bisecting fixing commit since 6b6446efedb27c2766745a04f9b5d4449f51391d building syzkaller on cba33199be220cbf61f7c0c8223d88a25a913d6f testing commit 6b6446efedb27c2766745a04f9b5d4449f51391d with gcc (GCC) 8.1.0 kernel signature: c47cdcc152b3cc0f6d32a4a3831df4ce642ab622c4fa50df20f29b1e90fdaaf7 all runs: crashed: INFO: task hung in rtnl_lock testing current HEAD 1752938529c614a8ed4432ecce6ebc95d3b87207 testing commit 1752938529c614a8ed4432ecce6ebc95d3b87207 with gcc (GCC) 8.1.0 kernel signature: 26b0a77ea6a928954f6befaa35bca9f5aa1b01fccbb7e0b4b4cdffd5e700b412 all runs: crashed: INFO: task hung in rtnl_lock revisions tested: 2, total time: 29m56.086757438s (build: 15m57.682407068s, test: 13m26.724780995s) the crash still happens on HEAD commit msg: Linux 4.14.213 crash: INFO: task hung in rtnl_lock Bluetooth: hci1 command 0x0406 tx timeout Bluetooth: hci0 command 0x0406 tx timeout Bluetooth: hci2 command 0x0406 tx timeout Bluetooth: hci3 command 0x0406 tx timeout Bluetooth: hci4 command 0x0406 tx timeout INFO: task kworker/0:0:3 blocked for more than 140 seconds. Not tainted 4.14.213-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/0:0 D26464 3 2 0x80000000 Workqueue: events disconnect_work Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x824/0x1ee0 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0x519/0x1490 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 rtnl_lock+0x12/0x20 net/core/rtnetlink.c:72 disconnect_work+0x16/0x1b0 net/wireless/sme.c:664 process_one_work+0x74f/0x1620 kernel/workqueue.c:2116 worker_thread+0xcc/0xed0 kernel/workqueue.c:2250 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 INFO: task kworker/1:0:18 blocked for more than 140 seconds. Not tainted 4.14.213-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/1:0 D25360 18 2 0x80000000 Workqueue: events_power_efficient reg_check_chans_work Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x824/0x1ee0 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0x519/0x1490 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 rtnl_lock+0x12/0x20 net/core/rtnetlink.c:72 reg_check_chans_work+0x73/0xc60 net/wireless/reg.c:1655 process_one_work+0x74f/0x1620 kernel/workqueue.c:2116 worker_thread+0xcc/0xed0 kernel/workqueue.c:2250 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 INFO: task kworker/1:1:23 blocked for more than 140 seconds. Not tainted 4.14.213-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/1:1 D26160 23 2 0x80000000 Workqueue: events linkwatch_event Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x824/0x1ee0 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0x519/0x1490 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 rtnl_lock+0x12/0x20 net/core/rtnetlink.c:72 linkwatch_event+0x9/0x50 net/core/link_watch.c:236 process_one_work+0x74f/0x1620 kernel/workqueue.c:2116 worker_thread+0xcc/0xed0 kernel/workqueue.c:2250 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 INFO: task kworker/0:2:2979 blocked for more than 140 seconds. Not tainted 4.14.213-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/0:2 D25728 2979 2 0x80000000 Workqueue: ipv6_addrconf addrconf_dad_work Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x824/0x1ee0 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0x519/0x1490 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 rtnl_lock+0x12/0x20 