bisecting fixing commit since 20b3a3dfdf6c55b50bbdc8e231a3dbf6bf965dc7 building syzkaller on 70c104a18f3d409bc6dde950b50258d3d280d99b testing commit 20b3a3dfdf6c55b50bbdc8e231a3dbf6bf965dc7 with gcc (GCC) 8.1.0 kernel signature: 7e4425500bdaab42bd12ee41af2bb3b011909e96da31158f2cc7073441176971 all runs: crashed: INFO: rcu detected stall in rtnl_newlink testing current HEAD d18b78abc0c6e7d3119367c931c583e02d466495 testing commit d18b78abc0c6e7d3119367c931c583e02d466495 with gcc (GCC) 8.1.0 kernel signature: 6bbf2d8d27631b6bdc24706f511fb288c8117cac07d59dc042e8e6b723da0827 all runs: crashed: INFO: rcu detected stall in rtnl_newlink revisions tested: 2, total time: 30m55.267477428s (build: 19m30.492227029s, test: 10m3.893514049s) the crash still happens on HEAD commit msg: Linux 4.19.141 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: 0-...!: (1 GPs behind) idle=2ee/1/0x4000000000000002 softirq=9397/9414 fqs=32 rcu: (t=10502 jiffies g=5661 q=54) rcu: rcu_preempt kthread starved for 10438 jiffies! g5661 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:1825 rcu_gp_kthread+0xd2b/0x23e0 kernel/rcu/tree.c:2202 kthread+0x324/0x3e0 kernel/kthread.c:246 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 NMI backtrace for cpu 0 CPU: 0 PID: 7860 Comm: syz-executor.1 Not tainted 4.19.141-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/0x22a lib/dump_stack.c:118 nmi_cpu_backtrace.cold.0+0x3c/0x78 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0xf5/0x119 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+0x5cc/0xd67 kernel/rcu/tree.c:2682 update_process_times+0x28/0x90 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:1067 [inline] smp_apic_timer_interrupt+0x114/0x540 arch/x86/kernel/apic/apic.c:1092 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:894 RIP: 0010:__write_once_size include/linux/compiler.h:219 [inline] RIP: 0010:debug_spin_unlock kernel/locking/spinlock_debug.c:103 [inline] RIP: 0010:do_raw_spin_unlock+0x12a/0x260 kernel/locking/spinlock_debug.c:134 Code: 80 3c 02 00 0f 85 44 01 00 00 4c 89 e2 48 c7 43 10 ff ff ff ff 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 0f b6 14 02 4c 89 e0 <83> e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 ee 00 00 00 48 c7 c7 68 RSP: 0018:ffff88808c3f6b60 EFLAGS: 00000a02 ORIG_RAX: ffffffffffffff13 RAX: ffff888086c27398 RBX: ffff888086c27390 RCX: ffffffff814ca8c4 RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff888086c27390 RBP: ffff88808c3f6b78 R08: ffffed1010d84e73 R09: ffffed1010d84e72 R10: ffffed1010d84e72 R11: ffff888086c27393 R12: ffff888086c27398 R13: ffff888086c273a0 R14: ffff888091047f98 R15: ffff88809e6dc080 __raw_spin_unlock_bh include/linux/spinlock_api_smp.h:175 [inline] _raw_spin_unlock_bh+0x22/0x40 kernel/locking/spinlock.c:200 spin_unlock_bh include/linux/spinlock.h:374 [inline] batadv_tt_local_purge+0x1f1/0x2c0 net/batman-adv/translation-table.c:1454 batadv_tt_local_resize_to_mtu+0x87/0xf0 net/batman-adv/translation-table.c:4205 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+0x171/0x200 net/core/rtnetlink.c:2321 do_setlink+0x94c/0x2ec0 net/core/rtnetlink.c:2455 rtnl_newlink+0xa1d/0x1320 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+0x666/0xc50 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: 0033:0x45c1f9 Code: 8d b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 5b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f84a6d86c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 000000000002b580 RCX: 000000000045c1f9 RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000004 RBP: 000000000078bf40 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000078bf0c R13: 00007fff9bbf24ef R14: 00007f84a6d879c0 R15: 000000000078bf0c net_ratelimit: 6767 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: 6936 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)