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Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [RFD] posix-timers: CRIU woes Content-Language: en-US To: Thomas Gleixner , Andrey Vagin Cc: Frederic Weisbecker , LKML , Anna-Maria Behnsen , Peter Zijlstra , syzbot+5c54bd3eb218bb595aa9@syzkaller.appspotmail.com, Dmitry Vyukov , Sebastian Siewior , Michael Kerrisk , Christian Brauner , Alexander Mikhalitsyn , Pavel Emelyanov References: <20230425181827.219128101@linutronix.de> <20230425183312.932345089@linutronix.de> <87zg6i2xn3.ffs@tglx> <87v8h62vwp.ffs@tglx> <878rdy32ri.ffs@tglx> <87v8h126p2.ffs@tglx> <875y911xeg.ffs@tglx> <87ednpyyeo.ffs@tglx> <87r0rnciqo.ffs@tglx> From: Pavel Tikhomirov In-Reply-To: <87r0rnciqo.ffs@tglx> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: KL1P15301CA0058.APCP153.PROD.OUTLOOK.COM (2603:1096:820:3d::18) To VE1PR08MB4989.eurprd08.prod.outlook.com (2603:10a6:803:114::19) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: VE1PR08MB4989:EE_|DB9PR08MB6571:EE_ X-MS-Office365-Filtering-Correlation-Id: c810316a-4b54-4a81-a0b5-08db52056ff4 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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It isn't good to ask users to update >>> CRIU to work on new kernels, but here are reasons and event improvements >>> for CRIU, so I think it's worth it. >> >> I agree, any API to create timers with specified id-s would work for new >> CRIU versions. > > The real question is whether this will cause any upheaval when a new > kernel meets a non-updated CRIU stack. Creation of posix timer would hang forever in this loop https://github.com/checkpoint-restore/criu/blob/33dd66c6fc93c47213aaa0447a94d97ba1fa56ba/criu/pie/restorer.c#L1185 if old criu is run on new kernel (without consecutive id allocation) AFAICS. > You know the UABI regression rules of the kernel... > > Thanks, > > tglx > -- Best regards, Tikhomirov Pavel Senior Software Developer, Virtuozzo.