bisecting fixing commit since 20b3a3dfdf6c55b50bbdc8e231a3dbf6bf965dc7 building syzkaller on 70c104a18f3d409bc6dde950b50258d3d280d99b testing commit 20b3a3dfdf6c55b50bbdc8e231a3dbf6bf965dc7 with gcc (GCC) 8.4.1 20210217 kernel signature: ba983a13295a6913f8667796fb2b630e265bb16aef54c7c8146078662474e102 run #0: crashed: INFO: rcu detected stall in rtnl_newlink run #1: crashed: INFO: rcu detected stall in rtnl_newlink run #2: crashed: INFO: rcu detected stall in rtnl_newlink run #3: crashed: INFO: rcu detected stall in batadv_iv_send_outstanding_bat_ogm_packet run #4: crashed: INFO: rcu detected stall in rtnl_newlink run #5: crashed: INFO: rcu detected stall in rtnl_newlink run #6: crashed: INFO: rcu detected stall in rtnl_newlink run #7: crashed: INFO: rcu detected stall in rtnl_newlink run #8: crashed: INFO: rcu detected stall in rtnl_newlink run #9: crashed: INFO: rcu detected stall in rtnl_newlink run #10: crashed: INFO: rcu detected stall in rtnl_newlink run #11: crashed: INFO: rcu detected stall in rtnl_newlink run #12: crashed: INFO: rcu detected stall in rtnl_newlink run #13: crashed: INFO: rcu detected stall in rtnl_newlink run #14: crashed: INFO: rcu detected stall in rtnl_newlink run #15: crashed: INFO: rcu detected stall in rtnl_newlink run #16: crashed: INFO: rcu detected stall in rtnl_newlink run #17: crashed: INFO: rcu detected stall in rtnl_newlink run #18: crashed: INFO: rcu detected stall in rtnl_newlink run #19: crashed: INFO: rcu detected stall in rtnl_newlink testing current HEAD 2d19be4653f5e74ed95560b69f94eb6791d49af3 testing commit 2d19be4653f5e74ed95560b69f94eb6791d49af3 with gcc (GCC) 8.4.1 20210217 kernel signature: b5538449182a5410030e6e5141d0b90c4c810dfad16b219d5a36acc056ae0d7b all runs: crashed: INFO: rcu detected stall in rtnl_newlink revisions tested: 2, total time: 26m49.091507956s (build: 16m6.665758293s, test: 9m39.220476596s) the crash still happens on HEAD commit msg: Linux 4.19.177 crash: INFO: rcu detected stall in rtnl_newlink batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) rcu: INFO: rcu_preempt self-detected stall on CPU rcu: 1-...!: (10496 ticks this GP) idle=40a/1/0x4000000000000002 softirq=9150/9150 fqs=0 rcu: (t=10500 jiffies g=5389 q=170) rcu: rcu_preempt kthread starved for 10500 jiffies! g5389 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=1 rcu: RCU grace-period kthread stack dump: rcu_preempt I29160 10 2 0x80000000 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x80c/0x1f70 kernel/sched/core.c:3517 schedule+0x7f/0x1b0 kernel/sched/core.c:3561 schedule_timeout+0x398/0xd20 kernel/time/timer.c:1818 rcu_gp_kthread+0xd2b/0x23e0 kernel/rcu/tree.c:2202 kthread+0x347/0x410 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 NMI backtrace for cpu 1 CPU: 1 PID: 7234 Comm: syz-executor.5 Not tainted 4.19.177-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x17c/0x226 lib/dump_stack.c:118 nmi_cpu_backtrace.cold.0+0x3c/0x78 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0xf5/0x120 lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline] rcu_dump_cpu_stacks+0x175/0x1c2 kernel/rcu/tree.c:1340 print_cpu_stall kernel/rcu/tree.c:1478 [inline] check_cpu_stall kernel/rcu/tree.c:1550 [inline] __rcu_pending kernel/rcu/tree.c:3293 [inline] rcu_pending kernel/rcu/tree.c:3336 [inline] rcu_check_callbacks.cold.62+0x5b1/0xd89 kernel/rcu/tree.c:2682 