rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P22351/1:b..l
	(detected by 0, t=10502 jiffies, g=201233, q=59 ncpus=2)
task:udevd           state:R  running task     stack:24448 pid:22351 ppid:3639   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 preempt_schedule_common+0x82/0xd0 kernel/sched/core.c:6730
 preempt_schedule+0xa7/0xb0 kernel/sched/core.c:6754
 preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:34
 __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:160 [inline]
 _raw_spin_unlock_irq+0x3c/0x40 kernel/locking/spinlock.c:202
 spin_unlock_irq include/linux/spinlock.h:401 [inline]
 loop_queue_work drivers/block/loop.c:894 [inline]
 loop_queue_rq+0x9d9/0xac0 drivers/block/loop.c:1874
 __blk_mq_issue_directly block/blk-mq.c:2631 [inline]
 __blk_mq_try_issue_directly+0x4ab/0x7a0 block/blk-mq.c:2684
 blk_mq_request_issue_directly block/blk-mq.c:2718 [inline]
 blk_mq_plug_issue_direct+0x233/0x620 block/blk-mq.c:2738
 blk_mq_flush_plug_list+0x7e7/0xd40 block/blk-mq.c:2838
 __blk_flush_plug+0x3c6/0x440 block/blk-core.c:1179
 blk_finish_plug+0x59/0x80 block/blk-core.c:1203
 read_pages+0x646/0x840 mm/readahead.c:184
 page_cache_ra_unbounded+0x690/0x770 mm/readahead.c:270
 do_page_cache_ra mm/readahead.c:300 [inline]
 force_page_cache_ra mm/readahead.c:331 [inline]
 page_cache_sync_ra+0x3d7/0x490 mm/readahead.c:713
 page_cache_sync_readahead include/linux/pagemap.h:1248 [inline]
 filemap_get_pages mm/filemap.c:2665 [inline]
 filemap_read+0x5ff/0x2f80 mm/filemap.c:2759
 blkdev_read_iter+0x3d5/0x500 block/fops.c:614
 call_read_iter include/linux/fs.h:2259 [inline]
 new_sync_read fs/read_write.c:389 [inline]
 vfs_read+0x434/0x920 fs/read_write.c:470
 ksys_read+0x143/0x240 fs/read_write.c:613
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f31e10a7407
RSP: 002b:00007fff39cf77d0 EFLAGS: 00000202 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f31e1798880 RCX: 00007f31e10a7407
RDX: 0000000000000200 RSI: 00007f31e176d000 RDI: 0000000000000009
RBP: 00005575b6bd9f80 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 000000000000003c
R13: 0000000000fff000 R14: 00005575b6bcc2c8 R15: 00007f31e185d39c
 </TASK>
rcu: rcu_preempt kthread starved for 10530 jiffies! g201233 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=1
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:I stack:27840 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 preempt_schedule_irq+0xb1/0x150 kernel/sched/core.c:6873
 irqentry_exit+0x63/0x70 kernel/entry/common.c:439
 asm_sysvec_reschedule_ipi+0x16/0x20 arch/x86/include/asm/idtentry.h:696
RIP: 0010:rcu_gp_fqs_loop+0x2e5/0x1310 kernel/rcu/tree.c:1706
Code: f3 ff 41 f6 c7 04 75 34 44 0f b7 3d 5d b2 46 0b 41 f6 c7 02 75 26 48 83 3d ff ac 46 0b 00 75 0a 48 83 3d 6d ad 46 0b 00 74 12 <48> 85 db 74 0d 48 89 df e8 ce cf b4 08 48 89 c3 eb ad 48 c7 c7 98
RSP: 0018:ffffc90000157cc0 EFLAGS: 00000282
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: dffffc0000000000 RSI: ffffffff8a8c0300 RDI: 00000000ffffffff
RBP: ffffc90000157e10 R08: dffffc0000000000 R09: fffffbfff1966094
R10: fffffbfff1966094 R11: 1ffffffff1966093 R12: 0000000000000000
R13: ffffffff8cb30440 R14: ffffc90000157d88 R15: 0000000000000000
 rcu_gp_kthread+0x95/0x380 kernel/rcu/tree.c:1905
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 1 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 1 skipped: idling at default_idle+0xb/0x10 arch/x86/kernel/process.c:741