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: INFO: rcu detected stall in ext4_file_write_iter run #13: crashed: INFO: rcu detected stall in sys_sendfile64 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 corrupted run #18: crashed: INFO: rcu detected stall in sys_sendfile64 run #19: crashed: INFO: rcu detected stall in sys_sendfile64 testing current HEAD eb575cd5d7f60241d016fdd13a9e86d962093c9b testing commit eb575cd5d7f60241d016fdd13a9e86d962093c9b with gcc (GCC) 8.4.1 20210217 kernel signature: ac12294998abe9604f6089388fa66038edd2c8c248b4f7f50a46638860f00be9 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: INFO: rcu detected stall in ext4_file_write_iter run #8: crashed: INFO: rcu detected stall in ext4_file_write_iter run #9: crashed: INFO: rcu detected stall in ext4_file_write_iter revisions tested: 2, total time: 34m38.781265135s (build: 23m41.745884668s, test: 9m50.900308246s) the crash still happens on HEAD commit msg: Linux 4.19.195 crash: INFO: rcu detected stall in ext4_file_write_iter 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 IPv6: ADDRCONF(NETDEV_UP): veth0_to_team: link is not ready rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: (detected by 1, t=10502 jiffies, g=3953, q=306) rcu: All QSes seen, last rcu_preempt kthread activity 10503 (4294952376-4294941873), jiffies_till_next_fqs=1, root ->qsmask 0x0 syz-executor.4 R running task 26536 6509 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:find_get_entry+0x1/0x600 mm/filemap.c:1447 Code: ff ff e8 52 14 18 00 e9 26 fb ff ff 4c 89 f7 e8 65 14 18 00 e9 e5 fa ff ff 4c 89 e7 e8 58 14 18 00 e9 d4 fc ff ff 0f 1f 00 55 <48> 89 e5 41 57 48 8d 85 78 ff ff ff 41 56 41 55 4c 8d 7d d8 48 c1 RSP: 0018:ffff8881ea6ff390 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13 RAX: fffffbfff11a75a3 RBX: 000000000000000e RCX: 00000000006200ca RDX: 000000000000000e RSI: 0000000000006863 RDI: ffff8881cc2ba6f8 RBP: ffff8881ea6ff3e8 R08: ffffed103ed24733 R09: ffffed103ed24732 R10: ffffed103ed24732 R11: ffff8881f6923993 R12: 00000000006200ca R13: dffffc0000000000 R14: ffff8881cc2ba6f8 R15: ffff8881e499e940 grab_cache_page_write_begin+0x55/0x90 mm/filemap.c:3120 ext4_da_write_begin+0x24c/0xb50 fs/ext4/inode.c:3075 generic_perform_write+0x289/0x480 mm/filemap.c:3170 __generic_file_write_iter+0x205/0x590 mm/filemap.c:3295 ext4_file_write_iter+0x282/0xe60 fs/ext4/file.c:272 call_write_iter include/linux/fs.h:1821 [inline] do_iter_readv_writev+0x4ae/0x960 fs/read_write.c:681 do_iter_write fs/read_write.c:960 [inline] do_iter_write+0x12a/0x510 fs/read_write.c:941 vfs_iter_write+0x5b/0xb0 fs/read_write.c:973 iter_file_splice_write+0x55d/0xc40 fs/splice.c:750 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:00007fdbe1ac51a8 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: 00007fdbe1ac56bc rcu: rcu_preempt kthread starved for 10553 jiffies! g3953 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