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=unavailable 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 9DE68C43215 for ; Wed, 20 Nov 2019 06:18:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7FE322243E for ; Wed, 20 Nov 2019 06:18:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727269AbfKTGSa (ORCPT ); Wed, 20 Nov 2019 01:18:30 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:7149 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726014AbfKTGSa (ORCPT ); Wed, 20 Nov 2019 01:18:30 -0500 Received: from DGGEMS405-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id 2070099B356093EE0547; Wed, 20 Nov 2019 14:18:27 +0800 (CST) Received: from [127.0.0.1] (10.133.224.57) by DGGEMS405-HUB.china.huawei.com (10.3.19.205) with Microsoft SMTP Server id 14.3.439.0; Wed, 20 Nov 2019 14:18:19 +0800 Subject: Re: [PATCH v2] pci: lock the pci_cfg_wait queue for the consistency of data To: Bjorn Helgaas CC: , , , , , , , , , , References: <20191119202305.GA214858@google.com> From: Xiang Zheng Message-ID: Date: Wed, 20 Nov 2019 14:18:18 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.1.0 MIME-Version: 1.0 In-Reply-To: <20191119202305.GA214858@google.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.133.224.57] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/11/20 4:23, Bjorn Helgaas wrote: > On Tue, Nov 19, 2019 at 09:15:45AM +0800, Xiang Zheng wrote: >> Commit "7ea7e98fd8d0" suggests that the "pci_lock" is sufficient, >> and all the callers of pci_wait_cfg() are wrapped with the "pci_lock". >> >> However, since the commit "cdcb33f98244" merged, the accesses to >> the pci_cfg_wait queue are not safe anymore. A "pci_lock" is >> insufficient and we need to hold an additional queue lock while >> read/write the wait queue. >> >> So let's use the add_wait_queue()/remove_wait_queue() instead of >> __add_wait_queue()/__remove_wait_queue(). Also move the wait queue >> functionality around the "schedule()" function to avoid reintroducing >> the deadlock addressed by "cdcb33f98244". > > Procedural nits: > > - Run "git log --oneline drivers/pci/access.c" and follow the > convention, e.g., starts with "PCI: " and first subsequent word is > capitalized. > > - Use conventional commit references, e.g., 7ea7e98fd8d0 ("PCI: > Block on access to temporarily unavailable pci device") and > cdcb33f98244 ("PCI: Avoid possible deadlock on pci_lock and > p->pi_lock") > > - IIRC you found that this actually caused a panic; please include > the lore.kernel.org URL to that report. > Got it, I will address these nits. > You can wait for a while to see if there are more substantive comments > to address before posting a v3. > OK. >> Signed-off-by: Xiang Zheng >> Cc: Heyi Guo >> Cc: Biaoxiang Ye >> --- >> >> v2: >> - Move the wait queue functionality around the "schedule()" function to >> avoid reintroducing the deadlock addressed by "cdcb33f98244" >> >> --- >> >> drivers/pci/access.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/pci/access.c b/drivers/pci/access.c >> index 2fccb5762c76..09342a74e5ea 100644 >> --- a/drivers/pci/access.c >> +++ b/drivers/pci/access.c >> @@ -207,14 +207,14 @@ static noinline void pci_wait_cfg(struct pci_dev *dev) >> { >> DECLARE_WAITQUEUE(wait, current); >> >> - __add_wait_queue(&pci_cfg_wait, &wait); >> do { >> set_current_state(TASK_UNINTERRUPTIBLE); >> raw_spin_unlock_irq(&pci_lock); >> + add_wait_queue(&pci_cfg_wait, &wait); >> schedule(); >> + remove_wait_queue(&pci_cfg_wait, &wait); >> raw_spin_lock_irq(&pci_lock); >> } while (dev->block_cfg_access); >> - __remove_wait_queue(&pci_cfg_wait, &wait); >> } >> >> /* Returns 0 on success, negative values indicate error. */ >> -- >> 2.19.1 >> >> > > . > -- Thanks, Xiang