syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
	(detected by 1, t=10502 jiffies, g=6749, q=180)
rcu: All QSes seen, last rcu_preempt kthread activity 10503 (4294954438-4294943935), jiffies_till_next_fqs=1, root ->qsmask 0x0
syz-executor.0  R  running task    28136  8307   8285 0x80004008
Call Trace:
 <IRQ>
 sched_show_task+0x40f/0x560 kernel/sched/core.c:5954
 print_other_cpu_stall kernel/rcu/tree_stall.h:410 [inline]
 check_cpu_stall kernel/rcu/tree_stall.h:538 [inline]
 rcu_pending kernel/rcu/tree.c:2827 [inline]
 rcu_sched_clock_irq+0x1861/0x1ad0 kernel/rcu/tree.c:2271
 update_process_times+0x12d/0x180 kernel/time/timer.c:1726
 tick_sched_handle kernel/time/tick-sched.c:167 [inline]
 tick_sched_timer+0x263/0x420 kernel/time/tick-sched.c:1310
 __run_hrtimer kernel/time/hrtimer.c:1514 [inline]
 __hrtimer_run_queues+0x403/0x840 kernel/time/hrtimer.c:1576
 hrtimer_interrupt+0x38c/0xda0 kernel/time/hrtimer.c:1638
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1110 [inline]
 smp_apic_timer_interrupt+0x109/0x280 arch/x86/kernel/apic/apic.c:1135
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
 </IRQ>
RIP: 0010:__memcg_kmem_uncharge+0x211/0x2e0 mm/memcontrol.c:2925
Code: 65 db a4 ff 48 c7 c7 98 4b 0d 89 e8 59 97 00 00 bf 01 00 00 00 e8 2f e3 9b ff 65 8b 05 d4 fd 4a 7e 85 c0 74 53 48 83 c4 08 5b <41> 5c 41 5d 41 5e 41 5f 5d c3 49 8d 5f 10 48 89 df be 08 00 00 00
RSP: 0018:ffffc90002217428 EFLAGS: 00000292 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000001 RBX: ffffea0002140c00 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffea0002140c00
RBP: ffffc90002217448 R08: dffffc0000000000 R09: fffffbfff120248a
R10: fffffbfff120248a R11: 0000000000000000 R12: ffffea0002140c00
R13: 1ffffd4000428187 R14: ffffea0002140c38 R15: 0000000000000000
 memcg_kmem_uncharge include/linux/memcontrol.h:1402 [inline]
 free_thread_stack+0x12e/0x590 kernel/fork.c:284
 release_task_stack kernel/fork.c:440 [inline]
 put_task_stack+0xa3/0x130 kernel/fork.c:451
 finish_task_switch+0x3f1/0x550 kernel/sched/core.c:3256
 context_switch kernel/sched/core.c:3388 [inline]
 __schedule+0x9a8/0xcc0 kernel/sched/core.c:4081
 preempt_schedule_common kernel/sched/core.c:4236 [inline]
 preempt_schedule+0xdb/0x120 kernel/sched/core.c:4261
 ___preempt_schedule+0x16/0x18 arch/x86/entry/thunk_64.S:50
 __raw_spin_unlock include/linux/spinlock_api_smp.h:152 [inline]
 _raw_spin_unlock+0x3a/0x40 kernel/locking/spinlock.c:183
 spin_unlock include/linux/spinlock.h:378 [inline]
 zap_pte_range+0x1732/0x1c30 mm/memory.c:1136
 zap_pmd_range mm/memory.c:1184 [inline]
 zap_pud_range mm/memory.c:1213 [inline]
 zap_p4d_range mm/memory.c:1234 [inline]
 unmap_page_range+0x9b5/0xb00 mm/memory.c:1255
 unmap_single_vma+0x1d4/0x2e0 mm/memory.c:1300
 unmap_vmas+0x163/0x2a0 mm/memory.c:1332
 exit_mmap+0x27b/0x530 mm/mmap.c:3140
 __mmput+0x120/0x3a0 kernel/fork.c:1082
 mmput+0x5d/0x70 kernel/fork.c:1103
 exit_mm+0x50a/0x590 kernel/exit.c:485
 do_exit+0x544/0x2020 kernel/exit.c:784
 do_group_exit+0x15c/0x2b0 kernel/exit.c:895
 get_signal+0x4ac/0x1d60 kernel/signal.c:2734
 do_signal+0x37/0x640 arch/x86/kernel/signal.c:815
 exit_to_usermode_loop arch/x86/entry/common.c:160 [inline]
 prepare_exit_to_usermode+0x32d/0x5b0 arch/x86/entry/common.c:195
 syscall_return_slowpath+0x113/0x4a0 arch/x86/entry/common.c:278
 do_syscall_64+0x11f/0x1c0 arch/x86/entry/common.c:304
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a679
Code: Bad RIP value.
RSP: 002b:00007f987b56acf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: 0000000000000000 RBX: 000000000075bf28 RCX: 000000000045a679
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000075bf28
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000075bf2c
R13: 00007ffc3515ed9f R14: 00007f987b56b9c0 R15: 000000000075bf2c
rcu: rcu_preempt kthread starved for 10538 jiffies! g6749 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: RCU grace-period kthread stack dump:
rcu_preempt     R  running task    29032    10      2 0x80004000
Call Trace:
 context_switch kernel/sched/core.c:3385 [inline]
 __schedule+0x9a0/0xcc0 kernel/sched/core.c:4081
 schedule+0x181/0x210 kernel/sched/core.c:4155
 schedule_timeout+0x14f/0x240 kernel/time/timer.c:1895
 rcu_gp_fqs_loop kernel/rcu/tree.c:1661 [inline]
 rcu_gp_kthread+0xed8/0x1770 kernel/rcu/tree.c:1821
 kthread+0x332/0x350 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352