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 9EEB2C5AD49 for ; Sun, 8 Jun 2025 13:57:02 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E662D6B0088; Sun, 8 Jun 2025 09:57:01 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E16DF6B0089; Sun, 8 Jun 2025 09:57:01 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CDE7D6B008A; Sun, 8 Jun 2025 09:57:01 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id A77276B0088 for ; Sun, 8 Jun 2025 09:57:01 -0400 (EDT) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 174541A15CF for ; Sun, 8 Jun 2025 13:57:01 +0000 (UTC) X-FDA: 83532384642.10.405C685 Received: from mx0a-00069f02.pphosted.com (mx0a-00069f02.pphosted.com [205.220.165.32]) by imf22.hostedemail.com (Postfix) with ESMTP id 8A39AC000C for ; Sun, 8 Jun 2025 13:56:57 +0000 (UTC) Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=oracle.com header.s=corp-2025-04-25 header.b="U/T37HTo"; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b=UkBdjLhy; spf=pass (imf22.hostedemail.com: domain of harry.yoo@oracle.com designates 205.220.165.32 as permitted sender) smtp.mailfrom=harry.yoo@oracle.com; dmarc=pass (policy=reject) header.from=oracle.com; arc=pass ("microsoft.com:s=arcselector10001:i=1") ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1749391017; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=iBpC1qbU6448jpuf0uVc5kL2Wn95SzKEstvDGxlkwUQ=; b=fwCauyqncA8nhE+l80+GUALb2xygnZErLYxjHthqbbaFz4NSy1AS5n2LXD0M+h4x6br9iw W5VXvn6fMYdIisQgEOr+5wBhuUk1ZzrF8JOt+1IgggOEjPpZNf+f8zS+blVReuY5CL0VMW GtX/uEp9FxheElOqA8vgzRzRLCPEZiM= ARC-Authentication-Results: i=2; imf22.hostedemail.com; dkim=pass header.d=oracle.com header.s=corp-2025-04-25 header.b="U/T37HTo"; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b=UkBdjLhy; spf=pass (imf22.hostedemail.com: domain of harry.yoo@oracle.com designates 205.220.165.32 as permitted sender) smtp.mailfrom=harry.yoo@oracle.com; dmarc=pass (policy=reject) header.from=oracle.com; arc=pass ("microsoft.com:s=arcselector10001:i=1") ARC-Seal: i=2; s=arc-20220608; d=hostedemail.com; t=1749391017; a=rsa-sha256; cv=pass; b=hU9AIJT23AetZWT7ufrp/M+NNbpItqwuO/TBV0ZY8X1j8AGysUBlgcQOGs8RpOGrxD6Bw2 tQKM9rIuwCSQooeXVZbXn3c7JpojFP9YG/jXbzeaUQ7ADMd4Em15SUODN2e8JU6ncAmwQK nakzTWyq2LhZUh/Jksns8SPC5qZPHdM= Received: from pps.filterd (m0246617.ppops.net [127.0.0.1]) by mx0b-00069f02.pphosted.com (8.18.1.2/8.18.1.2) with ESMTP id 558BlMbZ023252; Sun, 