rcu: INFO: rcu_preempt self-detected stall on CPU rcu: 0-...!: (10499 ticks this GP) idle=6ee/1/0x4000000000000002 softirq=11531/11531 fqs=40 (t=10500 jiffies g=5769 q=73) rcu: rcu_preempt kthread starved for 10419 jiffies! g5769 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1 rcu: RCU grace-period kthread stack dump: rcu_preempt R running task 29048 10 2 0x80004000 Call Trace: context_switch kernel/sched/core.c:3385 [inline] __schedule+0x9a0/0xcc0 kernel/sched/core.c:4081 schedule+0x181/0x210 kernel/sched/core.c:4155 schedule_timeout+0x14f/0x240 kernel/time/timer.c:1895 rcu_gp_fqs_loop kernel/rcu/tree.c:1661 [inline] rcu_gp_kthread+0xed8/0x1770 kernel/rcu/tree.c:1821 kthread+0x332/0x350 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 NMI backtrace for cpu 0 CPU: 0 PID: 8131 Comm: udevd Not tainted 5.4.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1fb/0x318 lib/dump_stack.c:118 nmi_cpu_backtrace+0xaf/0x1a0 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x174/0x290 lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x10/0x20 arch/x86/kernel/apic/hw_nmi.c:38 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline] rcu_dump_cpu_stacks+0x15a/0x220 kernel/rcu/tree_stall.h:254 print_cpu_stall kernel/rcu/tree_stall.h:455 [inline] check_cpu_stall kernel/rcu/tree_stall.h:529 [inline] rcu_pending kernel/rcu/tree.c:2827 [inline] rcu_sched_clock_irq+0xe25/0x1ad0 kernel/rcu/tree.c:2271 update_process_times+0x12d/0x180 kernel/time/timer.c:1726 tick_sched_handle kernel/time/tick-sched.c:167 [inline] tick_sched_timer+0x263/0x420 kernel/time/tick-sched.c:1310 __run_hrtimer kernel/time/hrtimer.c:1514 [inline] __hrtimer_run_queues+0x403/0x840 kernel/time/hrtimer.c:1576 hrtimer_interrupt+0x38c/0xda0 kernel/time/hrtimer.c:1638 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1110 [inline] smp_apic_timer_interrupt+0x109/0x280 arch/x86/kernel/apic/apic.c:1135 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829 RIP: 0010:__read_once_size include/linux/compiler.h:199 [inline] RIP: 0010:check_kcov_mode kernel/kcov.c:70 [inline] RIP: 0010:__sanitizer_cov_trace_pc+0x1c/0x50 kernel/kcov.c:102 Code: cc 07 48 89 de e8 64 02 3b 00 5b 5d c3 cc 48 8b 04 24 65 48 8b 0c 25 c0 1d 02 00 65 8b 15 b8 81 8b 7e f7 c2 00 01 1f 00 75 2c <8b> 91 80 13 00 00 83 fa 02 75 21 48 8b 91 88 13 00 00 48 8b 32 48 RSP: 0018:ffffc90001ea79f0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13 RAX: ffffffff81487433 RBX: 0000000000000000 RCX: ffff88808c8ee200 RDX: 0000000000000001 RSI: 00000000fffffffc RDI: ffffea0001b13200 RBP: ffffc90001ea7a18 R08: 000000000003a768 R09: fffffbfff120248a R10: fffffbfff120248a R11: 0000000000000000 R12: dffffc0000000000 R13: dffffc0000000000 R14: 00000000fffffffc R15: ffff88809c7b58e8 free_thread_stack+0x168/0x590 kernel/fork.c:280 release_task_stack kernel/fork.c:440 [inline] put_task_stack+0xa3/0x130 kernel/fork.c:451 finish_task_switch+0x3f1/0x550 kernel/sched/core.c:3256 context_switch kernel/sched/core.c:3388 [inline] __schedule+0x9a8/0xcc0 kernel/sched/core.c:4081 preempt_schedule_irq+0xc1/0x140 kernel/sched/core.c:4338 retint_kernel+0x1b/0x2b RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:752 [inline] RIP: 0010:kfree+0x1a3/0x200 mm/slab.c:3758 Code: 48 83 3d 67 19 59 07 00 74 68 4c 89 f7 57 9d 0f 1f 44 00 00 eb 19 e8 ec b7 ca ff 48 83 3d 4c 19 59 07 00 74 51 4c 89 f7 57 9d <0f> 1f 44 00 00 5b 41 5c 41 5e 41 5f 5d c3 48 ff c9 48 89 c8 e9 c8 RSP: 0018:ffffc90001ea7c70 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff02 RAX: ffff88808c8eea94 RBX: ffff8880aa8008c0 RCX: ffffffff815c0597 RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000286 RBP: ffffc90001ea7c90 R08: ffff88808c8eea58 R09: fffffbfff13c851e R10: fffffbfff13c851e R11: 0000000000000000 R12: ffff8880a30f9e00 R13: ffffffffffffffc3 R14: 0000000000000286 R15: ffffffff83510b46 smk_fetch security/smack/smack_lsm.c:302 [inline] smack_d_instantiate+0x9f6/0xd70 security/smack/smack_lsm.c:3453 security_d_instantiate+0xa5/0x100 security/security.c:1874 d_instantiate+0x55/0x90 fs/dcache.c:1952 shmem_symlink+0x619/0x6f0 mm/shmem.c:3148 vfs_symlink+0x36f/0x4f0 fs/namei.c:4123 do_symlinkat+0x187/0x3f0 fs/namei.c:4150 __do_sys_symlink fs/namei.c:4169 [inline] __se_sys_symlink fs/namei.c:4167 [inline] __x64_sys_symlink+0x60/0x70 fs/namei.c:4167 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7f65ec580517 Code: 09 01 00 00 0f 05 48 3d 00 f0 ff ff 77 02 f3 c3 48 8b 15 14 39 2b 00 f7 d8 64 89 02 83 c8 ff c3 90 90 90 b8 58 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d f1 38 2b 00 31 d2 48 29 c2 64 RSP: 002b:00007ffe886340e8 EFLAGS: 00000206 ORIG_RAX: 0000000000000058 RAX: ffffffffffffffda RBX: 0000000001c79250 RCX: 00007f65ec580517 RDX: 0000000000000002 RSI: 00007ffe88634110 RDI: 0000000001c7ada0 RBP: 0000000001c792d0 R08: 00007ffe88633cc0 R09: 00007f65ec5d4de0 R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000020 R13: 0000000001c7b810 R14: 0000000001c79250 R15: 000000000000000b