From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754684AbdKANCM (ORCPT ); Wed, 1 Nov 2017 09:02:12 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46756 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751525AbdKANCK (ORCPT ); Wed, 1 Nov 2017 09:02:10 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 11C31C059741 Authentication-Results: ext-mx08.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx08.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=jasowang@redhat.com Subject: Re: [PATCH net-next V2 3/3] tun: add eBPF based queue selection method To: "Michael S. Tsirkin" Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, willemdebruijn.kernel@gmail.com, tom@herbertland.com References: <1509445938-4345-1-git-send-email-jasowang@redhat.com> <1509445938-4345-4-git-send-email-jasowang@redhat.com> <20171031184002-mutt-send-email-mst@kernel.org> From: Jason Wang Message-ID: <43c86606-2911-768d-704f-8b25e04cb47b@redhat.com> Date: Wed, 1 Nov 2017 21:02:03 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <20171031184002-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Wed, 01 Nov 2017 13:02:10 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2017年11月01日 00:45, Michael S. Tsirkin wrote: >> +static void __tun_set_steering_ebpf(struct tun_struct *tun, >> + struct bpf_prog *new) >> +{ >> + struct bpf_prog *old; >> + >> + old = rtnl_dereference(tun->steering_prog); >> + rcu_assign_pointer(tun->steering_prog, new); >> + >> + if (old) { >> + synchronize_net(); >> + bpf_prog_destroy(old); >> + } >> +} >> + > Is this really called under rtnl? Yes it is __tun_chr_ioctl() will call rtnl_lock(). > If no then rtnl_dereference > is wrong. If yes I'm not sure you can call synchronize_net > under rtnl. > Are you worrying about the long wait? Looking at synchronize_net(), it does: void synchronize_net(void) {     might_sleep();     if (rtnl_is_locked())         synchronize_rcu_expedited();     else         synchronize_rcu(); } EXPORT_SYMBOL(synchronize_net); Thanks