bisecting fixing commit since 63bbbcd8ed53c404649e0b4248c1e5d42c41ac97 building syzkaller on 34bf9440bd06034f86b5d9ac8afbf078129cbdae testing commit 63bbbcd8ed53c404649e0b4248c1e5d42c41ac97 with gcc (GCC) 8.1.0 kernel signature: b5deef03c2699841661c8e1452fa0861134dbd1859e9822efb22a57b8f51d756 run #0: crashed: INFO: rcu detected stall in sys_sendfile64 run #1: crashed: INFO: rcu detected stall in ext4_file_write_iter run #2: crashed: INFO: rcu detected stall in ext4_file_write_iter run #3: crashed: INFO: rcu detected stall in ext4_file_write_iter run #4: crashed: INFO: rcu detected stall in sys_sendfile64 run #5: crashed: INFO: rcu detected stall in corrupted run #6: crashed: INFO: rcu detected stall in ext4_file_write_iter run #7: crashed: INFO: rcu detected stall in sys_sendfile64 run #8: crashed: INFO: rcu detected stall in sys_sendfile64 run #9: crashed: INFO: rcu detected stall in ext4_file_write_iter testing current HEAD 7cdefde351b6911ec5ef39322980296c091f6c52 testing commit 7cdefde351b6911ec5ef39322980296c091f6c52 with gcc (GCC) 8.1.0 kernel signature: 919c546328efd1d425592b6255a8c961de6bd1b7f47dd41b5937389927d5fe76 run #0: crashed: INFO: rcu detected stall in sys_sendfile64 run #1: crashed: INFO: rcu detected stall in sys_sendfile64 run #2: crashed: INFO: rcu detected stall in ext4_file_write_iter run #3: crashed: INFO: rcu detected stall in ext4_file_write_iter run #4: crashed: INFO: rcu detected stall in sys_sendfile64 run #5: crashed: INFO: rcu detected stall in ext4_file_write_iter run #6: crashed: INFO: rcu detected stall in ext4_file_write_iter run #7: crashed: INFO: rcu detected stall in sys_sendfile64 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: 28m59.718927898s (build: 18m19.278088801s, test: 9m55.280960799s) the crash still happens on HEAD commit msg: Linux 4.19.100 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 1, t=10502 jiffies, g=5449, q=270) rcu: All QSes seen, last rcu_preempt kthread activity 10503 (4294953689-4294943186), jiffies_till_next_fqs=1, root ->qsmask 0x0 syz-executor.4 R running task 26536 7210 7185 0x00000000 Call Trace: sched_show_task.cold.86+0x2ee/0x35d kernel/sched/core.c:5338 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.82+0xa71/0xd3d kernel/rcu/tree.c:2682 update_process_times+0x2a/0x60 kernel/time/timer.c:1638 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:893 RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:789 [inline] RIP: 0010:lock_is_held_type+0x18b/0x210 kernel/locking/lockdep.c:3943 Code: ff df 41 c7 84 24 7c 08 00 00 00 00 00 00 48 89 fa 48 c1 ea 03 80 3c 02 00 75 63 48 83 3d 24 01 a7 06 00 74 30 48 89 df 57 9d <0f> 1f 44 00 00 48 83 c4 08 44 89 e8 5b 41 5c 41 5d 5d c3 48 83 c4 RSP: 0018:ffff888095e77778 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13 RAX: dffffc0000000000 RBX: 0000000000000286 RCX: ffffffff81799827 RDX: 1ffffffff0fe40e9 RSI: ffffffff87f99e60 RDI: 0000000000000286 RBP: ffff888095e77798 R08: fffff94000356837 R09: fffff94000356836 R10: fffff94000356836 R11: ffffea0001ab41b7 R12: ffff888075f3a040 R13: 0000000000000000 R14: 0000000000000838 R15: ffffea0001ab4180 lock_is_held include/linux/lockdep.h:344 [inline] ___might_sleep+0x1fe/0x2a0 kernel/sched/core.c:6157 generic_file_buffered_read mm/filemap.c:2104 [inline] generic_file_read_iter+0x58e/0x2050 mm/filemap.c:2385 ext4_file_read_iter+0x139/0x350 fs/ext4/file.c:77 call_read_iter include/linux/fs.h:1814 [inline] generic_file_splice_read+0x378/0x6f0 fs/splice.c:308 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: 0033:0x4592c9 Code: fd 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 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007ff72d37ec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00000000004592c9 RDX: 0000000020000000 RSI: 0000000000000003 RDI: 0000000000000003 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 00008080fffffffe R11: 0000000000000246 R12: 00007ff72d37f6d4 R13: 00000000004c689d R14: 00000000004db828 R15: 00000000ffffffff rcu: rcu_preempt kthread starved for 10540 jiffies! g5449 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:2826 [inline] __schedule+0x78c/0x1c10 kernel/sched/core.c:3515 schedule+0x7f/0x1b0 kernel/sched/core.c:3559 schedule_timeout+0x3ab/0xda0 kernel/time/timer.c:1806 rcu_gp_kthread+0xcf8/0x23d0 kernel/rcu/tree.c:2202 kthread+0x324/0x3e0 kernel/kthread.c:246 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415