bisecting fixing commit since 63bbbcd8ed53c404649e0b4248c1e5d42c41ac97 building syzkaller on 34bf9440bd06034f86b5d9ac8afbf078129cbdae testing commit 63bbbcd8ed53c404649e0b4248c1e5d42c41ac97 with gcc (GCC) 8.1.0 kernel signature: 176f5f009b913ce5e96c84fb58ae2a64641900fbdfedfd08834e226f6885d135 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 sys_sendfile64 run #3: crashed: INFO: rcu detected stall in sys_sendfile64 run #4: crashed: INFO: rcu detected stall in sys_sendfile64 run #5: crashed: INFO: rcu detected stall in sys_sendfile64 run #6: crashed: INFO: rcu detected stall in sys_sendfile64 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 sys_sendfile64 testing current HEAD dda0e2920330128e0dbdeb11c8f25031aa40b11c testing commit dda0e2920330128e0dbdeb11c8f25031aa40b11c with gcc (GCC) 8.1.0 kernel signature: 0d10507564ba02e3f95574ce16d1678396b2fbd4a030b5429f3f0f5b03aaf999 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 sys_sendfile64 run #3: crashed: INFO: rcu detected stall in sys_sendfile64 run #4: crashed: INFO: rcu detected stall in corrupted run #5: crashed: INFO: rcu detected stall in sys_sendfile64 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 ext4_file_write_iter run #9: crashed: INFO: rcu detected stall in ext4_file_write_iter revisions tested: 2, total time: 26m55.583821483s (build: 16m59.240435929s, test: 9m22.386050175s) the crash still happens on HEAD commit msg: Linux 4.19.114 crash: INFO: rcu detected stall in ext4_file_write_iter hsr0: Slave B (hsr_slave_1) is not up; please bring it up to get a fully working HSR network IPv6: ADDRCONF(NETDEV_UP): hsr0: 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=5089, q=264) rcu: All QSes seen, last rcu_preempt kthread activity 10503 (4294952260-4294941757), jiffies_till_next_fqs=1, root ->qsmask 0x0 syz-executor.2 R running task 26968 7121 6218 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.81+0xa80/0xd67 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:__radix_tree_lookup+0x146/0x330 lib/radix-tree.c:1059 Code: ba 00 00 00 00 00 fc ff df 4c 89 d1 48 c1 e9 03 80 3c 11 00 0f 85 b1 01 00 00 4d 89 22 48 83 c4 30 5b 41 5c 41 5d 41 5e 41 5f <5d> c3 48 39 cb 0f 82 3f ff ff ff 49 8d 85 28 02 00 00 48 39 c3 0f RSP: 0018:ffff8880910df248 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13 RAX: ffffea00019836c0 RBX: 1ffff1101221be4b RCX: 1ffff1101221be4f RDX: dffffc0000000000 RSI: 000000000000708a RDI: 0000000000000000 RBP: ffff8880910df248 R08: ffff888075083980 R09: ffff8880750839c0 R10: ffff8880910df278 R11: 0000000000000040 R12: 00000000006200ca R13: dffffc0000000000 R14: ffff888075083978 R15: ffff8880910df370 radix_tree_lookup_slot+0x5d/0xa0 lib/radix-tree.c:1079 find_get_entry+0xe0/0x600 mm/filemap.c:1454 pagecache_get_page+0x45/0x6d0 mm/filemap.c:1564 grab_cache_page_write_begin+0x55/0x90 mm/filemap.c:3112 ext4_da_write_begin+0x24c/0xb50 fs/ext4/inode.c:3067 generic_perform_write+0x289/0x480 mm/filemap.c:3162 __generic_file_write_iter+0x201/0x580 mm/filemap.c:3287 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+0x12a/0x510 fs/read_write.c:960 vfs_iter_write+0x5b/0xb0 fs/read_write.c:973 iter_file_splice_write+0x558/0xc30 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+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:00007f75b9ab7c78 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: 00007f75b9ab86d4 R13: 00000000004c689d R14: 00000000004db828 R15: 00000000ffffffff rcu: rcu_preempt kthread starved for 10551 jiffies! g5089 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: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+0xce6/0x23d0 kernel/rcu/tree.c:2202 kthread+0x324/0x3e0 kernel/kthread.c:246 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415