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To: Venkat Rao Bagalkote , Madhavan Srinivasan , Mukesh Kumar Chaurasiya , Ritesh Harjani Cc: linuxppc-dev , LKML , Srikar Dronamraju , Peter Zijlstra References: <7904105b-9dfa-4efd-a5ef-bc0276ed255d@linux.ibm.com> Content-Language: en-US From: Shrikanth Hegde In-Reply-To: <7904105b-9dfa-4efd-a5ef-bc0276ed255d@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=Zt3d7d7G c=1 sm=1 tr=0 ts=6a1d4def cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=VnNF1IyMAAAA:8 a=MOXgsU-1MZsgqN46v8YA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: ckjTMxoUwkLA0CuP0bdespoYdhlwuX4l X-Proofpoint-ORIG-GUID: upWfRYD4QUYHq4eldDYmwbKhho2zQjNJ X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjAxMDA5MSBTYWx0ZWRfXyDCIjMjnzxdH gTP7/OF/7KT6EIyUSVSx7DQSnFVWX3HqBKEng2AgLQCw5rsktpowNbiLg7TU7awM2UYwxltRcqg 5m1T8DrQrNUNPRCCkSnzTeTpbtU/1ZnbHPlE3dyvgg5X92RXqqROZd0BYBRliFHydlJteLjhmQo nLj72HuqQD2FtoZtZVuN7atUAX4yBRTXagVvCakr+J4MuC4U9O+vPWr5VpDkfFndfCEi4lrRqAm eBji08L187kEMi/9Y1Mh8Vm30Dhn8Sq3kYjY3QOhS42aiCOdFGxi4C4AMhFOaKYznb7fWRiwdWw mUja0Mm5ou7iNMCoBuXWazohFAX27l+Vi2R7MqUuSCBTfXOsB29Ex2MzJqtxKwDGFHcdWR0SFz9 j1QwIvKSRCEc8juTVJoZ6HKLhQ6ZMQYQLHz/qBfnAStn8Ua6Nc+NBJ4Qipbk0oMnQrPxDfzVSWu 4J8RB+zxbF0syEz0yPw== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-01_02,2026-05-28_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 suspectscore=0 priorityscore=1501 bulkscore=0 clxscore=1015 phishscore=0 spamscore=0 malwarescore=0 adultscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605210000 definitions=main-2606010091 Hi Venkat. Thanks for the report. + mukesh, ritesh On 6/1/26 12:11 PM, Venkat Rao Bagalkote wrote: > Greetings!!! > > > I hit a kernel BUG on a linux-next kernel running on ppc64le (Power11 > LPAR). The issue was observed once in CI (Avocado tests) and I haven’t > been able to reproduce it reliably yet. > Can you run with lockdep and see if you can hit it? > Architecture: ppc64le (Power11, pSeries) > Kernel: 7.1.0-rc5-next-20260529 > Config: PREEMPT(lazy) > CPUs: large system (NR_CPUS=8192) > This is with GENERIC_ENTRY. > > So far, I have not reproduced the crash, but I am trying to stress > similar conditions using: > > parallel read workloads (fio / dd) > memory pressure > > > Traces: > >  (5/8) /home/upstreamci/avocado-fvt-wrapper/tests/avocado-misc-tests/ > cpu/ppc64_cpu_test.py:PPC64Test.test_smt_loop;run-run_type- > upstream-9cfe: STARTED > [ 1885.176400] crash hp: kexec_trylock() failed, kdump image may be > inaccurate > [ 1885.296164] crash hp: kexec_trylock() failed, kdump image may be > inaccurate > [ 1885.386120] crash hp: kexec_trylock() failed, kdump image may be > inaccurate > [ 1885.556134] crash hp: kexec_trylock() failed, kdump image may be > inaccurate > [ 1886.576119] crash hp: kexec_trylock() failed, kdump image may be > inaccurate > [ 1886.806060] crash hp: kexec_trylock() failed, kdump image may be > inaccurate > [ 1887.026051] crash hp: kexec_trylock() failed, kdump image may be > inaccurate > [ 1887.456075] ------------[ cut here ]------------ > [ 1887.456101] kernel BUG at kernel/sched/core.c:7512! > [ 1887.456107] Oops: Exception in kernel mode, sig: 5 [#1] > [ 1887.456111] LE