bisecting fixing commit since 63bbbcd8ed53c404649e0b4248c1e5d42c41ac97 building syzkaller on 34bf9440bd06034f86b5d9ac8afbf078129cbdae testing commit 63bbbcd8ed53c404649e0b4248c1e5d42c41ac97 with gcc (GCC) 8.1.0 kernel signature: e3a8953944e745ecca22c4babd631ee3765ac3674a753346cae21e01934250ee 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 testing current HEAD 610bdbf6a174c9a91e34e276a9594114b44bef74 testing commit 610bdbf6a174c9a91e34e276a9594114b44bef74 with gcc (GCC) 8.1.0 kernel signature: bf3da0ceb1b338b0a1f5eabba29e8f14a3525a0b9488570eee3bcd3aa8ffc37b 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: 26m4.924809688s (build: 16m28.856415562s, test: 8m41.403792342s) the crash still happens on HEAD commit msg: Linux 4.19.166 crash: INFO: rcu detected stall in sys_sendfile64 IPv6: ADDRCONF(NETDEV_UP): hsr0: link is not ready IPv6: ADDRCONF(NETDEV_CHANGE): hsr0: link becomes 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=4481, q=687) rcu: All QSes seen, last rcu_preempt kthread activity 10503 (4294952051-4294941548), jiffies_till_next_fqs=1, root ->qsmask 0x0 syz-executor.3 R running task 26968 6581 5659 0x00000000 Call Trace: sched_show_task.cold.86+0x2ee/0x35d kernel/sched/core.c:5337 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+0xa80/0xd67 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:1401 [inline] __hrtimer_run_queues+0x2f7/0xab0 kernel/time/hrtimer.c:1463 hrtimer_interrupt+0x2df/0x760 kernel/time/hrtimer.c:1521 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1067 [inline] smp_apic_timer_interrupt+0x114/0x540 arch/x86/kernel/apic/apic.c:1092 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:894 RIP: 0010:touch_atime+0xb0/0x240 fs/inode.c:1725 Code: c1 ea 03 80 3c 02 00 0f 85 70 01 00 00 48 b8 00 00 00 00 00 fc ff df 4c 8b 6b 08 49 8d 7d 58 48 89 fa 48 c1 ea 03 80 3c 02 00 <0f> 85 43 01 00 00 4d 8b 6d 58 48 89 df 4c 89 ee e8 cb f9 ff ff 84 RSP: 0018:ffff8881ddbe7950 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13 RAX: dffffc0000000000 RBX: ffff8881e1c1c790 RCX: 0000000000000000 RDX: 1ffff11039d1f0bb RSI: 1ffff1103c3838ff RDI: ffff8881ce8f85d8 RBP: ffff8881ddbe79d8 R08: ffff8881e2386ba8 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 1ffff1103bb7cf2a R13: ffff8881ce8f8580 R14: ffff8881e38b6c20 R15: ffff8881e1c1c7f8 file_accessed include/linux/fs.h:2124 [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+0x481/0xd00 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: 0033:0x459349 Code: 7d b7 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 4b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f8937da8c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000459349 RDX: 0000000020000000 RSI: 0000000000000003 RDI: 0000000000000003 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 00008080fffffffe R11: 0000000000000246 R12: 00007f8937da96d4 R13: 00000000004c691d R14: 00000000004db8a8 R15: 00000000ffffffff rcu: rcu_preempt kthread starved for 10537 jiffies! g4481 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+0x78c/0x1c10 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