8 Jun 2025 13:56:52 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=cc :content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s= corp-2025-04-25; bh=iBpC1qbU6448jpuf0uVc5kL2Wn95SzKEstvDGxlkwUQ=; b= U/T37HToOmLX+h6dZ522ztjEGbtEJyZPft2uj/DbKFiyiuW/vEwQTMyeipxo3pUh CUheAXD+BE23lW8LJtXqB+EwL52ujwb1QIMB9dtlkbhJhqZ042OifTae8DPdXv4L INyy1bhHW3te/wNsiLwH9taSqwYq31lZhbz12JVYIXsj5RY3iIw0TsIx35wWrl8I J49gvl0RCIm2clf30/fI3RwhRh7K0pJBquhQYhLgHkb1XFm49b89lrFMAWWqvDoI EkU25DeEu7IpX63g4yzdlYhq3awrAhBeRgF6BQV9k94QspoaELDwcPRO8oNca8mb CAxVT/YajmcdYjlQh/ruWw== Received: from iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com (iadpaimrmta02.appoci.oracle.com [147.154.18.20]) by mx0b-00069f02.pphosted.com (PPS) with ESMTPS id 474dyws0ap-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Sun, 08 Jun 2025 13:56:51 +0000 (GMT) Received: from pps.filterd (iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com [127.0.0.1]) by iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com (8.18.1.2/8.18.1.2) with ESMTP id 558BHYAv003992; Sun, 8 Jun 2025 13:56:50 GMT Received: from nam11-dm6-obe.outbound.protection.outlook.com (mail-dm6nam11on2040.outbound.protection.outlook.com [40.107.223.40]) by iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com (PPS) with ESMTPS id 474bv6mpqf-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Sun, 08 Jun 2025 13:56:50 +0000 ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=JX9XSCsyIwHcqzGFipv405raIOIXLmS5Ffd+7WWZEUIMOHGFAcVH4kngvCsUZex7W939UT+Twt/tFi7DBwOznZs84AXpziTuw42BjfRapSCVEbexrynGhOv3K/BcvCuOTc7b5VFYEqK5RMGp+6uaPr3ciOAZ4vXIJjMPyIujsHwALTeGgKcwO+8H4KsjGz3lY0DHFvvUJ9kTgNaAdUXWAUQUCJnRLBwhlmlB6w1fngpbPIYf7GCYCrwu0CGbF8oIPb5m5p+9C26tXeQ6wFr1h0P+p2uv5vWBF3PmXC1HJX5r8PfEu/MHhrju941a0kehXiSlQoRuWs0pWEgatk9TEg== 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=iBpC1qbU6448jpuf0uVc5kL2Wn95SzKEstvDGxlkwUQ=; b=guuhEhP+mOhTVG1vt48daksROZegfP+Bvfei97M8rNR5MObVlpljgluAnqamz1CnpFkGXYo5FuvbF2wN8AdP8e+qVA+40/2tjBRGbnCNzbP082TG+jqkdP2yK2Wz9e2izxAChrtksHxJFnBRRpR6ybNqWaghP3e3ORhuu/BvlEZfw8fbTFfPHRcTZSPVFeitEfRuFx4VJqtnQtEF4qMoPEI9srYyYophab9pXl83/2mlO2jn/mq0+MWnkCDRVhhbqz/Th6csgaQO9/2tK47zDpMS7jYfWKMSMWTO4g5Drc6kEK6Wt2u60kUpjQM0mOvCgk5+ECxi/Jy/Bl0EFxa/EQ== 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=iBpC1qbU6448jpuf0uVc5kL2Wn95SzKEstvDGxlkwUQ=; b=UkBdjLhyrOy1hHFfCU2mv8TL06w2G7pVSHEyiqr2F+KrgjXFBFlUQexLRG4Fzg37RUKz10tjxazDmXMoUJbVP7LwWDMnUoE4BwnIKDlWrZPIZEJPQOFUgmq0W31kRGrbCEyp+Wnkx1pWMpK9ZdPSPcBdrRY/yMgFlXJQBsPclIE= Received: from CH3PR10MB7329.namprd10.prod.outlook.com (2603:10b6:610:12c::16) by CH3PR10MB6902.namprd10.prod.outlook.com (2603:10b6:610:14e::6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.8813.19; Sun, 8 Jun 2025 13:56:46 +0000 Received: from CH3PR10MB7329.namprd10.prod.outlook.com ([fe80::f238:6143:104c:da23]) by CH3PR10MB7329.namprd10.prod.outlook.com ([fe80::f238:6143:104c:da23%4]) with mapi id 15.20.8813.022; Sun, 8 Jun 2025 13:56:46 +0000 Date: Sun, 8 Jun 2025 22:56:34 +0900 From: Harry Yoo To: Yeo Reum Yun Cc: "linux-mm@kvack.org" Subject: Re: [Question] Question about GFP_ATOMIC allocations on PREEMPT_RT kernel Message-ID: References: Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-ClientProxiedBy: SE2P216CA0167.KORP216.PROD.OUTLOOK.COM (2603:1096:101:2cb::17) To CH3PR10MB7329.namprd10.prod.outlook.com (2603:10b6:610:12c::16) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH3PR10MB7329:EE_|CH3PR10MB6902:EE_ X-MS-Office365-Filtering-Correlation-Id: 3a16fe56-5d2b-4b5d-8f19-08dda6944e7f X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|376014; X-Microsoft-Antispam-Message-Info: =?utf-8?B?WlJsUnZyVXJzbkJ0SHBwMm5abTFFWFBUU1pnenFoT1VHSkZ6UjRrQXFpbnRI?= =?utf-8?B?WDN4eCs0ejhGZXA5RjlzQVJVVEJHSlRld3RIRzhwQ1BpOHZTY3pIVzZUS2hX?= =?utf-8?B?bjJidHpmeVZ2WHpScnhiRXpEd0syTVRRSE51RnI5U2pNQmV3eXdsSEZtSXh6?= =?utf-8?B?VmhWTFlFdTlCdzJZRVoxYUlDVjVXb3I0WWxxaXlhaFNFR2JqeTJ1WVhaM1Nz?= =?utf-8?B?SG4vNWh4ckdnQjFMeGczKzV4ZDJpS2s2QzBld3NuZk1kc2NOZ2lYN3BHbmVj?= =?utf-8?B?bHpVVTh4ZXVqMEYrOHhqUFQxUEhibkNhbEhhMEk3K1ROWGFxaXI5UEpTUlNp?= =?utf-8?B?VzRqTEg1dHJmeHNKY3lRem04dG1OQUVuSzZUWXZkWkR2Z3NJbGZwQmZlZ2hq?= =?utf-8?B?eXZPWkg1VmpUY0FiSkVLaENXZnVCcC9lVkpiTXpTbGlHQ2lFNXRkRjFhT2NU?= =?utf-8?B?dnBaVUVVbGdoVFFtY1VHenBsTitoK3pRWXpEdXpCUzg1QWZzMlMyTFRxVDZU?= =?utf-8?B?VmlWQTVaaEpIT3EvNG9RR3ZvMlhCeVB6SGtKdWJ5SjFmVkpmV0UxT0J5UDJq?= =?utf-8?B?L0IrN0Q0TDhOVGQ0VkVITHJra1EzaUdHL3g3c0NuaVAvcVVwL0ZUcE5XODAw?= =?utf-8?B?UEgvTEZxTVZjbWE5dWl2U1YvUEt4Z0JYdGdVQy9qNG12czQ1LzQ1andTd2NC?= =?utf-8?B?U0NpVERCdjA4bFJIdGUyMEt0YUNMUDRmUlhUWnJLMWhXWXVTMlZxTWYwMlBR?= =?utf-8?B?d1Q4WVNKTDJkemprZyt3UExPb1BpRFZpTG8zbGFFVWlHU1FwME9maGdPbmJl?= =?utf-8?B?amJSWlBZeHVOdXFGTnBEejVnVFpxU3YzSDR4Z2xDZWRyT1IrSG9UUmZlWjdL?= =?utf-8?B?eVhjdE9PZE92U2VaQVBkMFB0akVVWmpldkJnMlNGaVVDTlRRcVdBUSt3OWpp?