linux-kernel - Re: + fix-soft-lockup-when-removing-netconsole-module.patch added to -mm tree

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Date:	Wed, 30 May 2007 14:51:23 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	Jason Wessel <jason.wessel@...driver.com>,
	Stephen Hemminger <shemminger@...ux-foundation.org>,
	"David S. Miller" <davem@...emloft.net>,
	linux-kernel@...r.kernel.org
Subject: Re: + fix-soft-lockup-when-removing-netconsole-module.patch added
 to -mm tree

On Thu, 31 May 2007 01:01:37 +0400
Oleg Nesterov <oleg@...sign.ru> wrote:

> Jason Wessel wrote:
> >
> > The netpoll_cleanup handler can hang the kernel if there is no work in the
> > work queue because a call to cancel_rearming_delayed_work() with no work
> > goes into an infinite loop.
> 
> This should not be true any longer, cancel_rearming_delayed_work() should work
> correctly in any case.
> 
> Could you please clarify?

We need a 2.6.21.x fix.

> > @@ -771,30 +771,32 @@ void netpoll_cleanup(struct netpoll *np)
> >
> > [...snip...]
> >
> > +		if (atomic_dec_and_test(&npinfo->refcnt)) {
> > +			skb_queue_purge(&npinfo->arp_tx);
> > +			skb_queue_purge(&npinfo->txq);
> > +			if (delayed_work_pending(&npinfo->tx_work)) {
> >  				cancel_rearming_delayed_work(&npinfo->tx_work);
> >  				flush_scheduled_work();
> 
> But this "if (delayed_work_pending())" is racy anyway?
> 

I guess so, a bit.
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