net/core/rtnetlink.c:72 addrconf_dad_work+0x8f/0xfa0 net/ipv6/addrconf.c:3917 process_one_work+0x74f/0x1620 kernel/workqueue.c:2116 worker_thread+0xcc/0xed0 kernel/workqueue.c:2250 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 INFO: task kworker/1:2:4055 blocked for more than 140 seconds. Not tainted 4.14.213-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/1:2 D25712 4055 2 0x80000000 Workqueue: ipv6_addrconf addrconf_dad_work Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x824/0x1ee0 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0x519/0x1490 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 rtnl_lock+0x12/0x20 net/core/rtnetlink.c:72 addrconf_dad_work+0x8f/0xfa0 net/ipv6/addrconf.c:3917 process_one_work+0x74f/0x1620 kernel/workqueue.c:2116 worker_thread+0xcc/0xed0 kernel/workqueue.c:2250 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 INFO: task syz-executor.4:7703 blocked for more than 140 seconds. Not tainted 4.14.213-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D24808 7703 1 0x00000004 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x824/0x1ee0 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0x519/0x1490 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 rtnl_lock net/core/rtnetlink.c:72 [inline] rtnetlink_rcv_msg+0x2c0/0x9e0 net/core/rtnetlink.c:4311 netlink_rcv_skb+0x12f/0x3b0 net/netlink/af_netlink.c:2433 rtnetlink_rcv+0x10/0x20 net/core/rtnetlink.c:4328 netlink_unicast_kernel net/netlink/af_netlink.c:1287 [inline] netlink_unicast+0x40b/0x610 net/netlink/af_netlink.c:1313 netlink_sendmsg+0x657/0xc60 net/netlink/af_netlink.c:1878 sock_sendmsg_nosec net/socket.c:646 [inline] sock_sendmsg+0xac/0xf0 net/socket.c:656 SYSC_sendto net/socket.c:1763 [inline] SyS_sendto+0x1e4/0x2c0 net/socket.c:1731 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x417937 RSP: 002b:00007ffc2679c720 EFLAGS: 00000293 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 00000000016a4300 RCX: 0000000000417937 RDX: 0000000000000020 RSI: 00000000016a4350 RDI: 0000000000000003 RBP: 0000000000000000 R08: 00007ffc2679c730 R09: 000000000000000c R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000000 R13: 0000000000000000 R14: 00000000016a4350 R15: 0000000000000003 INFO: task syz-executor.0:7707 blocked for more than 140 seconds. Not tainted 4.14.213-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.0 D24984 7707 1 0x00000004 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x824/0x1ee0 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0x519/0x1490 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 rtnl_lock net/core/rtnetlink.c:72 [inline] rtnetlink_rcv_msg+0x2c0/0x9e0 net/core/rtnetlink.c:4311 netlink_rcv_skb+0x12f/0x3b0 net/netlink/af_netlink.c:2433 rtnetlink_rcv+0x10/0x20 net/core/rtnetlink.c:4328 netlink_unicast_kernel net/netlink/af_netlink.c:1287 [inline] netlink_unicast+0x40b/0x610 net/netlink/af_netlink.c:1313 netlink_sendmsg+0x657/0xc60 net/netlink/af_netlink.c:1878 sock_sendmsg_nosec net/socket.c:646 [inline] sock_sendmsg+0xac/0xf0 net/socket.c:656 SYSC_sendto net/socket.c:1763 [inline] SyS_sendto+0x1e4/0x2c0 net/socket.c:1731 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x417937 RSP: 002b:00007fffcbfd07b0 EFLAGS: 00000293 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 00000000016a4300 RCX: 0000000000417937 RDX: 