Hello. While doing some tracing, observed this kernel panic on powerpc.
It is quite easy reproduce this. - keep it preempt=full/lazy - enable some bcc tools. for example: ./stackcount nohz_balance_exit_idle - Run some workload such as "hackbench 10 process 1000 loops" I remember seeing this across other bcc tools. Seen this on tip/master: commit 5d3b0106245d467fd5ba0bd9a373a13356684f6e (HEAD -> master, origin/master, origin/HEAD) Merge: 93368366738f e21279b73ef6 Author: Ingo Molnar <[email protected]> Date: Tue Jan 6 09:04:47 2026 +0100 Merge branch into tip/master: 'x86/sev' Panic log: attempted to read user page (6b8) - exploit attempt? (uid: 0) BUG: Kernel NULL pointer dereference on read at 0x000006b8 Faulting instruction address: 0xc00000000013cf10 Oops: Kernel access of bad area, sig: 11 [#1] CPU: 38 UID: 0 PID: 2938 Comm: hackbench Kdump: loaded Not tainted 6.19.0-rc4+ #326 PREEMPT(full) NIP: c00000000013cf10 LR: c00000000013ced0 CTR: c0000000004a7f08 REGS: c0000000a7f96b60 TRAP: 0300 Not tainted (6.19.0-rc4+) MSR: 8000000000001033 <SF,ME,IR,DR,RI,LE> CR: 88022828 XER: 20040000 CFAR: c00000000050490c DAR: 00000000000006b8 DSISR: 40000000 IRQMASK: 3 GPR00: c00000000013ced0 c0000000a7f96e00 c000000001c38100 0000000000000000 GPR04: 00007fffda01fea8 0000000000000008 0000000000000000 00007fff94f05e84 GPR08: c0000000a7f90000 0000000000000000 00007fffda0205d0 0000000000004000 GPR12: c000000002dbdddc c0000017fd891c80 c0000000001e08f4 0000000000000000 GPR16: 0000000000000000 0000000000000000 0000000000000000 00000d9842ecbda0 GPR20: c0000000c5c54a00 0000000000000026 0000000000000000 0000000000000000 GPR24: 0000000000000001 fffffffffffffe00 c0000000c5c54a00 000ffffffffffff8 GPR28: 00007fffffffffdf 0000000000000000 00007fffda01fea0 c0000000a7f96ef0 NIP [c00000000013cf10] perf_callchain_user_64+0x1b0/0x4f0 LR [c00000000013ced0] perf_callchain_user_64+0x170/0x4f0 Call Trace: perf_callchain_user_64+0x170/0x4f0 (unreliable) perf_callchain_user+0x20/0x3c get_perf_callchain+0x1b0/0x3dc bpf_get_stackid+0x94/0xec bpf_prog_1ca8f9c0bc38eaa6_trace_count+0x70/0x1bc trace_call_bpf+0x124/0x3c4 kprobe_perf_func+0x54/0x2f8 kprobe_ftrace_handler+0x1dc/0x298 ftrace_regs_call+0x4/0xa0 nohz_balance_exit_idle+0x10/0x120 nohz_balancer_kick+0x50/0x3e4 sched_tick+0x140/0x334 update_process_times+0xf0/0x144 tick_nohz_handler+0xc4/0x274 __hrtimer_run_queues+0x1c4/0x480 hrtimer_interrupt+0x12c/0x30c timer_interrupt+0x140/0x394 __replay_soft_interrupts+0xa0/0x154 arch_local_irq_restore.part.0+0x1ac/0x224 _raw_spin_unlock_irqrestore+0x50/0xa0 try_to_wake_up+0x3e8/0xa58 wake_up_q+0x88/0xe4 rwsem_wake.isra.0+0x98/0xd8 up_write+0xa8/0xb4 unlink_file_vma_batch_process+0xc8/0xf0 unlink_file_vma_batch_add+0x5c/0xa4 free_pgtables+0x110/0x394 exit_mmap+0x1a0/0x5a8 __mmput+0x64/0x194 exit_mm+0xe0/0x170 do_exit+0x21c/0x5d0 do_group_exit+0x4c/0xc0 pid_child_should_wake+0x0/0x7c system_call_exception+0x128/0x390 system_call_vectored_common+0x15c/0x2ec Looks like venkat had reported similar one earlier. https://lore.kernel.org/all/[email protected]/ Venkat, can you give above mentioned steps a try on linux-next latest?
