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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5F619C38142 for ; Wed, 18 Jan 2023 01:10:45 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B44646B0072; Tue, 17 Jan 2023 20:10:44 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id AA6066B0075; Tue, 17 Jan 2023 20:10:44 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8F8006B0078; Tue, 17 Jan 2023 20:10:44 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 81A626B0072 for ; Tue, 17 Jan 2023 20:10:44 -0500 (EST) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 5815F1C605A for ; Wed, 18 Jan 2023 01:10:44 +0000 (UTC) X-FDA: 80366140008.14.F5B8410 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by imf14.hostedemail.com (Postfix) with ESMTP id EDFF6100009 for ; Wed, 18 Jan 2023 01:10:40 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=jR92Ivh8; arc=reject ("signature check failed: fail, {[1] = sig:microsoft.com:reject}"); spf=pass (imf14.hostedemail.com: domain of feng.tang@intel.com designates 134.134.136.24 as permitted sender) smtp.mailfrom=feng.tang@intel.com; dmarc=pass (policy=none) header.from=intel.com ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1674004241; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=G+0mvfH6XaBFfgNEMNsdL3J+JMc/pt+7o6surz8EAL8=; b=jYYJwr5NBDtPa+Qt4AR7JfE3EqaU51731XKJlYRVaH/2j05vxC3mmarsiEZoHcBlki6WXA Eg3p/akt6kGux4ghv8VZZNY04VlVT+WFKLq4L8HhsSV5SRakRRCC57u5OVqku99x5aL7FB mIkeTWcr6XZNqILCWqOAxY/Sw4uYajA= ARC-Authentication-Results: i=2; imf14.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=jR92Ivh8; arc=reject ("signature check failed: fail, {[1] = sig:microsoft.com:reject}"); spf=pass (imf14.hostedemail.com: domain of feng.tang@intel.com designates 134.134.136.24 as permitted sender) smtp.mailfrom=feng.tang@intel.com; dmarc=pass (policy=none) header.from=intel.com ARC-Seal: i=2; s=arc-20220608; d=hostedemail.com; t=1674004241; a=rsa-sha256; cv=fail; b=RoLPXPwD1UfIzmZS1fi95tk6ikGbwJCG3QJE1ZnWdnAwbQsAvqrwQIgzvDs5lmndYjQj/5 hOjCuer7urLNf17PJUbc7u1B5SMvh+9fUZWbBiFuQPRXUMU4wvsOskXZEkk8Mdo3WHOBGt hW/+780MU8urQLqke6O4O/CxX2dIVpo= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1674004241; x=1705540241; h=date:from:to:cc:subject:message-id:references: in-reply-to:mime-version; bh=aYL77OZpwXg+cgwTPtNR/wH0EaNDSKb2auj2Ip7d31k=; b=jR92Ivh8yYhBdiykG1jCy4el+Gy+a/XJnSqLOqTkHowLRpsTHTGZcaJ/ FE1X/GE6jLfu2YkIZi74nipZb1QglZl9KsWSPokQxVsYgSoC6qV2kVE7u pjHt9COLKvATmlfO35LN3mdx6bYBkHCN8ENWc19/2ampu8rS6VXvEuS9t ulNRu22Svzrq2GqwTSk5m1lnk2zSUaGzNMVW01i4PAGLTSx/57a/8UXLO gDB7Cw4FzMP5dQTbUAEZRldaV2enhTRGknCWVXI/oG6IoxL56gZW3SqyV /QxmtYr0EsiTTIWB+D7MYp2mn8faj2KFDtKXvJ5zCamgPMvwjAkDt/JXa w==; X-IronPort-AV: E=McAfee;i="6500,9779,10593"; a="326140374" X-IronPort-AV: E=Sophos;i="5.97,224,1669104000"; d="scan'208";a="326140374" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Jan 2023 17:10:39 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6500,9779,10593"; a="748247675" X-IronPort-AV: E=Sophos;i="5.97,224,1669104000"; d="scan'208";a="748247675" Received: from fmsmsx602.amr.corp.intel.com ([10.18.126.82]) by FMSMGA003.fm.intel.com with ESMTP; 17 Jan 2023 17:10:38 -0800 Received: from fmsmsx610.amr.corp.intel.com (10.18.126.90) by fmsmsx602.amr.corp.intel.com (10.18.126.82) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.16; Tue, 17 Jan 2023 17:10:38 -0800 Received: from fmsedg602.ED.cps.intel.com (10.1.192.136) by fmsmsx610.amr.corp.intel.com (10.18.126.90) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.16 via Frontend Transport; Tue, 17 Jan 2023 17:10:38 -0800 Received: from NAM11-DM6-obe.outbound.protection.outlook.com (104.47.57.171) by edgegateway.intel.com (192.55.55.71) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.16; Tue, 17 Jan 2023 17:10:38 -0800 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=NsxbJ/3cl47wxrT4lwxZ78w8tqcM7YuBDGf5qc41iHcw3yFgehVVUONIsQQyM2Dunrhh8w19gxvvzQ2P54uRwJcfHKAem7gTDFBVs2wEVFW11F4Q+BajHf7cJR15kZ+DRsHVv23iLc2dp9HbQox1V3SJYOkcgJaUWrSc5qb15inlweIXR+FDgPUiLRdOwn5KFaOoaVFXIMLwt0RyhnOlb+Lyr05YbnwpP0LSHusAfvsSd5EpsWgR43H1OyP4h9WieUguaFfeOFncED06xMlKja8pz8kda+5Gzw+J6VwBFM85LhTp7Ciz1Kkq9L/sBLia/sAEDu72YMA2JZSymXM5UA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=G+0mvfH6XaBFfgNEMNsdL3J+JMc/pt+7o6surz8EAL8=; b=KI8EyKdBUeVM2Qqi+dYxnG286p1o4Wq8/hscFFqG1NBVbkjSmU5qgl0UpKsR9HkjlALOlSSRsxo59IA01Uc2xfsXfJbRmRS2Ulo/5eg19NfFJzlgoal8f+5NFgTs3wVRpeToPYE0aAMa5OSIDDvyy9gJZNpnKqET2jcHqkEAjcy4EmMNY+afohBg3XqUvmdjKeZ9x4NoXGqESDjTfxMiRRMwfQoi7HS/rme2jb6lkC4juFSrg8+7o7JHOYl4HBT1zaTH1ranLXRfjqLwjsF1zCbcNx/a73zK3+4KeL9M4H8dL5jYZ1f6tAOGoqM2ed5gcMTipzGqM9xuLcDX6A5/WA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=intel.com; dmarc=pass action=none header.from=intel.com; dkim=pass header.d=intel.com; arc=none Received: from MN0PR11MB6304.namprd11.prod.outlook.com (2603:10b6:208:3c0::7) by CY8PR11MB6913.namprd11.prod.outlook.com (2603:10b6:930:5b::9) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5986.23; Wed, 18 Jan 2023 01:10:34 +0000 Received: from MN0PR11MB6304.namprd11.prod.outlook.com ([fe80::868b:ff1f:d827:188d]) by MN0PR11MB6304.namprd11.prod.outlook.com ([fe80::868b:ff1f:d827:188d%3]) with mapi id 15.20.5986.023; Wed, 18 Jan 2023 01:10:34 +0000 Date: Wed, 18 Jan 2023 09:07:50 +0800 From: Feng Tang To: Linus Torvalds CC: Vlastimil Babka , "Sang, Oliver" , Mike Kravetz , "oe-lkp@lists.linux.dev" , lkp , "linux-kernel@vger.kernel.org" , Jann Horn , "Song, Youquan" , Andrea Arcangeli , Jan Kara , John Hubbard , "Kirill A . Shutemov" , Matthew Wilcox , Michal Hocko , Muchun Song , Andrew Morton , "linux-mm@kvack.org" , Hyeonggon Yoo <42.hyeyoo@gmail.com>, "Yin, Fengwei" , Subject: Re: [linus:master] [hugetlb] 7118fc2906: kernel_BUG_at_lib/list_debug.c Message-ID: References: <202301170941.49728982-oliver.sang@intel.com> <2f483247-da76-9ec9-3e51-f690939f4585@suse.cz> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: SG2PR02CA0038.apcprd02.prod.outlook.com (2603:1096:3:18::26) To MN0PR11MB6304.namprd11.prod.outlook.com (2603:10b6:208:3c0::7) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MN0PR11MB6304:EE_|CY8PR11MB6913:EE_ X-MS-Office365-Filtering-Correlation-Id: 85cc8bc3-84ec-409e-5c9a-08daf8f0cce0 X-LD-Processed: 46c98d88-e344-4ed4-8496-4ed7712e255d,ExtAddr X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:MN0PR11MB6304.namprd11.