bisecting fixing commit since ae4b064e2a616b545acf02b8f50cc513b32c7522 building syzkaller on 08003f6440deafc4e193b159c4acece64f7864b1 testing commit ae4b064e2a616b545acf02b8f50cc513b32c7522 with gcc (GCC) 8.1.0 kernel signature: 9c4c8411e693785eb6e8c19a6144ee7b2b8372b5d757351156fc3d6fde7bb12c run #0: crashed: INFO: rcu detected stall in corrupted run #1: crashed: INFO: rcu detected stall in corrupted run #2: crashed: INFO: rcu detected stall in chrdev_open run #3: crashed: INFO: rcu detected stall in chrdev_open run #4: crashed: INFO: rcu detected stall in corrupted run #5: crashed: INFO: rcu detected stall in chrdev_open run #6: crashed: INFO: rcu detected stall in chrdev_open run #7: crashed: INFO: rcu detected stall in corrupted run #8: crashed: INFO: rcu detected stall in chrdev_open run #9: crashed: INFO: rcu detected stall in chrdev_open testing current HEAD 8632e9b5645bbc2331d21d892b0d6961c1a08429 testing commit 8632e9b5645bbc2331d21d892b0d6961c1a08429 with gcc (GCC) 8.1.0 kernel signature: 1f36877cb64bac82df5594254864d018cd323a8d364402ada819173bf7dc9ba0 run #0: crashed: INFO: rcu detected stall in corrupted run #1: crashed: INFO: rcu detected stall in corrupted run #2: crashed: INFO: rcu detected stall in corrupted run #3: crashed: INFO: rcu detected stall in chrdev_open run #4: crashed: INFO: rcu detected stall in corrupted run #5: crashed: INFO: rcu detected stall in chrdev_open run #6: crashed: INFO: rcu detected stall in corrupted run #7: crashed: INFO: rcu detected stall in corrupted run #8: crashed: INFO: rcu detected stall in corrupted run #9: crashed: INFO: rcu detected stall in chrdev_open revisions tested: 2, total time: 23m1.114267824s (build: 12m7.093253721s, test: 10m23.708350259s) the crash still happens on HEAD commit msg: Merge tag 'hyperv-fixes-signed' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux crash: INFO: rcu detected stall in chrdev_open rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: (detected by 1, t=10502 jiffies, g=10249, q=295) rcu: All QSes seen, last rcu_preempt kthread activity 10502 (4294954969-4294944467), jiffies_till_next_fqs=1, root ->qsmask 0x0 syz-executor.1 R running task 26824 9554 7097 0x00004000 Call Trace: sched_show_task.cold.100+0x2ee/0x35d kernel/sched/core.c:5961 print_other_cpu_stall kernel/rcu/tree_stall.h:430 [inline] check_cpu_stall kernel/rcu/tree_stall.h:558 [inline] rcu_pending kernel/rcu/tree.c:3225 [inline] rcu_sched_clock_irq.cold.87+0xaa3/0xc50 kernel/rcu/tree.c:2296 update_process_times+0x23/0x50 kernel/time/timer.c:1727 tick_sched_handle+0x77/0x140 kernel/time/tick-sched.c:176 tick_sched_timer+0x43/0x100 kernel/time/tick-sched.c:1320 __run_hrtimer kernel/time/hrtimer.c:1520 [inline] __hrtimer_run_queues+0x524/0xc00 kernel/time/hrtimer.c:1584 hrtimer_interrupt+0x2df/0x760 kernel/time/hrtimer.c:1646 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1113 [inline] smp_apic_timer_interrupt+0x163/0x5f0 arch/x86/kernel/apic/apic.c:1138 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829 RIP: 0010:kmem_cache_alloc_trace+0x1d/0x780 mm/slab.c:3546 Code: 0b 66 90 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5 41 57 41 56 41 89 f6 41 55 49 89 fd 41 54 53 48 83 ec 48 8b 1d c3 a1 39 08 <48> 89 55 d0 21 f3 89 df 41 89 df e8 e3 16 f8 ff 89 df e8 fc 16 f8 RSP: 0018:ffffc900050df790 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13 RAX: fffffbfff118e891 RBX: 0000000000ffffff RCX: ffffffff874ef6a3 RDX: 0000000000000020 RSI: 0000000000000cc0 RDI: ffff8880aa4001c0 RBP: ffffc900050df800 R08: ffffed1012ab6059 R09: ffffed1012ab6059 R10: ffff8880955b02c7 R11: ffffed1012ab6058 R12: ffff8880a84e9d00 R13: ffff8880aa4001c0 R14: 0000000000000cc0 R15: 1ffff1101509d3d6 kmalloc include/linux/slab.h:555 [inline] tty_alloc_file drivers/tty/tty_io.c:189 [inline] tty_open+0x154/0xa00 drivers/tty/tty_io.c:2025 chrdev_open+0x1ed/0x5c0 fs/char_dev.c:414 do_dentry_open+0x40f/0x1140 fs/open.c:797 vfs_open+0x9a/0xc0 fs/open.c:911 do_open fs/namei.c:3229 [inline] path_openat+0xdf7/0x2560 fs/namei.c:3346 do_filp_open+0x171/0x240 fs/namei.c:3373 do_sys_openat2+0x309/0x590 fs/open.c:1148 do_sys_open+0x90/0xe0 fs/open.c:1164 __do_sys_openat fs/open.c:1178 [inline] __se_sys_openat fs/open.c:1173 [inline] __x64_sys_openat+0x98/0xf0 fs/open.c:1173 do_syscall_64+0xca/0x630 arch/x86/entry/common.c:295 entry_SYSCALL_64_after_hwframe+0x49/0xb3 RIP: 0033:0x45a909 Code: ad 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 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fb4379a7c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 000000000045a909 RDX: 0000000000000000 RSI: 0000000020000380 RDI: ffffffffffffff9c RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007fb4379a86d4 R13: 00000000004c8678 R14: 00000000004dfa28 R15: 00000000ffffffff rcu: rcu_preempt kthread starved for 10502 jiffies! g10249 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0 rcu: RCU grace-period kthread stack dump: rcu_preempt R running task 29096 10 2 0x80004000 Call Trace: context_switch kernel/sched/core.c:3372 [inline] __schedule+0x8ae/0x19c0 kernel/sched/core.c:4088 schedule+0xc3/0x2b0 kernel/sched/core.c:4163 schedule_timeout+0x2bd/0x710 kernel/time/timer.c:1898 rcu_gp_fqs_loop kernel/rcu/tree.c:1674 [inline] rcu_gp_kthread+0x9da/0x1a40 kernel/rcu/tree.c:1836 kthread+0x354/0x420 kernel/kthread.c:268 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352