bisecting fixing commit since 63bbbcd8ed53c404649e0b4248c1e5d42c41ac97
building syzkaller on 34bf9440bd06034f86b5d9ac8afbf078129cbdae
testing commit 63bbbcd8ed53c404649e0b4248c1e5d42c41ac97 with gcc (GCC) 8.1.0
kernel signature: 31b9124b0643d85c79fa6734fbbb1f7315554160d247221404964895ca06b560
run #0: crashed: INFO: rcu detected stall in ext4_file_write_iter
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 ext4_file_write_iter
run #4: crashed: INFO: rcu detected stall in ext4_file_write_iter
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 sys_sendfile64
run #8: crashed: INFO: rcu detected stall in sys_sendfile64
run #9: crashed: INFO: rcu detected stall in sys_sendfile64
testing current HEAD dce0f88600e49746b4bda873965b671a23ff4313
testing commit dce0f88600e49746b4bda873965b671a23ff4313 with gcc (GCC) 8.1.0
kernel signature: d5c913213c7f49510a8eea573de86ec832a031976775d21cc41033ecea5798e4
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 corrupted
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 corrupted
run #9: crashed: INFO: rcu detected stall in sys_sendfile64
revisions tested: 2, total time: 27m41.379660432s (build: 17m1.506633947s, test: 9m34.354078381s)
the crash still happens on HEAD
commit msg: Linux 4.19.132
crash: INFO: rcu detected stall in sys_sendfile64
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=4693, q=273)
rcu: All QSes seen, last rcu_preempt kthread activity 10503 (4294952371-4294941868), jiffies_till_next_fqs=1, root ->qsmask 0x0
syz-executor.4  R  running task    26968  7143   6256 0x00000000
Call Trace:
 <IRQ>
 sched_show_task.cold.86+0x2ee/0x35d kernel/sched/core.c:5339
 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:894
 </IRQ>
RIP: 0010:unwind_next_frame.part.8+0x4b/0xa20 arch/x86/kernel/unwind_frame.c:282
Code: 53 48 89 fb 49 8d 14 04 48 81 ec 88 00 00 00 48 c7 85 78 ff ff ff b3 8a b5 41 48 c7 45 80 ae 6b cc 87 48 c7 45 88 60 06 2b 81 <c7> 02 f1 f1 f1 f1 c7 42 04 00 f2 f2 f2 65 48 8b 0c 25 28 00 00 00
RSP: 0018:ffff888095dff4f8 EFLAGS: 00000292 ORIG_RAX: ffffffffffffff13
RAX: dffffc0000000000 RBX: ffff888095dff5d0 RCX: 0000000000000009
RDX: ffffed1012bbfea4 RSI: ffffffff8199eb11 RDI: ffff888095dff5d0
RBP: ffff888095dff5a8 R08: 1ffff11012bbfec4 R09: ffff888095dff580
R10: ffff888095dff608 R11: ffff888095dff62f R12: 1ffff11012bbfea4
R13: 0000000000000000 R14: ffff88809cc2e6c0 R15: ffff8880946340ff
 unwind_next_frame+0x3e/0x50 arch/x86/kernel/unwind_frame.c:287
 __save_stack_trace+0x86/0x100 arch/x86/kernel/stacktrace.c:44
 save_stack_trace+0x1a/0x20 arch/x86/kernel/stacktrace.c:60
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
 slab_post_alloc_hook mm/slab.h:445 [inline]
 slab_alloc mm/slab.c:3397 [inline]
 __do_kmalloc mm/slab.c:3725 [inline]
 __kmalloc+0x144/0x770 mm/slab.c:3736
 kmalloc_array include/linux/slab.h:637 [inline]
 kcalloc include/linux/slab.h:648 [inline]
 iter_file_splice_write+0x12c/0xc30 fs/splice.c:693
 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: 0033:0x459349
Code: 7d 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 4b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f072ff60c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000459349
RDX: 0000000020000000 RSI: 0000000000000003 RDI: 0000000000000003
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 00008080fffffffe R11: 0000000000000246 R12: 00007f072ff616d4
R13: 00000000004c691d R14: 00000000004db8a8 R15: 00000000ffffffff
rcu: rcu_preempt kthread starved for 10548 jiffies! g4693 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+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