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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8E1D7D5E147 for ; Fri, 8 Nov 2024 07:56:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:MIME-Version:Content-Type: Message-ID:Date:In-reply-to:Subject:Cc:To:From:References:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=MGHDOL6VT5hQ0NlZaLWKTl0Iy2QTFArhJOZ1uOMaT3o=; b=3YMxDdt2i1WQEqlx2ZUX7xBpTD wHi3kHDygHtD9pA3AyXyHWiSIX9euEbBZvGH2ItOlPeo4gKxL2xVImFYn/JPG+NRx7XrmCKvci6gm f7VWA+SrheVhq6VUVdEFJn0oQ6tAx8vY+4+Uv+38NGQnkqQL280fZNaorOlEVBEy4FcLkRI4uBuXw pt2rjXjM7pVUCCZu7FVEBBodIN/K7lSdo1Ifpq5hiLEA43JivpFLjWzkagl45xhAdEKWeqKh1rcT9 h/68Z5fgHAFTwplX/h8jnLBSQrFZWQI3n9ML7LVGoyJ+oArAcGhAtg86T3Uc73MFfPvJuJJWdG9KF Zi+wN/SA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1t9Jqj-00000009gwP-3nhS; Fri, 08 Nov 2024 07:56:09 +0000 Received: from mx0a-00069f02.pphosted.com ([205.220.165.32]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1t9Joz-00000009gmG-28ri for linux-arm-kernel@lists.infradead.org; Fri, 08 Nov 2024 07:54:23 +0000 Received: from pps.filterd (m0246627.ppops.net [127.0.0.1]) by mx0b-00069f02.pphosted.com (8.18.1.2/8.18.1.2) with ESMTP id 4A87pKgx025373; Fri, 8 Nov 2024 07:53:47 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=cc :content-type:date:from:in-reply-to:message-id:mime-version :references:subject:to; s=corp-2023-11-20; bh=MGHDOL6VT5hQ0NlZaL WKTl0Iy2QTFArhJOZ1uOMaT3o=; b=LU0Yqbx+OIOYKF2kgXHvfMomhXa/PQXbU+ yPq1GtYQHc7VtjIhDcN8IIKpMgtjnrPaco5nLPqCoRVOdSL57F36dmMmnY7Fh/+0 6Jeo5GzMPPdGJ+lljc19aPJ7SpEH98y8TxYaow6CbeS/kGfGDVkHO9OuFErJJur8 VpKJ2EvdU+0S2zWajHnnAJrIKRDTm0H+y0pL4MFp1ExrXPcPFSSmXD8bjLEVD/X8 JxwdQdyJgQDQzgnGOSiHXK3U8eAAdWp8KCfA4a43/jHOYJKLjOolnvOHReJj95jy Pqc9O6T9kuT9EU9X/Qh0w3QRbTLsiXVAdfn92c0VMfEvaDqN58Kw== Received: from iadpaimrmta01.imrmtpd1.prodappiadaev1.oraclevcn.com (iadpaimrmta01.appoci.oracle.com [130.35.100.223]) by mx0b-00069f02.pphosted.com (PPS) with ESMTPS id 42s6gj0npe-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 08 Nov 2024 07:53:47 +0000 (GMT) Received: from pps.filterd (iadpaimrmta01.imrmtpd1.prodappiadaev1.oraclevcn.com [127.0.0.1]) by iadpaimrmta01.imrmtpd1.prodappiadaev1.oraclevcn.com (8.18.1.2/8.18.1.2) with ESMTP id 4A87jLoB036880; Fri, 8 Nov 2024 07:53:46 GMT Received: from nam10-dm6-obe.outbound.protection.outlook.com (mail-dm6nam10lp2043.outbound.protection.outlook.com [104.47.58.43]) by iadpaimrmta01.imrmtpd1.prodappiadaev1.oraclevcn.com (PPS) with ESMTPS id 42nahba5c7-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 