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McKenney" , Joel Fernandes , Josh Triplett , Boqun Feng Cc: Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Zqiang , linux-arm-kernel@lists.infradead.org, rcu@vger.kernel.org, linux-kernel@vger.kernel.org, Stefan Wiehler Subject: [PATCH] arm: smp: Avoid false positive CPU hotplug Lockdep-RCU splat Date: Thu, 7 Mar 2024 17:09:51 +0100 Message-ID: <20240307160951.3607374-1-stefan.wiehler@nokia.com> X-Mailer: git-send-email 2.42.0 X-ClientProxiedBy: FR4P281CA0404.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:cf::6) To PAWPR07MB9688.eurprd07.prod.outlook.com (2603:10a6:102:383::17) Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PAWPR07MB9688:EE_|PAXPR07MB8723:EE_ X-MS-Office365-Filtering-Correlation-Id: 7fdf6f0d-e30c-4ed5-2c3d-08dc3ec12017 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: gG1garISxyrd+MJmcPm0zLk/CmEY0xyBIIjf3+WJ40kkyJ0AVdrptjYpyEDVc/j1hm0XxbxmhcwmHBZAgr/Y4b9M7cZ7WZjeyxtYkYPEL5IksOD5JHmlGpgZ1reofC1VnXbXsWpcJw4GAasD20bX1ivincElvYjhSTu2ex9QYrY/opcn8dax3wau+P0l6vlP0nuAJJKTWQeC7C2HhxD93KNF1Q9wISy3hflk4Vle/eVFE9afmzpTNjYw1HUglJxzJ3KbVQs0f6BtioJ/sDiar6yvG2TqIZAbZ2etkU4vAvjUAqVn2CQlOxTo4vugTOQywHcOXSqnEgUuTp20pK/ccc5HDYwJ+EQh4sMQaKIMoLBIxvkh8uVeuAfJhUVi9Hg6YEUliPGBWQrnM7X1zXAFkHJ1xGC65FSCnQoTh7T1aoktTMYsxj+9T+Kj5SFQhe3FpG8lMUOw5kxn1D+NDn4lWYTCJJ4+R1t4Cp4MHHUSPjQ3q6Q+1A/O53+WMz32zXGtEXicc2l3ZZ29KomxePlGeUNPT9VRpCRd9WtfVRfLLHuNQQtgG3dNUZ9pxb19RSu8gTwryfTLJKZDW3w6zHAnPWEDvGEV2wmQnsVNLEx25JICpBQ+/ial5cTNOWxl4b8Dx8xEfF1kkPZLjzS47hUtQkmjFHcIo3I7Sac66WHky36P4IIeJHsRtZ4BpLdj8uOMGpWFQGzWsKb28GFwR2H2JNp3/oJDoUjJp5J+DD88VJ4= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:PAWPR07MB9688.eurprd07.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230031)(376005)(38350700005);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: 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 X-OriginatorOrg: nokia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 7fdf6f0d-e30c-4ed5-2c3d-08dc3ec12017 X-MS-Exchange-CrossTenant-AuthSource: PAWPR07MB9688.eurprd07.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Mar 2024 16:10:36.8441 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 5d471751-9675-428d-917b-70f44f9630b0 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 7VgSLwm8oHtCNKSrEck7Vr1ikBN/RZA2G0t8WRH6u9LlL7PadTI1mUtX6xnAzXwLyVJgRtOhX9kwVf5egrEQUKeOLLok74Efsl5llcRdAx4= X-MS-Exchange-Transport-CrossTenantHeadersStamped: PAXPR07MB8723 With CONFIG_PROVE_RCU_LIST=y and by executing $ echo 0 > /sys/devices/system/cpu/cpu1/online one can trigger the following Lockdep-RCU splat on ARM: ============================= WARNING: suspicious RCU usage 6.8.0-rc7-00001-g0db1d0ed8958 #10 Not tainted ----------------------------- kernel/locking/lockdep.c:3762 RCU-list traversed in non-reader section!! other info that might help us debug this: RCU used illegally from offline CPU! rcu_scheduler_active = 2, debug_locks = 1 no locks held by swapper/1/0. stack backtrace: CPU: 1 PID: 0 Comm: swapper/1 Not tainted 6.8.0-rc7-00001-g0db1d0ed8958 #10 Hardware name: Allwinner sun8i Family unwind_backtrace from show_stack+0x10/0x14 show_stack from dump_stack_lvl+0x60/0x90 dump_stack_lvl from lockdep_rcu_suspicious+0x150/0x1a0 lockdep_rcu_suspicious from __lock_acquire+0x11fc/0x29f8 __lock_acquire from lock_acquire+0x10c/0x348 lock_acquire from _raw_spin_lock_irqsave+0x50/0x6c _raw_spin_lock_irqsave from check_and_switch_context+0x7c/0x4a8 check_and_switch_context from arch_cpu_idle_dead+0x10/0x7c arch_cpu_idle_dead from do_idle+0xbc/0x138 do_idle from cpu_startup_entry+0x28/0x2c cpu_startup_entry from secondary_start_kernel+0x11c/0x124 secondary_start_kernel from 0x401018a0 The CPU is already reported as offline from RCU perspective in cpuhp_report_idle_dead() before arch_cpu_idle_dead() is invoked. Above RCU-Lockdep splat is then triggered by check_and_switch_context() acquiring the ASID spinlock. Avoid the false-positive Lockdep-RCU splat by briefly reporting the CPU as online again while the spinlock is held. Signed-off-by: Stefan Wiehler --- arch/arm/kernel/smp.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index 3431c0553f45..6875e2c5dd50 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -319,7 +319,14 @@ void __noreturn arch_cpu_idle_dead(void) { unsigned int cpu = smp_processor_id(); + /* + * Briefly report CPU as online again to avoid false positive + * Lockdep-RCU splat when check_and_switch_context() acquires ASID + * spinlock. + */ + rcutree_report_cpu_starting(cpu); idle_task_exit(); + rcutree_report_cpu_dead(); local_irq_disable();