 7.10/Gutsy) reliably hangs on
> > boot. Sysrq-T shows 12 "consolechars" processes stuck in do_exit call.
> > 
> > The bisection said "Sucker is
> > patches/signals-send_signal-factor-out-signal_group_exit-checks.patch"
> > 
> > Actually, it's 2.6.25-rc5-mm1 + add-warn_on_secs-macro-fix-fix.patch,
> > I guess this patch is innocent.

Laurent, thanks a lot!

What was the state of consolechars? Where exactly did it hang? do_exit+??

> Actually I later dropped
> signals-send_signal-factor-out-signal_group_exit-checks.patch at Oleg's
> request.
> 
> But I don't think we did that because it was known to be buggy, so perhaps
> the same bug crept back in in another form..

Yes, currently I suspect we have another bug.

And. While doing this patch I forgot we should fix the bugs with init first!
(will try to make the patch soon).

Laurent, any chance you can try 2.6.25-rc5-mm1 + the patch below?
Unlikely it can help, but would be great to be sure.

Oleg.

--- MM/kernel/signal.c~	2008-03-14 08:08:07.000000000 +0300
+++ MM/kernel/signal.c	2008-03-14 08:08:17.000000000 +0300
@@ -719,6 +719,10 @@ static void complete_signal(int sig, str
 		/*
 		 * This signal will be fatal to the whole group.
 		 */
+if (is_global_init(p)) {
+	printk(KERN_CRIT "ERR!! init is killed by %d\n", sig);
+	WARN_ON_ONCE(1);
+} else
 		if (!sig_kernel_coredump(sig)) {
 			/*
 			 * Start a group exit and wake everybody up.

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