From nobody Tue Sep 9 05:51:28 2025 Received: from NAM12-BN8-obe.outbound.protection.outlook.com (mail-bn8nam12on2040.outbound.protection.outlook.com [40.107.237.40]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2DBD11B3935 for ; Fri, 5 Sep 2025 22:42:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=40.107.237.40 ARC-Seal: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757112141; cv=fail; b=CaabMaLOtVbQTj+MqV34fY9fe5tvjTiTidnW0SPBIUjirKpUiPtarI+4F94ZJOtgtgETM23or3VggdVlC53SkaiOLGcWQ/toLmf2YJNEroUtSUYiB7bj1yZ+z5TKcJHMJQ0wACZvIrYFgvPxwt0YaUgS723xkUsNeriq0QQt/ao= ARC-Message-Signature: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757112141; c=relaxed/simple; bh=i8THVDHgiRJLC0boocs2/W3CZD3yYa8tE8ypERQDBF8=; h=Message-ID:Date:From:Subject:To:Cc:Content-Type:MIME-Version; b=UU/l73PG6u1O7q2VNrdkaAICtyj1sthAFfdbXB166/yKoaJ5tp3Ql6Mys7r2yg7gThJUqb15Yr26aU7dOkgyyh3AuBha2Xa81YdZ3zjtahNEIMUICiozh7sMk4a1mpxmOFtAPtjnFOXytrrXZAESE4Q6r85HaqOqVGy9MrTs3s0= ARC-Authentication-Results: i=2; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com; spf=fail smtp.mailfrom=nvidia.com; dkim=pass (2048-bit key) header.d=Nvidia.com header.i=@Nvidia.com header.b=rgXg0qC1; arc=fail smtp.client-ip=40.107.237.40 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=nvidia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=Nvidia.com header.i=@Nvidia.com header.b="rgXg0qC1" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=GomhA9+J7LM5J8v9A0UhMl9BnFLrCqLrONxeEFmfGZKYF+q6tebE8ivslqV/eKBPIhx28oPkMaE6OUiLPoOA6FNzOS+RrlRzm+Q/U9c3q//TAqYjrr4nm5wymVpGVWk3ylFaUu4Eo0NsICH11faxvIVPzJDgnB1e/FhpwsV8mXlAAq8ymkiTUilB6TdzKSxYPwbttem1eGqlqmKXc0bMkSMD9Up2mscZt9b1JUGBoX3dAdKn3Hs63AL8mun8eFFybyk26Jn5UHB3YwWxLjwSTiuKI9urjbCoF6JXdVP+kAzni2YM9UcJ6fVSw6EWedbXJ3j0vSdNUsTfmgPrYcFhXQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; 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=vU/bebcp3HREI3sP9u0d7XhT++cBICW1iGA0162/QV0=; b=aypz1LDpSa+u3E6F5zRUk6BX95jvJWtyNlOv8xE7LaJSgJcOyrAR6Ln+bGKYnJarXl4u0Tculex9pKJiFvFqCcZ1eB8aO9M559P4cUoQUq0OVdg4naL/q3GduOL39dmFCv0vFiGhJ1LpAcwylv+fuQhSaLLQ5MBNRjuf2XFo5FMcVz/V4uvCS5/Gfcg/nBQj6RadkGsAk0W87JrvgOSswxDzii4WwE9WUmdZEjtJGd4Yj+KiLF6RYxaYxg3W026xSHV+BCBAaDSvbrV13IdZv6U5vTPYrrPnxyHcLhDQoNYKjTdXc0CBJG0zyAnd8rLn1NdTLZRMjJ9hq6FBJPgvZw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com; dkim=pass header.d=nvidia.