= =?utf-8?B?YzhLNGV5M2kzV2ZNeTI5SE1WcTAySmV6SnRYUTkwTVZscGJXWFgyUE9rOVJU?= =?utf-8?B?d0lHUW9teWg3K3g1bGlNdjlPcnNUNkVrNGVwV1BSTFFzRXNJL1pGN0FyS2Yx?= =?utf-8?B?TnBkU0h0R1RZT3gzQ0FpcXNhVThPNzBhWHh3anJzQ3dsTG5nT0VrNnNoWGM4?= =?utf-8?B?V2h5OUZIOVVOa3lZdTc1bEQyNGdUSExTa2dtWFFCZ1JUVkdKQ2Nxa0w1SzhW?= =?utf-8?B?ZUd4Tm9sOFZwQTJjTXh2YjVCTytRNmpqcDJXUlpqdWloandyOGs2QkNYWi9I?= =?utf-8?B?Y3VDazVhdkxJM3JkN0s5QzBJaWFubjFDUGw1amg4UUFZWlkyL2dFMjVvaVZx?= =?utf-8?B?bERhTzMyYmkybDE0WWgvbWpxNlk1Sng3enI1T2d1d3pLa0p6TkNVME9MRGZS?= =?utf-8?B?Ym40cDdYL29NOEt6ZW8yZ2RWeXRHQ3RKUThtczVBWjBIYllhbFJaeFpNRE9E?= =?utf-8?B?cWVpemtPQzArbGNleWNvQjlBaTBTdk9JM2J4UVZWelgyWTc4Z1hPMnR0cmR6?= =?utf-8?B?UzBRUnJES2RDenZSYmNBZUZhUWtuMkVzNC9iTzJJb0hpV3FXMW9jdXlrY0RK?= =?utf-8?B?MW1TNUtyNjZGRzVmTzBla1BXQmljOUFqVk5vYkp4Q25rNFpwTVkydmtPa25U?= =?utf-8?B?NkRscXZFOG1mMUszS0ZONUg4Q1FjTDV2Z0JYN2s5RlhsajFCYk1KcUdUeUVp?= =?utf-8?B?dmJuYlBDbVNqOHExUU1LR0VSVGpQdWN6bndGdzRKNDRPMUV3ZEVXM2JIK1Vz?= =?utf-8?B?TWVVUEs0aGJ1STVweFFGSDBZbmgwdmxKMTRoczFFcjU4TWpieDFrMnFqU1J2?= =?utf-8?B?RUg2WGRQN1N2QzdVdVVZaXFPWWVMWHF5bUh0VEZTWEp0Uk8rTTBDd3BJV3Qx?= =?utf-8?B?UTBTV283Q24yamFvRGF3NHYyOTVHRVVpMGxEeWZjVThOWjl3SjBnU0psSFgx?= =?utf-8?Q?3kATV9qgI5HDoMinJ6tg1JlFsvGLxH9b?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:CH3PR10MB7329.namprd10.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(1800799024)(366016)(376014);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?bGkwTTg0Myt0a1pxWUFxZWJ2anFTTFpoZkowblhDNjZBcThGQjBQUmhTaHZK?= =?utf-8?B?SEZFMXNWWHh3d1hJMW5nR05nZHRDNG9PNkRsWTJtVk9YbG1lZGtQTHVtVGJz?= =?utf-8?B?MzViL1kvSUUyalhkMFo2UU9PdVlGcXJvTEpJWU85dzJ0MWliNnVjMG1LN1pO?= =?utf-8?B?b3NEUWljQ3ArZ280dlVjdTVkdllNb1o4ZndTRjRFYm9IeWtJNHpPVk5LTzRa?= =?utf-8?B?ZHoxTVZsalhCNDNiSlNVc3VzNkdxOHlWVklPakhuRENtbjhDWERXUVFTN0hy?= =?utf-8?B?a1FkaDZDTkRoNG1qcGVvSFlpRDJiZjB6ZzZiR2JsZW4zZmJocEFEVmdvcFRU?= =?utf-8?B?RS9LWktUMFE0b1YrbUplb29KcUE0YkdIOW1ZeFc5NlVndHVaMFNEdExRTnZ0?= =?utf-8?B?czAvbEh6MmYzY3VYMGplU2ZIZTVuSjZhNWd2Wk0xUFMydmN6SWVlTFJaRjkz?= =?utf-8?B?UGhSMjQ2eHRlaW5Fdy95MVpZa3FnemQxeHRsVDBMMXlCdy9zQWdJM3hCOVE3?= =?utf-8?B?OXNZSWtDYU53SUN6QkhRS2Q0Q2RER0l2Umd2SEVJWHVIYWtaQ3VhRkZXMFBQ?= =?utf-8?B?MjY2L3NWNEJreHlGb0N5OGRCRThQaERFQ2FGQ2M3V05wNEs4OGRBM2JkeVNQ?= =?utf-8?B?cGQyb0dFQ2hpOG1FbXBwaXB3eG1qcitjWmxwMDdwVWxRUVFOOWpGUnVKOWoz?= =?utf-8?B?bzBGaU1wYjdUanI4ZFNEWjFkd3ZEN3VyTGhqQnRRQ0FkWFF2dndMUDhnVzN5?= =?utf-8?B?WldUOTVZc1NWeUM1eS9BVE9qbXdVTDZJUlh5b2tQZlQycW9EaFlEZG5nODIx?