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 X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 389CAC10DCE for ; Wed, 18 Mar 2020 05:27:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 132AA20663 for ; Wed, 18 Mar 2020 05:27:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727003AbgCRF14 (ORCPT ); Wed, 18 Mar 2020 01:27:56 -0400 Received: from mga17.intel.com ([192.55.52.151]:55088 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726478AbgCRF14 (ORCPT ); Wed, 18 Mar 2020 01:27:56 -0400 IronPort-SDR: zw2HLDlMOcu2DBo3Yy2tZdFq6JirdkSixExbqtuwI08s1f0Tdnom/cV5NFMh5fGur7zgR1K8IU LvPhWCY9mIqQ== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Mar 2020 22:27:56 -0700 IronPort-SDR: uZEuCHI+tEzJyoqs0pj1nsWFmlhiL3CqHyjZh9IskV9mrJQUfPSjNCQIs+AwzKnKtdhWXFt1tu TFHnYSwAOQvw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,566,1574150400"; d="scan'208";a="263274199" Received: from blu2-mobl3.ccr.corp.intel.com (HELO [10.254.212.140]) ([10.254.212.140]) by orsmga002.jf.intel.com with ESMTP; 17 Mar 2020 22:27:54 -0700 Cc: baolu.lu@linux.intel.com, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] iommu/vt-d: silence a RCU-list debugging warning To: Qian Cai , jroedel@suse.de References: <20200317150326.1659-1-cai@lca.pw> From: Lu Baolu Message-ID: <36b9e69b-ee3f-c17d-1788-64448ce8bc14@linux.intel.com> Date: Wed, 18 Mar 2020 13:27:53 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200317150326.1659-1-cai@lca.pw> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/3/17 23:03, Qian Cai wrote: > dmar_find_atsr() calls list_for_each_entry_rcu() outside of an RCU read > side critical section but with dmar_global_lock held. Silence this > false positive. > > drivers/iommu/intel-iommu.c:4504 RCU-list traversed in non-reader section!! > 1 lock held by swapper/0/1: > #0: ffffffff9755bee8 (dmar_global_lock){+.+.}, at: intel_iommu_init+0x1a6/0xe19 > > Call Trace: > dump_stack+0xa4/0xfe > lockdep_rcu_suspicious+0xeb/0xf5 > dmar_find_atsr+0x1ab/0x1c0 > dmar_parse_one_atsr+0x64/0x220 > dmar_walk_remapping_entries+0x130/0x380 > dmar_table_init+0x166/0x243 > intel_iommu_init+0x1ab/0xe19 > pci_iommu_init+0x1a/0x44 > do_one_initcall+0xae/0x4d0 > kernel_init_freeable+0x412/0x4c5 > kernel_init+0x19/0x193 > > Signed-off-by: Qian Cai How about changing the commit subject to "iommu/vt-d: Silence RCU-list debugging warning in dmar_find_atsr()"? Acked-by: Lu Baolu Best regards, baolu > --- > drivers/iommu/intel-iommu.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c > index 4be549478691..ef0a5246700e 100644 > --- a/drivers/iommu/intel-iommu.c > +++ b/drivers/iommu/intel-iommu.c > @@ -4501,7 +4501,8 @@ static struct dmar_atsr_unit *dmar_find_atsr(struct acpi_dmar_atsr *atsr) > struct dmar_atsr_unit *atsru; > struct acpi_dmar_atsr *tmp; > > - list_for_each_entry_rcu(atsru, &dmar_atsr_units, list) { > + list_for_each_entry_rcu(atsru, &dmar_atsr_units, list, > + dmar_rcu_check()) { > tmp = (struct acpi_dmar_atsr *)atsru->hdr; > if (atsr->segment != tmp->segment) > continue; >