0000000000000040 RSI: 00000000016a4350 RDI: 0000000000000003 RBP: 0000000000000000 R08: 00007fffcbfd07c0 R09: 000000000000000c R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000000 R13: 0000000000000000 R14: 00000000016a4350 R15: 0000000000000003 INFO: task syz-executor.5:7708 blocked for more than 140 seconds. Not tainted 4.14.213-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.5 D24712 7708 1 0x00000004 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x824/0x1ee0 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0x519/0x1490 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 rtnl_lock net/core/rtnetlink.c:72 [inline] rtnetlink_rcv_msg+0x2c0/0x9e0 net/core/rtnetlink.c:4311 netlink_rcv_skb+0x12f/0x3b0 net/netlink/af_netlink.c:2433 rtnetlink_rcv+0x10/0x20 net/core/rtnetlink.c:4328 netlink_unicast_kernel net/netlink/af_netlink.c:1287 [inline] netlink_unicast+0x40b/0x610 net/netlink/af_netlink.c:1313 netlink_sendmsg+0x657/0xc60 net/netlink/af_netlink.c:1878 sock_sendmsg_nosec net/socket.c:646 [inline] sock_sendmsg+0xac/0xf0 net/socket.c:656 SYSC_sendto net/socket.c:1763 [inline] SyS_sendto+0x1e4/0x2c0 net/socket.c:1731 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x417937 RSP: 002b:00007ffeb61efa90 EFLAGS: 00000293 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 00000000016a4300 RCX: 0000000000417937 RDX: 0000000000000028 RSI: 00000000016a4350 RDI: 0000000000000003 RBP: 0000000000000000 R08: 00007ffeb61efaa0 R09: 000000000000000c R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000000 R13: 0000000000000000 R14: 00000000016a4350 R15: 0000000000000003 INFO: task syz-executor.1:7710 blocked for more than 140 seconds. Not tainted 4.14.213-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.1 D24616 7710 1 0x00000004 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x824/0x1ee0 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0x519/0x1490 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 genl_lock net/netlink/genetlink.c:33 [inline] genl_rcv_msg+0x10e/0x140 net/netlink/genetlink.c:623 netlink_rcv_skb+0x12f/0x3b0 net/netlink/af_netlink.c:2433 genl_rcv+0x23/0x40 net/netlink/genetlink.c:636 netlink_unicast_kernel net/netlink/af_netlink.c:1287 [inline] netlink_unicast+0x40b/0x610 net/netlink/af_netlink.c:1313 netlink_sendmsg+0x657/0xc60 net/netlink/af_netlink.c:1878 sock_sendmsg_nosec net/socket.c:646 [inline] sock_sendmsg+0xac/0xf0 net/socket.c:656 SYSC_sendto net/socket.c:1763 [inline] SyS_sendto+0x1e4/0x2c0 net/socket.c:1731 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x417937 RSP: 002b:00007fffa8a3a320 EFLAGS: 00000293 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 00000000016a4300 RCX: 0000000000417937 RDX: 0000000000000028 RSI: 00000000016a4350 RDI: 0000000000000003 RBP: 0000000000000000 R08: 00007fffa8a3a330 R09: 000000000000000c R10: 0000000000000000 R11: 0000000000000293 R12: 00007fffa8a3a394 R13: 0000000000000010 R14: 00000000016a4350 R15: 0000000000000003 INFO: task syz-executor.3:9145 blocked for more than 140 seconds. Not tainted 4.14.213-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.3 D29080 9145 7711 0x00000004 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x824/0x1ee0 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0x519/0x1490 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 genl_lock