bisecting fixing commit since f4cc0ed9b2c72687303b035379c5824a02224354 building syzkaller on 7509bf360eba1461ac6059e4cacfbc29c9d2d4c7 testing commit f4cc0ed9b2c72687303b035379c5824a02224354 with gcc (GCC) 8.1.0 kernel signature: 0b5bd00018402f0615d32d3e88647f186389d5d5 run #0: crashed: INFO: rcu detected stall in corrupted run #1: crashed: INFO: rcu detected stall in sendfile64 run #2: crashed: INFO: rcu detected stall in corrupted run #3: crashed: INFO: rcu detected stall in sendfile64 run #4: crashed: INFO: rcu detected stall in corrupted 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 sendfile64 run #8: crashed: INFO: rcu detected stall in sendfile64 run #9: crashed: INFO: rcu detected stall in sendfile64 testing current HEAD 4c5bf01e16a7ec59e59a38a61f793c5d1d5560c7 testing commit 4c5bf01e16a7ec59e59a38a61f793c5d1d5560c7 with gcc (GCC) 8.1.0 kernel signature: 7d26041e844a7288ff5cc550e3627537c9e97861 run #0: crashed: INFO: rcu detected stall in sendfile64 run #1: crashed: INFO: rcu detected stall in corrupted run #2: crashed: INFO: rcu detected stall in corrupted run #3: crashed: INFO: rcu detected stall in ext4_file_write_iter run #4: crashed: INFO: rcu detected stall in ext4_file_write_iter run #5: crashed: INFO: rcu detected stall in corrupted run #6: crashed: INFO: rcu detected stall in corrupted run #7: crashed: INFO: rcu detected stall in sendfile64 run #8: crashed: INFO: rcu detected stall in corrupted run #9: crashed: INFO: rcu detected stall in sendfile64 revisions tested: 2, total time: 27m14.505373422s (build: 16m31.399685294s, test: 9m53.618671572s) the crash still happens on HEAD commit msg: Linux 4.14.161 crash: INFO: rcu detected stall in sendfile64 IPv6: ADDRCONF(NETDEV_CHANGE): hsr0: link becomes ready 8021q: adding VLAN 0 to HW filter on device batadv0 IPv6: ADDRCONF(NETDEV_UP): vxcan1: link is not ready 8021q: adding VLAN 0 to HW filter on device batadv0 INFO: rcu_preempt detected stalls on CPUs/tasks: (detected by 0, t=10502 jiffies, g=1303, c=1302, q=786) All QSes seen, last rcu_preempt kthread activity 10503 (4294953724-4294943221), jiffies_till_next_fqs=1, root ->qsmask 0x0 syz-executor.0 R running task 27000 6953 6873 0x00000000 Call Trace: sched_show_task.cold.89+0x2e1/0x342 kernel/sched/core.c:5168 print_other_cpu_stall kernel/rcu/tree.c:1501 [inline] check_cpu_stall kernel/rcu/tree.c:1616 [inline] __rcu_pending kernel/rcu/tree.c:3390 [inline] rcu_pending kernel/rcu/tree.c:3452 [inline] rcu_check_callbacks.cold.77+0xc96/0xcfa kernel/rcu/tree.c:2792 update_process_times+0x2a/0x60 kernel/time/timer.c:1590 tick_sched_handle+0x7b/0x140 kernel/time/tick-sched.c:161 tick_sched_timer+0x34/0xf0 kernel/time/tick-sched.c:1219 __run_hrtimer kernel/time/hrtimer.c:1220 [inline] __hrtimer_run_queues+0x297/0xaf0 kernel/time/hrtimer.c:1284 hrtimer_interrupt+0x1ae/0x600 kernel/time/hrtimer.c:1318 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1075 [inline] smp_apic_timer_interrupt+0x11f/0x5d0 arch/x86/kernel/apic/apic.c:1100 apic_timer_interrupt+0x96/0xa0 arch/x86/entry/entry_64.S:792 RIP: 0010:page_cache_pipe_buf_release+0x1b/0x100 fs/splice.c:94 RSP: 0018:ffff8880915e7960 EFLAGS: 00000a02 ORIG_RAX: ffffffffffffff10 RAX: dffffc0000000000 RBX: ffffed10120d0969 RCX: 0000000000000000 RDX: 1ffff11015318ca2 RSI: ffff8880a98c6510 RDI: ffff888090684a80 RBP: ffff8880915e7970 R08: 1ffffffff0d28c1a R09: 0000000000000000 R10: 0000000000000050 R11: ffff88809029a0c0 R12: ffff8880a98c6510 R13: 0000000000000000 R14: dffffc0000000000 R15: ffff888090684a80 pipe_buf_release include/linux/pipe_fs_i.h:138 [inline] iter_file_splice_write+0x664/0xc20 fs/splice.c:763 do_splice_from fs/splice.c:851 [inline] direct_splice_actor+0x104/0x1c0 fs/splice.c:1018 splice_direct_to_actor+0x27c/0x750 fs/splice.c:973 do_splice_direct+0x144/0x250 fs/splice.c:1061 do_sendfile+0x463/0xd00 fs/read_write.c:1441 SYSC_sendfile64 fs/read_write.c:1496 [inline] SyS_sendfile64+0x97/0x110 fs/read_write.c:1488 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x459519 RSP: 002b:00007efe09840c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000459519 RDX: 0000000020000000 RSI: 0000000000000003 RDI: 0000000000000003 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 00008080fffffffe R11: 0000000000000246 R12: 00007efe098416d4 R13: 00000000004c6af0 R14: 00000000004dbd68 R15: 00000000ffffffff rcu_preempt kthread starved for 10532 jiffies! g1303 c1302 f0x2 RCU_GP_WAIT_FQS(3) ->state=0x0 ->cpu=0 rcu_preempt R running task 29720 8 2 0x80000000 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x780/0x1d20 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_timeout+0x40c/0xcc0 kernel/time/timer.c:1746 rcu_gp_kthread+0xbbf/0x1e00 kernel/rcu/tree.c:2255 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404