============================================ WARNING: possible recursive locking detected 5.6.0-rc3-syzkaller #0 Not tainted -------------------------------------------- kworker/u4:4/19167 is trying to acquire lock: ffff8880685da210 (k-sk_lock-AF_INET6){+.+.}, at: lock_sock include/net/sock.h:1541 [inline] ffff8880685da210 (k-sk_lock-AF_INET6){+.+.}, at: inet_csk_accept+0x69f/0xd30 net/ipv4/inet_connection_sock.c:492 but task is already holding lock: ffff8880a35cc150 (k-sk_lock-AF_INET6){+.+.}, at: lock_sock include/net/sock.h:1541 [inline] ffff8880a35cc150 (k-sk_lock-AF_INET6){+.+.}, at: inet_csk_accept+0x8d/0xd30 net/ipv4/inet_connection_sock.c:445 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(k-sk_lock-AF_INET6); lock(k-sk_lock-AF_INET6); *** DEADLOCK *** May be due to missing lock nesting notation 3 locks held by kworker/u4:4/19167: #0: ffff8880a8d1b528 ((wq_completion)krdsd){+.+.}, at: __write_once_size include/linux/compiler.h:226 [inline] #0: ffff8880a8d1b528 ((wq_completion)krdsd){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff8880a8d1b528 ((wq_completion)krdsd){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:855 [inline] #0: ffff8880a8d1b528 ((wq_completion)krdsd){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:40 [inline] #0: ffff8880a8d1b528 ((wq_completion)krdsd){+.+.}, at: set_work_data kernel/workqueue.c:615 [inline] #0: ffff8880a8d1b528 ((wq_completion)krdsd){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:642 [inline] #0: ffff8880a8d1b528 ((wq_completion)krdsd){+.+.}, at: process_one_work+0x82a/0x1690 kernel/workqueue.c:2235 #1: ffffc90002a07dd0 ((work_completion)(&rtn->rds_tcp_accept_w)){+.+.}, at: process_one_work+0x85e/0x1690 kernel/workqueue.c:2239 #2: ffff8880a35cc150 (k-sk_lock-AF_INET6){+.+.}, at: lock_sock include/net/sock.h:1541 [inline] #2: ffff8880a35cc150 (k-sk_lock-AF_INET6){+.+.}, at: inet_csk_accept+0x8d/0xd30 net/ipv4/inet_connection_sock.c:445 stack backtrace: CPU: 1 PID: 19167 Comm: kworker/u4:4 Not tainted 5.6.0-rc3-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: krdsd rds_tcp_accept_worker Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x188/0x20d lib/dump_stack.c:118 print_deadlock_bug kernel/locking/lockdep.c:2370 [inline] check_deadlock kernel/locking/lockdep.c:2411 [inline] validate_chain kernel/locking/lockdep.c:2954 [inline] __lock_acquire.cold+0x114/0x288 kernel/locking/lockdep.c:3954 lock_acquire+0x197/0x420 kernel/locking/lockdep.c:4484 lock_sock_nested+0xc5/0x110 net/core/sock.c:2947 lock_sock include/net/sock.h:1541 [inline] inet_csk_accept+0x69f/0xd30 net/ipv4/inet_connection_sock.c:492 inet_accept+0xe9/0x7c0 net/ipv4/af_inet.c:734 rds_tcp_accept_one+0x1c2/0xb70 net/rds/tcp_listen.c:149 rds_tcp_accept_worker+0x50/0x80 net/rds/tcp.c:525 process_one_work+0x94b/0x1690 kernel/workqueue.c:2264 worker_thread+0x96/0xe20 kernel/workqueue.c:2410 kthread+0x357/0x430 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352