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 5818ED1F9DB for ; Tue, 15 Oct 2024 21:56:30 +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=CpddGkmrgUlRFbpDvn74spenQBNRm7gMkCpqSs+G1uo=; b=3qCRdfe38yQvH8Vlov1EC3CrI+ r14JKZIOygWfXIgTVz2oHGH55ynqDcl4xYf1LpbPngwlOmz1c/RS42+YoE8khLJtANU8n7kEVXzW4 wKOofQY+Tx1j+QwQ2hu8KwZrfbevSH5iPrGe7RrH693jKJFlscMm9L+uRriBvMooX30F3rZQR21sc 3hYc8Cafx5HYWWpkVA4/ZC/PBUapHujh5pGjKxuBrr3tJesd1sjAcMEJGrC+svGVEOLd1hxB8LaGH J/KEUAK58J288aj3tTymbkkvaN5VSFnI29CIunekLGuX8h8bATrCeyChMV/7rkf8w58faGzJ14GIK 9vc2b7BA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1t0pWd-00000009jjS-2W9h; Tue, 15 Oct 2024 21:56:19 +0000 Received: from mx0b-00069f02.pphosted.com ([205.220.177.32]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1t0pVD-00000009jbS-45IX for linux-arm-kernel@lists.infradead.org; Tue, 15 Oct 2024 21:54:53 +0000 Received: from pps.filterd (m0246631.ppops.net [127.0.0.1]) by mx0b-00069f02.pphosted.com (8.18.1.2/8.18.1.2) with ESMTP id 49FHtdIE029006; Tue, 15 Oct 2024 21:54:17 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=CpddGkmrgUlRFbpDvn 74spenQBNRm7gMkCpqSs+G1uo=; b=FV6FnDNNWbfjefWPQq7zxGuSO3yqRY5iH7 n5LT/WDKwyWQ+rfnYCwPyZ0mU4a5NNOm61bABTTcjSE491S5l4YsCoDspA21agoK mh+wP6m4X45rNjxr69yCmODJ+2RyjKx1Gi20hwOruxQZtjh5LDxsniKpid4KXOwp cIs34sILkUKVXQ+5PWzk5HkPlh83hDkbFtInaxyC4hgpghNRuik1jbM/vGvIAmGD bGI/b9j5YiYrmr9Vv2NtMR8Is6gwey5hQMrVIDPgKTaQ+yTqbudpY4LjkMDK31dD nBaPj0oZIuf8ecBcHq6lbS+ppUlO+vGivwN2Jp9v2rmae0YVYegQ== Received: from phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com (phxpaimrmta02.appoci.oracle.com [147.154.114.232]) by mx0b-00069f02.pphosted.com (PPS) with ESMTPS id 427fw2jdcx-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 15 Oct 2024 21:54:16 +0000 (GMT) Received: from pps.filterd (phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com [127.0.0.1]) by phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com (8.18.1.2/8.18.1.2) with ESMTP id 49FL1mWq019862; Tue, 15 Oct 2024 21:54:02 GMT Received: from nam11-dm6-obe.outbound.protection.outlook.com (mail-dm6nam11lp2170.outbound.protection.outlook.com [104.47.57.170]) by phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com (PPS) with ESMTPS id 427fj82dn2-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 15 Oct 2024 21:54:02 +0000 ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=TfdokG5/Gt0LRr7T9hb1uBhR+4+TGdQDmatU0+yvvO9PYYYN67mSmxaT4LAcUuhbpH1MudufDf0XYxzUk/Rv1p5G+ECj04rOy/LhCHF5lSHQQCv/utpHRbovtfRUzpGmO2b3lxJj6AuozZtrrH4dIRli5oBt0A7baE9/S58mNbz3kQdRNEG0Mf9BVVfrNPKPS/npfRjo+g4SOHiNAVfHi6KSJ8GVRg0NneGmuuavbCKCn7giqy+qhNDY0E1sBC5fBekN2NmcNoRWmWCDUcFbODuupSK+mdJAKYiKn9YoPOng/ejjWVqowfJpsUjf9rmR2POMviPraDTrYAZDF3N4qQ== 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=CpddGkmrgUlRFbpDvn74spenQBNRm7gMkCpqSs+G1uo=; b=i7ZouruW4vJdSISL/EdKU6FYiSflfp/0G7+2CDEbFz8Az6aYlv6D3vGqLPTe2/9uu8EibiJd8CiOPXjnb+B+j+rUGYjXD2uN3pxmlMTJerTZOwHAjJrgoGbdFsrTeZVr7o7GBVskWZOsgBEuubDP2zLi8m7iJhf04dWJ/osa++3ucppX5xs6FRX684LnEtO6nc9SLOY6U3ib/CigG5HdyiGJqg7cJQ31uArXoq9PEVMM9qCBfTLGx/NvPHQusWMykPf3C43FE6gndEE4v74qeU9NEGtIZ2J03mlCwRrIpnnip0wNj+zP54oR/bLLhX5HYIeY9/2eIARwAkRfBanZew== 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=CpddGkmrgUlRFbpDvn74spenQBNRm7gMkCpqSs+G1uo=; b=Zs6xlJWJUx5lbzVB5M9UbUNthT6ZplKOHMckVC2/py7o/fyv4YMjWjN1ihz45jiRBcxIr3S8/IOQdIWXgEqq3+bE/T2XX3hWJeQ8HLSlP9tUrf1DhPE35Kxl2a23arLi+w9XPsNrLAG5iV2YQM8cggNd1U1t6d+HVBD89rXk+Lk= Received: from CO6PR10MB5409.namprd10.prod.outlook.com (2603:10b6:5:357::14) by PH7PR10MB6506.namprd10.prod.outlook.com (2603:10b6:510:201::16) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.8069.18; Tue, 15 Oct 2024 21:53:59 +0000 Received: from CO6PR10MB5409.namprd10.prod.outlook.com ([fe80::25a9:32c2:a7b0:de9e]) by CO6PR10MB5409.namprd10.prod.outlook.com ([fe80::25a9:32c2:a7b0:de9e%4]) with mapi id 15.20.8069.016; Tue, 15 Oct 2024 21:53:59 +0000 References: <20240925232425.2763385-1-ankur.a.arora@oracle.com> <20240925232425.2763385-2-ankur.a.arora@oracle.com> <086081ed-e2a8-508d-863c-21f2ff7c5490@gentwo.org> <1e56e83e-83b3-d4fd-67a8-0bc89f3e3d20@gentwo.org> User-agent: mu4e 1.4.10; emacs 27.2 From: Ankur Arora To: Catalin Marinas Cc: "Christoph Lameter (Ampere)" , Ankur Arora , linux-pm@vger.kernel.org, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, 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, wanpengli@tencent.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, misono.tomohiro@fujitsu.com, maobibo@loongson.cn, joao.m.martins@oracle.