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: INFO: rcu detected stall in ext4_file_write_iter run #14: crashed: INFO: rcu detected stall in ext4_file_write_iter run #15: crashed: INFO: rcu detected stall in ext4_file_write_iter run #16: crashed: INFO: rcu detected stall in ext4_file_write_iter run #17: crashed: INFO: rcu detected stall in sys_sendfile64 run #18: crashed: INFO: rcu detected stall in ext4_file_write_iter run #19: crashed: INFO: rcu detected stall in sys_sendfile64 testing current HEAD 125222814e7b8f84df767d6ab622aff2a6d2f234 testing commit 125222814e7b8f84df767d6ab622aff2a6d2f234 with gcc (GCC) 8.4.1 20210217 kernel signature: 5860aff43fba5609fcf7ce6df4a41df0b83750047b5c8a81010eefbe9c90c947 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: INFO: rcu detected stall in sys_sendfile64 revisions tested: 2, total time: 25m11.926908132s (build: 15m7.176902067s, test: 9m22.518975455s) the crash still happens on HEAD commit msg: Linux 4.19.182 crash: INFO: rcu detected stall in sys_sendfile64 IPv6: ADDRCONF(NETDEV_UP): vxcan1: link is not ready 8021q: adding VLAN 0 to HW filter on device batadv0 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 1, t=10502 jiffies, g=4785, q=128) rcu: All QSes seen, last rcu_preempt kthread activity 10503 (4294952361-4294941858), jiffies_till_next_fqs=1, root ->qsmask 0x0 syz-executor.0 R running task 26536 6521 5608 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:arch_local_irq_restore arch/x86/include/asm/paravirt.h:789 [inline] RIP: 0010:seqcount_lockdep_reader_access include/linux/seqlock.h:83 [inline] RIP: 0010:read_seqcount_begin include/linux/seqlock.h:164 [inline] RIP: 0010:ktime_get_coarse_real_ts64+0x193/0x220 kernel/time/timekeeping.c:2169 Code: c3 e8 d1 47 11 00 48 c7 c7 08 01 12 88 48 89 f8 48 c1 e8 03 42 80 3c 38 00 75 5b 48 83 3d fc 0a be 06 00 74 23 48 89 df 57 9d <0f> 1f 44 00 00 e9 54 ff ff ff f3 90 8b 02 a8 01 0f 84 5d ff ff ff RSP: 0018:ffff8881e84af830 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13 RAX: 1ffffffff1024021 RBX: 0000000000000282 RCX: 1ffff1103d0d85b5 RDX: 0000000000000000 RSI: ffff8881e86c2d88 RDI: 0000000000000282 RBP: ffff8881e84af868 R08: ffff8881e86c2da8 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8881e84af8a0 R13: ffffffff88120100 R14: fffffbfff1024022 R15: dffffc0000000000 current_kernel_time64 include/linux/timekeeping.h:277 [inline] current_time+0x6b/0x140 fs/inode.c:2162 atime_needs_update+0x1ca/0x570 fs/inode.c:1711 touch_atime+0xc5/0x240 fs/inode.c:1728 file_accessed include/linux/fs.h:2123 [inline] generic_file_splice_read+0x49c/0x6f0 fs/splice.c:311 do_splice_to+0xe3/0x120 fs/splice.c:881 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:00007f0862fab1a8 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: 00007f0862fab6bc rcu: rcu_preempt kthread starved for 10548 jiffies! g4785 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1 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