From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932852AbeB1TCr (ORCPT ); Wed, 28 Feb 2018 14:02:47 -0500 Received: from mail2.candelatech.com ([208.74.158.173]:57724 "EHLO mail2.candelatech.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932088AbeB1TCp (ORCPT ); Wed, 28 Feb 2018 14:02:45 -0500 Subject: Re: [PATCH net] virtio-net: disable NAPI only when enabled during XDP set To: David Miller , jasowang@redhat.com References: <1519813204-10002-1-git-send-email-jasowang@redhat.com> <20180228.122231.1811613646832502397.davem@davemloft.net> Cc: mst@redhat.com, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org From: Ben Greear Organization: Candela Technologies Message-ID: Date: Wed, 28 Feb 2018 11:02:42 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.0 MIME-Version: 1.0 In-Reply-To: <20180228.122231.1811613646832502397.davem@davemloft.net> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/28/2018 09:22 AM, David Miller wrote: > From: Jason Wang > Date: Wed, 28 Feb 2018 18:20:04 +0800 > >> We try to disable NAPI to prevent a single XDP TX queue being used by >> multiple cpus. But we don't check if device is up (NAPI is enabled), >> this could result stall because of infinite wait in >> napi_disable(). Fixing this by checking device state through >> netif_running() before. >> >> Fixes: 4941d472bf95b ("virtio-net: do not reset during XDP set") >> Signed-off-by: Jason Wang > > Yes, mis-paired NAPI enable/disable are really a pain. > > Probably, we can do something in the interfaces or mechanisms to make > this less error prone and less fragile. > > Anyways, applied and queued up for -stable, thanks! I just hit a similar bug in ath10k. It seems like napi has plenty of free bit flags so it could keep track of 'is-enabled' state and allow someone to call napi_disable multiple times w/out deadlocking. Thanks, Ben -- Ben Greear Candela Technologies Inc http://www.candelatech.com