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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 9F161C3404C for ; Thu, 20 Feb 2020 04:55:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6BE1724656 for ; Thu, 20 Feb 2020 04:55:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727806AbgBTEz1 (ORCPT ); Wed, 19 Feb 2020 23:55:27 -0500 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:41932 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727576AbgBTEz1 (ORCPT ); Wed, 19 Feb 2020 23:55:27 -0500 Received: from callcc.thunk.org (guestnat-104-133-8-109.corp.google.com [104.133.8.109] (may be forged)) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 01K4tEIg025137 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 19 Feb 2020 23:55:15 -0500 Received: by callcc.thunk.org (Postfix, from userid 15806) id 03B064211EF; Wed, 19 Feb 2020 23:55:13 -0500 (EST) Date: Wed, 19 Feb 2020 23:55:13 -0500 From: "Theodore Y. Ts'o" To: Shijie Luo Cc: linux-ext4@vger.kernel.org, jack@suse.cz, lutianxiong@huawei.com Subject: Re: [PATCH] ext4: add cond_resched() to __ext4_find_entry() Message-ID: <20200220045513.GD476845@mit.edu> References: <20200215080206.13293-1-luoshijie1@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200215080206.13293-1-luoshijie1@huawei.com> Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Sat, Feb 15, 2020 at 03:02:06AM -0500, Shijie Luo wrote: > We tested a soft lockup problem in linux 4.19 which could also > be found in linux 5.x. > > When dir inode takes up a large number of blocks, and if the > directory is growing when we are searching, it's possible the > restart branch could be called many times, and the do while loop > could hold cpu a long time. > > Here is the call trace in linux 4.19. > > [ 473.756186] Call trace: > [ 473.756196] dump_backtrace+0x0/0x198 > [ 473.756199] show_stack+0x24/0x30 > [ 473.756205] dump_stack+0xa4/0xcc > [ 473.756210] watchdog_timer_fn+0x300/0x3e8 > [ 473.756215] __hrtimer_run_queues+0x114/0x358 > [ 473.756217] hrtimer_interrupt+0x104/0x2d8 > [ 473.756222] arch_timer_handler_virt+0x38/0x58 > [ 473.756226] handle_percpu_devid_irq+0x90/0x248 > [ 473.756231] generic_handle_irq+0x34/0x50 > [ 473.756234] __handle_domain_irq+0x68/0xc0 > [ 473.756236] gic_handle_irq+0x6c/0x150 > [ 473.756238] el1_irq+0xb8/0x140 > [ 473.756286] ext4_es_lookup_extent+0xdc/0x258 [ext4] > [ 473.756310] ext4_map_blocks+0x64/0x5c0 [ext4] > [ 473.756333] ext4_getblk+0x6c/0x1d0 [ext4] > [ 473.756356] ext4_bread_batch+0x7c/0x1f8 [ext4] > [ 473.756379] ext4_find_entry+0x124/0x3f8 [ext4] > [ 473.756402] ext4_lookup+0x8c/0x258 [ext4] > [ 473.756407] __lookup_hash+0x8c/0xe8 > [ 473.756411] filename_create+0xa0/0x170 > [ 473.756413] do_mkdirat+0x6c/0x140 > [ 473.756415] __arm64_sys_mkdirat+0x28/0x38 > [ 473.756419] el0_svc_common+0x78/0x130 > [ 473.756421] el0_svc_handler+0x38/0x78 > [ 473.756423] el0_svc+0x8/0xc > [ 485.755156] watchdog: BUG: soft lockup - CPU#2 stuck for 22s! [tmp:5149] > > Add cond_resched() to avoid soft lockup and to provide a better > system responding. > > Signed-off-by: Shijie Luo Thanks, applied. - Ted