From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from EUR01-DB5-obe.outbound.protection.outlook.com (mail-eopbgr150075.outbound.protection.outlook.com [40.107.15.75]) by sourceware.org (Postfix) with ESMTPS id 7D105384F6FD for ; Mon, 21 Nov 2022 16:56:26 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 7D105384F6FD Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=arm.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=armh.onmicrosoft.com; s=selector2-armh-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=hQZuVgACnNGq2Whr8dbt4QcSko4OW9YlVyVI/FHjdTw=; b=Y3rXKdxeoWkcepKmuRcz2Fc1GSKIWgKH8jPpgJ6k9zRTS1dwSQaYgSZ3A+hEW3oiU6hhycPAZks5rGscaxcRU55r6CF4sKaRq8Kpu//Nkj4lq2pN1LCsKWdfJVNIjB/RpHMIEPOIaPc3YjtSXAxmtSuAWMmcrw7sd74dkQB419k= Received: from DUZPR01CA0050.eurprd01.prod.exchangelabs.com (2603:10a6:10:469::20) by DBBPR08MB6185.eurprd08.prod.outlook.com (2603:10a6:10:207::22) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5857.17; Mon, 21 Nov 2022 16:56:21 +0000 Received: from DBAEUR03FT036.eop-EUR03.prod.protection.outlook.com (2603:10a6:10:469:cafe::2b) by DUZPR01CA0050.outlook.office365.com (2603:10a6:10:469::20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5834.15 via Frontend Transport; Mon, 21 Nov 2022 16:56:21 +0000 X-MS-Exchange-Authentication-Results: spf=pass (sender IP is 63.35.35.123) smtp.mailfrom=arm.com; dkim=pass (signature was verified) header.d=armh.onmicrosoft.com;dmarc=pass action=none header.from=arm.com; Received-SPF: Pass (protection.outlook.com: domain of arm.com designates 63.35.35.123 as permitted sender) receiver=protection.outlook.com; client-ip=63.35.35.123; helo=64aa7808-outbound-1.mta.getcheckrecipient.com; pr=C Received: from 64aa7808-outbound-1.mta.getcheckrecipient.com (63.35.35.123) by DBAEUR03FT036.mail.protection.outlook.com (100.127.142.193) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5834.8 via Frontend Transport; Mon, 21 Nov 2022 16:56:21 +0000 Received: ("Tessian outbound 58faf9791229:v130"); Mon, 21 Nov 2022 16:56:21 +0000 X-CheckRecipientChecked: true X-CR-MTA-CID: b34be7bfa2544782 X-CR-MTA-TID: 64aa7808 Received: from c361d211405c.1 by 64aa7808-outbound-1.mta.getcheckrecipient.com id 2CC60F44-8ED9-45BF-9986-DE2E21C92A0A.1; Mon, 21 Nov 2022 16:56:20 +0000 Received: from EUR04-DB3-obe.outbound.protection.outlook.com by 64aa7808-outbound-1.mta.getcheckrecipient.com with ESMTPS id c361d211405c.1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384); Mon, 21 Nov 2022 16:56:20 +0000 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=YZ1xIO4RC83ackxUo99ppY8C3TyCBBIb8zNWikAsnYBK32A8jIfPcU9k85SdwJyHMghi25zrgJYjFM3LXeHACWIdDmlIY/nKNd3yvP9eTYz98X9WYvlIrhbNivd/CA1ESdvsFknvV6JCCOtTERskRADxZpwD5b9cho53yXE8+xVJ0OVB7Eg9Xm/8SxjflPIM5qoZtl4I7gCLJR2vrMjDCLdmf0OlCqmj7Ii139r/B/A+MOaUqAPfdIzpoZMa6Et1xkchZdB0U1D7ZQPobmtyDP+lW19LoYi8VDDtiFnil69fWNRzgJrv5UrEwpTGZHp5wi2SBWYcytQ7fZt8oRkh3A== 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=hQZuVgACnNGq2Whr8dbt4QcSko4OW9YlVyVI/FHjdTw=; b=DDoA5+H7SPVSz89MqCiP634PSIy+rj1/eN0U6/Xh7esSfLzLjc1dhOdMrdYOdEEDemhLzRSC0quZFuybSO6o1tSZExfqf6qBrQZDzM+6I1qg0lmzQNcymkpRnyGel9Ip+7ZP2Lrtzafj+y0kabfLByyrPrzHyp0ZWB91f06MKbZNoAUeLfoHVDjtDkzjY2HebvP9cdb/nq5KfL1f0hmSCqVrQrLrlK+uT/jFcm+6Uk5Tl4a64seF+02WU164KtGPa0iPu94N98Quk5NxvTllmnu7m3W/XUi81dHzTAznZV4RYEC/XyDO6ely0PgkugPK3uM+HtWs80129reGrGPfkQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=arm.com; dmarc=pass action=none header.from=arm.com; dkim=pass header.d=arm.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=armh.onmicrosoft.com; s=selector2-armh-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=hQZuVgACnNGq2Whr8dbt4QcSko4OW9YlVyVI/FHjdTw=; b=Y3rXKdxeoWkcepKmuRcz2Fc1GSKIWgKH8jPpgJ6k9zRTS1dwSQaYgSZ3A+hEW3oiU6hhycPAZks5rGscaxcRU55r6CF4sKaRq8Kpu//Nkj4lq2pN1LCsKWdfJVNIjB/RpHMIEPOIaPc3YjtSXAxmtSuAWMmcrw7sd74dkQB419k= Received: from PAWPR08MB8982.eurprd08.prod.outlook.com (2603:10a6:102:33f::20) by DU0PR08MB7691.eurprd08.prod.outlook.com (2603:10a6:10:3a5::16) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5857.8; Mon, 21 Nov 2022 16:56:19 +0000 Received: from PAWPR08MB8982.eurprd08.prod.outlook.com ([fe80::4c73:7d14:fc39:a3cb]) by PAWPR08MB8982.eurprd08.prod.outlook.com ([fe80::4c73:7d14:fc39:a3cb%3]) with mapi id 15.20.5857.017; Mon, 21 Nov 2022 16:56:19 +0000 From: Wilco Dijkstra To: Florian Weimer CC: 'GNU C Library' Subject: Re: [PATCH] malloc: Use correct C11 atomics for fastbin Thread-Topic: [PATCH] malloc: Use correct C11 atomics for fastbin Thread-Index: AQHY/cJS/cK/f0PorUWetLVbA8LI1q5JjmOUgAADHq8= Date: Mon, 21 Nov 2022 16:56:19 +0000 Message-ID: References: <87fsecth5r.fsf@oldenburg.str.redhat.com> In-Reply-To: <87fsecth5r.fsf@oldenburg.str.redhat.com> Accept-Language: en-GB, en-US Content-Language: en-GB X-MS-Has-Attach: X-MS-TNEF-Correlator: msip_labels: Authentication-Results-Original: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=arm.com; x-ms-traffictypediagnostic: PAWPR08MB8982:EE_|DU0PR08MB7691:EE_|DBAEUR03FT036:EE_|DBBPR08MB6185:EE_ X-MS-Office365-Filtering-Correlation-Id: 9effa358-c19e-4aa6-6f04-08dacbe1512b x-checkrecipientrouted: true nodisclaimer: true X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam-Untrusted: BCL:0; X-Microsoft-Antispam-Message-Info-Original: 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 X-Forefront-Antispam-Report-Untrusted: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:PAWPR08MB8982.eurprd08.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230022)(4636009)(396003)(346002)(136003)(366004)(376002)(39860400002)(451199015)(9686003)(71200400001)(2906002)(478600001)(7696005)(6506007)(26005)(83380400001)(38100700002)(122000001)(52536014)(186003)(33656002)(316002)(4744005)(6916009)(55016003)(8676002)(4326008)(91956017)(5660300002)(38070700005)(86362001)(41300700001)(66556008)(66476007)(8936002)(66446008)(76116006)(64756008)(66946007);DIR:OUT;SFP:1101; Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-Transport-CrossTenantHeadersStamped: DU0PR08MB7691 Original-Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=arm.com; X-EOPAttributedMessage: 0 X-MS-Exchange-Transport-CrossTenantHeadersStripped: DBAEUR03FT036.eop-EUR03.prod.protection.outlook.com X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id-Prvs: 598040d4-f208-4f1c-b787-08dacbe14fe4 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:63.35.35.123;CTRY:IE;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:64aa7808-outbound-1.mta.getcheckrecipient.com;PTR:ec2-63-35-35-123.eu-west-1.compute.amazonaws.com;CAT:NONE;SFS:(13230022)(4636009)(136003)(39860400002)(346002)(376002)(396003)(451199015)(36840700001)(46966006)(40470700004)(41300700001)(40480700001)(8936002)(52536014)(316002)(70586007)(4326008)(5660300002)(8676002)(70206006)(55016003)(86362001)(6506007)(82740400003)(478600001)(83380400001)(26005)(2906002)(356005)(81166007)(33656002)(7696005)(6862004)(4744005)(336012)(186003)(47076005)(82310400005)(9686003)(40460700003)(36860700001);DIR:OUT;SFP:1101; X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 Nov 2022 16:56:21.6071 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 9effa358-c19e-4aa6-6f04-08dacbe1512b X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[63.35.35.123];Helo=[64aa7808-outbound-1.mta.getcheckrecipient.com] X-MS-Exchange-CrossTenant-AuthSource: DBAEUR03FT036.eop-EUR03.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DBBPR08MB6185 X-Spam-Status: No, score=-5.1 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,FORGED_SPF_HELO,KAM_DMARC_NONE,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_PASS,SPF_NONE,TXREP,UNPARSEABLE_RELAY autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: Message-ID: <20221121165619.1XXGdv8oIMATy51qKHfqUYmCR9UrXl9aQl_hyjOnvAk@z> Hi Florian,=0A= =0A= >> Fix memory ordering issues in the fastbin implementation: in REMOVE_FB t= he=0A= >> next pointer is read before any MO synchronization, however in the C11 a= tomic=0A= >> model this is only correct after a load acquire. Refactor the fastbin co= de=0A= >> and add a dedicated fastbin_push/pop implementation. The number of acqui= re=0A= >> or release atomics remains the same, and the new functions are inlined, = so=0A= >> performance is unaffected.=0A= >>=0A= >> Passes regress, OK for commit?=0A= >=0A= > Did you actually observe any problems resulting from this?=A0 We=0A= > previously concluded that the dependency chain would mae this valid=0A= > (outside the C11 memory model).=0A= =0A= No, I believe it works in most weak memory models (except for Alpha).=0A= However the code always looked weird with the acquire done after several=0A= non-atomic accesses... The key is that we need to do the acquire/release=0A= only once per iteration in the CAS loop, and that avoids regressions.=0A= =0A= Cheers,=0A= Wilco=