Date: Fri, 23 Nov 2007 13:20:33 -0600
From: Matt Mackall <mpm@selenic.com>
To: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Cc: Andrew Morton <akpm@linux-foundation.org>,
       Simon Arlott <simon@fire.lp0.eu>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       netdev@vger.kernel.org, Ingo Molnar <mingo@redhat.com>
Subject: Re: 2.6.23 WARNING: at kernel/softirq.c:139 local_bh_enable()
Message-ID: <20071123192032.GB19691@waste.org>
References: <4745DCD7.8070805@simon.arlott.org.uk> <20071123002157.cb27f4a1.akpm@linux-foundation.org> <20071123105518.GA22062@2ka.mipt.ru> <20071123170756.GV19691@waste.org> <20071123175757.GA23991@2ka.mipt.ru> <20071123185943.GZ19691@waste.org> <20071123191524.GA6273@2ka.mipt.ru>
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On Fri, Nov 23, 2007 at 10:15:24PM +0300, Evgeniy Polyakov wrote:
> On Fri, Nov 23, 2007 at 12:59:43PM -0600, Matt Mackall (mpm@selenic.com) wrote:
> > So I'd be surprised if that was a problem. But I can imagine having
> > problems for skbs without destructors which run into one of these in
> > __kfree_skb:
> > 
> > dst_release
> > secpath_put
> > nf_conntrack_put
> > nf_conntrack_put_reasm
> > nf_bridge_put
> > 
> > ..some or all of which assume a softirq context.
> 
> bridging is ok, others require softirq context.
> I've sent a patch (the last one should be ok) to guard against xfrm and
> connection tracking.
> 
> > > No matter if we are under memory pressure or whatever - it is not
> > > allowed - a lot of skbs are supposed to be freed in softirq context,
> > > that is why dev_kfree_skb_any() exists.
> > 
> > Some skbs we definitely -can- free in irq context. The only ones we
> > care about are the ones generated by netpoll. If there's a reason you
> > think netpoll's own skbs can't be freed, please describe it.
> 
> Only some and to distinguish them we can not use destructor - if it is
> set (even empty function) it will fire an alarm.

Yep, please look at the patch I just posted.

-- 
Mathematics is the supreme nostalgia of our time.
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