rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: 0-...!: (1 GPs behind) idle=fba/1/0x4000000000000000 softirq=49551/49552 fqs=0 (detected by 1, t=10502 jiffies, g=75921, q=40) ============================================ WARNING: possible recursive locking detected 5.11.0-rc5-syzkaller #0 Not tainted -------------------------------------------- syz-executor.4/21044 is trying to acquire lock: ffffffff8bd154d8 (rcu_node_0){-.-.}-{2:2}, at: rcu_dump_cpu_stacks+0x96/0x2e0 kernel/rcu/tree_stall.h:334 but task is already holding lock: ffffffff8bd154d8 (rcu_node_0){-.-.}-{2:2}, at: print_other_cpu_stall kernel/rcu/tree_stall.h:493 [inline] ffffffff8bd154d8 (rcu_node_0){-.-.}-{2:2}, at: check_cpu_stall kernel/rcu/tree_stall.h:652 [inline] ffffffff8bd154d8 (rcu_node_0){-.-.}-{2:2}, at: rcu_pending kernel/rcu/tree.c:3751 [inline] ffffffff8bd154d8 (rcu_node_0){-.-.}-{2:2}, at: rcu_sched_clock_irq+0xd2a/0x22d0 kernel/rcu/tree.c:2580 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(rcu_node_0); lock(rcu_node_0); *** DEADLOCK *** May be due to missing lock nesting notation 1 lock held by syz-executor.4/21044: #0: ffffffff8bd154d8 (rcu_node_0){-.-.}-{2:2}, at: print_other_cpu_stall kernel/rcu/tree_stall.h:493 [inline] #0: ffffffff8bd154d8 (rcu_node_0){-.-.}-{2:2}, at: check_cpu_stall kernel/rcu/tree_stall.h:652 [inline] #0: ffffffff8bd154d8 (rcu_node_0){-.-.}-{2:2}, at: rcu_pending kernel/rcu/tree.c:3751 [inline] #0: ffffffff8bd154d8 (rcu_node_0){-.-.}-{2:2}, at: rcu_sched_clock_irq+0xd2a/0x22d0 kernel/rcu/tree.c:2580 stack backtrace: CPU: 1 PID: 21044 Comm: syz-executor.4 Not tainted 5.11.0-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:79 [inline] dump_stack+0x137/0x1be lib/dump_stack.c:120 __lock_acquire+0x2333/0x5e90 kernel/locking/lockdep.c:4670 lock_acquire+0x114/0x5e0 kernel/locking/lockdep.c:5442 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x73/0xa0 kernel/locking/spinlock.c:159 rcu_dump_cpu_stacks+0x96/0x2e0 kernel/rcu/tree_stall.h:334 print_other_cpu_stall kernel/rcu/tree_stall.h:510 [inline] check_cpu_stall kernel/rcu/tree_stall.h:652 [inline] rcu_pending kernel/rcu/tree.c:3751 [inline] rcu_sched_clock_irq+0x1a0e/0x22d0 kernel/rcu/tree.c:2580 update_process_times+0x197/0x200 kernel/time/timer.c:1782 tick_sched_handle kernel/time/tick-sched.c:226 [inline] tick_sched_timer+0x27d/0x420 kernel/time/tick-sched.c:1369 __run_hrtimer kernel/time/hrtimer.c:1519 [inline] __hrtimer_run_queues+0x485/0xa00 kernel/time/hrtimer.c:1583 hrtimer_interrupt+0x393/0xf70 kernel/time/hrtimer.c:1645 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1085 [inline] __sysvec_apic_timer_interrupt+0xf9/0x270 arch/x86/kernel/apic/apic.c:1102 asm_call_irq_on_stack+0xf/0x20 __run_sysvec_on_irqstack arch/x86/include/asm/irq_stack.h:37 [inline] run_sysvec_on_irqstack_cond arch/x86/include/asm/irq_stack.h:89 [inline] sysvec_apic_timer_interrupt+0x9f/0xf0 arch/x86/kernel/apic/apic.c:1096 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:628 RIP: 0010:csd_lock_wait kernel/smp.c:227 [inline] RIP: 0010:smp_call_function_single+0x227/0x4d0 kernel/smp.c:512 Code: 44 89 ee 83 e6 01 31 ff e8 c6 3d 0b 00 41 83 e5 01 75 10 e8 ab 39 0b 00 e9 0d 01 00 00 66 0f 1f 44 00 00 f3 90 42 0f b6 04 23 <84> c0 75 15 f7 44 24 28 01 00 00 00 0f 84 e9 00 00 00 e8 82 39 0b RSP: 0018:ffffc90017a77ce0 EFLAGS: 00000246 RAX: 0000000000000000 RBX: 1ffff92002f4efa1 RCX: 0000000000040000 RDX: ffffc90011a56000 RSI: 000000000003ffff RDI: 0000000000040000 RBP: ffffc90017a77d98 R08: ffffffff816c928a R09: ffffed1017386af1 R10: ffffed1017386af1 R11: 0000000000000000 R12: dffffc0000000000 R13: 0000000000000001 R14: ffffc90017a77d08 R15: 0000000000000000 smp_call_function_many_cond+0x93e/0xa60 kernel/smp.c:648 smp_call_function_many kernel/smp.c:711 [inline] smp_call_function kernel/smp.c:733 [inline] on_each_cpu+0x5c/0x160 kernel/smp.c:832 clock_was_set+0x18/0x20 kernel/time/hrtimer.c:871 do_settimeofday64+0x59d/0x6f0 kernel/time/timekeeping.c:1326 __do_sys_clock_settime kernel/time/posix-timers.c:1079 [inline] __se_sys_clock_settime kernel/time/posix-timers.c:1067 [inline] __x64_sys_clock_settime+0x195/0x1c0 kernel/time/posix-timers.c:1067 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x45e219 Code: 0d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f91dfe95c68 EFLAGS: 00000246 ORIG_RAX: 00000000000000e3 RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 000000000045e219 RDX: 0000000000000000 RSI: 0000000020000400 RDI: 0000000000000000 RBP: 000000000119bfb8 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000119bf8c R13: 00007ffcbc85d04f R14: 00007f91dfe969c0 R15: 000000000119bf8c