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com Subject: Re: [PATCH v8 01/11] cpuidle/poll_state: poll via smp_cond_load_relaxed() In-reply-to: Date: Tue, 15 Oct 2024 14:53:58 -0700 Message-ID: <87jze9rq15.fsf@oracle.com> Content-Type: text/plain X-ClientProxiedBy: MW4PR04CA0320.namprd04.prod.outlook.com (2603:10b6:303:82::25) To CO6PR10MB5409.namprd10.prod.outlook.com (2603:10b6:5:357::14) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CO6PR10MB5409:EE_|PH7PR10MB6506:EE_ X-MS-Office365-Filtering-Correlation-Id: 1da764f5-32e4-4a9a-194f-08dced63dfec X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|376014|7416014|1800799024; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?Y7vaR+UfFvCZbOmux7N7B4jXxuI/TI43Aq5H2mrAwqeNPBfTPM4z2S6KSYmO?= =?us-ascii?Q?zQZZImQ1l2OL6ZrIqzMO0yo3rsAjLhlYPiN6xa7Zpza6mWLZVt/S29UouKNJ?= =?us-ascii?Q?GuUQAKMyH54bFDEI8VOLpNWMrFvCdb45I0yS9YzEohF5EdbvungdxCPbgUJu?= =?us-ascii?Q?9ixsb14JnP4Be0H6r1sehyZOBjx7Jo8h6fOnnk6IWyp+t4GbibJiItDlMR4K?= =?us-ascii?Q?jhJmSv0XsdIAzuh1/hYWdT7V0mYtsBgPDjlzzDevbR0LpLzsAfU6F3F+AL48?= =?us-ascii?Q?rBgZl+SDdEBw3eVm80E+CitA8nMBJLZRjw39MrlQh2kuVPYUzpKJIXECb8uQ?= =?us-ascii?Q?qM2AT6Wemt62WT6yvEw+tJnlYBx00etcZ3B+Nwvct9c/1uKPn0gF7VhMIXWp?= =?us-ascii?Q?mdHUmEYcg4fJ9YWwEdIApY3e/tKiCyEgrDUsfGTazwI68PyJ8xfC6FqllOFz?= =?us-ascii?Q?MvOaorWL2Et+xmNqSjJMdDJ9psRO+BC3X//0KP3krJyTkHo3H6JQfnKAO6dI?= =?us-ascii?Q?nvOItK1mxnbx3anwIaBLhgEoeVSd4S3QRdcu6Mb3jKQtiM7Gti4fbaI8H/zw?= =?us-ascii?Q?SNlagQ2+K/erEaGpkUrxdR1UirScKXi/Qkt1fHFa9Q8LVzvkc4pOwguOY5ll?= =?us-ascii?Q?8bDANrKHlE8qEHQkU9EnDG1E+mIradsxBZx24bJWKXUKgDHdx7QtuNAkdRiV?= =?us-ascii?Q?9SKAMU5kCL2N2WPQ/xZb3PA0JPvUd5DgsodgUKNv6tYk/gLlDqsbVfjVVuIG?= =?us-ascii?Q?nu4AzCvMSaWdJzZBbW1OiQ9k7WxDG6PNIaiHAkFQEPQoXnhyVxZ3XCVo2Bn/?= =?us-ascii?Q?jvHLmjNnOpTzdNZSEeVOD8WutlOetfi8gw/HpXfVuxXg+Bf8IyH3LcfMeQ3W?= =?us-ascii?Q?NenWqcHzcQVuCJL9L23g2/pPuYD7cz1jxAVM7l8/ruqevCHOxi/IEdMJ50OH?= =?us-ascii?Q?ONht/tnRdQEa8u/HYKaqvA0el2T5FfVq6kjgqK9ji6T2dQhJlK5RCx9VKl7v?= =?us-ascii?Q?LGbLMzSC5hkdt9nO90BBi65ZqCOUDrHC1AdvzFebFfkW4TZqoONRluVEKroV?= =?us-ascii?Q?adVRwxfCdWN/yHNuG1RreQxhLmwmqxDJ5mT19MKp3ryNwV8OSUz/SKovBnpw?= =?us-ascii?Q?hpZFatID5mO2bw2HeXuk3kIzd9CYkHBu/luTv/HbJ9kM/rTdQy9tjk8x73LE?= =?us-ascii?Q?6bcWvOWWeh4m7qmCCenJSg0ydJLuF1Zy+L0UWOxDzLaQbNasRhMP6UXOZSV/?= =?us-ascii?Q?Jp0wUu36ieMmLviOkVda2xf/fx/ze1pXSE0MT2SD+Q=3D=3D?= 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)(376014)(7416014)(1800799024);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?YsHB1P4pitdOPr3YYWWzOa6yPgKEFrvTw7mavMK0fx5bHOe7mstXqKyOFW02?= =?us-ascii?Q?GxuHDPrlpmnLiVWMEvf5VDckb5pRvHzzlCQCS+tcS4Nu2y57uEAQr+Sfz3IJ?= =?us-ascii?Q?U5d5aajCkM8eaifZOSpokBvJjo5rd9ZD2ubehQqyUaLa3N20IkT+5JsgYx9B?= =?us-ascii?Q?wlJAQlm0nqfzWLcSv6JPxerxSYxPApTSMHJKW4qzaZY08dsKb0df+UtLgNnz?