08 Nov 2024 07:53:45 +0000 ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=PLTYsipwQumg5HJitxDPHtHmH0H6btIa4unayS8l1tvstzqbABaKYzQVZXk1EaSJI6p0kGVW+xWJLdlrwt3IDrgLEt3ZCF2xzAXtBoGG9A68ZerxODJFPMlR8Ci55wGNNmcmf0qr2oAl54zAWQNX1BG2SQgWS9ZCATzTCtzbZOLE1xaPucbpjW0/ejLNLuCj3wA1SelTNrXEWDn8D8+zXBBymYaEvCaTFcU2hUrmZ8PF8AdceLt8N9JQzYbX7Zzi3ZbuuffOHOVmzmtToGU4M1ej8zV/KBjB2NYK4IG8yN8ONSobUNWmangO/s3G5ml8LgTd4smUUKU7Qf4/pEbGqQ== 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=MGHDOL6VT5hQ0NlZaLWKTl0Iy2QTFArhJOZ1uOMaT3o=; b=QkGPyMA9M4ZRpTm39lIHpbZ+hMef8onyqD/9IKkG+ZO//ybn0Yn0zLlR1llhT2Mrrl2Z6DuV8DAetNbuFscfNqutHVY49EtEtWkd9U54GURlUhQP1SiwfSdN4I2APRxuX9zZDKA6Rzo3Yn+NVy87UMhmFf/zL3opppI0EoTz6axYsqpnHTMK5Cp53nYRBc4vLPpWwJFCwiVRD2jxG0G4sIZUQN8HGy/YSexpzMccmKEU2HWG1nTbmz8BpAHTqvCpLC8gzS2RCPbAEUH2IbQp2c2IHBxE9dMbu/SDKFbElPeQ9FbolOlundr3SCkzr+xL9ZQEIRSQ583A3ckZGtVoww== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=oracle.com; dmarc=pass action=none header.from=oracle.com; dkim=pass header.d=oracle.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.onmicrosoft.com; s=selector2-oracle-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=MGHDOL6VT5hQ0NlZaLWKTl0Iy2QTFArhJOZ1uOMaT3o=; b=Y6f9SDq4TXhqodGigReU/bRIYjwqh4rN2PibKJBmjOcQVvXgnQ9fb7JWKtpZP1eGK2fJK1vhB9s6MbKvd+V2rE0TivyMZ2vN07qpgqfg3qWdWoQzqXGPTdGjahJBFgyDWTnGUky03JVRPxN7H1ipGj0g8VhPg8zNLlo64XSvEuE= Received: from CO6PR10MB5409.namprd10.prod.outlook.com (2603:10b6:5:357::14) by CH3PR10MB7187.namprd10.prod.outlook.com (2603:10b6:610:120::16) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.8137.20; Fri, 8 Nov 2024 07:53:38 +0000 Received: from CO6PR10MB5409.namprd10.prod.outlook.com ([fe80::25a9:32c2:a7b0:de9e]) by CO6PR10MB5409.namprd10.prod.outlook.com ([fe80::25a9:32c2:a7b0:de9e%5]) with mapi id 15.20.8137.019; Fri, 8 Nov 2024 07:53:38 +0000 References: <20241107190818.522639-1-ankur.a.arora@oracle.com> <20241107190818.522639-2-ankur.a.arora@oracle.com> <9cecd8a5-82e5-69ef-502b-45219a45006b@gentwo.org> User-agent: mu4e 1.4.10; emacs 27.2 From: Ankur Arora To: "Christoph Lameter (Ampere)" Cc: Ankur Arora , linux-pm@vger.kernel.org, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, catalin.marinas@arm.com, will@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, pbonzini@redhat.com, vkuznets@redhat.com, rafael@kernel.org, daniel.lezcano@linaro.org, peterz@infradead.org, arnd@arndb.de, lenb@kernel.org, mark.rutland@arm.com, harisokn@amazon.com, mtosatti@redhat.com, sudeep.holla@arm.com, maz@kernel.org, misono.tomohiro@fujitsu.com, maobibo@loongson.cn, zhenglifeng1@huawei.com, joao.m.martins@oracle.