From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [BUG] net: cpu offline cause napi stall
Date: Wed, 01 Jun 2011 14:13:19 +0200
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References: <20110601103356.GA45482@tuxmaker.boeblingen.de.ibm.com>
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To: Frank Blaschka <blaschka@linux.vnet.ibm.com>
Cc: davem@davemloft.net, netdev@vger.kernel.org, linux-s390@vger.kernel.org, heiko.carstens@de.ibm.com
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Le mercredi 01 juin 2011 =C3=A0 12:33 +0200, Frank Blaschka a =C3=A9cri=
t :
> Hi Dave, Eric,
>=20
> during heavy network load we turn off/on cpus.
> Sometimes this causes a stall on the network device.
> Digging into the dump I found out following:
>=20
> napi is scheduled but does not run. From the I/O buffers
> and the napi state I see napi/rx_softirq processing has stopped
> because the budget was reached. napi stays in the
> softnet_data poll_list and the rx_softirq was raised again.
>=20
> I assume at this time the cpu offline comes in.
> the rx softirq is raised/moved to another cpu but napi stays in the p=
oll_list
> of the softnet_data of the now offline cpu.
>=20
> reviewing dev_cpu_callback (net/core/dev.c) I did not find the poll_l=
ist
> is transfered to the new cpu. Do you think this could cause the stall=
 or
> did I miss something?
>=20
> Thx for your help.

Hi Frank

I believe you are right, I cant see where the poll_list transfert from
dead cpu to online cpu is done.

Do you want to prepare a patch ?

Thanks !