From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751741AbbLMWpv (ORCPT ); Sun, 13 Dec 2015 17:45:51 -0500 Received: from mail-pa0-f51.google.com ([209.85.220.51]:35107 "EHLO mail-pa0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751630AbbLMWpt (ORCPT ); Sun, 13 Dec 2015 17:45:49 -0500 Message-ID: <1450046747.9768.48.camel@edumazet-glaptop2.roam.corp.google.com> Subject: Re: [PATCH 3.16.y-ckt 009/126] sit: fix sit0 percpu double allocations From: Eric Dumazet To: Ben Hutchings Cc: Luis Henriques , Eric Dumazet , Steffen Klassert , "David S. Miller" , linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Date: Sun, 13 Dec 2015 14:45:47 -0800 In-Reply-To: <1450043388.3944.6.camel@decadent.org.uk> References: <1449653896-5236-1-git-send-email-luis.henriques@canonical.com> <1449653896-5236-10-git-send-email-luis.henriques@canonical.com> <1449893906.3836.5.camel@decadent.org.uk> <20151213185429.GA31826@charon> <1450038035.3944.2.camel@decadent.org.uk> <1450039390.9768.30.camel@edumazet-glaptop2.roam.corp.google.com> <1450041762.3944.4.camel@decadent.org.uk> <1450043078.9768.37.camel@edumazet-glaptop2.roam.corp.google.com> <1450043388.3944.6.camel@decadent.org.uk> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4-0ubuntu2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 2015-12-13 at 21:49 +0000, Ben Hutchings wrote: > On Sun, 2015-12-13 at 13:44 -0800, Eric Dumazet wrote: > > On Sun, 2015-12-13 at 21:22 +0000, Ben Hutchings wrote: > > > On Sun, 2015-12-13 at 12:43 -0800, Eric Dumazet wrote: > > > > > > 1) Sorry Ben, I do not understand the problem you mention. > > > > What is a partially initialized device exactly ? > > > > > > A tunnel device which is registered but hasn't had its private > > > structure fully initialised yet. > > > > And you see this happening after my patch ? I am blind. > > > > I am referring to current linux kernel, not to a backport to pre 3.18 > > kernels, that was not considered when I wrote this patch. > > > > By the time ipip6_fb_tunnel_init() is called, dev->tstats had been > > already allocated in ipip6_tunnel_init(), so what is missing ? > > You moved this initialisation below the registration: > > > ipip6_tunnel_clone_6rd(sitn->fb_tunnel_dev, sitn); > > ipip6_fb_tunnel_init(sitn->fb_tunnel_dev); Okay, so what is the exact problem you are seeing Ben ? ipip6_tunnel_clone_6rd() looks to not contain a fatal race or mem leak. Note that ipip6_tunnel_clone_6rd() can be called later from ioctl() path. ipip6_fb_tunnel_init() must be done once device is ready, as it publishes state for packet processing. rcu_assign_pointer(sitn->tunnels_wc[0], tunnel); Looks like a rather correct way to register a device : init all fields, then publish the RCU protected pointer for packets to catch it. Really, I do not see a problem, please elaborate.