bisecting fixing commit since 7cc2a8ea104820dd9e702202621e8fd4d9f6c8cf building syzkaller on 510951950dc0ee69cfdaf746061d3dbe31b49fd8 testing commit 7cc2a8ea104820dd9e702202621e8fd4d9f6c8cf with gcc (GCC) 8.1.0 kernel signature: 115830f1606205015fc1a5b5ab11588f2c7310dd34bd3e0b03c84634bc0cfb67 run #0: crashed: INFO: rcu detected stall in tc_modify_qdisc run #1: crashed: INFO: rcu detected stall in do_sys_open run #2: crashed: INFO: rcu detected stall in sys_clock_settime run #3: crashed: INFO: rcu detected stall in sys_clock_settime run #4: crashed: INFO: rcu detected stall in corrupted run #5: crashed: BUG: soft lockup in smp_call_function run #6: crashed: BUG: soft lockup in smp_call_function run #7: crashed: INFO: rcu detected stall in sys_clock_settime run #8: crashed: INFO: rcu detected stall in sys_clock_settime run #9: crashed: INFO: rcu detected stall in sys_clock_settime testing current HEAD dd9fb9bb3340c791a2be106fdc895db75f177343 testing commit dd9fb9bb3340c791a2be106fdc895db75f177343 with gcc (GCC) 8.1.0 kernel signature: d72bf4d26d7927c34695319083718b22ee9810dc9df2c066940aac14f55ab47d run #0: crashed: INFO: rcu detected stall in sys_clock_settime run #1: crashed: INFO: rcu detected stall in smp_call_function run #2: crashed: INFO: rcu detected stall in sys_clock_settime run #3: crashed: BUG: soft lockup in smp_call_function run #4: crashed: BUG: soft lockup in smp_call_function run #5: crashed: BUG: soft lockup in smp_call_function run #6: crashed: INFO: rcu detected stall in corrupted run #7: crashed: INFO: rcu detected stall in sys_clock_settime run #8: crashed: INFO: rcu detected stall in smp_call_function run #9: crashed: INFO: rcu detected stall in addrconf_dad_work revisions tested: 2, total time: 23m36.764451416s (build: 9m25.66502623s, test: 13m34.84739764s) the crash still happens on HEAD commit msg: Merge tags 'auxdisplay-for-linus-v5.9-rc4', 'clang-format-for-linus-v5.9-rc4' and 'compiler-attributes-for-linus-v5.9-rc4' of git://github.com/ojeda/linux crash: INFO: rcu detected stall in addrconf_dad_work rcu: INFO: rcu_preempt self-detected stall on CPU rcu: 1-...!: (1 GPs behind) idle=eea/1/0x4000000000000000 softirq=9675/9676 fqs=0 (t=27267 jiffies g=3669 q=488) rcu: rcu_preempt kthread starved for 27267 jiffies! g3669 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0 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:14376 pid: 10 ppid: 2 flags:0x00004000 Call Trace: context_switch kernel/sched/core.c:3778 [inline] __schedule+0x404/0x8a0 kernel/sched/core.c:4527 schedule+0x37/0xe0 kernel/sched/core.c:4602 schedule_timeout+0x1af/0x2d0 kernel/time/timer.c:1879 rcu_gp_fqs_loop kernel/rcu/tree.c:1888 [inline] rcu_gp_kthread+0x707/0xc60 kernel/rcu/tree.c:2058 kthread+0x148/0x170 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 NMI backtrace for cpu 1 CPU: 1 PID: 6522 Comm: kworker/1:4 Not tainted 5.9.0-rc3-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: ipv6_addrconf addrconf_dad_work Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0xa3/0xcc lib/dump_stack.c:118 nmi_cpu_backtrace.cold.8+0x3e/0x58 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0xd5/0xec 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:3637 [inline] rcu_sched_clock_irq.cold.94+0x61/0x52d kernel/rcu/tree.c:2519 update_process_times+0x1f/0x60 kernel/time/timer.c:1710 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:1524 [inline] __hrtimer_run_queues+0x1e1/0x510 kernel/time/hrtimer.c:1588 hrtimer_interrupt+0xf9/0x210 kernel/time/hrtimer.c:1650 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1080 [inline] __sysvec_apic_timer_interrupt+0x8e/0x2b0 arch/x86/kernel/apic/apic.c:1097 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:706 __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline] run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline] sysvec_apic_timer_interrupt+0xc1/0xe0 arch/x86/kernel/apic/apic.c:1091 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:581 RIP: 0010:_raw_spin_unlock_bh+0x0/0x30 kernel/locking/spinlock.c:206 Code: c6 26 1f fe bf 01 00 00 00 e8 fc 68 1b fe 65 8b 05 55 ec fc 7c 85 c0 74 02 5b c3 e8 01 b8 fb fd 5b c3 0f 1f 84 00 00 00 00 00 <53> 48 8b 74 24 08 48 89 fb 48 8d 7f 18 e8 ce c9 1e fe 48 89 df e8 RSP: 0018:ffffc900049bbd18 EFLAGS: 00000282 RAX: 0000000000000000 RBX: ffff88810ec53300 RCX: 0000000000000002 RDX: 0000000000000000 RSI: ffffffff83ed56bb RDI: ffff88810ec533a8 RBP: ffff88810ec533a8 R08: 0000000000000001 R09: 0000000000000001 R10: ffff88811d7ce480 R11: 7cd007e64576f5ae R12: ffff88810fff5000 R13: 0000000000000000 R14: ffff88810f80cd88 R15: ffff88810ec53300 spin_unlock_bh include/linux/spinlock.h:399 [inline] igmp6_group_added+0x66/0xf0 net/ipv6/mcast.c:671 __ipv6_dev_mc_inc+0x27c/0x4a0 net/ipv6/mcast.c:928 addrconf_join_solict.part.63+0x3d/0x60 net/ipv6/addrconf.c:2167 addrconf_join_solict net/ipv6/addrconf.c:2163 [inline] addrconf_dad_begin net/ipv6/addrconf.c:3933 [inline] addrconf_dad_work+0x8a/0x500 net/ipv6/addrconf.c:4060 process_one_work+0x26a/0x5f0 kernel/workqueue.c:2269 worker_thread+0x38/0x380 kernel/workqueue.c:2415 kthread+0x148/0x170 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294