= =?utf-8?B?bFVHdEdJc0UvL0xEUFRYNGloZ3VDd08vQVNQdjBSYWhoL2lpVzNiWkhCa2Uz?= =?utf-8?B?SWoyemRTUmdKajE0b2gvZ3YzVFU2dzh1ZEJIWlFFZXgzTUJKZzlXcTJla2Vw?= =?utf-8?B?N1R4Ny9EeEMwdEkxYlEzZ25vSDU5aUFQSkU4WkY0cllTL011c2NHRGptNi9m?= =?utf-8?B?bDZqSzI5K1FGbS82anhjY1RTRXVZcWlXVDVFakg1ekR6YlpwUVFvSWVMZkha?= =?utf-8?B?ZWwvNkF0MEc2NUoyQ3FZaHE2NEdQb3NQUU0vQWdQM2RXeTYzMG42NW52OHZy?= =?utf-8?B?WitaSnJpN2E2VXUvYmRMYWoyOUlncm1DTWtveEx6bmRFNDJsQlgvQm0rYXZI?= =?utf-8?B?VDZQNk9NQm5STGhyUUdUUlBESEhYcW5XVjEzalZMZEFvb0lBdWorczZTUWlR?= =?utf-8?B?ZHMzbHhFcEkrdEgyV1lmcXlnOVllYUxEenE1dXlvWUE2VWlwakdDSGMzWFI3?= =?utf-8?B?a0UvcVAyUHNHTHBiZG9ic0dOL1J5VTRjenpyeU03SDlGNWRkV25VOXpXNE1K?= =?utf-8?B?VHJWeGtTL2J6NWNtYUp5czZzcFMydC9YREtDampWUmljdTVSbFZOcHpOS2VE?= =?utf-8?B?Z093alpocXQ1emdxRFFpRlNwcVpnSkJSZk1hM3hDeTFxYVdNWWt6VHU0eldK?= =?utf-8?B?STh0MmhhaGxuTGVqQ25GUi9RSmZnU0ZpU2ZUSi84OFpUY0pCdXZVVU9GSDBO?= =?utf-8?B?eGNjajZwd1hxTzUwMDVZNS9MUGRIWmZPMDh2WjVQOVp4dDNpd2h4ajhIMG5D?= =?utf-8?B?RUdML1p6RnprZ0ZFR2xtMzB6Qm0vWnVHRnJTc2NGM0ptSUNQZzYrQlZ6WGdV?= =?utf-8?B?RXgzc3hMakV4RWtqaGhsbXJ0VlRZQ2liT2JZZEN1dFFHTmpQbU12YmF6U1hM?= =?utf-8?B?eHdydUtHL21wN0NVQUxTeVRaSnRtMzRZQVZWcis4L01ZaVNML3JyS2g2MDZD?= =?utf-8?B?Y1NFZXQ5SzJoQXE1aVY3cU9MYXJVVDlzWUN2M05xd1hwRjREdmRjOEdzNGNI?= =?utf-8?B?VkJoZ0xROHRic2p2TjhPNlBGdEppd1F3WEVHY3RVdWhpaHVqTjdLeVJIVUty?= =?utf-8?B?RXNEeDV4VzRMU1RLd2JDWXY0dWxUTWJ2Mis0OU5hL1lZRHZVaGxFRG4vbFp6?= =?utf-8?B?d2VHUWMyNS9IZjFhRytaZWFkWFg5MWM4dGlrMTd6cHZJWFQrTStNOExNMGVu?= =?utf-8?B?QVZreWxwWGZQRTdzelpwQXp6cklwUWs5cUsrcTdBUzJmWEhBVTZNbGxQNmJ3?= =?utf-8?Q?ygzpvCztlcbtqz2lM/8K1ePRU?= 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: 3a16fe56-5d2b-4b5d-8f19-08dda6944e7f X-MS-Exchange-CrossTenant-AuthSource: CH3PR10MB7329.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Jun 2025 13:56:46.0203 (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: TA0p4W1qeT4mG2/hBI93e8x7G44/7f9X5d4Mdf3zRK+DkRL7rcdzKs5i64nZxu7eOlPNxBP7Q+7cc9PpMFJ0jQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH3PR10MB6902 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.0.736,FMLib:17.12.80.40 definitions=2025-06-08_01,2025-06-05_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 malwarescore=0 mlxscore=0 mlxlogscore=999 phishscore=0 spamscore=0 suspectscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2505160000 definitions=main-2506080110 X-Authority-Analysis: v=2.4 cv=fdaty1QF c=1 sm=1 tr=0 ts=684596a3 b=1 cx=c_pps a=e1sVV491RgrpLwSTMOnk8w==:117 