net/netlink/genetlink.c:33 [inline] genl_rcv_msg+0x10e/0x140 net/netlink/genetlink.c:623 netlink_rcv_skb+0x12f/0x3b0 net/netlink/af_netlink.c:2433 genl_rcv+0x23/0x40 net/netlink/genetlink.c:636 netlink_unicast_kernel net/netlink/af_netlink.c:1287 [inline] netlink_unicast+0x40b/0x610 net/netlink/af_netlink.c:1313 netlink_sendmsg+0x657/0xc60 net/netlink/af_netlink.c:1878 sock_sendmsg_nosec net/socket.c:646 [inline] sock_sendmsg+0xac/0xf0 net/socket.c:656 SYSC_sendto net/socket.c:1763 [inline] SyS_sendto+0x1e4/0x2c0 net/socket.c:1731 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x417937 RSP: 002b:00007f61b4a5cb40 EFLAGS: 00000293 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 00007f61b4a5cbf0 RCX: 0000000000417937 RDX: 0000000000000020 RSI: 00007f61b4a5cc40 RDI: 0000000000000004 RBP: 0000000000000000 R08: 00007f61b4a5cb50 R09: 000000000000000c R10: 0000000000000000 R11: 0000000000000293 R12: 00007f61b4a5cbb4 R13: 0000000000000010 R14: 00007f61b4a5cc40 R15: 0000000000000004 Showing all locks held in the system: 3 locks held by kworker/0:0/3: #0: ("events"){+.+.}, at: [] process_one_work+0x681/0x1620 kernel/workqueue.c:2087 #1: (cfg80211_disconnect_work){+.+.}, at: [] process_one_work+0x6b4/0x1620 kernel/workqueue.c:2091 #2: (rtnl_mutex){+.+.}, at: [] rtnl_lock+0x12/0x20 net/core/rtnetlink.c:72 3 locks held by kworker/1:0/18: #0: ("events_power_efficient"){+.+.}, at: [] process_one_work+0x681/0x1620 kernel/workqueue.c:2087 #1: ((reg_check_chans).work){+.+.}, at: [] process_one_work+0x6b4/0x1620 kernel/workqueue.c:2091 #2: (rtnl_mutex){+.+.}, at: [] rtnl_lock+0x12/0x20 net/core/rtnetlink.c:72 3 locks held by kworker/1:1/23: #0: ("events"){+.+.}, at: [] process_one_work+0x681/0x1620 kernel/workqueue.c:2087 #1: ((linkwatch_work).work){+.+.}, at: [] process_one_work+0x6b4/0x1620 kernel/workqueue.c:2091 #2: (rtnl_mutex){+.+.}, at: [] rtnl_lock+0x12/0x20 net/core/rtnetlink.c:72 1 lock held by khungtaskd/1528: #0: (tasklist_lock){.+.+}, at: [] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4548 3 locks held by kworker/0:2/2979: #0: ("%s"("ipv6_addrconf")){+.+.}, at: [] process_one_work+0x681/0x1620 kernel/workqueue.c:2087 #1: ((&(&ifa->dad_work)->work)){+.+.}, at: [] process_one_work+0x6b4/0x1620 kernel/workqueue.c:2091 #2: (rtnl_mutex){+.+.}, at: [] rtnl_lock+0x12/0x20 net/core/rtnetlink.c:72 3 locks held by kworker/1:2/4055: #0: ("%s"("ipv6_addrconf")){+.+.}, at: [] process_one_work+0x681/0x1620 kernel/workqueue.c:2087 #1: ((&(&ifa->dad_work)->work)){+.+.}, at: [] process_one_work+0x6b4/0x1620 kernel/workqueue.c:2091 #2: (rtnl_mutex){+.+.}, at: [] rtnl_lock+0x12/0x20 net/core/rtnetlink.c:72 1 lock held by syz-executor.4/7703: #0: (rtnl_mutex){+.+.}, at: [] rtnl_lock net/core/rtnetlink.c:72 [inline] #0: (rtnl_mutex){+.+.}, at: [] rtnetlink_rcv_msg+0x2c0/0x9e0 net/core/rtnetlink.c:4311 1 lock held by syz-executor.0/7707: #0: (rtnl_mutex){+.+.}, at: [] rtnl_lock net/core/rtnetlink.c:72 [inline] #0: (rtnl_mutex){+.+.}, at: [] rtnetlink_rcv_msg+0x2c0/0x9e0 net/core/rtnetlink.c:4311 1 lock held by syz-executor.5/7708: #0: (rtnl_mutex){+.+.}, at: [] rtnl_lock net/core/rtnetlink.c:72 [inline] #0: (rtnl_mutex){+.+.}, at: [] rtnetlink_rcv_msg+0x2c0/0x9e0 net/core/rtnetlink.c:4311 2 locks held by syz-executor.1/7710: #0: (cb_lock){++++}, at: [] genl_rcv+0x14/0x40 net/netlink/genetlink.c:635 #1: (genl_mutex){+.