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McKenney" , Chris Kennelly , regressions@lists.linux.dev, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Peter Zijlstra , Ingo Molnar , Blake Oler References: <87zf2u28d1.ffs@tglx> <87wlxy22x7.ffs@tglx> From: Mathieu Desnoyers Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: YT4PR01CA0344.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:fc::29) To YT2PR01MB9175.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:be::5) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: YT2PR01MB9175:EE_|YT2PR01MB8952:EE_ X-MS-Office365-Filtering-Correlation-Id: 7da60632-af83-42b9-03ea-08dea133fe33 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|366016|1800799024|56012099003|18002099003|22082099003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:YT2PR01MB9175.CANPRD01.PROD.OUTLOOK.COM;PTR:;CAT:NONE;SFS:(13230040)(376014)(7416014)(366016)(1800799024)(56012099003)(18002099003)(22082099003);DIR:OUT;SFP:1102; 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The > kernel no longer reliably provides clearing of rseq_cs on preemption, > right? > > https://git.kernel.org/pub/scm/libs/librseq/librseq.git/tree/doc/man/rseq.2#n241 I'm maintaining this manual page in librseq. > > "and set to NULL by the kernel when it restarts an assembly > instruction sequence block, > as well as when the kernel detects that it is preempting or delivering > a signal outside of the range targeted by the rseq_cs." I think you got two things confused here. 1) There is currently a bug on arm64 where it fails to honor the rseq ABI contract wrt critical section abort. AFAIU there is a fix proposed for this. 2) Thomas relaxed the implementation of cpu_id_start field updates so it only stores to the rseq area when the current cpu actually changes (migration). So AFAIU the statement in the man page is still fine. It's just arm64 that needs fixing. Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com