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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 E7F1DC18E5B for ; Tue, 17 Mar 2020 01:41:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C84BD20679 for ; Tue, 17 Mar 2020 01:41:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726619AbgCQBlb (ORCPT ); Mon, 16 Mar 2020 21:41:31 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:11652 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726597AbgCQBlb (ORCPT ); Mon, 16 Mar 2020 21:41:31 -0400 Received: from DGGEMS407-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 85B2E639728DADF0C2D2; Tue, 17 Mar 2020 09:41:29 +0800 (CST) Received: from [127.0.0.1] (10.133.210.141) by DGGEMS407-HUB.china.huawei.com (10.3.19.207) with Microsoft SMTP Server id 14.3.487.0; Tue, 17 Mar 2020 09:41:29 +0800 Subject: Re: [locks] 6d390e4b5d: will-it-scale.per_process_ops -96.6% regression To: Linus Torvalds , Jeff Layton CC: NeilBrown , kernel test robot , LKML , , Bruce Fields , Al Viro References: <20200308140314.GQ5972@shao2-debian> <875zfbvrbm.fsf@notabene.neil.brown.name> <0066a9f150a55c13fcc750f6e657deae4ebdef97.camel@kernel.org> <87v9nattul.fsf@notabene.neil.brown.name> <87o8t2tc9s.fsf@notabene.neil.brown.name> <877dznu0pk.fsf@notabene.neil.brown.name> <87pndcsxc6.fsf@notabene.neil.brown.name> From: yangerkun Message-ID: <7c8d3752-6573-ab83-d0af-f3dd4fc373f5@huawei.com> Date: Tue, 17 Mar 2020 09:41:27 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.133.210.141] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/3/17 1:26, Linus Torvalds wrote: > On Mon, Mar 16, 2020 at 4:07 AM Jeff Layton wrote: >> >> >> + /* >> + * If fl_blocker is NULL, it won't be set again as this thread "owns" >> + * the lock and is the only one that might try to claim the lock. >> + * Because fl_blocker is explicitly set last during a delete, it's >> + * safe to locklessly test to see if it's NULL. If it is, then we know >> + * that no new locks can be inserted into its fl_blocked_requests list, >> + * and we can therefore avoid doing anything further as long as that >> + * list is empty. >> + */ >> + if (!smp_load_acquire(&waiter->fl_blocker) && >> + list_empty(&waiter->fl_blocked_requests)) >> + return status; > > Ack. This looks sane to me now. > > yangerkun - how did you find the original problem?\ While try to fix CVE-2019-19769, add some log in __locks_wake_up_blocks help me to rebuild the problem soon. This help me to discern the problem soon. > > Would you mind using whatever stress test that caused commit > 6d390e4b5d48 ("locks: fix a potential use-after-free problem when > wakeup a waiter") with this patch? And if you did it analytically, > you're a champ and should look at this patch too! I will try to understand this patch, and if it's looks good to me, will do the performance test! Thanks