syzbot

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-...!: (10498 ticks this GP) idle=57b/1/0x4000000000000000 softirq=19186/19186 fqs=737 
	(t=10500 jiffies g=28729 q=185)
rcu: rcu_preempt kthread starved for 8945 jiffies! g28729 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:27808 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0x11b8/0x43b0 kernel/sched/core.c:6376
 schedule+0x11b/0x1e0 kernel/sched/core.c:6459
 schedule_timeout+0x15c/0x280 kernel/time/timer.c:1914
 rcu_gp_fqs_loop+0x29e/0x11b0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0x98/0x350 kernel/rcu/tree.c:2145
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 1 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 1 skipped: idling at default_idle+0xb/0x10 arch/x86/kernel/process.c:728
NMI backtrace for cpu 0
CPU: 0 PID: 6764 Comm: syz.0.663 Not tainted 5.15.186-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <IRQ>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x397/0x3d0 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:166 [inline]
 rcu_dump_cpu_stacks+0x22f/0x380 kernel/rcu/tree_stall.h:349
 print_cpu_stall+0x31d/0x5f0 kernel/rcu/tree_stall.h:633
 check_cpu_stall kernel/rcu/tree_stall.h:727 [inline]
 rcu_pending kernel/rcu/tree.c:3932 [inline]
 rcu_sched_clock_irq+0x6d8/0x1110 kernel/rcu/tree.c:2619
 update_process_times+0x193/0x200 kernel/time/timer.c:1818
 tick_sched_handle kernel/time/tick-sched.c:254 [inline]
 tick_sched_timer+0x37d/0x560 kernel/time/tick-sched.c:1473
 __run_hrtimer kernel/time/hrtimer.c:1690 [inline]
 __hrtimer_run_queues+0x4fe/0xc40 kernel/time/hrtimer.c:1754
 hrtimer_interrupt+0x3bb/0x8d0 kernel/time/hrtimer.c:1816
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
 __sysvec_apic_timer_interrupt+0x137/0x4a0 arch/x86/kernel/apic/apic.c:1114
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0x9b/0xc0 arch/x86/kernel/apic/apic.c:1108
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:vmx_do_interrupt_nmi_irqoff+0x10/0x20 arch/x86/kvm/vmx/vmenter.S:334
Code: 41 5b 41 5a 41 59 41 58 5e 5f 5a 59 58 5d c3 90 90 90 90 90 90 90 90 90 90 90 55 48 89 e5 48 83 e4 f0 6a 18 55 9c 6a 10 ff d7 <48> 89 ec 5d c3 00 00 cc cc 00 00 cc cc 00 00 cc 55 41 57 41 56 53
RSP: 0018:ffffc9000331f430 EFLAGS: 00000086
RAX: 0000000000000000 RBX: ffff888044760000 RCX: 736d92273acee600
RDX: 0000000000000cf0 RSI: ffffffff8a0468c0 RDI: ffffffff89c00cf0
RBP: ffffc9000331f430 R08: dffffc0000000000 R09: ffffed10088ec04d
R10: ffffed10088ec04d R11: 1ffff110088ec04c R12: 1ffff92000663e8c
R13: dffffc0000000000 R14: fffffe0000000ecb R15: ffffffff89c00cf0
 handle_interrupt_nmi_irqoff arch/x86/kvm/vmx/vmx.c:6488 [inline]
 handle_external_interrupt_irqoff arch/x86/kvm/vmx/vmx.c:6518 [inline]
 vmx_handle_exit_irqoff+0x358/0x800 arch/x86/kvm/vmx/vmx.c:6530
 vcpu_enter_guest+0x5e50/0x70e0 arch/x86/kvm/x86.c:10021
 vcpu_run arch/x86/kvm/x86.c:10162 [inline]
 kvm_arch_vcpu_ioctl_run+0xdea/0x1f40 arch/x86/kvm/x86.c:10399
 kvm_vcpu_ioctl+0x887/0xb80 virt/kvm/kvm_main.c:3894
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f1eb1379929
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f1eaf1e1038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f1eb15a0fa0 RCX: 00007f1eb1379929
RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005
RBP: 00007f1eb13fbb39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f1eb15a0fa0 R15: 00007ffc85d3da08
 </TASK>