rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: 1-...!: (0 ticks this GP) idle=ec6/1/0x4000000000000000 softirq=107772/107772 fqs=0 (detected by 0, t=10502 jiffies, g=191685, q=276) ============================================ WARNING: possible recursive locking detected 5.11.0-rc3-syzkaller #0 Not tainted -------------------------------------------- syz-executor.2/16496 is trying to acquire lock: ffffffff8c315318 (rcu_node_0){-.-.}-{2:2}, at: rcu_dump_cpu_stacks+0x96/0x2e0 kernel/rcu/tree_stall.h:334 but task is already holding lock: ffffffff8c315318 (rcu_node_0){-.-.}-{2:2}, at: print_other_cpu_stall kernel/rcu/tree_stall.h:493 [inline] ffffffff8c315318 (rcu_node_0){-.-.}-{2:2}, at: check_cpu_stall kernel/rcu/tree_stall.h:652 [inline] ffffffff8c315318 (rcu_node_0){-.-.}-{2:2}, at: rcu_pending kernel/rcu/tree.c:3751 [inline] ffffffff8c315318 (rcu_node_0){-.-.}-{2:2}, at: rcu_sched_clock_irq+0xde9/0x23e0 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 3 locks held by syz-executor.2/16496: #0: ffff8880a317e8b0 (&ctx->mutex){+.+.}-{3:3}, at: perf_event_release_kernel+0x6ef/0xd60 kernel/events/core.c:5008 #1: ffff88805d77d2a8 (&event->child_mutex){+.+.}-{3:3}, at: perf_event_release_kernel+0x6f9/0xd60 kernel/events/core.c:5009 #2: ffffffff8c315318 (rcu_node_0){-.-.}-{2:2}, at: print_other_cpu_stall kernel/rcu/tree_stall.h:493 [inline] #2: ffffffff8c315318 (rcu_node_0){-.-.}-{2:2}, at: check_cpu_stall kernel/rcu/tree_stall.h:652 [inline] #2: ffffffff8c315318 (rcu_node_0){-.-.}-{2:2}, at: rcu_pending kernel/rcu/tree.c:3751 [inline] #2: ffffffff8c315318 (rcu_node_0){-.-.}-{2:2}, at: rcu_sched_clock_irq+0xde9/0x23e0 kernel/rcu/tree.c:2580 stack backtrace: CPU: 0 PID: 16496 Comm: syz-executor.2 Not tainted 5.11.0-rc3-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+0x183/0x22e lib/dump_stack.c:120 __lock_acquire+0x246b/0x5e40 kernel/locking/lockdep.c:4670 lock_acquire+0x174/0x6c0 kernel/locking/lockdep.c:5437 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xb3/0x100 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+0x1b16/0x23e0 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+0x4cb/0xa60 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+0x277/0x530 kernel/smp.c:512 Code: 8b 6c 24 68 44 89 ee 83 e6 01 31 ff e8 62 af 0b 00 41 83 e5 01 75 0c e8 47 ab 0b 00 e9 f9 00 00 00 66 90 f3 90 42 0f b6 04 23 <84> c0 75 15 f7 44 24 68 01 00 00 00 0f 84 d9 00 00 00 e8 22 ab 0b RSP: 0018:ffffc900174bfa00 EFLAGS: 00000293 RAX: 0000000000000000 RBX: 1ffff92002e97f4d RCX: ffff888027fdb780 RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000 RBP: ffffc900174bfb10 R08: ffffffff8171712e R09: fffffbfff1e540ae R10: fffffbfff1e540ae R11: 0000000000000000 R12: dffffc0000000000 R13: 0000000000000001 R14: 0000000000000000 R15: ffffc900174bfa68 task_function_call kernel/events/core.c:118 [inline] event_function_call+0x467/0x6e0 kernel/events/core.c:286 perf_remove_from_context+0xb0/0x1e0 kernel/events/core.c:2377 perf_event_release_kernel+0x75d/0xd60 kernel/events/core.c:5019 perf_release+0x37/0x40 kernel/events/core.c:5060 __fput+0x34d/0x7a0 fs/file_table.c:280 task_work_run+0x137/0x1c0 kernel/task_work.c:140 tracehook_notify_resume include/linux/tracehook.h:189 [inline] exit_to_user_mode_loop kernel/entry/common.c:174 [inline] exit_to_user_mode_prepare+0x10b/0x1e0 kernel/entry/common.c:201 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline] syscall_exit_to_user_mode+0x48/0x190 kernel/entry/common.c:302 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x417b71 Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 a4 1a 00 00 c3 48 83 ec 08 e8 0a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 53 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01 RSP: 002b:00007fff31da7770 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000417b71 RDX: 0000001b2cd20000 RSI: 0000000080000000 RDI: 0000000000000003 RBP: 0000000000000001 R08: 000000000000009c R09: 00000000e1f4c0a0 R10: 00007fff31da7850 R11: 0000000000000293 R12: 000000000119ca00 R13: 000000000119ca00 R14: 00000000000003e8 R15: 000000000119c184