INFO: rcu detected stall in do_signal

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: bfb9e5c0 Linux 4.14.159
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=173727dee00000
kernel config: https://syzkaller.appspot.com/x/.config?x=8b2dd838381e2c80
dashboard link: https://syzkaller.appspot.com/bug?extid=b03d37a1162672cb821b
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+b03d37...@syzkaller.appspotmail.com

net_ratelimit: 26 callbacks suppressed
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
INFO: rcu_preempt detected stalls on CPUs/tasks:
(detected by 1, t=10502 jiffies, g=2730, c=2729, q=34)
All QSes seen, last rcu_preempt kthread activity 10503
(4294968882-4294958379), jiffies_till_next_fqs=1, root ->qsmask 0x0
syz-executor.2 R running task 28496 7845 7155 0x00000000
Call Trace:
<IRQ>
sched_show_task kernel/sched/core.c:5168 [inline]
sched_show_task.cold+0x2f0/0x351 kernel/sched/core.c:5143
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+0xcb1/0xd0a kernel/rcu/tree.c:2792
update_process_times+0x31/0x70 kernel/time/timer.c:1590
tick_sched_handle+0x85/0x160 kernel/time/tick-sched.c:161
tick_sched_timer+0x43/0x130 kernel/time/tick-sched.c:1219
__run_hrtimer kernel/time/hrtimer.c:1220 [inline]
__hrtimer_run_queues+0x270/0xbc0 kernel/time/hrtimer.c:1284
hrtimer_interrupt+0x1d8/0x5d0 kernel/time/hrtimer.c:1318
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1075 [inline]
smp_apic_timer_interrupt+0x11c/0x5e0 arch/x86/kernel/apic/apic.c:1100
apic_timer_interrupt+0x96/0xa0 arch/x86/entry/entry_64.S:792
</IRQ>
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:779
[inline]
RIP: 0010:lock_release+0x44d/0x940 kernel/locking/lockdep.c:4016
RSP: 0000:ffff88805463fc50 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff10
RAX: 1ffffffff0fe2d29 RBX: 1ffff1100a8c7f90 RCX: 1ffff11011c011be
RDX: dffffc0000000000 RSI: 0000000000000001 RDI: 0000000000000282
RBP: ffff88805463fce8 R08: ffff88808e008580 R09: 0000000000000000
R10: 0000000000000000 R11: ffff88808e008580 R12: ffff88808e008580
R13: ffffffff817cef50 R14: 0000000000000003 R15: ffff88805463fcc0
__might_fault mm/memory.c:4584 [inline]
__might_fault+0x183/0x1d0 mm/memory.c:4569
__copy_to_user include/linux/uaccess.h:102 [inline]
__setup_rt_frame arch/x86/kernel/signal.c:495 [inline]
setup_rt_frame arch/x86/kernel/signal.c:704 [inline]
handle_signal arch/x86/kernel/signal.c:748 [inline]
do_signal+0xde0/0x19a0 arch/x86/kernel/signal.c:816
exit_to_usermode_loop+0x15c/0x220 arch/x86/entry/common.c:160
prepare_exit_to_usermode+0x1b5/0x220 arch/x86/entry/common.c:199
retint_user+0x8/0x18
RIP: 0033:0x4057e9
RSP: 002b:00007f385641ea70 EFLAGS: 00010206
RAX: 0000000023ce2f30 RBX: 0000000000000007 RCX: 0000000000414717
RDX: 82e73ce2f35488d4 RSI: 0000000000000000 RDI: 0000000000000006
RBP: 000000000075c070 R08: 00007f385641ea70 R09: 000000000075c070
R10: 0000000000000000 R11: 0000000000000000 R12: 00007f385641f6d4
R13: 00000000004cae58 R14: 00000000004e4478 R15: 00000000ffffffff
rcu_preempt kthread starved for 10525 jiffies! g2730 c2729 f0x2
RCU_GP_WAIT_FQS(3) ->state=0x0 ->cpu=1
rcu_preempt R running task 29776 8 2 0x80000000
Call Trace:
context_switch kernel/sched/core.c:2808 [inline]
__schedule+0x7b8/0x1cd0 kernel/sched/core.c:3384
schedule+0x92/0x1c0 kernel/sched/core.c:3428
schedule_timeout+0x43e/0xe10 kernel/time/timer.c:1746
rcu_gp_kthread+0xbf4/0x1ec0 kernel/rcu/tree.c:2255
kthread+0x319/0x430 kernel/kthread.c:232
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404


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[syzbot]

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