rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: 0-....: (0 ticks this GP) idle=202/1/0x4000000000000002 softirq=16258/16258 fqs=4278 (detected by 1, t=10502 jiffies, g=20137, q=131643) ============================================ WARNING: possible recursive locking detected 5.10.0-syzkaller #0 Not tainted -------------------------------------------- kworker/u4:10/11125 is trying to acquire lock: ffffffff8b342118 (rcu_node_0){-.-.}-{2:2}, at: rcu_dump_cpu_stacks+0x9c/0x21e kernel/rcu/tree_stall.h:334 but task is already holding lock: ffffffff8b342118 (rcu_node_0){-.-.}-{2:2}, at: print_other_cpu_stall kernel/rcu/tree_stall.h:493 [inline] ffffffff8b342118 (rcu_node_0){-.-.}-{2:2}, at: check_cpu_stall kernel/rcu/tree_stall.h:652 [inline] ffffffff8b342118 (rcu_node_0){-.-.}-{2:2}, at: rcu_pending kernel/rcu/tree.c:3751 [inline] ffffffff8b342118 (rcu_node_0){-.-.}-{2:2}, at: rcu_sched_clock_irq.cold+0xbc/0xec3 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 6 locks held by kworker/u4:10/11125: #0: ffff888147790938 ((wq_completion)krdsd){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff888147790938 ((wq_completion)krdsd){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline] #0: ffff888147790938 ((wq_completion)krdsd){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline] #0: ffff888147790938 ((wq_completion)krdsd){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:616 [inline] #0: ffff888147790938 ((wq_completion)krdsd){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline] #0: ffff888147790938 ((wq_completion)krdsd){+.+.}-{0:0}, at: process_one_work+0x821/0x15a0 kernel/workqueue.c:2246 #1: ffffc900017dfda8 ((work_completion)(&(&cp->cp_conn_w)->work)){+.+.}-{0:0}, at: process_one_work+0x854/0x15a0 kernel/workqueue.c:2250 #2: ffff888013c10088 (&tc->t_conn_path_lock){+.+.}-{3:3}, at: rds_tcp_conn_path_connect+0x174/0x880 net/rds/tcp_connect.c:107 #3: ffff88802037d360 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1594 [inline] #3: ffff88802037d360 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: __inet_bind+0x827/0xbc0 net/ipv4/af_inet.c:514 #4: ffffc90007846138 (&tcp_hashinfo.bhash[i].lock){+.-.}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:359 [inline] #4: ffffc90007846138 (&tcp_hashinfo.bhash[i].lock){+.-.}-{2:2}, at: inet_csk_find_open_port net/ipv4/inet_connection_sock.c:229 [inline] #4: ffffc90007846138 (&tcp_hashinfo.bhash[i].lock){+.-.}-{2:2}, at: inet_csk_get_port+0x9b1/0x1690 net/ipv4/inet_connection_sock.c:367 #5: ffffffff8b342118 (rcu_node_0){-.-.}-{2:2}, at: print_other_cpu_stall kernel/rcu/tree_stall.h:493 [inline] #5: ffffffff8b342118 (rcu_node_0){-.-.}-{2:2}, at: check_cpu_stall kernel/rcu/tree_stall.h:652 [inline] #5: ffffffff8b342118 (rcu_node_0){-.-.}-{2:2}, at: rcu_pending kernel/rcu/tree.c:3751 [inline] #5: ffffffff8b342118 (rcu_node_0){-.-.}-{2:2}, at: rcu_sched_clock_irq.cold+0xbc/0xec3 kernel/rcu/tree.c:2580 stack backtrace: CPU: 1 PID: 11125 Comm: kworker/u4:10 Not tainted 5.10.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: krdsd rds_connect_worker 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+0x15e/0x3b0 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/0x21e 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+0x6db/0xec3 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:1376 __run_hrtimer kernel/time/hrtimer.c:1519 [inline] __hrtimer_run_queues+0x1ce/0xea0 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:lockdep_enabled kernel/locking/lockdep.c:90 [inline] RIP: 0010:lockdep_enabled+0x74/0xa0 kernel/locking/lockdep.c:82 Code: 00 48 8d bb 84 09 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 0f b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 04 <84> d2 75 1b 8b 83 84 09 00 00 85 c0 0f 94 c0 5b c3 48 c7 c7 dc b4 RSP: 0018:ffffc900017df8d8 EFLAGS: 00000202 RAX: 0000000000000007 RBX: ffff88801dd8b580 RCX: 1ffffffff19db69b RDX: 0000000000000000 RSI: 00000000ffffffff RDI: ffff88801dd8bf04 RBP: ffffffff8b339f60 R08: 0000000000000000 R09: ffffffff8ced830f R10: fffffbfff19db061 R11: 0000000000000000 R12: 0000000000000001 R13: ffff8880617cc800 R14: 00000000ffffffff R15: 0000000000000000 lock_is_held_type+0x19/0x100 kernel/locking/lockdep.c:5469 lock_is_held include/linux/lockdep.h:271 [inline] rcu_read_lock_sched_held+0x3a/0x70 kernel/rcu/update.c:123 trace_lock_release include/trace/events/lock.h:58 [inline] lock_release+0x5b7/0x710 kernel/locking/lockdep.c:5448 __raw_spin_unlock_bh include/linux/spinlock_api_smp.h:174 [inline] _raw_spin_unlock_bh+0x12/0x30 kernel/locking/spinlock.c:207 spin_unlock_bh include/linux/spinlock.h:399 [inline] inet_csk_find_open_port net/ipv4/inet_connection_sock.c:240 [inline] inet_csk_get_port+0xae8/0x1690 net/ipv4/inet_connection_sock.c:367 __inet_bind+0x796/0xbc0 net/ipv4/af_inet.c:528 inet_bind+0xf0/0x170 net/ipv4/af_inet.c:457 rds_tcp_conn_path_connect+0x532/0x880 net/rds/tcp_connect.c:144 rds_connect_worker+0x1a5/0x2c0 net/rds/threads.c:176 process_one_work+0x933/0x15a0 kernel/workqueue.c:2275 worker_thread+0x64c/0x1120 kernel/workqueue.c:2421 kthread+0x3b1/0x4a0 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296