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com Subject: Re: [PATCH v9 01/15] asm-generic: add barrier smp_cond_load_relaxed_timeout() In-reply-to: <9cecd8a5-82e5-69ef-502b-45219a45006b@gentwo.org> Date: Thu, 07 Nov 2024 23:53:37 -0800 Message-ID: <87v7wy2mbi.fsf@oracle.com> Content-Type: text/plain X-ClientProxiedBy: MW4PR02CA0011.namprd02.prod.outlook.com (2603:10b6:303:16d::28) To CO6PR10MB5409.namprd10.prod.outlook.com (2603:10b6:5:357::14) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CO6PR10MB5409:EE_|CH3PR10MB7187:EE_ X-MS-Office365-Filtering-Correlation-Id: 579ffa1a-e5ae-4fcb-91e3-08dcffca7467 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|1800799024|376014|7416014; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?66o/5N/IGsVp+n+aom8eJGWyWArMdvDEAJvoPmdzOOI9+actoepX6o2fQhaC?= =?us-ascii?Q?uQdVhDfnukGzxcDMMf+RFAPMNKw5Gvp+yKbsqlmznrEYL+wJ5uW8RqMp/r4P?= =?us-ascii?Q?ATuTaDq/n1C0UoIWvRdB1KaQ0RAGwEfuKsHHdDyFU83ur3VwpjpPwmqbc17i?= =?us-ascii?Q?eaReR+j/e9xrgI9zglIJ8A/N9WcY5eUp/8UDW27s3w8X/ieUXRXjqZC1KsI4?= =?us-ascii?Q?uGnGKS+J8kTpF++Lxy8cs3+bWn1syEdaNdQZYMikmnKhge9K/KVwsPtD8iKx?= =?us-ascii?Q?LZgOKYxFOzUtelAASevSZpN5X/sb8wyNR3CtD49fzgAIlOIU91UKjNCQu3SA?= =?us-ascii?Q?Wqyg71rDPAu7RrR+CXsDi1fPH++gZB4qQNgw+DBKHOwM4qDiyqZa6pSru9QH?= =?us-ascii?Q?TJNAInzqRahFin6spoTfdTiy8cJ7B+wr9xZw0xk1XCPlg/hPhPZ5Do19SNxm?= =?us-ascii?Q?OTL5bErCeFtTZkLhRy3afBT3gmy9627YuQEp8SFzFFj2PSU2pq84DjL5MrOZ?= =?us-ascii?Q?01himp+zVQHBHykm22PmqJz+Vi73j1jY6/QrMrh0QJ9iecCemHnKEVmo97Sc?= =?us-ascii?Q?2rfp3mewxyu2VCKkS2pV3+xFibC4HwSeogNBzL2mfI2TVTaowbMkGqECRlhF?= =?us-ascii?Q?/DadttGPiLVfooMZshp/bY66qjG9QRov4Y7a6mag+KrTZjy9jqZxQIUO9ih8?= =?us-ascii?Q?aTuC3K5JXLc5FJtmutfXGRc+dbzqNqo2jsXYajuWgs/+LGpuuEwSdCgmZuLR?= =?us-ascii?Q?YtQb14jM8M6LQpehvOYW0fgNBHaTUR0FEbb6xTmpdavkp/JzGb876S3t7CAi?= =?us-ascii?Q?+7DzpyQnG1OP3BFlyR8YE4IKDsosTgvhWKaZUOemptWKfJFrJdQVBqoT+aBK?= =?us-ascii?Q?rih458NldzkTutI+YoRxVN5hqmTF8Hm3fLmNICFMMSZFQNSPCtP6sM5ndltf?= =?us-ascii?Q?lQsQ/EC4l/6OHniU7xt4jvc2EkVyezSHBbv0NnyKzIeWKjK5WTd2MtIrUzGl?= =?us-ascii?Q?uwU1Y54sCPmedPePaTxBuaZgCC9istu3fbtpkHPQ5AxmiHmGYRFr43oVnbkE?= =?us-ascii?Q?z1N6ec+Kgbmpi6OkgX5rI+qxpMmkSThf2VqjeCYxzcB9zNnMkWi74QLBz9Ka?= =?us-ascii?Q?KBkRB6rvQpaiMa++OOXNoANnEZscc/zrlyKWUN0NxEMG9vsVBNkQF/JIp0zh?= =?us-ascii?Q?n5STaNwng98IFu2832jIo0SUadYFiqdyKMLQmGyyy+WdyWaPQwgU1eY6cQfb?= =?us-ascii?Q?oXjNVhUnjzc4UP0cbe3xXn7JsCoc/ZIC/wxqCddyTp9I2M15UsjH9pA7X0V8?= =?us-ascii?Q?vI2/b0FvifIZFzn2vnn9wZwQ?