PAGE_SIZE=4K MMU=Radix  SMP NR_CPUS=8192 NUMA pSeries > [ 1887.456116] Modules linked in: nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 > nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct > nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 bonding > tls ip_set rfkill nf_tables fsdev_dax kmem device_dax pseries_rng > vmx_crypto dax_pmem fuse ext4 crc16 mbcache jbd2 sd_mod nd_pmem papr_scm > sg libnvdimm ibmvscsi ibmveth scsi_transport_srp pseries_wdt > [ 1887.456173] CPU: 28 UID: 0 PID: 85305 Comm: kexec Not tainted 7.1.0- > rc5-next-20260529 #1 PREEMPT(lazy) > [ 1887.456180] Hardware name: IBM,9080-HEX Power11 (architected) > 0x820200 0xf000007 of:IBM,FW1110.01 (NH1110_069) hv:phyp pSeries > [ 1887.456185] NIP:  c0000000013a8e8c LR: c0000000003483bc CTR: > 0000000000000000 > [ 1887.456190] REGS: c000000069f03070 TRAP: 0700   Not tainted (7.1.0- > rc5-next-20260529) > [ 1887.456195] MSR:  8000000000029033   CR: > 24428222  XER: 0000005a > [ 1887.456208] CFAR: c0000000003483b8 IRQMASK: 0 > [ 1887.456208] GPR00: c0000000003483bc c000000069f03330 c000000001a82100 > c000000069f033e0 > [ 1887.456208] GPR04: 0000000000000000 0000000000000001 0000000000000001 > c000000006dd3b00 > [ 1887.456208] GPR08: ffffffffffffff00 0000000000000001 0000000000000000 > 0000000024428220 > [ 1887.456208] GPR12: 0000000000000300 c000000effdbef00 0000000000000000 > 0000000000000000 > [ 1887.456208] GPR16: 0000000000000000 0000000000000000 0000000000000000 > 0000000000000000 > [ 1887.456208] GPR20: 0000000000000000 0000000000000000 0000000000000000 > 0000000000000000 > [ 1887.456208] GPR24: 0000000000000000 0000000000000000 0000000000000000 > 0000000000000000 > [ 1887.456208] GPR28: 0000000000000000 0000000000000000 0000000000000000 > c000000069f033e0 > [ 1887.456265] NIP [c0000000013a8e8c] preempt_schedule_irq+0x44/0x118 > [ 1887.456274] LR [c0000000003483bc] > dynamic_irqentry_exit_cond_resched+0x40/0x1a4 > [ 1887.456282] Call Trace: > [ 1887.456284] [c000000069f03360] [c0000000003483bc] > dynamic_irqentry_exit_cond_resched+0x40/0x1a4 > [ 1887.456291] [c000000069f03380] [c00000000014f3bc] > do_page_fault+0xc0/0x104 > [ 1887.456298] [c000000069f033b0] [c000000000008be0] > data_access_common_virt+0x210/0x220 > [ 1887.456306] ---- interrupt: 300 at __copy_tofrom_user_base+0xac/0x5a4 > [ 1887.456313] NIP:  c00000000017fc38 LR: c000000000aaa684 CTR: > 0000000000000000 > [ 1887.456317] REGS: c000000069f033e0 TRAP: 0300   Not tainted (7.1.0- > rc5-next-20260529) > [ 1887.456322] MSR:  8000000002009033   CR: > 24428220  XER: 2004005a > [ 1887.456334] CFAR: c00000000017fc34 DAR: 00003fff879a8000 DSISR: > 42000000 IRQMASK: 0 > [ 1887.456334] GPR00: 0000000000000000 c000000069f036a0 c000000001a82100 > 00003fff879a8000 > [ 1887.456334] GPR04: c0000000bb314ff0 0000000000001000 69f0000606480600 > 0200c4080368f028 > [ 1887.456334] GPR08: 09036af00005d9c4 0600000200e80803 0000000000000000 > 0000000000000030 > [ 1887.456334] GPR12: 0000000000000040 c000000effdbef00 0000000000000000 > 000000000000000e > [ 1887.456334] GPR16: 0000000004a00000 000000000000001f c000000069f038a0 > c00000006e73e500 > [ 1887.456334] GPR20: c00000006f0ff6a8 0000000000000000 c00000006f0ff540 > 