From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D23B2C433EF for ; Thu, 21 Jul 2022 14:05:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230034AbiGUOFM (ORCPT ); Thu, 21 Jul 2022 10:05:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44446 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229480AbiGUOFK (ORCPT ); Thu, 21 Jul 2022 10:05:10 -0400 Received: from mail-yb1-xb29.google.com (mail-yb1-xb29.google.com [IPv6:2607:f8b0:4864:20::b29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6C2B3637D for ; Thu, 21 Jul 2022 07:05:09 -0700 (PDT) Received: by mail-yb1-xb29.google.com with SMTP id e69so2955918ybh.2 for ; Thu, 21 Jul 2022 07:05:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=5RleLJjzore0hrU6Ayka4+YUanubDQ3xuIKFETK5cTk=; b=W+edDvnLZ9Sr9mcSIQ7TiS0u8MtrXcbwNUizswad0LOHm3QTu2DE1BmhPPtbXxYudZ ukWmVX0gHJ/OjvEUWvBYiJCvDhFoipqP7oQ6920RbA2bS3PrndgzbWOn/bSBfL2Ywdej xTPnRQeShtZEbvuqyEoDVmkeXu1aVGAS5sjDq9Y6zyoVVVfzgwa4J/yW17hmqXoEXUYb iFkcfmM2+7cXVRG8bMynC9RDHETWVH0E3dACthWCGLe/KvQjtjgcSDp+OLEYEOl61lsa pcR+AiBYE2tfOtnyqh0SdPLLR3jNYxxJS0tPCp4Yx09GGs/kwJvVga68RlfZsYEbSZVe Qt8Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=5RleLJjzore0hrU6Ayka4+YUanubDQ3xuIKFETK5cTk=; b=33KLTRjHnpnf5EeN7YkdnZPKpp9KJRT/lHDsqfVzmlRNCd4wqtO0mt2IoC+pTE2zAz QwUxk+osRFRlyvRPL2cZj8oeLxvelvnZ2w9ELT4Bwwji78cut8ueO0dVNNO/ne3DERv9 GtBKRNZtH/SZBMCQNiYPEQLRWa0D6LPmLHDqMWZh0sleW4J9Ufqyk4iqmh6OAWfsSiEY VJ34ccf9/D5b7mFzM3+CrrmJSKPNhpTkugfm+g8Xgzxb/NvOwgXviasrbXcWiIq4eH7V uQaCYZMI0Eeug8040CcEKWORVNbU3o0k2XR0nekY2ocriEq2YDfFMkukrEtFpKkzRPLN LOrw== X-Gm-Message-State: AJIora+JpOTrmddljpyJCCG3/cZQ01lAI8/bzhN2ChoksnXlECP6s2Q5 zDXaiX5bbyW3PQaHF+RckGnUZJtmZdv3cP/5LLvrcw== X-Google-Smtp-Source: AGRyM1v9hiMjb+QWMEdJeXGRq/47gCmys36Vgg6njVoQP5wHj8e85n7mqoPDzhe5lc7M3J7dvSoQt44DVg8cX+U99Uk= X-Received: by 2002:a25:aacc:0:b0:66f:f1ca:409c with SMTP id t70-20020a25aacc000000b0066ff1ca409cmr30608213ybi.36.1658412308298; Thu, 21 Jul 2022 07:05:08 -0700 (PDT) MIME-Version: 1.0 References: <20220721120316.17070-1-ap420073@gmail.com> In-Reply-To: <20220721120316.17070-1-ap420073@gmail.com> From: Eric Dumazet Date: Thu, 21 Jul 2022 16:04:57 +0200 Message-ID: Subject: Re: [PATCH net] net: mld: do not use system_wq in the mld To: Taehee Yoo Cc: David Miller , Jakub Kicinski , Paolo Abeni , Hideaki YOSHIFUJI , David Ahern , netdev Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, Jul 21, 2022 at 2:03 PM Taehee Yoo wrote: > > mld works are supposed to be executed in mld_wq. > But mld_{query | report}_work() calls schedule_delayed_work(). > schedule_delayed_work() internally uses system_wq. > So, this would cause the reference count leak. I do not think the changelog is accurate. At least I do not understand it yet. We can not unload the ipv6 module, so destroy_workqueue(mld_wq) is never used. > > splat looks like: > unregister_netdevice: waiting for br1 to become free. Usage count = 2 > leaked reference. > ipv6_add_dev+0x3a5/0x1070 > addrconf_notify+0x4f3/0x1760 > notifier_call_chain+0x9e/0x180 > register_netdevice+0xd10/0x11e0 > br_dev_newlink+0x27/0x100 [bridge] > __rtnl_newlink+0xd85/0x14e0 > rtnl_newlink+0x5f/0x90 > rtnetlink_rcv_msg+0x335/0x9a0 > netlink_rcv_skb+0x121/0x350 > netlink_unicast+0x439/0x710 > netlink_sendmsg+0x75f/0xc00 > ____sys_sendmsg+0x694/0x860 > ___sys_sendmsg+0xe9/0x160 > __sys_sendmsg+0xbe/0x150 > do_syscall_64+0x3b/0x90 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > Fixes: f185de28d9ae ("mld: add new workqueues for process mld events") > Signed-off-by: Taehee Yoo > --- > net/ipv6/mcast.c | 14 ++++++++------ > 1 file changed, 8 insertions(+), 6 deletions(-) > > diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c > index 7f695c39d9a8..87c699d57b36 100644 > --- a/net/ipv6/mcast.c > +++ b/net/ipv6/mcast.c > @@ -1522,7 +1522,6 @@ static void mld_query_work(struct work_struct *work) > > if (++cnt >= MLD_MAX_QUEUE) { > rework = true; > - schedule_delayed_work(&idev->mc_query_work, 0); > break; > } > } > @@ -1533,8 +1532,10 @@ static void mld_query_work(struct work_struct *work) > __mld_query_work(skb); > mutex_unlock(&idev->mc_lock); > > - if (!rework) > - in6_dev_put(idev); > + if (rework && queue_delayed_work(mld_wq, &idev->mc_query_work, 0)) It seems the 'real issue' was that schedule_delayed_work(&idev->mc_query_work, 0) could be a NOP because the work queue was already scheduled ? > + return; > + > + in6_dev_put(idev); > } > > /* called with rcu_read_lock() */ > @@ -1624,7 +1625,6 @@ static void mld_report_work(struct work_struct *work) > > if (++cnt >= MLD_MAX_QUEUE) { > rework = true; > - schedule_delayed_work(&idev->mc_report_work, 0); > break; > } > } > @@ -1635,8 +1635,10 @@ static void mld_report_work(struct work_struct *work) > __mld_report_work(skb); > mutex_unlock(&idev->mc_lock); > > - if (!rework) > - in6_dev_put(idev); > + if (rework && queue_delayed_work(mld_wq, &idev->mc_report_work, 0)) > + return; > + > + in6_dev_put(idev); > } > > static bool is_in(struct ifmcaddr6 *pmc, struct ip6_sf_list *psf, int type, > -- > 2.17.1 >