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=vU/bebcp3HREI3sP9u0d7XhT++cBICW1iGA0162/QV0=; b=rgXg0qC1ftmaAnQj7teRqtfTqF8VENkHT3kiL4gcHSXCHddttYQ2GzqB2z5CL92AbhssenJaDbwODTBMN+YG27ujpK3AuPfpVX6j6/gL2x/WCgBJihnFe9tcjYCuVm99Emm8DWv+Yxrqcq0EW+hZe369gPBoBQee2wzCOmT27wY9nNTg1Y6KttdgzECZxAKagJGVKh1Dt/GOYUYOjKE4JbJS+CkuPo2jVl4jQaeCrK3vGpzdLlClCpfkOQGEeZhYmgzLT3mWWmeIlBP/Uj3hwosYtL0kfYPiJ1/gvH5dh4gOCeKczCtg0ASviWVWctZ1ebYhWwaZlCVGr59uewqsQQ== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from BL1PR12MB5205.namprd12.prod.outlook.com (2603:10b6:208:308::17) by IA1PR12MB7685.namprd12.prod.outlook.com (2603:10b6:208:423::21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9073.27; Fri, 5 Sep 2025 22:42:17 +0000 Received: from BL1PR12MB5205.namprd12.prod.outlook.com ([fe80::604c:d57f:52e0:73fe]) by BL1PR12MB5205.namprd12.prod.outlook.com ([fe80::604c:d57f:52e0:73fe%4]) with mapi id 15.20.9094.018; Fri, 5 Sep 2025 22:42:17 +0000 Message-ID: Date: Fri, 5 Sep 2025 15:42:14 -0700 User-Agent: Mozilla Thunderbird From: Vlad Dumitrescu Subject: [PATCH v2] percpu: fix race on alloc failed warning limit To: Dennis Zhou , Tejun Heo , Christoph Lameter , Baoquan He Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Language: en-US Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: SJ0PR13CA0014.namprd13.prod.outlook.com (2603:10b6:a03:2c0::19) To BL1PR12MB5205.namprd12.prod.outlook.com (2603:10b6:208:308::17) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BL1PR12MB5205:EE_|IA1PR12MB7685:EE_ X-MS-Office365-Filtering-Correlation-Id: babcdc8b-6787-483a-1373-08ddeccd7723 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|1800799024|376014; X-Microsoft-Antispam-Message-Info: =?utf-8?B?Z3ZTamx1TVpXcE1GK3gvNzlaK0pycTQyM1hQU1lXVFQzMXhEUGZXaUpDQW9Q?= =?utf-8?B?djlhblVNeStrUWk5UEttMFhZaEVBQmRtMGFjeEtrcUtHU1VaazY0MENnZmlZ?= =?utf-8?B?R3RCejltSkxNVWVNN3hQTmdqdC9YbFJWLzhFejhsUnA1MVpwODZSTGZBZXNZ?= =?utf-8?B?Z3lvbzYzN1lxaVRaWnhRNUVORXJybXp4eUg4YTVNNVJjaUt0eERldkkvK2ZK?= =?utf-8?B?UGRDN2ZuYTJXZ01PRmZmMmdGeVRQMy9ObFNqdTExaWNkMzlOV1doM1FQZjdi?= =?utf-8?B?aW1oUFNlclBxd0JCV0hMR2M2RHl0V3MrbUQ2WmtydlBJQS9mRGlYYU5oRStt?= =?utf-8?B?TG12UlJORTRFVWJ6M1RNVVdBVnZqeTIreUp0dURJbVdGZ2JvNGlmR0d0dGxs?= =?utf-8?B?bFRLVHJFTDVKOEppRk9CdWNsYkVmRlBkTjJSN0xpUmhmSDBDZTlleHhwSkho?= =?utf-8?B?UXprRFpHWmlkVEdYNXdjWW9TcGxkcGZBd3ZWV0FsbFN3R2N5K25HZk40Q2RU?= =?utf-8?B?Qy9nOGE4S1VYVER4OTV3Z0s2QmpXWXk5eHRCWGdENFBiRWNOZkN5TTljWU5N?= =?utf-8?B?YWNNeVFsc2hYWGFOOFZteUkrWVAweTZvUTdzalhJenVBVGhiZENKWWNla1JL?