= =?us-ascii?Q?CWKevP1pdm+2bcn5Bg5eq0U4ms2X5UJieMEvkLRkp65T9bnHvTAi5nFMioY2?= =?us-ascii?Q?YmPT92tsgaPkVv8AOG0RUCMyC1rFP3E2EDxLD8Z8YOr4sHF8hK/H8iK+Gs2h?= =?us-ascii?Q?V9PbwDrCtlyCk8k1x/7yPo0PFSgwr1D+G29sH6LeGp/osKQAGxoT5K/10MKm?= =?us-ascii?Q?D9Mk9ZUuvu4HDIOvOAM+Y2p96U5DQqZyuPTPjmTwQiumZUHgU9xosXufI01H?= =?us-ascii?Q?/NCzct4qg0ur4TJU/QhKtlDCyfWKvgSXhd4YybHeEnWHgPVP1aQ6ZN/TPFFJ?= =?us-ascii?Q?t7BX6pHUYtGBtEUvRUgN9II+8SxOWm8rjYiRQF3bKXjE5Bdie0eQ7N/obw1X?= =?us-ascii?Q?4i2HFzVE5Ju8BH/hneQZpZ0FkFP2aq/PF1YFUf+ldDLlcMJl1jEP8SZaWSS4?= =?us-ascii?Q?CDgq+tHiKaG8gqiaO+WVsFzM+jdJqRQHZuG9dLtfj91iqPJw3Z8tZW1VZKHe?= =?us-ascii?Q?tcJ5xxkzV3KSE+w5YSUdYzjCxJVLok51I5MLvW1vA1PFxQo2OCX9+d8fmAbA?= =?us-ascii?Q?2NfRRg4dvQMhtzvHiLNcDrSBbfQHRPuh2NCv7ad2doX3dnLseza4TloVnqf5?= =?us-ascii?Q?8Ts2S4MGu0T8CLESHkkpMBxj4mOH7h+akZwf1kh21nNAJ8BNojYRV3fYhsTs?= =?us-ascii?Q?M/JyCWjnATp+Q5xztRrCwl36ZJ9bzNg14FM2WtdFkbhF1UIAFT1jPcpzWPTZ?= =?us-ascii?Q?mqPlLYgGfCASX/qvaOWnUn+8lbI2KrakPnOuQaF80rLi73ulXkuVtAMZl1u2?= =?us-ascii?Q?diufmqHgYbxm3M9wD38M2h/PH29sghsoOUz/YBtTk6K/KNbc3+6mimbZlqhi?= =?us-ascii?Q?ZaBUvSOM9/lzb86Indbro5WaUZH1VwiL0alBFCvsJpjYmrBx8Y7z5VEz+zUe?= =?us-ascii?Q?a81FAHmaKhqi0Z7YNRsYDLoGQ8FegBJN69BBLzpe/5QygkpawvRTOAxeAyAO?= =?us-ascii?Q?4TftpZjDH8CZrdDSKaqkOpQU/duRVQMpWCj5HdLkjI6jkpCdT8PnzTt1mUUM?= =?us-ascii?Q?mq0vuBVpPATD9X27IKqBNSc0Sg3IU+sTPKH6Ja6tBkAup0FKPdaoeCSPwDzz?= =?us-ascii?Q?79SE33k5M7Io1+JGd18hzK0BEk5Pp/FiVUWgShu6aw8uhXIbOY2Lcoc09SRN?= =?us-ascii?Q?0KyXCGQM/E96hyVd9c9GWWMiuEktNAYWWN6Toref8ADwjhdCIw9Am23Ndi+t?= =?us-ascii?Q?p2LY40QaYUZoILvltxDeG/Ypc9xNY/Lpuj+BsMaGvuvC7KNYuQGAgYyZ+G6T?= =?us-ascii?Q?d8e8oiV4OtdwmKfu1873QGwkdLuhzQEyu6cwmUuRsWeYGfHyzQ3QYUtUOuin?= =?us-ascii?Q?O20I+2vLc2o6KM+P4xMSlE5hJfQxrvTqVwPaYmgmykqcDqvJnbMxIoPokCX0?= =?us-ascii?Q?1g=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: 1da764f5-32e4-4a9a-194f-08dced63dfec X-MS-Exchange-CrossTenant-AuthSource: CO6PR10MB5409.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Oct 2024 21:53:59.5461 (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: SNEwOPRwM0CJ4kj0gFQBBS4Qq3Zt2PFO1ZFITAVD4aRbIUUHZ48/D/b3u0WgsCNcNAemhg/BUM0ar51GDX//S2yNnqky5d6qdu8/V3CfCwM= X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR10MB6506 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1051,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-10-15_17,2024-10-15_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=846 