INFO: rcu detected stall in sys_sendfile64

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 4b0e041c Linux 4.19.35
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1070567b200000
kernel config: https://syzkaller.appspot.com/x/.config?x=bb1bcac868b1655e
dashboard link: https://syzkaller.appspot.com/bug?extid=affbda6ea3b78f6bcfeb
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+affbda...@syzkaller.appspotmail.com

protocol 88fb is buggy, dev hsr_slave_1
protocol 88fb is buggy, dev hsr_slave_0
protocol 88fb is buggy, dev hsr_slave_1
protocol 88fb is buggy, dev hsr_slave_0
protocol 88fb is buggy, dev hsr_slave_1
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: (detected by 1, t=10502 jiffies, g=91009, q=498)
rcu: All QSes seen, last rcu_preempt kthread activity 10495
(4295034113-4295023618), jiffies_till_next_fqs=1, root ->qsmask 0x0
syz-executor.2 R running task 25008 16095 7621 0x00000000
Call Trace:
<IRQ>
sched_show_task kernel/sched/core.c:5297 [inline]
sched_show_task.cold+0x292/0x30b kernel/sched/core.c:5272
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+0xaa1/0xd93 kernel/rcu/tree.c:2682
update_process_times+0x32/0x80 kernel/time/timer.c:1636
tick_sched_handle+0xa2/0x190 kernel/time/tick-sched.c:164
tick_sched_timer+0x47/0x130 kernel/time/tick-sched.c:1274
__run_hrtimer kernel/time/hrtimer.c:1398 [inline]
__hrtimer_run_queues+0x33e/0xde0 kernel/time/hrtimer.c:1460
hrtimer_interrupt+0x314/0x770 kernel/time/hrtimer.c:1518
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1029 [inline]
smp_apic_timer_interrupt+0x120/0x570 arch/x86/kernel/apic/apic.c:1054
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:867
</IRQ>
RIP: 0010:memset_erms+0x9/0x10 arch/x86/lib/memset_64.S:66
Code: c1 e9 03 40 0f b6 f6 48 b8 01 01 01 01 01 01 01 01 48 0f af c6 f3 48
ab 89 d1 f3 aa 4c 89 c8 c3 90 49 89 f9 40 88 f0 48 89 d1 <f3> aa 4c 89 c8
c3 90 49 89 fa 40 0f b6 ce 48 b8 01 01 01 01 01 01
RSP: 0018:ffff88805074f8c8 EFLAGS: 00010246 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000000 RBX: 00000000006080c0 RCX: 0000000000000080
RDX: 0000000000000100 RSI: 0000000000000000 RDI: ffff88805be6a0c0
RBP: ffff88805074f948 R08: ffff888085fb46c0 R09: ffff88805be6a040
R10: 0000000000000000 R11: 0000000000000000 R12: ffff88805be6a040
R13: 0000000000000100 R14: 00000000006080c0 R15: ffff88812c3f07c0
kmalloc_array include/linux/slab.h:637 [inline]
kcalloc include/linux/slab.h:648 [inline]
iter_file_splice_write+0x16e/0xbe0 fs/splice.c:693
do_splice_from fs/splice.c:852 [inline]
direct_splice_actor+0x126/0x1a0 fs/splice.c:1019
splice_direct_to_actor+0x2ea/0x890 fs/splice.c:974
do_splice_direct+0x1da/0x2a0 fs/splice.c:1062
do_sendfile+0x597/0xce0 fs/read_write.c:1446
__do_sys_sendfile64 fs/read_write.c:1507 [inline]
__se_sys_sendfile64 fs/read_write.c:1493 [inline]
__x64_sys_sendfile64+0x1dd/0x220 fs/read_write.c:1493
do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x458c29
Code: ad b8 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 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f567dd72c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000458c29
RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000006
RBP: 000000000073bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 00008000fffffffe R11: 0000000000000246 R12: 00007f567dd736d4
R13: 00000000004c5e10 R14: 00000000004da5c8 R15: 00000000ffffffff
rcu: rcu_preempt kthread starved for 10495 jiffies! g91009 f0x2
RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: RCU grace-period kthread stack dump:
rcu_preempt R running task 29104 10 2 0x80000000
Call Trace:
context_switch kernel/sched/core.c:2826 [inline]
__schedule+0x813/0x1d00 kernel/sched/core.c:3474
schedule+0x92/0x1c0 kernel/sched/core.c:3518
schedule_timeout+0x4db/0xfd0 kernel/time/timer.c:1804
rcu_gp_kthread+0xd5c/0x2190 kernel/rcu/tree.c:2202
kthread+0x357/0x430 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:413


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.