syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P1635/1:b..l
	(detected by 1, t=10502 jiffies, g=5985, q=94)
task:kworker/u4:6    state:R  running task     stack:    0 pid: 1635 ppid:     2 flags:0x00000008
Workqueue: netns cleanup_net
Call trace:
 __switch_to+0x308/0x588 arch/arm64/kernel/process.c:518
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0xf10/0x1e48 kernel/sched/core.c:6376
 preempt_schedule_irq+0x90/0x274 kernel/sched/core.c:6780
 arm64_preempt_schedule_irq+0x174/0x2c4 arch/arm64/kernel/entry-common.c:260
 el1_interrupt+0x40/0x58 arch/arm64/kernel/entry-common.c:463
 el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:470
 el1h_64_irq+0x78/0x7c arch/arm64/kernel/entry.S:522
 __sanitizer_cov_trace_cmp8+0x0/0xc0 kernel/kcov.c:268
 dccp_v4_exit_batch+0x20/0x2c net/dccp/ipv4.c:1040
 ops_exit_list net/core/net_namespace.c:177 [inline]
 cleanup_net+0x6bc/0xa9c net/core/net_namespace.c:618
 process_one_work+0x790/0x11b8 kernel/workqueue.c:2310
 worker_thread+0x910/0x1034 kernel/workqueue.c:2457
 kthread+0x37c/0x45c kernel/kthread.c:334
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:870
rcu: rcu_preempt kthread starved for 10499 jiffies! g5985 f0x0 RCU_GP_DOING_FQS(6) ->state=0x0 ->cpu=0
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:    0 pid:   15 ppid:     2 flags:0x00000008
Call trace:
 __switch_to+0x308/0x588 arch/arm64/kernel/process.c:518
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0xf10/0x1e48 kernel/sched/core.c:6376
 preempt_schedule_common+0x140/0x260 kernel/sched/core.c:6552
 preempt_schedule+0x64/0x84 kernel/sched/core.c:6577
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
 _raw_spin_unlock_irqrestore+0x114/0x158 kernel/locking/spinlock.c:194
 rcu_initiate_boost+0x184/0x2cc kernel/rcu/tree_plugin.h:1232
 force_qs_rnp kernel/rcu/tree.c:2655 [inline]
 rcu_gp_fqs kernel/rcu/tree.c:-1 [inline]
 rcu_gp_fqs_loop+0x944/0x13d4 kernel/rcu/tree.c:1986
 rcu_gp_kthread+0xc4/0x2c4 kernel/rcu/tree.c:2145
 kthread+0x37c/0x45c kernel/kthread.c:334
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:870
rcu: Stack dump where RCU GP kthread last ran:
Task dump for CPU 0:
task:syz.3.32        state:R  running task     stack:    0 pid: 4221 ppid:  4145 flags:0x00000001
Call trace:
 __switch_to+0x308/0x588 arch/arm64/kernel/process.c:518
 unwind_frame+0x31c/0x550 arch/arm64/kernel/stacktrace.c:113
 0xffff800020817c80