mlxscore=0 phishscore=0 adultscore=0 bulkscore=0 suspectscore=0 spamscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2409260000 definitions=main-2410150145 X-Proofpoint-GUID: onGdm2AGHE1oCCmMy_DN4n-NsyNfx6ru X-Proofpoint-ORIG-GUID: onGdm2AGHE1oCCmMy_DN4n-NsyNfx6ru X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241015_145452_137253_3EF6EA06 X-CRM114-Status: GOOD ( 23.18 ) 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 Catalin Marinas writes: > On Tue, Oct 15, 2024 at 10:17:13AM -0700, Christoph Lameter (Ampere) wrote: >> On Tue, 15 Oct 2024, Catalin Marinas wrote: >> > > Setting of need_resched() from another processor involves sending an IPI >> > > after that was set. I dont think we need to smp_cond_load_relaxed since >> > > the IPI will cause an event. For ARM a WFE would be sufficient. >> > >> > I'm not worried about the need_resched() case, even without an IPI it >> > would still work. >> > >> > The loop_count++ side of the condition is supposed to timeout in the >> > absence of a need_resched() event. You can't do an smp_cond_load_*() on >> > a variable that's only updated by the waiting CPU. Nothing guarantees to >> > wake it up to update the variable (the event stream on arm64, yes, but >> > that's generic code). >> >> Hmm... I have WFET implementation here without smp_cond modelled after >> the delay() implementation ARM64 (but its not generic and there is >> an additional patch required to make this work. Intermediate patch >> attached) > > At least one additional patch ;). But yeah, I suggested hiding all this > behind something like smp_cond_load_timeout() which would wait on > current_thread_info()->flags but with a timeout. The arm64 > implementation would follow some of the logic in __delay(). Others may > simply poll with cpu_relax(). > > Alternatively, if we get an IPI anyway, we can avoid smp_cond_load() and > rely on need_resched() and some new delay/cpu_relax() API that waits for > a timeout or an IPI, whichever comes first. E.g. cpu_relax_timeout() > which on arm64 it's just a simplified version of __delay() without the > 'while' loops. AFAICT when polling (which we are since poll_idle() calls current_set_polling_and_test()), the scheduler will elide the IPI by remotely setting the need-resched bit via set_nr_if_polling(). Once we stop polling then the scheduler should take the IPI path because call_function_single_prep_ipi() will fail. -- ankur