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Tue, 6 Sep 2022 16:49:55 +0000 From: Wilco Dijkstra To: Florian Weimer , Wilco Dijkstra via Libc-alpha Subject: Re: [PATCH] Use C11 atomics instead of atomic_bit_set/bit_test_set Thread-Topic: [PATCH] Use C11 atomics instead of atomic_bit_set/bit_test_set Thread-Index: AQHYwUVpNZ5UYNp6Mk2+9/hh6vxlA63SUTg1gABF/yw= Date: Tue, 6 Sep 2022 16:49:54 +0000 Message-ID: References: <87mtbc66t4.fsf@oldenburg.str.redhat.com> In-Reply-To: <87mtbc66t4.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-Office365-Filtering-Correlation-Id: 5e3b63e2-6c02-47dc-7535-08da9027db55 x-ms-traffictypediagnostic: DBBPR08MB6106:EE_|AM7EUR03FT040:EE_|DBBPR08MB6282:EE_ x-checkrecipientrouted: true nodisclaimer: true X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam-Untrusted: BCL:0; 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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Sep 2022 16:50:08.3656 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 5e3b63e2-6c02-47dc-7535-08da9027db55 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: AM7EUR03FT040.eop-EUR03.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DBBPR08MB6282 X-Spam-Status: No, score=-5.2 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,T_SCC_BODY_TEXT_LINE,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: Hi Florian,=0A= =0A= > Why is acquire MO required here?=A0 I don't see any synchronizing store.= =0A= > Isn't this mostly a compiler barrier for use-after-free detection?=0A= =0A= You're right, it looks like the only reason for atomic is to ensure memory= =0A= is only freed once. A few cancelhandling accesses use acquire, and there=0A= are various relaxed loads and even non-atomic loads of it, but not a=0A= single release store, so there is no use for acquire MO here.=0A= =0A= Cheers,=0A= Wilco=0A= =0A= v2: =0A= =0A= =0A=