bisecting fixing commit since 92ed301919932f777713b9172e525674157e983d building syzkaller on cb93dc6ac64225e09f44bac6c6cce1dae1b248b0 testing commit 92ed301919932f777713b9172e525674157e983d with gcc (GCC) 8.1.0 kernel signature: 739b9eee671fdbc197d0b2e426661cd3b75318847c9fcadd130360cdce07d548 all runs: crashed: INFO: rcu detected stall in rtnl_newlink testing current HEAD e28c0d7c92c89016c12a677616668957351e7542 testing commit e28c0d7c92c89016c12a677616668957351e7542 with gcc (GCC) 8.1.0 kernel signature: 91662ab99e9720a5be033cdb4eae46d687f835ee46edaaa8af015d6c1a55a9ff all runs: crashed: INFO: rcu detected stall in rtnl_newlink revisions tested: 2, total time: 18m58.789151647s (build: 9m26.338556757s, test: 8m51.765877332s) the crash still happens on HEAD commit msg: Merge branch 'akpm' (patches from Andrew) crash: INFO: rcu detected stall in rtnl_newlink rcu: INFO: rcu_preempt self-detected stall on CPU rcu: 1-...!: (10494 ticks this GP) idle=4c2/1/0x4000000000000000 softirq=9661/9661 fqs=0 (t=10502 jiffies g=3729 q=101) rcu: rcu_preempt kthread starved for 10502 jiffies! g3729 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=1 rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior. rcu: RCU grace-period kthread stack dump: task:rcu_preempt state:I stack:14552 pid: 10 ppid: 2 flags:0x00004000 Call Trace: context_switch kernel/sched/core.c:3774 [inline] __schedule+0x404/0x890 kernel/sched/core.c:4523 schedule+0x38/0xe0 kernel/sched/core.c:4601 schedule_timeout+0x1be/0x2e0 kernel/time/timer.c:1871 rcu_gp_fqs_loop kernel/rcu/tree.c:1925 [inline] rcu_gp_kthread+0x707/0xc60 kernel/rcu/tree.c:2099 kthread+0x145/0x170 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296 NMI backtrace for cpu 1 CPU: 1 PID: 8223 Comm: syz-executor.3 Not tainted 5.10.0-rc3-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+0xa3/0xc8 lib/dump_stack.c:118 nmi_cpu_backtrace.cold.8+0x53/0x6d lib/nmi_backtrace.c:105 nmi_trigger_cpumask_backtrace+0xd5/0xf0 lib/nmi_backtrace.c:62 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline] rcu_dump_cpu_stacks+0xa2/0xce kernel/rcu/tree_stall.h:318 print_cpu_stall kernel/rcu/tree_stall.h:551 [inline] check_cpu_stall kernel/rcu/tree_stall.h:625 [inline] rcu_pending kernel/rcu/tree.c:3694 [inline] rcu_sched_clock_irq.cold.93+0x61/0x52b kernel/rcu/tree.c:2567 update_process_times+0x50/0x80 kernel/time/timer.c:1709 tick_sched_handle.isra.24+0x1a/0x50 kernel/time/tick-sched.c:176 tick_sched_timer+0x6c/0x80 kernel/time/tick-sched.c:1328 __run_hrtimer kernel/time/hrtimer.c:1519 [inline] __hrtimer_run_queues+0x1e3/0x4f0 kernel/time/hrtimer.c:1583 hrtimer_interrupt+0xf9/0x210 kernel/time/hrtimer.c:1645 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1080 [inline] __sysvec_apic_timer_interrupt+0x8e/0x290 arch/x86/kernel/apic/apic.c:1097 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+0xcc/0xf0 arch/x86/kernel/apic/apic.c:1091 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:631 RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:653 [inline] RIP: 0010:lock_is_held_type+0x11d/0x160 kernel/locking/lockdep.c:5477 Code: 9c e8 83 e8 e5 0a 00 00 b8 ff ff ff ff 65 0f c1 05 88 af f5 7c 83 f8 01 75 37 48 83 3d 43 e3 20 01 00 74 2b 48 8b 3c 24 57 9d <0f> 1f 44 00 00 eb 05 bd 01 00 00 00 48 83 c4 08 89 e8 5b 5d 41 5c RSP: 0018:ffffc90002ccf410 EFLAGS: 00000286 RAX: 0000000000000001 RBX: ffff88811d55ae78 RCX: 0000000000000001 RDX: 0000000000000000 RSI: ffffffff83e89c37 RDI: 0000000000000286 RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000001 R11: ffffc90002ccf360 R12: ffff88811d55a540 R13: ffff88811d55ae50 R14: 00000000ffffffff R15: 0000000000000002 lock_is_held include/linux/lockdep.h:271 [inline] rcu_read_lock_sched_held+0x4d/0x80 kernel/rcu/update.c:123 trace_lock_acquire include/trace/events/lock.h:13 [inline] lock_acquire+0x2f2/0x420 kernel/locking/lockdep.c:5407 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline] _raw_spin_lock_bh+0x2f/0x40 kernel/locking/spinlock.c:175 spin_lock_bh include/linux/spinlock.h:359 [inline] batadv_tt_local_purge_pending_clients+0x58/0x100 net/batman-adv/translation-table.c:3895 batadv_tt_local_resize_to_mtu+0x46/0x90 net/batman-adv/translation-table.c:4198 batadv_update_min_mtu net/batman-adv/hard-interface.c:626 [inline] batadv_hardif_activate_interface.part.15.cold.26+0x2f/0x78 net/batman-adv/hard-interface.c:653 batadv_hardif_activate_interface include/linux/refcount.h:199 [inline] batadv_hardif_enable_interface+0x27e/0x2c0 net/batman-adv/hard-interface.c:792 batadv_softif_slave_add+0x3c/0x90 net/batman-adv/soft-interface.c:891 do_setlink+0x321/0x10b0 net/core/rtnetlink.c:2713 __rtnl_newlink+0x538/0x8a0 net/core/rtnetlink.c:3374 rtnl_newlink+0x3e/0x60 net/core/rtnetlink.c:3500 rtnetlink_rcv_msg+0x173/0x480 net/core/rtnetlink.c:5562 netlink_rcv_skb+0x49/0xf0 net/netlink/af_netlink.c:2494 netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline] netlink_unicast+0x19a/0x270 net/netlink/af_netlink.c:1330 netlink_sendmsg+0x248/0x480 net/netlink/af_netlink.c:1919 sock_sendmsg_nosec net/socket.c:651 [inline] sock_sendmsg+0x2b/0x40 net/socket.c:671 ____sys_sendmsg+0x1ed/0x230 net/socket.c:2353 ___sys_sendmsg+0x77/0xb0 net/socket.c:2407 __sys_sendmsg+0x52/0xa0 net/socket.c:2440 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x45c369 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:00007fe379203c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 000000000002b740 RCX: 000000000045c369 RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000004 RBP: 000000000078bf40 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000078bf0c R13: 00007ffccc7ae2ff R14: 00007fe3792049c0 R15: 000000000078bf0c