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Mon, 5 May 2025 17:25:29 +0000 (GMT) Message-ID: Date: Mon, 5 May 2025 22:55:28 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] sched/numa: add statistics of numa balance task migration Content-Language: en-GB To: "Chen, Yu C" , "Jain, Ayush" , Andrew Morton Cc: Ingo Molnar , Tejun Heo , Johannes Weiner , Jonathan Corbet , Mel Gorman , Michal Hocko , Michal Koutny , Muchun Song , Roman Gushchin , Shakeel Butt , "Chen, Tim C" , Aubrey Li , Libo Chen , cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, K Prateek Nayak , Madadi Vineeth Reddy , Neeraj.Upadhyay@amd.com, Peter Zijlstra , Madhavan Srinivasan References: <20250430103623.3349842-1-yu.c.chen@intel.com> <8b248ff3-43ae-4e40-9fa4-ba4a04f3c18b@amd.com> From: Venkat Rao Bagalkote In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: qoipdVZaZz7nT96xSUl1qc8aL2V8KBQW X-Authority-Analysis: v=2.4 cv=dMSmmPZb c=1 sm=1 tr=0 ts=6818f494 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=dt9VzEwgFbYA:10 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=KvdA8ODPaR-T82k_2AgA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-ORIG-GUID: qoipdVZaZz7nT96xSUl1qc8aL2V8KBQW X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNTA1MDE2MiBTYWx0ZWRfXxlYdk0EnQEEu eL4fu+fCjITVHTBGGSQ9V/R93yl5wNuL6vS4lDZGgEt++m87yTmVkswA1G4IkslixerWxKLgDr/ U2lcsmLaKzYP/TSRLNP+4ADXdWTwuKBivcp5OKCBs46tsC69lhkG+P2xa3syhxtY/fwU4yrfPrH 7wW2eyR3TA4FMENrRQo72LRSQpmEbTLlaPSgRLtCcV9IH+l2TICB/41o2FKVyRPRyAZmJpK5ES4 hge2qIH5fn44kvONKuC+PqvLJEROj7YY4/mnhqsDHmzMFC0BKyLbiTsE3vBo1UT9Xz3jujdkfAW I6/wd4JVAIMjKmuD4XqZBg7HX/GxxdfrL1j/ZVnGku6QbEVlAm5NNjUyT07UnW1ILoL0tTLPb9s j6n4i96G0ouzk/EytpA6b5J5QI9VZz6tmEgE4inOC8JDgmzzINBHuU9sReG74G7awKWwXD4E X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.0.736,FMLib:17.12.80.40 definitions=2025-05-05_07,2025-05-05_01,2025-02-21_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 clxscore=1011 mlxlogscore=999 bulkscore=0 spamscore=0 suspectscore=0 adultscore=0 mlxscore=0 malwarescore=0 phishscore=0 impostorscore=0 lowpriorityscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2504070000 definitions=main-2505050162 On 05/05/25 8:33 pm, Chen, Yu C wrote: > On 5/5/2025 2:43 PM, Jain, Ayush wrote: >> >> Hello, >> >> Hitting Kernel Panic on latest-next while running rcutorture tests >> >> 37ff6e9a2ce3 ("Add linux-next specific files for 20250502") >> >> reverting this patch fixes it >> 3b2339eeb032 >> ("sched-numa-add-statistics-of-numa-balance-task-migration-v3") >> https://web.git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/kernel/sched/core.c?id=3b2339eeb032627e9329daf70a4ba8cd62c9cc8d >> >> >> by looking at RIP pointer >> >> $ ./scripts/faddr2line vmlinux __migrate_swap_task+0x2e/0x180 >> __migrate_swap_task+0x2e/0x180: >> count_memcg_events_mm at include/linux/memcontrol.h:987 >> (inlined by) count_memcg_events_mm at include/linux/memcontrol.h:978 >> (inlined by) __migrate_swap_task at kernel/sched/core.c:3356 >> >> memcg = mem_cgroup_from_task(rcu_dereference(mm->owner)); >> mm->owner -> NULL >> >> Attaching kernel logs below: >> >> [ 1070.635450] rcu-torture: rcu_torture_read_exit: End of episode >> [ 1074.047617] BUG: kernel NULL pointer dereference, address: >> 0000000000000498 > > Thanks Ayush, > > According to this address, >    4c 8b af 50 09 00 00    mov    0x950(%rdi),%r13  <--- r13 = p->mm; >    49 8b bd 98 04 00 00    mov    0x498(%r13),%rdi  <--- p->mm->owner > It seems that this task to be swapped has NULL mm_struct. > > Does the following help? > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 96db6947bc92..0cb8cc4d551d 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -3353,7 +3353,8 @@ void set_task_cpu(struct task_struct *p, > unsigned int new_cpu) >  static void __migrate_swap_task(struct task_struct *p, int cpu) >  { >         __schedstat_inc(p->stats.numa_task_swapped); > -       count_memcg_event_mm(p->mm, NUMA_TASK_SWAP); > +       if (p->mm) > +               count_memcg_event_mm(p->mm, NUMA_TASK_SWAP); > >         if (task_on_rq_queued(p)) { >                 struct rq *src_rq, *dst_rq; > Hello Chenyu, This issue is reported even on IBM Power servers. Proposed fix works fine. Hence, Tested-by: Venkat Rao Bagalkote Regards, Venkat. > > > Hi Andrew, > May I know if we can hold this patch and not merge it for now, > besides this regression, Libo has another comment related to > this patch and I'll address it in next version. Sorry for > inconvenience. > > thanks, > Chenyu >