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:CO6PR10MB5409.namprd10.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(366016)(1800799024)(376014)(7416014);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?DtbXF3y5kCDmTBZQ67YrZhtFL0dq38Omnd5EZXYoR9YphUusKtPQpDYQPvuW?= =?us-ascii?Q?iGtZQyGb5aHlyXUnCaqSnX5wXGDWEcZ9stgjEcGkQxii9ZkLRqQ78UewJ5ki?= =?us-ascii?Q?AVQMRigOd82UXd+YkgussbUeBAxKFaHVDMMB+QeebGoPVSVZv9H9kFtU2wbq?= =?us-ascii?Q?8VbuVoF8+3rk8OfjqdIMww8fNFKHmP4DW44N8RbDDGO1LXejo88DSE+AKcuK?= =?us-ascii?Q?jQP614Oy9Sc8gsrrb92uULT86BsozhQBwI1h01inFOeispvOJWFzcW0OMHuL?= =?us-ascii?Q?zpp2FfIFOg11i46Ju9PbDWC3sq3UW3fI2fKuD7ajh6ETH9S+Gb0Xq/1aCDDY?= =?us-ascii?Q?4rRf1Dh5DAGoNf0ujOysZvkkYGibPrVRZ7/7VwTm3AHmv10xI6l7R+VMXFkd?= =?us-ascii?Q?H2/fjGGf7L1toJBpVwOdQOEjV96Kvxd9hqNP39nYdXgIwxQC8l9BmdDGIkO/?= =?us-ascii?Q?xCmbC/zgWMTGPellne++QRChXKHVEWqxWfhV3nopbvbOQm/gKni9HGn47ePc?= =?us-ascii?Q?iBGh6eY1qgeCCGk/amks95YKW376D8AKNnY1JL9SAYBIOn/FKBkySI12f6hc?= =?us-ascii?Q?BIOTK7BOS9iz2cSTCHqsRIpBpy73WFF8NK0SA1CMSiDP4H2wmTVCMee/aV+s?= =?us-ascii?Q?c/13Q04PRaKctEopCEGwL0LrZZzSyEaFVqPF73JNoI4QhXJiDIJyx5nLyOcR?= =?us-ascii?Q?cQn/umpVX3RVPwEupO2MDrRYblOcW5VECv67AqOg2h54kJMbHq9h11zFWf5K?= =?us-ascii?Q?zhMjm+M1tICRskud1Y+0+psgwStoK8YQDTTIeYX6nJT5skDDtx7A4jjH3Ld0?= =?us-ascii?Q?KZbaEDl1bVlMcWg7GqLuYQF5W6KqGCXwnwljxLH9+YQP/zrBYgvxB4rztpYv?= =?us-ascii?Q?idXAMw/xeJyGu7emDbL3MIBaZQGFHH+2z6Dn7F+su71aG3vCbBkJMErYLTHi?= =?us-ascii?Q?zuIFtiSlsUyvhTrhKdSw6lyW3/ju8sz3nNJbvQfnfXk5l2bKTjuL6UYrmm6Y?= =?us-ascii?Q?pS0MzgctPwEDLZYn1anxtiOXaOjb5DLxfIYbNK+Cwuqm2ExbuI0O5Ua6lnjp?= =?us-ascii?Q?wl/bPORuaLKtd5sbGtJg5gmIj6FJJSeYQ3Y43VeTOfP9C5PBLblTTp/b6ZbH?= =?us-ascii?Q?Iej4qfch8Hf1t3Uzq9CcfcObmD6s73gAlinr6rhgshopED+4l2UqBuZ0rZ/L?= =?us-ascii?Q?1uDap4suj5sOWPt8banzTbbQZ/OOIxAJE8UuTjnJFSMKRRZEgpLAl8gkhYLt?= =?us-ascii?Q?K8iIUKn+UfLqTfCLUZ0YlVdWvLS6RsYbX7dgCwL1JZyvWe/xtDZ8QUKtFVKg?= =?us-ascii?Q?vIX6yDVzE3axVZRk5WN6ImJxlwKEjkQoP89Xj3ki58S4HrLxezCnAvIN0mKH?= =?us-ascii?Q?MeU5nkJO5lTQU0ZrNaYQ+JveRNVzFOR8B5PLIbaLhrrM/Q3vBUzg6W3JWyUM?= =?us-ascii?Q?UGy1IoceQQI9vpC1YeIDhUfKv1K6jAR+P/U/h8LsMcqWHIeGNVBTqVXI6Dfi?= =?us-ascii?Q?oacZT2Nn5bRkR8+dDWFwq3MbvKg7AjbltoDisFs60Qdd4CmY+z4XdVzDhRPj?= =?us-ascii?Q?fFU2aSyw24glPt4Tg0lmLee/fmLqoBodBgRS5LdH7DJrtLp1GerJsmE/1z+D?= =?us-ascii?Q?cA=3D=3D?= X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: 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 X-OriginatorOrg: oracle.com X-MS-Exchange-CrossTenant-Network-Message-Id: 579ffa1a-e5ae-4fcb-91e3-08dcffca7467 X-MS-Exchange-CrossTenant-AuthSource: CO6PR10MB5409.