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Fri, 27 Jun 2025 07:33:36 +0000 Message-ID: Date: Fri, 27 Jun 2025 15:33:29 +0800 User-Agent: Mozilla Thunderbird Subject: Re: [BUG] Kernel panic in __migrate_swap_task() on 6.16-rc2 (NULL pointer dereference) From: "Chen, Yu C" To: Jirka Hladky , Abhigyan ghosh CC: , Chen Yu References: <07D9F8BC-47A7-4E87-8655-C978C056E308@gmail.com> <31bd3395-cfe3-4af5-bc1c-fa8d26629b93@intel.com> Content-Language: en-US In-Reply-To: <31bd3395-cfe3-4af5-bc1c-fa8d26629b93@intel.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: SGAP274CA0002.SGPP274.PROD.OUTLOOK.COM (2603:1096:4:b6::14) To DM4PR11MB6020.namprd11.prod.outlook.com (2603:10b6:8:61::19) 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: DM4PR11MB6020:EE_|SA2PR11MB4826:EE_ X-MS-Office365-Filtering-Correlation-Id: aa702c8a-5496-4cf5-87bb-08ddb54ced66 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|376014|1800799024; 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>                                           p->flags |= PF_EXITING >                                        exit_mm >                                           p->mm = NULL; > >    migrate_swap_stop >      __migrate_swap_task((arg->src_task, arg->dst_cpu) >       count_memcg_event_mm(p->mm, NUMA_TASK_SWAP)# p->mm is NULL > > Could you please help check if the following debug patch works, Attached the patch: diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 8988d38d46a3..82fc966b390c 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3364,7 +3364,12 @@ static void __migrate_swap_task(struct task_struct *p, int cpu) { __schedstat_inc(p->stats.numa_task_swapped); count_vm_numa_event(NUMA_TASK_SWAP); - count_memcg_event_mm(p->mm, NUMA_TASK_SWAP); + if (unlikely(!p->mm)) { + trace_printk("!! (%d %s) flags=%lx\n", p->pid, p->comm, + p->flags); + } else { + count_memcg_event_mm(p->mm, NUMA_TASK_SWAP); + } if (task_on_rq_queued(p)) { struct rq *src_rq, *dst_rq; -- 2.25.1 > and if there is no issue found after you ran several tests, > could you please provide the > /sys/kernel/debug/tracing/trace > > BTW, is it possible to share your test script for stress-ng, > stream? It looks like the stress-ng's fork test case would > trigger this issue easier in theory. > > thanks, > Chenyu > >