a=e1sVV491RgrpLwSTMOnk8w==:17 a=6eWqkTHjU83fiwn7nKZWdM+Sl24=:19 a=lCpzRmAYbLLaTzLvsPZ7Mbvzbb8=:19 a=wKuvFiaSGQ0qltdbU6+NXLB8nM8=:19 a=Ol13hO9ccFRV9qXi2t6ftBPywas=:19 a=xqWC_Br6kY4A:10 a=IkcTkHD0fZMA:10 a=6IFa9wvqVegA:10 a=GoEa3M9JfhUA:10 a=VwQbUJbxAAAA:8 a=gfrzBx4ME0TrB5gni64A:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=XhQ3FY-fmj0A:10 a=1gCXawTtZ44A:10 cc=ntf awl=host:14714 X-Proofpoint-ORIG-GUID: HuAkDL100wgWGf1b4GDTxMzYcHoEW5PH X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNjA4MDExMCBTYWx0ZWRfX0H+y8qKwhwYy nAOrBVN0CP/xuvaI9EIKfCcAZ0SoV4cdd3emE8cxj8c5hrkZnw37h4ymIge4yKQDoKxJc69iDxF gR69BaacL8SR+f99W4XW8VpKVVotzY+r1cI65lH9hhn2OhxwAUHHsLvHs2/o2p84uEOwwEk+JfV E+CCLoz/YuDlLlk7SXT1RQuBH1CelNpl4/qvsXocSIjG2wghOTRJ/f547KAz5GtJhzgPic9LZ9+ v2WLKitgN3pPOsK8M9L+ILdkEXL6bbDAmCwdZkCBPJxbe3EvO5Kunc8zWnNWSZmTDSrg1h/APQX MB/NMIdX4/gidsdzNQwLdTJ2Txy/6iUk0M7sPDurl3V7eyDNU6ZA0X3idTV5b2KkVf3Mb9RF3fQ vhLWQ7smhEsxSXl4IJGE/fDhKTR4Fzq2YYbk7YdPOYOLFo4dJM6mFg/DnU6YH6GoLROy3DOD X-Proofpoint-GUID: HuAkDL100wgWGf1b4GDTxMzYcHoEW5PH X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 8A39AC000C X-Stat-Signature: ud9nqtsc3qn33cbpoxjshrwd3wirp8pi X-Rspam-User: X-HE-Tag: 1749391017-481773 X-HE-Meta: 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 C06IO76r CjXNhRtsteUarABCqQkxQ+L/By1AzuGAZVpYNzsECIXePK7xnGiRrczJoGD4Nf/dZiMPHokE2wVIoPqheR4in/Yq6zEZw7kJhR1REF70uHWT3a6H3QNq3eGbPSX7LxG6XHZ4ZmtghU3umwqYkSBxAxDQrenThhdkprKNbjau5sRsfdw4tYsjggjl52NVhMSlwNtRcwsJDIUZ0wNgZ75E9x0fcW3NMxGjz6rfXgxQIJepQyuniOKvt0in7yvD3wNUBhVfmNtzpEZKyT9GCUDhjm8/q7iyPmVzmY8JViYfsXF9qbiWor941gXOaaZRLpMLcuD5wZ5h48ucMHx7pdbmYZG5qiNmQpSZBxcZiAAID0f50sepsuXOQaQeFip0Xp2nEccWbP+sPp+RzufvXAXIKTlSBCVBydIt1Yq29tEkUrx5O0G5rpF0obzb43gh8qAPN49IK1nugN8nlIK+K17g4uQMiyYHII0UyV6fg9yVQtRdxY1qBI3Ms7vB9mSXrxUNmHl72BHcUsQG8wIEN9V2BZrzB7Z0s6dYCdgq9YLh3HnjnzAXNmmA8gczx11QXl6Y7BlQ1nktMKgYpzvnaSdUuQldrjWYMQ7ddzXTGyxNcxmFxVoBit7swiy8mzZLKL8tI8sVCJrNtyuTbH22+3CowKU4d6ImB9KRg1X2EZEPnvIZN1qeRVJ9B3/uJEUU0/GAaE2fOYx6hzZBkB7THlRYsh9Bh1EEnolui36Uw5CpzigwlbkecfQXnPvcZvFPTNNH+ruB9qBexXWWOasUp+wtzSX4/LxAeF/13YYnb6xSpqUoAkJrIjt8QPao48Sod4JpbaqJN5KqHWXf4+tZOfa0ipXup5VpYIH028sl4V540dj96lwRMLrGeBhH9gbpDoXKAkTo04lqPNQ4duhE= 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: List-Subscribe: List-Unsubscribe: On Sun, Jun 08, 2025 at 01:33:14PM +0000, Yeo Reum Yun wrote: > Hi mm experts, > > I have a (possibly silly) question regarding