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230022)(7916004)(376002)(346002)(136003)(366004)(39860400002)(396003)(451199015)(478600001)(6486002)(107886003)(6666004)(53546011)(38100700002)(86362001)(6506007)(33716001)(186003)(9686003)(82960400001)(26005)(6512007)(83380400001)(66476007)(8676002)(8936002)(7416002)(4326008)(5660300002)(44832011)(66556008)(2906002)(54906003)(6916009)(41300700001)(66946007)(316002);DIR:OUT;SFP:1102; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?90Lr60P8X6WFWLwtpMCqhQrK7F2qCOYDHdDT+ysV1QaBNgUxigmtykUBCDv6?= =?us-ascii?Q?1qZpbaXU3l5OBP1MeLdev2lRBwwIcUCgObPJqQqOMcrSD1ox4NQwFMCVb3HM?= =?us-ascii?Q?/y28OLHYnqf/PAZoT6tZaRdwmF0W0tjip/a8k9dwKGK97njaWEcRDdaKQlRF?= =?us-ascii?Q?HHri8xHZparqfiF6bfwkUtTgXknSVz6T9fQlBRh1sRSUs052PIeat+0/qfwa?= =?us-ascii?Q?ynvTZylmDoDcu5lPwoRI3CgJlfuDAQ1AIJQk+zuH3B/TjiO7lOc6usZb8v4D?= =?us-ascii?Q?mDxfJ1avhG1Zo+ZlUijdfDoH4ASJKdpLHq5XDNOuGZhAi63gcnb3tZxiPP4C?= =?us-ascii?Q?jUdSr2Alrj9hssGv8cbcsEQCL7VZYdXqUZcUxEMJ9bWFN+SmIAaTX7GqNWxT?= =?us-ascii?Q?4Gwmd4TMExUq2VsIkT60xjQRVICgqy+uOkETaafi3i3/nvIel74tGdiz+p2t?= =?us-ascii?Q?0miT1bzR7gqTUq+lNQNm0uuvZ3Ow4TZQfPftPTlvR9X/i6PM6Wr4McbLyhG0?= =?us-ascii?Q?iR9ShmnZx5fQzoGa+gFL5nOa/F6ppRzID34x47T9pjpBZ3IQVW6nOqcu/X36?= =?us-ascii?Q?ubrl5KMe9nGl6buFVf9OT0htGv1h2FNBtYewFp/JCyV/HjVREI3rz2HT1Vay?= =?us-ascii?Q?ExK7dd9cWUwFNwwJJU99Hb9KEzQfnBTBXF24gOwO24oPu4fnfCb3puzGKykB?= =?us-ascii?Q?Z6Y7ph9TPmNK2hHkJQPHELKeW3o3ASfvpRcBnvq9yH4C0wPbLV6jeyqWs2BX?= =?us-ascii?Q?TyoSGPNEoUtyTGSLxu+NztlJ5ZKJWhgq9iZtx94jBPV2bLrnxE7QJ/BVC3Yt?= =?us-ascii?Q?vcCP6Oni1Rs8c8JTwtfZMNDcoIWBrxWupJGv4Ja/mBnqIw7hhzCYSYt3Vwgw?= =?us-ascii?Q?hHaMm/laNl0yL5Z80AEUFnC0y57oQuo/dlUjvcwWmrtQs5qrx0ID4qbPhE4h?= =?us-ascii?Q?U3wo/D936u+CqpJUBvoc2ltOOsr5nG5txX3zvS2GcbUUmsh/V6mI4vC7n8mp?= =?us-ascii?Q?i/sr/mctsLu1doCmvWEpfNQodQHXUA6EZ3x/ZDTHDv8ZOgTLuzWd1q+I1ojm?= =?us-ascii?Q?TfYj1ZswxXsjG1ZyMjPRtOrLWCEP4fi+SiV1+cZc1q/EwO9DF8ANUWGoXgfv?= =?us-ascii?Q?g5punRvnyc4gpqxP+ADffeeV46BzJg5R6oxkZ8PmJMnG1skFx6gMMbU+RJ5K?= =?us-ascii?Q?yz8Y9lM/rtE+TIMkAaZEZ83Anc49kVoxCHBAoB8uFKbZBwZmqfInv9ws6O5E?= =?us-ascii?Q?mlBmdJxbnHN0FwnwEohEXdTq/dX82QTbfO4/6PnfjmQClHsbaQB9RgZ+uma/?= =?us-ascii?Q?G1MQW61CVP8OLYyzmzoXbdvUPTWRjUewYx9V6nACc+RCIyFDgMcosnAfucr2?= =?us-ascii?Q?DULXIqaZmCnBvMRp/1eSyDsRzmeE6+gfyv49fflS3FoFn9MDsBSbkoR3Xkg/?= =?us-ascii?Q?fnm2YtU9d5mppOruHXyRHeMRmC2YXJZ9+bVreEW0zlXuHV8BJ/diDVh9RAMK?= =?us-ascii?Q?pBPrs0v1fdRJxNG/SoOXaoAc2qd+0dsH73nYBRxCqB6booBvKdJUmnwf3bfv?= =?us-ascii?Q?E7zuoe2WCdZejGNH6DabVniiDAUNtIt65T1QU9vp?= X-MS-Exchange-CrossTenant-Network-Message-Id: 85cc8bc3-84ec-409e-5c9a-08daf8f0cce0 X-MS-Exchange-CrossTenant-AuthSource: MN0PR11MB6304.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Jan 2023 01:10:34.1941 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: aOrSALsTCZZpT1Ns3CxZnIFNIpTyzP7Oeovky6EmwYWOZMkdbIZpkHRodOZQzzDdoceCW3QxXjeuR7GN5cIFUg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY8PR11MB6913 X-OriginatorOrg: intel.com X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: EDFF6100009 X-Rspam-User: X-Stat-Signature: ghzb6d3jmtwq6pi5grj9g4bzewa4fddo X-HE-Tag: 1674004240-576963 X-HE-Meta: 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 XlgaFALB gOeA/mnPVIw/0aeR1KmJLjFGPhrA3FZYAc94R4TE3GTCBVH9VVfrmkILxbCiVA4M8OpQ//xy83U0Svu5DsErY+05z8Ef6Ud+baXVtvGhtlH+ukiKw3DW48RwG1UNsQDpT6CsP5hDg2N89zBU= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Jan 17, 2023 at 10:25:17AM -0800, Linus Torvalds wrote: > On Tue, Jan 17, 2023 at 4:22 AM Feng Tang wrote: > > > > With