rcu: INFO: rcu_preempt self-detected stall on CPU rcu: 0-....: (3870 ticks this GP) idle=3c6/1/0x4000000000000000 softirq=139664/139667 fqs=2881 (t=10500 jiffies g=219401 q=9986) NMI backtrace for cpu 0 CPU: 0 PID: 13 Comm: ksoftirqd/0 Not tainted 5.14.0-rc5-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x1ae/0x29f lib/dump_stack.c:105 nmi_cpu_backtrace+0x16c/0x190 lib/nmi_backtrace.c:105 nmi_trigger_cpumask_backtrace+0x191/0x2f0 lib/nmi_backtrace.c:62 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline] rcu_dump_cpu_stacks+0x22d/0x390 kernel/rcu/tree_stall.h:342 print_cpu_stall kernel/rcu/tree_stall.h:625 [inline] check_cpu_stall kernel/rcu/tree_stall.h:700 [inline] rcu_pending kernel/rcu/tree.c:3922 [inline] rcu_sched_clock_irq+0x1d0d/0x2a30 kernel/rcu/tree.c:2641 update_process_times+0x197/0x200 kernel/time/timer.c:1785 tick_sched_handle kernel/time/tick-sched.c:226 [inline] tick_sched_timer+0x27d/0x420 kernel/time/tick-sched.c:1421 __run_hrtimer kernel/time/hrtimer.c:1537 [inline] __hrtimer_run_queues+0x4cb/0xa60 kernel/time/hrtimer.c:1601 hrtimer_interrupt+0x3b3/0x1040 kernel/time/hrtimer.c:1663 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1089 [inline] __sysvec_apic_timer_interrupt+0xf9/0x270 arch/x86/kernel/apic/apic.c:1106 sysvec_apic_timer_interrupt+0x8c/0xb0 arch/x86/kernel/apic/apic.c:1100 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:638 RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline] RIP: 0010:_raw_spin_unlock_irqrestore+0xbc/0x120 kernel/locking/spinlock.c:191 Code: f0 48 c1 e8 03 42 80 3c 20 00 74 08 4c 89 f7 e8 1a 60 ed f7 f6 44 24 21 02 75 4e 41 f7 c7 00 02 00 00 74 01 fb bf 01 00 00 00 4f 77 7b f7 65 8b 05 b0 cd 25 76 85 c0 74 3f 48 c7 04 24 0e 36 RSP: 0018:ffffc90000d276a0 EFLAGS: 00000206 RAX: 1ffff920001a4ed8 RBX: ffff888146c80000 RCX: ffffffff8162c8d9 RDX: dffffc0000000000 RSI: 0000000000000101 RDI: 0000000000000001 RBP: ffffc90000d27730 R08: dffffc0000000000 R09: fffffbfff1f5e7d9 R10: fffffbfff1f5e7d9 R11: 0000000000000000 R12: dffffc0000000000 R13: 1ffff920001a4ed4 R14: ffffc90000d276c0 R15: 0000000000000a06 dummy_timer+0x2fff/0x30f0 drivers/usb/gadget/udc/dummy_hcd.c:1996 call_timer_fn+0xf6/0x210 kernel/time/timer.c:1421 expire_timers kernel/time/timer.c:1466 [inline] __run_timers+0x703/0x8f0 kernel/time/timer.c:1734 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1747 __do_softirq+0x372/0x783 kernel/softirq.c:558 run_ksoftirqd+0xa2/0x100 kernel/softirq.c:920 smpboot_thread_fn+0x533/0x9d0 kernel/smpboot.c:164 kthread+0x453/0x480 kernel/kthread.c:319 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 ---------------- Code disassembly (best guess): 0: f0 48 c1 e8 03 lock shr $0x3,%rax 5: 42 80 3c 20 00 cmpb $0x0,(%rax,%r12,1) a: 74 08 je 0x14 c: 4c 89 f7 mov %r14,%rdi f: e8 1a 60 ed f7 callq 0xf7ed602e 14: f6 44 24 21 02 testb $0x2,0x21(%rsp) 19: 75 4e jne 0x69 1b: 41 f7 c7 00 02 00 00 test $0x200,%r15d 22: 74 01 je 0x25 24: fb sti 25: bf 01 00 00 00 mov $0x1,%edi 2a: e8 4f 77 7b f7 callq 0xf77b777e <-- trapping instruction 2f: 65 8b 05 b0 cd 25 76 mov %gs:0x7625cdb0(%rip),%eax # 0x7625cde6 36: 85 c0 test %eax,%eax 38: 74 3f je 0x79 3a: 48 rex.W 3b: c7 .byte 0xc7 3c: 04 24 add $0x24,%al 3e: 0e (bad) 3f: 36 ss