From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH net] net: fix race on decreasing number of TX queues Date: Wed, 14 Feb 2018 14:16:13 -0500 (EST) Message-ID: <20180214.141613.66054944399992487.davem@davemloft.net> References: <20180213053531.13080-1-jakub.kicinski@netronome.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: john.fastabend@gmail.com, alexander.duyck@gmail.com, tom@herbertland.com, netdev@vger.kernel.org, oss-drivers@netronome.com To: jakub.kicinski@netronome.com Return-path: Received: from shards.monkeyblade.net ([184.105.139.130]:57484 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1162439AbeBNTQP (ORCPT ); Wed, 14 Feb 2018 14:16:15 -0500 In-Reply-To: <20180213053531.13080-1-jakub.kicinski@netronome.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Jakub Kicinski Date: Mon, 12 Feb 2018 21:35:31 -0800 > netif_set_real_num_tx_queues() can be called when netdev is up. > That usually happens when user requests change of number of > channels/rings with ethtool -L. The procedure for changing > the number of queues involves resetting the qdiscs and setting > dev->num_tx_queues to the new value. When the new value is > lower than the old one, extra care has to be taken to ensure > ordering of accesses to the number of queues vs qdisc reset. > > Currently the queues are reset before new dev->num_tx_queues > is assigned, leaving a window of time where packets can be > enqueued onto the queues going down, leading to a likely > crash in the drivers, since most drivers don't check if TX > skbs are assigned to an active queue. > > Fixes: e6484930d7c7 ("net: allocate tx queues in register_netdevice") > Signed-off-by: Jakub Kicinski > --- > Also reported: http://lists.openwall.net/netdev/2017/04/26/211, > GSO just made it more likely. Looks good, applied and queued up for -stable, thanks!