= =?utf-8?B?bm0xdmNlTTZPWE1Na2VHTlEvV2NuQktyMFhrNVJ3anRUY1NrTTFRbkVSbFp4?= =?utf-8?B?aDVOUkE1M3JMRFhqWGlyUm40a3B1QXlkOWJDL0pkU2Q2YjJKWnhWaWpYOTFu?= =?utf-8?B?TDVxOWhiVWxSSkFMSmsyZVBWcDJtTDZTa1U0QnRsL25zODVEYXJxcHZDcGFk?= =?utf-8?B?a1RxaDlYeWtkWkJMSXRQQ0tESjA2aUQ3aUhiZ3BjVG00OC9TWVcySjdUSkRP?= =?utf-8?B?YVVhKy9tWUxINFZwdVFzbU9PZDU5L003eFBYRVMySlJPbENoNXpWVnhZK0JS?= =?utf-8?B?Y21hd0Zxd0wxMU5IRU1CNWxzVnZOWEFjNDVla3R1Z3lHQ1pRQTg1SEdOT0lx?= =?utf-8?B?WjJLYXR5OGR1dVFKWlp2UGxWVmJKZitFWWtJL2NHcHNJa0dkTGNtTFRhdGxq?= =?utf-8?B?dElQNnprOWgxM3dnQVVtVWh3cjI2NFBRSWw0ZmZVNUF0eGlLWlpMSWpEK2lF?= =?utf-8?B?bFgzeld3ZEZBbjgxMmtNRG8yK0hsVEM4bU9JRVJtU3VXa3ZLZjEwbDJxMHZW?= =?utf-8?B?MkpYRFM1RWYwNTVGZlp3Sy9adDRIaW03bXVGeG1CZnk1d2hjVnVGOGJnOFBh?= =?utf-8?B?RllLMDVCWFlJeUgxZGIrYTlSbHkzakpwZFVHSWNwS09ncDBwak5nOTNOUUgz?= =?utf-8?B?U3ZYdjE1L0V2VjB5d1dTT0x3RkEvMFlHaWRqTU42Ulo3UlJEaTMwcWpqandC?= =?utf-8?B?TUNDWVZsVjhTbDlNVnR5Mk5zcnFaeS9Sb0pxR2Q5ZW1NWlhsT0MxVUZZbEZU?= =?utf-8?B?d3RqbDg4M0FQdTdjU3ZTZDlLakFwaEdhMGRyZENMdlgxL2ZGM3NXcHIwWlpl?= =?utf-8?B?NUFqYmEwMENOTjBDZFl0Zkp5N3dqRGliZXBGa3JnU2h6VVlwTC80UkVaUkR4?= =?utf-8?B?eG1ob2U5VG9Ha0x5MnhWWU9MRTd1c2NqeGtyQ2NoaytUdVpjS2xWS0ZnNHBL?= =?utf-8?B?NFBSWWNkMDVOSVNhRDRscUU2aTlndjVpMC9ERnRWcDRRWDBIMDZxRHh3SGRW?= =?utf-8?B?ZytiSjB6SkNrZW5tejFnZGdzK0k0NUM0Y1NMK3hzemVyWVpjT3pTTEZOKyt2?= =?utf-8?B?L3pLMWdKdzhzNG9YcEJualVWQnZPWE82NDh0dlFYTlQ1UStGdzdnL0VHMTE0?= =?utf-8?B?RnJ5NDZMeENlSnorOXV1azhaQUJCSWY3ZHBOMVFtNTJudG1pS2VVOTVmRWJa?= =?utf-8?B?V1dRU1ZDNHRub0I1QjZoMERMQWkrdXBhYUp0ajlPTW1Wbnh2dHE4SVV0V0hj?= =?utf-8?Q?tOXxaiNFJHM=3D?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:BL1PR12MB5205.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(366016)(1800799024)(376014);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?bXluSy9TdXlRcGRiV3dZeHF2aThZRjhNemZlRDNhVGlWRTJIL2NERjJwdjc3?= =?utf-8?B?ZzI0R1FWL1lDa0RSVUF1WWNHVHhEYW85LzRIenZVYjVSWWxLMzNLQzFkUVA2?= =?utf-8?B?YVNuRWdWNFpNNDgxVUhHMVhRUTVMTlFwWWJOMGpmdDRlWkE5RmYxajM1V1Rz?= =?utf-8?B?MndpRWYyeitDZTJ5U3AwSHVEY2ZReUFHcWl6SFFIeU1GMjRCVit4KzRVMElC?= =?utf-8?B?ZWVlZkFXOUNoREdhb2I0dEdHeDBxVkwyYzdnMnNrQnNIK0ovcnQrcG9jUkhZ?= =?utf-8?B?N2ZoRjN4YmI4WW1va3lVaGtoL2xmbFVSOHMrU2dYUlFHWk01WHR1dk9WODZK?= =?utf-8?B?UHBBbWRLakJDMUc1cjJqNVJoeWJXN1BWSzVqQ3pCd0laSjRHdlM3T0lSeDFN?= =?utf-8?B?Y241OUVhZlZOaGpkT2tBTHRPZks0S29CTHBaV0wzMkoxNk9PUmVxZVh4U0ZP?= =?utf-8?B?UWN3ZmZPL010MWY3T01QSE9waUtHdTFrdDhoLzREV1crR0NXUHB0bnBWQlhi?