From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752159AbeDTTvU (ORCPT ); Fri, 20 Apr 2018 15:51:20 -0400 Received: from mail-ve1eur01on0101.outbound.protection.outlook.com ([104.47.1.101]:53792 "EHLO EUR01-VE1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751159AbeDTTvS (ORCPT ); Fri, 20 Apr 2018 15:51:18 -0400 Authentication-Results: 01.org; dkim=none (message not signed) header.d=none;01.org; dmarc=none action=none header.from=virtuozzo.com; Subject: Re: [kcov] watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [swapper/0:1] To: Yury Norov Cc: Fengguang Wu , Dmitry Vyukov , Kefeng Wang , linux-kernel@vger.kernel.org, lkp@01.org References: <20180419030135.nn454aqxlqdwe7ah@wfg-t540p.sh.intel.com> <20180420164523.zrjykc4jhx73cfjo@yury-thinkpad> From: Andrey Ryabinin Message-ID: <2c5e3996-d50b-416c-92aa-a554085cd656@virtuozzo.com> Date: Fri, 20 Apr 2018 22:52:07 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20180420164523.zrjykc4jhx73cfjo@yury-thinkpad> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [195.214.232.6] X-ClientProxiedBy: HE1PR0301CA0020.eurprd03.prod.outlook.com (2603:10a6:3:76::30) To AM6PR08MB3255.eurprd08.prod.outlook.com (2603:10a6:209:47::20) X-MS-PublicTrafficType: Email X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(4534165)(7168020)(4627221)(201703031133081)(201702281549075)(5600026)(2017052603328)(7153060)(7193020);SRVR:AM6PR08MB3255; 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[swapper/0:1] >>> [ 52.050031] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.17.0-rc1 #210 >>> [ 52.050031] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 >>> [ 52.050031] RIP: 0010:__sanitizer_cov_trace_pc+0x65/0x66: >>> __sanitizer_cov_trace_pc at kernel/kcov.c:111 >>> [ 52.050031] RSP: 0000:ffff88000fd43e40 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13 >>> [ 52.050031] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000017 >>> [ 52.050031] RDX: 0000000000000000 RSI: ffff88000fd3e000 RDI: 0000000000000002 >>> [ 52.050031] RBP: 0000000000050000 R08: 0000000000000008 R09: 0000000000000000 >>> [ 52.050031] R10: ffff88000fd3e000 R11: 00000000222e2c32 R12: ffffffff85565d90 >>> [ 52.050031] R13: 0000000000030f80 R14: 0000000000030f80 R15: 0000000000000000 >>> [ 52.050031] FS: 0000000000000000(0000) GS:ffff88001f600000(0000) knlGS:0000000000000000 >>> [ 52.050031] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >>> [ 52.050031] CR2: 0000000000000000 CR3: 0000000003c6a000 CR4: 00000000000006b0 >>> [ 52.050031] Call Trace: >>> [ 52.050031] find_first_bit+0x66/0x7c: >>> find_first_bit at lib/find_bit.c:106 (discriminator 1) >>> [ 52.050031] test_find_first_bit+0x3a/0x93 >> >> >> I suppose test_find_first_bit() needs a little more than zero cond_resched() calls. > > Or just decrease length of bitmap in this test. find_first_bit() takes > lion's share of time of the test. > Yeah, that would be better. > Start testing find_bit() with random-filled bitmap > find_next_bit: 240043 cycles, 164062 iterations > find_next_zero_bit: 312848 cycles, 163619 iterations > find_last_bit: 193748 cycles, 164062 iterations > find_first_bit: 177720874 cycles, 164062 iterations > > I'll test the patch and send it soon if you OK with it. > > Yury >