the use of memory allocation with GFP_ATOMIC. > > According to the latest documentation in core-api/memory-allocation.html, > using GFP_ATOMIC is acceptable in interrupt handlers: > > GFP_ATOMIC: > “(GFP_KERNEL | __GFP_HIGH) & ~__GFP_DIRECT_RECLAIM (aka GFP_ATOMIC) – > non-sleeping allocation with an expensive fallback, > so it can access some portion of memory reserves. > Usually used from interrupt/bottom-half context with an expensive slow path fallback.” > > This makes sense on non-RT kernels, where spin_lock() is non-sleepable. > > However, how does this behave on a PREEMPT_RT kernel? > > From what I see in the buddy allocator, even allocations using GFP_ATOMIC > can potentially sleep, since some of the locks used (e.g., zone->lock) > are implemented as sleepable rtmutex under PREEMPT_RT. > > This seems fine for most interrupt handlers, since on PREEMPT_RT, > they are handled in dedicated IRQ threads — which means they run in a sleepable context. > > But what about interrupt handlers registered with IRQF_NO_THREAD? You're not supposed allocate (even with GFP_ATOMIC) or free memory on PREEMPT_RT in non-threaded interrupt context [1]. I think it somwhow implied in [2]? (Ok, probably not that obvious) "Acquiring a raw_spinlock_t disables preemption and possibly also interrupts, so the critical section must avoid acquiring a regular spinlock_t or rwlock_t, for example, the critical section must avoid allocating memory." "But this code fails on PREEMPT_RT kernels because the memory allocator is fully preemptible and therefore cannot be invoked from truly atomic contexts." [1] https://lore.kernel.org/linux-mm/YwZSUpYY9l442Lxr@linutronix.de [2] https://www.kernel.org/doc/html/latest/locking/locktypes.html#raw-spinlock-t-on-rt > Those handlers run in hard interrupt context, which is non-sleepable. > If an allocation with GFP_ATOMIC involves a sleepable lock (like zone->lock), > wouldn’t that be problematic? > > To my knowledge, it’s not clearly documented whether memory allocation functions like > kmalloc(), alloc_pages(), or folio_alloc() are explicitly forbidden in truly > non-sleepable contexts under PREEMPT_RT. > > So my question is: > Is it always safe to call GFP_ATOMIC allocations from a non-sleepable context, regardless of the kernel configuration (i.e., RT vs non-RT)? > > Thanks! > IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you. > -- Cheers, Harry / Hyeonggon