bisecting fixing commit since 63bbbcd8ed53c404649e0b4248c1e5d42c41ac97 building syzkaller on 34bf9440bd06034f86b5d9ac8afbf078129cbdae testing commit 63bbbcd8ed53c404649e0b4248c1e5d42c41ac97 compiler: gcc version 8.4.1 20210217 (GCC) 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 rw_verify_area run #18: crashed: INFO: rcu detected stall in do_iter_write run #19: crashed: INFO: rcu detected stall in sys_sendfile64 testing current HEAD b172b44fcb1771e083aad806fa96f3f60e2ddfac testing commit b172b44fcb1771e083aad806fa96f3f60e2ddfac compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: 61f3738f2d916d84da2f1ce3fe5134952c44e6822c2c12e8e137c88dbf034cb1 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: INFO: rcu detected stall in corrupted run #7: crashed: INFO: rcu detected stall in sys_sendfile64 run #8: crashed: INFO: rcu detected stall in ext4_file_write_iter run #9: crashed: INFO: rcu detected stall in sys_sendfile64 revisions tested: 2, total time: 28m23.204896388s (build: 17m23.303156109s, test: 10m0.628071226s) the crash still happens on HEAD commit msg: Linux 4.19.206 crash: INFO: rcu detected stall in sys_sendfile64 8021q: adding VLAN 0 to HW filter on device batadv0 IPv6: ADDRCONF(NETDEV_UP): vxcan1: 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=3885, q=456) rcu: All QSes seen, last rcu_preempt kthread activity 10503 (4294951721-4294941218), jiffies_till_next_fqs=1, root ->qsmask 0x0 syz-executor.5 R running task 26968 6540 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:iter_file_splice_write+0x55d/0xc40 fs/splice.c:751 Code: e8 be 05 00 00 00 4c 89 e7 e8 5f 46 4b 01 48 8b 85 98 fe ff ff 31 c9 4c 89 e6 48 8b bd 78 fe ff ff 48 8d 50 18 e8 e3 78 f4 ff <48> 85 c0 49 89 c7 0f 8e 30 ff ff ff 48 8b 95 a0 fe ff ff 48 01 45 RSP: 0018:ffff8881ce4e7980 EFLAGS: 00000296 ORIG_RAX: ffffffffffffff13 RAX: 000000000000001c RBX: ffff8881e67ee300 RCX: 1ffff1103e8afe22 RDX: dffffc0000000000 RSI: 0000000000000000 RDI: 1ffff11039c9cf00 RBP: ffff8881ce4e7b10 R08: 0000000000000000 R09: 0000000000000000 R10: ffff8881ce4e78b0 R11: 000000000000001c R12: ffff8881ce4e7a28 R13: 000000000000001c R14: dffffc0000000000 R15: 0000000000000000 do_splice_from fs/splice.c:852 [inline] direct_splice_actor+0x104/0x1c0 fs/splice.c:1025 splice_direct_to_actor+0x304/0x870 fs/splice.c:980 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:00007f1144d2d1a8 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: 00007f1144d2d6bc rcu: rcu_preempt kthread starved for 10538 jiffies! g3885 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 ---------------- Code disassembly (best guess): 0: e8 be 05 00 00 callq 0x5c3 5: 00 4c 89 e7 add %cl,-0x19(%rcx,%rcx,4) 9: e8 5f 46 4b 01 callq 0x14b466d e: 48 8b 85 98 fe ff ff mov -0x168(%rbp),%rax 15: 31 c9 xor %ecx,%ecx 17: 4c 89 e6 mov %r12,%rsi 1a: 48 8b bd 78 fe ff ff mov -0x188(%rbp),%rdi 21: 48 8d 50 18 lea 0x18(%rax),%rdx 25: e8 e3 78 f4 ff callq 0xfff4790d * 2a: 48 85 c0 test %rax,%rax <-- trapping instruction 2d: 49 89 c7 mov %rax,%r15 30: 0f 8e 30 ff ff ff jle 0xffffff66 36: 48 8b 95 a0 fe ff ff mov -0x160(%rbp),%rdx 3d: 48 rex.W 3e: 01 .byte 0x1 3f: 45 rex.RB