= =?utf-8?B?WklBdVc3anRLZUNFRU9VcG4renNWSXU0Ymh5U3poYi9wMzExSW5zcC80QjhC?= =?utf-8?B?VWFkS1J3TGNuR2JSTjVRUHBGby82cjZFdEFmb0lHWXpWOVE4aW1kb0FWMUVE?= =?utf-8?B?SWZwY3JPMGdLNE8rN3NoYmsxd0I3ZkZaeFJyQXordUlXdEYrMmp1b01FQlhD?= =?utf-8?B?N05ERXZlQlROc0duNXd2QmNkYmNRMGM4U0FNZnJhNVZUT3BvSitDZEZnaEc4?= =?utf-8?B?bHQ5QVM5Rk10bUR1UW0zQ29qT0dJOUQ4dEQ1aHpiWk1Pd0RkcjJVVVVHVnZi?= =?utf-8?B?UUNNTjJmSFBBalhJWHhUSnlFTXhNMEt2bmNhakwvS2tmY2MrQ3dqTXYyN3Y3?= =?utf-8?B?ZStvNG1ZNXR3ajRzUzZDdzZVaFA5Z3RoNWhPVmxUMHNkUW9zcUxVUnlhN21B?= =?utf-8?B?VXRpdW5oaXF1ZEZDN2hkZ215bi9abTN0T0V0SEx4VzVadFF2aGt4aHZ0TWJ5?= =?utf-8?B?VFN1R0Z2TkZhV2laWWxoa1BmTUFuT0xGd3lBUDVWZ2ZZdE5XVUNuSmluSi9L?= =?utf-8?B?UG1NMnhwNEVRL2pNRHBEOWxmKzBIVVRNMTRYY3FoM1dvS040alBtZUVCcFZq?= =?utf-8?B?Yi9hcFgxZ1ZxcXhWaVRFd29JTWF2TlFZc3RWNzBPTHBjN1I0RzAyVXJVRW10?= =?utf-8?B?Q1ZqamZxbkJCbm1UYmF4RVpLSWQwRG1NK2ZzdCs0SHRFRjcrRmpFMXdyNXdn?= =?utf-8?B?U3ZYQ2k0ZzJaQWlhRUYwVmYzQUtHZVQ5ZlByeGt2ODV1by9MU3M5VXc5WHdP?= =?utf-8?B?Wkc3RytMbThMdVZyRVJzS0E0SkI4STFaVDJWNVk5dXNKYkttS2x4ZGx4c1lJ?= =?utf-8?B?di9tSXpCL0VGaWdXQWFnNTEyZHJucld0eUhsOEM2MlNuaDExY1d4OVhSRUlO?= =?utf-8?B?ZEdTaXRRS3llOFdOOEU1KzdxRHRneEpXS2JYMHZXdENJWWgyNGpLSmh6U2hJ?= =?utf-8?B?aHl6YVEvUmp0RHBrakxOQnJWZFA1bjQ3M0RxYlVJWDBqZW9xdjJaYjd0ZDhF?= =?utf-8?B?YjQ5Um1HTGFzQzIydVkzRi9wSXpldklZRXpDOTdlY05tMEYycjdSSFhib0Jn?= =?utf-8?B?dDFUMmRWNWtCTlpONE4rS0dEUTZ5d1Qwck1oNFBRd0lpMTI2NU01bk9uTHd0?= =?utf-8?B?eUo1SDVZRlJCU3BoOVFzc3dteGk3VzVUczBseitSTGJ1QUhKemI3SjViMVBT?= =?utf-8?B?MDh0Mmt6ZTRQeXg3TktFcG1peE5vSVArczZPTklMYTNUblF1OFdHVnQrMTln?= =?utf-8?B?aUE5RWNrTEJVWDBXRTNEdzFIWElFaWVSRDF1d0NEMzlmbVlZK0VQMkx6OCtx?= =?utf-8?B?MjlhcDBGYjhnRlUxbFp0L0ZBV1RBN2drTEQ3c0JCenhacUI0Z0k4cnVQby9a?= =?utf-8?B?L01GUkZDU0hqbmNNODh6ZHM4cUhScUU4L3RlY0UxNDBkZjNWc05FQmZQbkxu?= =?utf-8?B?S1IzUXlYNjlTa3F6YzZDQzFvV0d1QzV4TTgzSkd0R2s4WlRLSjNobGZuaXVB?= =?utf-8?B?SlZ5YmFUS3YrQ2ZFNTEwZVBPU05qRGR2Nlg2S3M3M0c3OFVsbkg0ZjdRZGxm?= =?utf-8?B?TVlGaUh5dHd6bStoTjVzYzhiS1pySmFuaTdyZmZmZ2dLUVBqZFFBSkNlazZj?= =?utf-8?B?NGc9PQ==?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: babcdc8b-6787-483a-1373-08ddeccd7723 X-MS-Exchange-CrossTenant-AuthSource: BL1PR12MB5205.