bisecting fixing commit since 63bbbcd8ed53c404649e0b4248c1e5d42c41ac97 building syzkaller on 34bf9440bd06034f86b5d9ac8afbf078129cbdae testing commit 63bbbcd8ed53c404649e0b4248c1e5d42c41ac97 with gcc (GCC) 8.4.1 20210217 kernel signature: 738c59085950aefb7d0ea98179c5d224c5a8608752e81628deac1aefe9daa82c run #0: crashed: BUG: workqueue lockup run #1: crashed: BUG: workqueue lockup run #2: crashed: BUG: workqueue lockup run #3: crashed: BUG: workqueue lockup run #4: crashed: BUG: workqueue lockup run #5: crashed: BUG: workqueue lockup run #6: crashed: BUG: workqueue lockup run #7: crashed: BUG: workqueue lockup run #8: crashed: BUG: workqueue lockup run #9: crashed: BUG: workqueue lockup run #10: crashed: BUG: workqueue lockup run #11: crashed: BUG: workqueue lockup run #12: crashed: BUG: workqueue lockup run #13: crashed: BUG: workqueue lockup run #14: crashed: INFO: rcu detected stall in sys_sendfile64 run #15: crashed: INFO: rcu detected stall in sys_sendfile64 run #16: crashed: INFO: rcu detected stall in sys_sendfile64 run #17: crashed: INFO: rcu detected stall in sys_sendfile64 run #18: crashed: INFO: rcu detected stall in sys_sendfile64 run #19: crashed: INFO: rcu detected stall in sys_sendfile64 testing current HEAD 2965db2e004cf9c92b87c1f559e9812c0ae878c1 testing commit 2965db2e004cf9c92b87c1f559e9812c0ae878c1 with gcc (GCC) 8.4.1 20210217 kernel signature: 978de443f48ce4dbb1d3ff87a89e1f47618543889de46bd348f5e430178f25df run #0: crashed: BUG: workqueue lockup run #1: crashed: BUG: workqueue lockup run #2: crashed: BUG: workqueue lockup run #3: crashed: BUG: workqueue lockup run #4: crashed: BUG: workqueue lockup run #5: crashed: BUG: workqueue lockup run #6: crashed: BUG: workqueue lockup run #7: crashed: BUG: workqueue lockup run #8: crashed: INFO: rcu detected stall in sys_sendfile64 run #9: crashed: INFO: rcu detected stall in sys_sendfile64 revisions tested: 2, total time: 26m12.042976839s (build: 15m41.159396317s, test: 9m48.977990811s) the crash still happens on HEAD commit msg: Linux 4.19.188 crash: INFO: rcu detected stall in sys_sendfile64 8021q: adding VLAN 0 to HW filter on device batadv0 IPv6: ADDRCONF(NETDEV_UP): veth1_to_bond: link is not ready IPv6: ADDRCONF(NETDEV_UP): vxcan1: link is not ready 8021q: adding VLAN 0 to HW filter on device batadv0 rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: (detected by 0, t=10502 jiffies, g=3937, q=196) rcu: All QSes seen, last rcu_preempt kthread activity 10503 (4294951613-4294941110), jiffies_till_next_fqs=1, root ->qsmask 0x0 syz-executor.3 R running task 26536 6543 5635 0x00000000 Call Trace: sched_show_task kernel/sched/core.c:5337 [inline] sched_show_task.cold.87+0x2f1/0x355 kernel/sched/core.c:5312 print_other_cpu_stall kernel/rcu/tree.c:1430 [inline] check_cpu_stall kernel/rcu/tree.c:1557 [inline] __rcu_pending kernel/rcu/tree.c:3293 [inline] rcu_pending kernel/rcu/tree.c:3336 [inline] rcu_check_callbacks.cold.81+0xaaa/0xd89 kernel/rcu/tree.c:2682 update_process_times+0x2a/0x60 kernel/time/timer.c:1650 tick_sched_handle+0x77/0x140 kernel/time/tick-sched.c:168 tick_sched_timer+0x37/0xf0 kernel/time/tick-sched.c:1278 __run_hrtimer kernel/time/hrtimer.c:1419 [inline] __hrtimer_run_queues+0x2f7/0xab0 kernel/time/hrtimer.c:1481 hrtimer_interrupt+0x2e2/0x760 kernel/time/hrtimer.c:1539 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1071 [inline] smp_apic_timer_interrupt+0x114/0x540 arch/x86/kernel/apic/apic.c:1096 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:894 RIP: 0010:debug_lockdep_rcu_enabled.part.3+0xa/0x60 kernel/rcu/update.c:251 Code: 45 a0 e8 d9 1b 40 00 48 8b 45 a0 e9 bc fd ff ff 48 8b 7d d0 e8 c7 1b 40 00 e9 95 fd ff ff 66 90 48 b8 00 00 00 00 00 fc ff df <55> 48 89 e5 53 65 48 8b 1c 25 40 ee 01 00 48 8d bb 84 08 00 00 48 RSP: 0018:ffff8881d1b07898 EFLAGS: 00000202 ORIG_RAX: ffffffffffffff13 RAX: dffffc0000000000 RBX: ffff8881eacb2000 RCX: ffffffff81513bc1 RDX: 0000000000000004 RSI: 0000000000000004 RDI: ffffffff884f14c0 RBP: ffff8881d1b078a0 R08: ffffed103ed04733 R09: ffffed103ed04732 R10: ffffed103ed04732 R11: ffff8881f6823993 R12: ffff8881f658f4e0 R13: ffff8881f658f4e0 R14: ffff8881e803ae80 R15: 1ffff1103a360f21 aa_file_perm+0x142/0xb70 security/apparmor/file.c:614 common_file_perm+0x120/0x590 security/apparmor/lsm.c:461 apparmor_file_permission+0x15/0x20 security/apparmor/lsm.c:474 security_file_permission+0x46/0x190 security/security.c:871 rw_verify_area+0xb8/0x2b0 fs/read_write.c:391 do_splice_to+0x6f/0x120 fs/splice.c:869 splice_direct_to_actor+0x296/0x870 fs/splice.c:959 do_splice_direct+0x14c/0x270 fs/splice.c:1068 do_sendfile+0x4a6/0xe50 fs/read_write.c:1447 __do_sys_sendfile64 fs/read_write.c:1502 [inline] __se_sys_sendfile64 fs/read_write.c:1494 [inline] __x64_sys_sendfile64+0x12e/0x1e0 fs/read_write.c:1494 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x460b89 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007efefd8e31a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 RAX: ffffffffffffffda RBX: 000000000052bf00 RCX: 0000000000460b89 RDX: 0000000020000000 RSI: 0000000000000003 RDI: 0000000000000003 RBP: 0000000000000004 R08: 0000000000000000 R09: 0000000000000000 R10: 00008080fffffffe R11: 0000000000000246 R12: 00000000ffffffff R13: 00000000004f4348 R14: 00000000004b2b92 R15: 00007efefd8e36bc rcu: rcu_preempt kthread starved for 10545 jiffies! g3937 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0 rcu: RCU grace-period kthread stack dump: rcu_preempt R running task 29208 10 2 0x80000000 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0xdb5/0x1d40 kernel/sched/core.c:3517 schedule+0x7f/0x1b0 kernel/sched/core.c:3561 schedule_timeout+0x3ab/0xe00 kernel/time/timer.c:1818 rcu_gp_kthread+0xce6/0x23d0 kernel/rcu/tree.c:2202 kthread+0x347/0x410 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415