+.}, at: [] genl_lock net/netlink/genetlink.c:33 [inline] #1: (genl_mutex){+.+.}, at: [] genl_rcv_msg+0x10e/0x140 net/netlink/genetlink.c:623 2 locks held by syz-executor.3/9145: #0: (cb_lock){++++}, at: [] genl_rcv+0x14/0x40 net/netlink/genetlink.c:635 #1: (genl_mutex){+.+.}, at: [] genl_lock net/netlink/genetlink.c:33 [inline] #1: (genl_mutex){+.+.}, at: [] genl_rcv_msg+0x10e/0x140 net/netlink/genetlink.c:623 2 locks held by syz-executor.3/9147: #0: (cb_lock){++++}, at: [] genl_rcv+0x14/0x40 net/netlink/genetlink.c:635 #1: (genl_mutex){+.+.}, at: [] genl_lock net/netlink/genetlink.c:33 [inline] #1: (genl_mutex){+.+.}, at: [] genl_rcv_msg+0x10e/0x140 net/netlink/genetlink.c:623 2 locks held by syz-executor.3/9148: #0: (cb_lock){++++}, at: [] genl_rcv+0x14/0x40 net/netlink/genetlink.c:635 #1: (genl_mutex){+.+.}, at: [] genl_lock net/netlink/genetlink.c:33 [inline] #1: (genl_mutex){+.+.}, at: [] genl_rcv_msg+0x10e/0x140 net/netlink/genetlink.c:623 2 locks held by syz-executor.3/9150: #0: (cb_lock){++++}, at: [] genl_rcv+0x14/0x40 net/netlink/genetlink.c:635 #1: (genl_mutex){+.+.}, at: [] genl_lock net/netlink/genetlink.c:33 [inline] #1: (genl_mutex){+.+.}, at: [] genl_rcv_msg+0x10e/0x140 net/netlink/genetlink.c:623 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1528 Comm: khungtaskd Not tainted 4.14.213-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x14b/0x1f1 lib/dump_stack.c:58 nmi_cpu_backtrace.cold.0+0x3c/0x78 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0xf6/0x11a lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 trigger_all_cpu_backtrace include/linux/nmi.h:140 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:195 [inline] watchdog+0x51b/0xa70 kernel/hung_task.c:274 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 8 Comm: rcu_preempt Not tainted 4.14.213-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff8881f533e200 task.stack: ffff8881f5388000 RIP: 0010:debug_lockdep_rcu_enabled+0x6e/0x90 kernel/rcu/update.c:299 RSP: 0018:ffff8881f538fa20 EFLAGS: 00000097 RAX: 0000000000000001 RBX: ffff8881f533e200 RCX: 0000000000000000 RDX: 0000000000000004 RSI: 0000000000000000 RDI: ffffffff893cede0 RBP: ffff8881f538fa20 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: ffff8881f533e200 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff8881f6500000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fc503ca2000 CR3: 0000000008e6a001 CR4: 00000000001606e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: trace_lock_acquire include/trace/events/lock.h:13 [inline] lock_acquire+0x30b/0x3e0 kernel/locking/lockdep.c:3997 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:160 debug_object_deactivate+0xe1/0x300 lib/debugobjects.c:502 debug_timer_deactivate kernel/time/timer.c:698 [inline] debug_deactivate kernel/time/timer.c:750 [inline] detach_timer kernel/time/timer.c:790 [inline] detach_if_pending+0x77/0x3b0 kernel/time/timer.c:809 try_to_del_timer_sync+0x98/0xf0 kernel/time/timer.c:1181 del_timer_sync+0x154/0x1e0 kernel/time/timer.c:1246 schedule_timeout+0x42e/0xcc0 kernel/time/timer.c:1748 rcu_gp_kthread+0xb69/0x1df0 kernel/rcu/tree.c:2255 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Code: 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 1c 8b 05 e2 43 f5 07 <85> c0 74 07 e8 29 ff ff ff 5d c3 31 c0 5d c3 e8 ae 7f 38 00 eb