bisecting fixing commit since f8f65382c98a28e3c2b20df9dd4231dca5a11682 building syzkaller on 6b5120a46407f0462e664e15fed3eae5da951c75 testing commit f8f65382c98a28e3c2b20df9dd4231dca5a11682 with gcc (GCC) 8.1.0 run #0: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #1: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #2: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #3: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #4: crashed: INFO: rcu detected stall in corrupted run #5: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #6: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #7: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #8: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #9: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl testing current HEAD 6e625a1a3f471d63989d3a66cdf6a0c307654848 testing commit 6e625a1a3f471d63989d3a66cdf6a0c307654848 with gcc (GCC) 8.1.0 run #0: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #1: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #2: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #3: crashed: INFO: rcu detected stall in corrupted run #4: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #5: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #6: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #7: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #8: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #9: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl revisions tested: 2, total time: 23m22.248252551s (build: 11m4.148950237s, test: 10m53.605208672s) the crash still happens on HEAD crash: INFO: rcu detected stall in kvm_vcpu_ioctl 8021q: adding VLAN 0 to HW filter on device team0 L1TF CPU bug present and SMT on, data leak possible. See CVE-2018-3646 and https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html for details. hrtimer: interrupt took 25275 ns rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: (detected by 0, t=10502 jiffies, g=4753, q=194) rcu: All QSes seen, last rcu_preempt kthread activity 10502 (4294955030-4294944528), jiffies_till_next_fqs=1, root ->qsmask 0x0 syz-executor5 R running task 26048 7043 5574 0x00000000 Call Trace: sched_show_task.cold.99+0x2e1/0x342 kernel/sched/core.c:5755 print_other_cpu_stall kernel/rcu/tree_stall.h:410 [inline] check_cpu_stall kernel/rcu/tree_stall.h:536 [inline] rcu_pending kernel/rcu/tree.c:2736 [inline] rcu_sched_clock_irq.cold.86+0xa5d/0xc4c kernel/rcu/tree.c:2183 update_process_times+0x2a/0x60 kernel/time/timer.c:1639 tick_sched_handle+0x77/0x140 kernel/time/tick-sched.c:167 tick_sched_timer+0x43/0x100 kernel/time/tick-sched.c:1296 __run_hrtimer kernel/time/hrtimer.c:1389 [inline] __hrtimer_run_queues+0x332/0xb60 kernel/time/hrtimer.c:1451 hrtimer_interrupt+0x2df/0x760 kernel/time/hrtimer.c:1509 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1068 [inline] smp_apic_timer_interrupt+0x16f/0x600 arch/x86/kernel/apic/apic.c:1093 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:830 RIP: 0010:kvm_after_interrupt arch/x86/kvm/x86.h:357 [inline] RIP: 0010:handle_external_interrupt_irqoff+0x184/0x200 arch/x86/kvm/vmx/vmx.c:6206 Code: 86 e8 d0 17 ef 01 65 4c 89 25 f8 86 eb 7e 48 c1 e3 20 4c 09 eb 4c 09 f3 48 89 e0 48 83 e4 f0 6a 18 50 9c 6a 10 e8 fc ef a9 05 <48> c7 c7 00 71 e3 86 e8 a0 17 ef 01 65 48 c7 05 c4 86 eb 7e 00 00 RSP: 0018:ffff8881ba297910 EFLAGS: 00000082 ORIG_RAX: ffffffffffffff13 RAX: ffff8881ba297910 RBX: ffffffff86a01750 RCX: 0000000000000000 RDX: 0000000000000001 RSI: 0000000000000001 RDI: ffffffff86e37100 RBP: ffff8881ba297930 R08: 0000006182947c80 R09: ffffed1037805702 R10: ffffed1037805701 R11: ffff8881bc02b80f R12: ffff8881d17a0080 R13: 0000000086a00000 R14: 0000000000001750 R15: ffff8881d17a00b0 vmx_handle_exit_irqoff+0x198/0x250 arch/x86/kvm/vmx/vmx.c:6215 vcpu_enter_guest+0x9ed/0x5360 arch/x86/kvm/x86.c:8043 vcpu_run arch/x86/kvm/x86.c:8151 [inline] kvm_arch_vcpu_ioctl_run+0x2f0/0x1370 arch/x86/kvm/x86.c:8359 kvm_vcpu_ioctl+0x452/0xb90 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2765 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:509 [inline] do_vfs_ioctl+0x199/0x1160 fs/ioctl.c:696 ksys_ioctl+0x62/0x90 fs/ioctl.c:713 __do_sys_ioctl fs/ioctl.c:720 [inline] __se_sys_ioctl fs/ioctl.c:718 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:718 do_syscall_64+0xd6/0x550 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4571e9 Code: fd b4 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 cb b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f92a3726c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f92a37276d4 RCX: 00000000004571e9 RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000006 RBP: 00000000009300a0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 00000000004cf7d0 R14: 00000000004c5a59 R15: 0000000000000000 rcu: rcu_preempt kthread starved for 10502 jiffies! g4753 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1 rcu: RCU grace-period kthread stack dump: rcu_preempt R running task 29280 10 2 0x80004000 Call Trace: context_switch kernel/sched/core.c:3254 [inline] __schedule+0x719/0x1530 kernel/sched/core.c:3880 schedule+0x8f/0x260 kernel/sched/core.c:3944 schedule_timeout+0x38b/0xad0 kernel/time/timer.c:1807 rcu_gp_fqs_loop kernel/rcu/tree.c:1611 [inline] rcu_gp_kthread+0x97d/0x1960 kernel/rcu/tree.c:1768 kthread+0x334/0x3f0 kernel/kthread.c:255 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352