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 Sep 2025 22:42:16.9502 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: VJdW4QaLpdVowfPkvEG0DtHEKuJ1Ue2WxawBN+MOM4G2GlF1cvHBTpA8LDK+Twxjz97n5hkaoyo1cIot5t9Ikw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR12MB7685 Content-Type: text/plain; charset="utf-8" The 'allocation failed, ...' warning messages can cause unlimited log spam, contrary to the implementation's intent. The warn_limit variable is accessed without synchronization. If more than threads enter the warning path at the same time, the variable will get decremented past 0. Once it becomes negative, the non-zero check will always return true leading to unlimited log spam. Use atomic operation to access warn_limit and change condition to test for non-negative (>=3D 0) - atomic_dec_if_positive will return -1 once warn_limit becomes 0. Continue to print disable message alongside the last warning. While the change cited in Fixes is only adjacent, the warning limit implementation was correct before it. Only non-atomic allocations were considered for warnings, and those happened to hold pcpu_alloc_mutex while accessing warn_limit. Fixes: f7d77dfc91f7 ("mm/percpu.c: print error message too if atomic alloc = failed") Signed-off-by: Vlad Dumitrescu --- v2 changes: * prevent warn_limit from going negative, as suggested by Christoph Lameter v1: https://lore.kernel.org/linux-mm/ab22061a-a62f-4429-945b-744e5cc4ba35@n= vidia.com/ mm/percpu.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) diff --git a/mm/percpu.c b/mm/percpu.c index a56f35dcc417..81462ce5866e 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -1734,7 +1734,7 @@ void __percpu *pcpu_alloc_noprof(size_t size, size_t = align, bool reserved, bool is_atomic; bool do_warn; struct obj_cgroup *objcg =3D NULL; - static int warn_limit =3D 10; + static atomic_t warn_limit =3D ATOMIC_INIT(10); struct pcpu_chunk *chunk, *next; const char *err; int slot, off, cpu, ret; @@ -1904,13 +1904,17 @@ void __percpu *pcpu_alloc_noprof(size_t size, size_= t align, bool reserved, fail: trace_percpu_alloc_percpu_fail(reserved, is_atomic, size, align); =20 - if (do_warn && warn_limit) { - pr_warn("allocation failed, size=3D%zu align=3D%zu atomic=3D%d, %s\n", - size, align, is_atomic, err); - if (!is_atomic) - dump_stack(); - if (!--warn_limit) - pr_info("limit reached, disable warning\n"); + if (do_warn) { + int remaining =3D atomic_dec_if_positive(&warn_limit); + + if (remaining >=3D 0) { + pr_warn("allocation failed, size=3D%zu align=3D%zu atomic=3D%d, %s\n", + size, align, is_atomic, err); + if (!is_atomic) + dump_stack(); + if (remaining =3D=3D 0) + pr_info("limit reached, disable warning\n"); + } } =20 if (is_atomic) { --=20 2.49.0