update_process_times+0x2a/0x60 kernel/time/timer.c:1650 tick_sched_handle.isra.5+0x6b/0x130 kernel/time/tick-sched.c:168 tick_sched_timer+0x3c/0xf0 kernel/time/tick-sched.c:1278 __run_hrtimer kernel/time/hrtimer.c:1401 [inline] __hrtimer_run_queues+0x2fa/0xaa0 kernel/time/hrtimer.c:1463 hrtimer_interrupt+0x2df/0x760 kernel/time/hrtimer.c:1521 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1071 [inline] smp_apic_timer_interrupt+0x114/0x540 arch/x86/kernel/apic/apic.c:1096 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:894 RIP: 0010:__local_bh_enable_ip+0x79/0x250 kernel/softirq.c:169 Code: 00 00 8b 0d b9 c9 60 07 85 c9 0f 84 85 00 00 00 65 4c 8b 2c 25 40 ee 01 00 49 8d bd 84 08 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 RSP: 0018:ffff8881ceb66b58 EFLAGS: 00000202 ORIG_RAX: ffffffffffffff13 RAX: dffffc0000000000 RBX: 0000000000000201 RCX: 0000000000000001 RDX: 0000000000000004 RSI: 0000000000000201 RDI: ffff8881d73f0944 RBP: ffff8881ceb66b70 R08: ffffed103a46d533 R09: ffffed103a46d532 R10: ffffed103a46d532 R11: ffff8881d236a993 R12: ffffffff86a80a1a R13: ffff8881d73f00c0 R14: ffff8881e630cc08 R15: ffff8881e7e76440 __raw_spin_unlock_bh include/linux/spinlock_api_smp.h:176 [inline] _raw_spin_unlock_bh+0x30/0x40 kernel/locking/spinlock.c:200 spin_unlock_bh include/linux/spinlock.h:374 [inline] batadv_tt_local_purge_pending_clients+0x22a/0x320 net/batman-adv/translation-table.c:3922 batadv_tt_local_resize_to_mtu+0x8f/0xf0 net/batman-adv/translation-table.c:4206 batadv_update_min_mtu net/batman-adv/hard-interface.c:637 [inline] batadv_hardif_activate_interface.part.3.cold.8+0xcb/0x313 net/batman-adv/hard-interface.c:664 batadv_hardif_activate_interface net/batman-adv/hard-interface.c:825 [inline] batadv_hardif_enable_interface+0x987/0xa40 net/batman-adv/hard-interface.c:817 batadv_softif_slave_add+0x7f/0xd0 net/batman-adv/soft-interface.c:898 do_set_master net/core/rtnetlink.c:2321 [inline] do_set_master+0x171/0x200 net/core/rtnetlink.c:2295 do_setlink+0x94c/0x2ec0 net/core/rtnetlink.c:2455 rtnl_newlink+0x96c/0x1350 net/core/rtnetlink.c:3077 rtnetlink_rcv_msg+0x34f/0x950 net/core/rtnetlink.c:4778 netlink_rcv_skb+0x13e/0x3d0 net/netlink/af_netlink.c:2455 rtnetlink_rcv+0x10/0x20 net/core/rtnetlink.c:4796 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x443/0x660 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x667/0xc60 net/netlink/af_netlink.c:1909 sock_sendmsg_nosec net/socket.c:622 [inline] sock_sendmsg+0xac/0xf0 net/socket.c:632 ___sys_sendmsg+0x647/0x950 net/socket.c:2115 __sys_sendmsg+0xd9/0x180 net/socket.c:2153 __do_sys_sendmsg net/socket.c:2162 [inline] __se_sys_sendmsg net/socket.c:2160 [inline] __x64_sys_sendmsg+0x73/0xb0 net/socket.c:2160 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x463b49 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f4dda9d7188 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 000000000055bf00 RCX: 0000000000463b49 RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000004 RBP: 00000000004ae538 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000055bf00 R13: 00007ffefbd9156f R14: 00007f4dda9d7300 R15: 0000000000022000 net_ratelimit: 6632 callbacks suppressed batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) net_ratelimit: 6929 callbacks suppressed batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224)