INFO: rcu detected stall in do_signal

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: c98875d9 Linux 4.19.36
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1250657f200000
kernel config: https://syzkaller.appspot.com/x/.config?x=5e40ac5fbcc6366d
dashboard link: https://syzkaller.appspot.com/bug?extid=3b7d87db90bbfce1eba5
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+3b7d87...@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 0, t=10715 jiffies, g=465505, q=3423)
rcu: All QSes seen, last rcu_preempt kthread activity 3286
(4295277383-4295274097), jiffies_till_next_fqs=1, root ->qsmask 0x0
syz-executor.4 R running task 28760 3790 7792 0x80000000
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:get_current arch/x86/include/asm/current.h:15 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x8/0x50 kernel/kcov.c:100
Code: 87 ea ff 48 c7 05 84 23 cb 08 00 00 00 00 e9 ca e9 ff ff 90 90 90 90
90 90 90 90 90 90 90 90 90 90 90 55 48 89 e5 48 8b 75 08 <65> 48 8b 04 25
40 ee 01 00 65 8b 15 a8 a8 96 7e 81 e2 00 01 1f 00
RSP: 0018:ffff88805d9df7e0 EFLAGS: 00000213 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000000 RBX: dffffc0000000000 RCX: ffffffff819afca4
RDX: 01fffc0000000000 RSI: ffffffff819afcb7 RDI: 0000000000000007
RBP: ffff88805d9df7e0 R08: ffff88809c6782c0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffea0001957b40
R13: ffffea0001957b40 R14: ffff88807f02bae8 R15: 000000000000015b
__read_once_size include/linux/compiler.h:193 [inline]
compound_head include/linux/page-flags.h:142 [inline]
PageSwapBacked include/linux/page-flags.h:295 [inline]
PageSwapCache include/linux/page-flags.h:340 [inline]
free_swap_cache mm/swap_state.c:290 [inline]
free_pages_and_swap_cache+0x127/0x3d0 mm/swap_state.c:318
tlb_flush_mmu_free+0x7e/0x150 mm/memory.c:249
tlb_flush_mmu mm/memory.c:258 [inline]
arch_tlb_finish_mmu+0x225/0x520 mm/memory.c:273
tlb_finish_mmu+0x9e/0x100 mm/memory.c:432
exit_mmap+0x2e2/0x530 mm/mmap.c:3094
__mmput kernel/fork.c:1001 [inline]
mmput+0x15f/0x4c0 kernel/fork.c:1022
exit_mm kernel/exit.c:546 [inline]
do_exit+0x838/0x2fa0 kernel/exit.c:863
do_group_exit+0x135/0x370 kernel/exit.c:979
get_signal+0x399/0x1d50 kernel/signal.c:2572
do_signal+0x95/0x1950 arch/x86/kernel/signal.c:816
exit_to_usermode_loop+0x244/0x2c0 arch/x86/entry/common.c:162
prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
do_syscall_64+0x52d/0x610 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x458da9
Code: Bad RIP value.
RSP: 002b:00007f38aea26cf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 000000000073bf08 RCX: 0000000000458da9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000073bf08
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000073bf0c
R13: 00007ffea609a56f R14: 00007f38aea279c0 R15: 000000000073bf0c
rcu: rcu_preempt kthread starved for 3286 jiffies! g465505 f0x2
RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: RCU grace-period kthread stack dump:
rcu_preempt R running task 29008 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
net_ratelimit: 2 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
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
protocol 88fb is buggy, dev hsr_slave_0
protocol 88fb is buggy, dev hsr_slave_1


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[syzbot]

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