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Nov 2024 07:53:38.2436 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: RhC9ICcmmd9Z6OlHpVBe2nAFcsc64b7logd0f8VQWXVgKe4k+zsVZAhmWXrqUGxqXEOdw/033uBdOHfV2o//E4uv8I2BkIsWCws8wK7ae0g= X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH3PR10MB7187 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-11-08_06,2024-11-07_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 adultscore=0 mlxscore=0 malwarescore=0 suspectscore=0 phishscore=0 spamscore=0 mlxlogscore=886 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2409260000 definitions=main-2411080065 X-Proofpoint-GUID: We2rN2w0yH1qRS3Sp-lghXSBo-62poDz X-Proofpoint-ORIG-GUID: We2rN2w0yH1qRS3Sp-lghXSBo-62poDz X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241107_235421_688504_95CE693A X-CRM114-Status: GOOD ( 14.94 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Christoph Lameter (Ampere) writes: > On Thu, 7 Nov 2024, Ankur Arora wrote: > >> +#ifndef smp_cond_time_check_count >> +/* >> + * Limit how often smp_cond_load_relaxed_timeout() evaluates time_expr_ns. >> + * This helps reduce the number of instructions executed while spin-waiting. >> + */ >> +#define smp_cond_time_check_count 200 >> +#endif > > I dont like these loops that execute differently depending on the > hardware. Can we use cycles and ns instead to have defined periods of > time? Later patches establish the infrastructure to convert cycles to > nanoseconds and microseconds. Use that? > >> +#ifndef smp_cond_load_relaxed_timeout >> +#define smp_cond_load_relaxed_timeout(ptr, cond_expr, time_expr_ns, \ >> + time_limit_ns) ({ \ >> + typeof(ptr) __PTR = (ptr); \ >> + __unqual_scalar_typeof(*ptr) VAL; \ >> + unsigned int __count = 0; \ >> + for (;;) { \ >> + VAL = READ_ONCE(*__PTR); \ >> + if (cond_expr) \ >> + break; \ >> + cpu_relax(); \ >> + if (__count++ < smp_cond_time_check_count) \ >> + continue; \ >> + if ((time_expr_ns) >= time_limit_ns) \ >> + break; \ > > Calling the clock retrieval function repeatedly should be fine and is > typically done in user space as well as in kernel space for functions that > need to wait short time periods. The problem is that you might have multiple CPUs polling in idle for prolonged periods of time. And, so you want to minimize your power/thermal envelope. For instance see commit 4dc2375c1a4e "cpuidle: poll_state: Avoid invoking local_clock() too often" which originally added a similar rate limit to poll_idle() where they saw exactly that issue. -- ankur