netdev - Re: [Bug 10238] Re: [PATCH] Re: netconsole still hangs

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Message-Id: <20080319142010.ed564c39.akpm@linux-foundation.org>
Date:	Wed, 19 Mar 2008 14:20:10 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Jarek Poplawski <jarkao2@...il.com>
Cc:	davem@...emloft.net, shemminger@...ux-foundation.org,
	netdev@...r.kernel.org, rjw@...k.pl,
	bugme-daemon@...zilla.kernel.org
Subject: Re: [Bug 10238] Re: [PATCH] Re: netconsole still hangs

On Wed, 19 Mar 2008 20:17:25 +0100
Jarek Poplawski <jarkao2@...il.com> wrote:

> On Tue, Mar 18, 2008 at 11:47:29PM +0100, Jarek Poplawski wrote:
> ...
> > Anyway... My first tests seemed to hang the box with syslog only. Now
> > I can't repeat it neither with syslog nor netconsole... So, this patch
> > is a bad hit or it's really about timing.
> 
> I've just repeated this this test with syslog only. After letting it
> go for ~5 min. I couldn't break it with any keys for at least next 10
> min., and I turned the power down. Then the same but with this sched.c
> patch reverted: ^C worked after a few seconds. It looks like time
> can really matter here.

Yeah, I was fiddling with that.  If you do

for i in $(seq 100)
do
	echo t > /proc/sysrq-trigger
done

then yes there's no response to ^C and the machine is basically dead.  But
when the loop finishes, things return to normal.

Perhaps it's something to do with longer holds on tasklist_lock, something
liek that.

> So, maybe it's again something accidental, I don't have another box
> around to stay idle while repeting this test, but it seems this could
> be not the best way to compare anything with 2.6.24 or older.

No.  I still haven't retested on the other offending machine.  Right now
I'm not sure that we any longer have anything which needs fixing.  Apart
from merging netpoll-zap_completion_queue-adjust-skb-users-counter.patch?
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