rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: 0-...!: (0 ticks this GP) idle=232/1/0x4000000000000000 softirq=38463/38463 fqs=2 (detected by 1, t=10502 jiffies, g=60377, q=93) ============================================ WARNING: possible recursive locking detected 5.12.0-rc5-syzkaller #0 Not tainted -------------------------------------------- syz-executor.0/19369 is trying to acquire lock: ffffffff8c714258 (rcu_node_0){-.-.}-{2:2}, at: rcu_dump_cpu_stacks+0xa1/0x390 kernel/rcu/tree_stall.h:336 but task is already holding lock: ffffffff8c714258 (rcu_node_0){-.-.}-{2:2}, at: print_other_cpu_stall kernel/rcu/tree_stall.h:541 [inline] ffffffff8c714258 (rcu_node_0){-.-.}-{2:2}, at: check_cpu_stall kernel/rcu/tree_stall.h:706 [inline] ffffffff8c714258 (rcu_node_0){-.-.}-{2:2}, at: rcu_pending kernel/rcu/tree.c:3830 [inline] ffffffff8c714258 (rcu_node_0){-.-.}-{2:2}, at: rcu_sched_clock_irq+0xf4e/0x28f0 kernel/rcu/tree.c:2650 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.0/19369: #0: ffffffff8c714258 (rcu_node_0){-.-.}-{2:2}, at: print_other_cpu_stall kernel/rcu/tree_stall.h:541 [inline] #0: ffffffff8c714258 (rcu_node_0){-.-.}-{2:2}, at: check_cpu_stall kernel/rcu/tree_stall.h:706 [inline] #0: ffffffff8c714258 (rcu_node_0){-.-.}-{2:2}, at: rcu_pending kernel/rcu/tree.c:3830 [inline] #0: ffffffff8c714258 (rcu_node_0){-.-.}-{2:2}, at: rcu_sched_clock_irq+0xf4e/0x28f0 kernel/rcu/tree.c:2650 stack backtrace: CPU: 1 PID: 19369 Comm: syz-executor.0 Not tainted 5.12.0-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+0x176/0x24e lib/dump_stack.c:120 __lock_acquire+0x2303/0x5e60 kernel/locking/lockdep.c:4738 lock_acquire+0x126/0x650 kernel/locking/lockdep.c:5510 __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+0xa1/0x390 kernel/rcu/tree_stall.h:336 print_other_cpu_stall kernel/rcu/tree_stall.h:559 [inline] check_cpu_stall kernel/rcu/tree_stall.h:706 [inline] rcu_pending kernel/rcu/tree.c:3830 [inline] rcu_sched_clock_irq+0x1dd4/0x28f0 kernel/rcu/tree.c:2650 update_process_times+0x197/0x200 kernel/time/timer.c:1796 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:1537 [inline] __hrtimer_run_queues+0x485/0xa00 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:632 RIP: 0010:__sanitizer_cov_trace_pc+0x42/0x60 kernel/kcov.c:202 Code: ff 00 74 11 f7 c2 00 01 00 00 74 35 83 b9 34 15 00 00 00 74 2c 8b 91 10 15 00 00 83 fa 02 75 21 48 8b 91 18 15 00 00 48 8b 32 <48> 8d 7e 01 8b 89 14 15 00 00 48 39 cf 73 08 48 89 44 f2 08 48 89 RSP: 0018:ffffc900018bfcd8 EFLAGS: 00000246 RAX: ffffffff816de40e RBX: 1ffff92000317fa1 RCX: ffff88807d7354c0 RDX: ffffc9000a577000 RSI: 000000000003ffff RDI: 0000000000040000 RBP: ffffc900018bfd88 R08: ffffffff816de3da R09: ffffed1017386ba1 R10: ffffed1017386ba1 R11: 0000000000000000 R12: dffffc0000000000 R13: 0000000000000001 R14: ffffc900018bfd08 R15: 0000000000000000 csd_lock_wait kernel/smp.c:228 [inline] smp_call_function_single+0x23e/0x4d0 kernel/smp.c:516 smp_call_function_many_cond+0x93e/0xa60 kernel/smp.c:652 smp_call_function_many kernel/smp.c:715 [inline] smp_call_function kernel/smp.c:737 [inline] on_each_cpu+0x62/0x1b0 kernel/smp.c:836 clock_was_set+0x18/0x20 kernel/time/hrtimer.c:889 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+0x44/0xae RIP: 0033:0x466459 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 bc ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f57f7604188 EFLAGS: 00000246 ORIG_RAX: 00000000000000e3 RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000466459 RDX: 0000000000000000 RSI: 0000000020001b80 RDI: 0000000000000000 RBP: 00000000004bf9fb R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60 R13: 00007ffd8d00757f R14: 00007f57f7604300 R15: 0000000000022000