the following patch to use 'O1' instead 'O2' gcc optoin for > > page_alloc.c, the list corruption issue can't be reproduced for > > commit 7118fc2906 in 1000 runs. > > Ugh. > > It would be lovely if you could just narrow it down with > > #pragma GCC optimize ("O1") > ... > #pragma GCC optimize ("O2") > > around just that prep_compound_page(), but when I tried it myself I > get some function attribute mismatch errors. Good to know, thanks! will try this. > > > As is can't be reproduced with X86_64 build, it could be i386 > > compiling related. > > Your particular config causes a huge amount of nasty 64-bit arithmetic > according to the objdump code, with sequences like > > c13b3cbb: 83 05 d0 28 6c c5 01 addl $0x1,0xc56c28d0 > c13b3cc2: 83 15 d4 28 6c c5 00 adcl $0x0,0xc56c28d4 > > which seems to be just from some coverage profiling being on > (CONFIG_GCOV?), or something. It makes it very hard to read the code. > > You also have UBSAN enabled, which - again - makes for some really > grotty asm that hides any actual logic. Yes, you are right, CONFIG_GCOV_PROFILE_ALL and a bunch of UBSAN configs are enabled. AFAIK, this is a random generated config for sanity test, Oliver/Philip can correct me on this. > Finally, your objdump version also does some horrendous decoding, like > > c13b3e29: 8d b4 26 00 00 00 00 lea 0x0(%esi,%eiz,1),%esi > > which is just a 7-byte 'nop' instruction, but again, it makes it > rather hard to actually read the code. > > With the i386 defconfig, gcc generates a function that is just ~30 > instructions for me, so this makes a huge difference in the legibility > of the code. > > I wonder if you can recreate the issue with a much more > straightforward config. By all means, leave DEBUG_PAGEALLOC and SLUB > debugging on, but without the things like UBSAN and GCOV. Oliver and I can try this, and will report back. > > I also objdumped 'prep_compound_page' for vmlinux of 7118fc2906 and > > its parent commit 48b8d744ea84, which have big difference than the > > simple 'set_page_count()' change, but I can't tell which part is > > abnormal, so attach them for further check. > > Yeah, I can't make heads or tails of them either, see above on how > illegible the objdump files are. And that's despite not even having > all of prep_compound_page() in them (it's missing > prep_compound_page.cold, which is probably just UBSAN fixup code, but > who knows..) > > That said, with the i386 defconfig, the only change from adding > set_page_count() to the loop seems to be exactly that: > > .L589: > - movl $1024, 12(%eax) > + movl $0, 28(%eax) > addl $32, %eax > + movl $1024, -20(%eax) > movl %esi, -28(%eax) > movl $0, -12(%eax) > cmpl %edx, %eax > > (don't ask me why gcc does *one* access using the pre-incremented > pointer, and then the rest to the post-incremented ones, but whatever > - it means that it's not just "add a mov $0", it's also changing how > the > > p->mapping = TAIL_MAPPING; > > instruction is done, which is that > > - movl $1024, 12(%eax) > + movl $1024, -20(%eax) > > part of the change) This version of assembly diff looks more reasonable. One thing I note is the sizeof(page) with this config is 32, while it's 40 for the randconfig used in this report. Thanks for the analyzing and debug suggestion! - Feng > Linus