0000000000000001 > [ 1887.456334] GPR24: 000000001816ce60 c0000000bb314000 c000000002e48730 > c000000069f03a30 > [ 1887.456334] GPR28: c0000000bb314000 00003fff879a7010 0000000000000010 > 0000000000001000 > [ 1887.456393] NIP [c00000000017fc38] __copy_tofrom_user_base+0xac/0x5a4 > [ 1887.456399] LR [c000000000aaa684] raw_copy_to_user+0x12c/0x314 > [ 1887.456405] ---- interrupt: 300 > [ 1887.456408] [c000000069f036a0] [c000000000aaa5f4] > raw_copy_to_user+0x9c/0x314 (unreliable) > [ 1887.456416] [c000000069f036e0] [c000000000aacd08] > _copy_to_iter+0xe4/0x79c > [ 1887.456423] [c000000069f037a0] [c000000000ab01ec] > copy_page_to_iter+0xd4/0x1a4 > [ 1887.456429] [c000000069f037f0] [c0000000005ddc34] > filemap_read+0x420/0x4f0 > [ 1887.456436] [c000000069f039c0] [c0080000043443e0] > ext4_file_read_iter+0x78/0x31c [ext4] > [ 1887.456517] [c000000069f03a10] [c000000000796498] vfs_read+0x2a8/0x3c8 > [ 1887.456524] [c000000069f03ac0] [c00000000079726c] ksys_read+0x88/0x140 > [ 1887.456530] [c000000069f03b10] [c000000000032f98] > system_call_exception+0x198/0x4e0 > [ 1887.456537] [c000000069f03e30] [c00000000000d05c] > system_call_vectored_common+0x15c/0x2ec > [ 1887.456544] ---- interrupt: 3000 at 0x3fff9b133cf4 > [ 1887.456549] NIP:  00003fff9b133cf4 LR: 00003fff9b133cf4 CTR: > 0000000000000000 > [ 1887.456554] REGS: c000000069f03e60 TRAP: 3000   Not tainted (7.1.0- > rc5-next-20260529) > [ 1887.456558] MSR:  800000000000f033   CR: > 44424402  XER: 00000000 > [ 1887.456572] IRQMASK: 0 > [ 1887.456572] GPR00: 0000000000000003 00003fffe5fb4190 0000000105087f00 > 0000000000000003 > [ 1887.456572] GPR04: 00003fff82e93010 000000001816ce60 0000000000000022 > 0000000000000000 > [ 1887.456572] GPR08: 0000000000000000 0000000000000000 0000000000000000 > 0000000000000000 > [ 1887.456572] GPR12: 0000000000000000 00003fff9b4cd860 000000010507f588 > 0000000000000000 > [ 1887.456572] GPR16: ffffffffffffffff 0000000000000000 0000000000000006 > 0000000000000000 > [ 1887.456572] GPR20: 0000000000000001 00003fff9b23039c 00003fff9b2303a0 > 00003fffe5fb5ee7 > [ 1887.456572] GPR24: 0000000000000000 0000000000000000 00003fffe5fb5ee7 > 00003fffe5fb42d0 > [ 1887.456572] GPR28: 0000000000000003 00003fff82e93010 000000001816ce60 > 0000000000000000 > [ 1887.456626] NIP [00003fff9b133cf4] 0x3fff9b133cf4 > [ 1887.456630] LR [00003fff9b133cf4] 0x3fff9b133cf4 > [ 1887.456634] ---- interrupt: 3000 > [ 1887.456637] Code: fbe1fff8 e92d0128 f8010010 f821ffd1 81490000 > 39200001 2c0a0000 40820014 892d0152 552907fe 7d290034 5529d97e > <0b090000> 60000000 3bc00000 ebed0128 > [ 1887.456657] ---[ end trace 0000000000000000 ]--- > > > If you happen to fix this, please add below tag. > > Reported-by: Venkat Rao Bagalkote > Ritesh, Mukesh, Is below possible scenario? do_page_fault seems to enable irq's in the interrupt handler? is that expected? if so, one might see -- do_page_fault (enter kernel mode) -- enables interrupts -- gets interrupt - Sets need_resched. -- irqentry_exit - Sees it is kernel mode. Just checks preempt count and calls preempt_schedule_irq, which catches both preempt_count and !irqs_disabled. Hence the panic? Should do_page_fault do preempt_disable when it enables the interrupts?