rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: 1-...!: (1 GPs behind) idle=3be/1/0x4000000000000000 softirq=32414/32415 fqs=22 (detected by 0, t=10502 jiffies, g=47337, q=378) ============================================ WARNING: possible recursive locking detected 5.11.0-rc3-syzkaller #0 Not tainted -------------------------------------------- syz-executor.5/17656 is trying to acquire lock: ffffffff8b37bbd8 (rcu_node_0){-.-.}-{2:2}, at: rcu_dump_cpu_stacks+0x9c/0x230 kernel/rcu/tree_stall.h:334 but task is already holding lock: ffffffff8b37bbd8 (rcu_node_0){-.-.}-{2:2}, at: print_other_cpu_stall kernel/rcu/tree_stall.h:493 [inline] ffffffff8b37bbd8 (rcu_node_0){-.-.}-{2:2}, at: check_cpu_stall kernel/rcu/tree_stall.h:652 [inline] ffffffff8b37bbd8 (rcu_node_0){-.-.}-{2:2}, at: rcu_pending kernel/rcu/tree.c:3751 [inline] ffffffff8b37bbd8 (rcu_node_0){-.-.}-{2:2}, at: rcu_sched_clock_irq.cold+0xbc/0xedf 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 2 locks held by syz-executor.5/17656: #0: ffff8880684900e0 (&type->s_umount_key#61/1){+.+.}-{3:3}, at: alloc_super+0x201/0xaf0 fs/super.c:229 #1: ffffffff8b37bbd8 (rcu_node_0){-.-.}-{2:2}, at: print_other_cpu_stall kernel/rcu/tree_stall.h:493 [inline] #1: ffffffff8b37bbd8 (rcu_node_0){-.-.}-{2:2}, at: check_cpu_stall kernel/rcu/tree_stall.h:652 [inline] #1: ffffffff8b37bbd8 (rcu_node_0){-.-.}-{2:2}, at: rcu_pending kernel/rcu/tree.c:3751 [inline] #1: ffffffff8b37bbd8 (rcu_node_0){-.-.}-{2:2}, at: rcu_sched_clock_irq.cold+0xbc/0xedf kernel/rcu/tree.c:2580 stack backtrace: CPU: 0 PID: 17656 Comm: syz-executor.5 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+0x107/0x163 lib/dump_stack.c:120 print_deadlock_bug kernel/locking/lockdep.c:2761 [inline] check_deadlock kernel/locking/lockdep.c:2804 [inline] validate_chain kernel/locking/lockdep.c:3595 [inline] __lock_acquire.cold+0x114/0x39e kernel/locking/lockdep.c:4832 lock_acquire kernel/locking/lockdep.c:5437 [inline] lock_acquire+0x29d/0x740 kernel/locking/lockdep.c:5402 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x39/0x50 kernel/locking/spinlock.c:159 rcu_dump_cpu_stacks+0x9c/0x230 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.cold+0x6f7/0xedf kernel/rcu/tree.c:2580 update_process_times+0x16d/0x200 kernel/time/timer.c:1782 tick_sched_handle+0x9b/0x180 kernel/time/tick-sched.c:226 tick_sched_timer+0x1b0/0x2d0 kernel/time/tick-sched.c:1369 __run_hrtimer kernel/time/hrtimer.c:1519 [inline] __hrtimer_run_queues+0x1c0/0xe40 kernel/time/hrtimer.c:1583 hrtimer_interrupt+0x334/0x940 kernel/time/hrtimer.c:1645 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1085 [inline] __sysvec_apic_timer_interrupt+0x146/0x540 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+0xbd/0x100 arch/x86/kernel/apic/apic.c:1096 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:628 RIP: 0010:check_kcov_mode+0x14/0x40 kernel/kcov.c:163 Code: fe ff ff 48 8b 3c 24 e8 1a c3 42 00 e9 18 fe ff ff cc cc cc cc cc 65 8b 05 19 2e 8f 7e 89 c2 81 e2 00 01 00 00 a9 00 01 ff 00 <74> 10 31 c0 85 d2 74 15 8b 96 cc 14 00 00 85 d2 74 0b 8b 86 a8 14 RSP: 0018:ffffc90002f1f850 EFLAGS: 00000246 RAX: 0000000000000002 RBX: 1ffff920005e3f10 RCX: 0000000000000001 RDX: 0000000000000000 RSI: ffff888068e95340 RDI: 0000000000000003 RBP: ffffc90002f1f938 R08: 0000000000000000 R09: ffffffff8ed318f7 R10: ffffffff816782d3 R11: 0000000000000000 R12: 0000000000000001 R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000008 write_comp_data kernel/kcov.c:218 [inline] __sanitizer_cov_trace_const_cmp4+0x1c/0x70 kernel/kcov.c:284 csd_lock_wait kernel/smp.c:227 [inline] smp_call_function_single+0x1c3/0x4b0 kernel/smp.c:512 smp_call_function_many_cond+0x25f/0x9d0 kernel/smp.c:648 on_each_cpu_cond_mask+0x50/0x160 kernel/smp.c:899 kill_bdev fs/block_dev.c:85 [inline] set_blocksize+0x35b/0x400 fs/block_dev.c:150 sb_set_blocksize+0x49/0x110 fs/block_dev.c:159 udf_load_vrs+0xe1/0xcb0 fs/udf/super.c:1967 udf_fill_super+0x7e2/0x1b00 fs/udf/super.c:2186 mount_bdev+0x34d/0x410 fs/super.c:1366 legacy_get_tree+0x105/0x220 fs/fs_context.c:592 vfs_get_tree+0x89/0x2f0 fs/super.c:1496 do_new_mount fs/namespace.c:2878 [inline] path_mount+0x13ad/0x20c0 fs/namespace.c:3208 do_mount fs/namespace.c:3221 [inline] __do_sys_mount fs/namespace.c:3429 [inline] __se_sys_mount fs/namespace.c:3406 [inline] __x64_sys_mount+0x27f/0x300 fs/namespace.c:3406 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x460c6a Code: b8 a6 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 ad 89 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 8a 89 fb ff c3 66 0f 1f 84 00 00 00 00 00 RSP: 002b:00007fd6acb18a78 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5 RAX: ffffffffffffffda RBX: 00007fd6acb18b10 RCX: 0000000000460c6a RDX: 0000000020000980 RSI: 00000000200009c0 RDI: 00007fd6acb18ad0 RBP: 00007fd6acb18ad0 R08: 00007fd6acb18b10 R09: 0000000020000980 R10: 0000000000010000 R11: 0000000000000202 R12: 0000000020000980 R13: 00000000200009c0 R14: 0000000020001d00 R15: 0000000020001dc0