netdev - Re: [BUG] net: cpu offline cause napi stall

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Date:	Wed, 1 Jun 2011 22:42:34 +0200
From:	Heiko Carstens <heiko.carstens@...ibm.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Frank Blaschka <blaschka@...ux.vnet.ibm.com>, davem@...emloft.net,
	netdev@...r.kernel.org, linux-s390@...r.kernel.org
Subject: Re: [BUG] net: cpu offline cause napi stall

On Wed, Jun 01, 2011 at 10:03:12PM +0200, Eric Dumazet wrote:
> Le mercredi 01 juin 2011 à 20:12 +0200, Heiko Carstens a écrit :
> > On Wed, Jun 01, 2011 at 06:55:21PM +0200, Eric Dumazet wrote:
> > > > +	/* Append NAPI poll list from offline CPU. */
> > > > +	list_splice_init(&oldsd->poll_list, &sd->poll_list);
> > > >  
> > > >  	raise_softirq_irqoff(NET_TX_SOFTIRQ);
> > > >  	local_irq_enable();
> > > 
> > > Please make sure we raise NET_RX_SOFTIRQ on new cpu if necessary.
> > 
> > Well, see two lines below the list_splice_init() call ;)
> 
> I see nothing... NET_TX_SOFTIRQ and NET_RX_SOFTIRQ are not the same 

Indeed. I must be blind.

diff --git a/net/core/dev.c b/net/core/dev.c
index 6561021..6189dac 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5981,6 +5981,11 @@ static int dev_cpu_callback(struct notifier_block *nfb,
 		oldsd->output_queue = NULL;
 		oldsd->output_queue_tailp = &oldsd->output_queue;
 	}
+	/* Append NAPI poll list from offline CPU. */
+	if (!list_empty(&oldsd->poll_list)) {
+		list_splice_init(&oldsd->poll_list, &sd->poll_list);
+		raise_softirq_irqoff(NET_RX_SOFTIRQ);
+	}
 
 	raise_softirq_irqoff(NET_TX_SOFTIRQ);
 	local_irq_enable();
--
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