syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P18875/1:b..l
	(detected by 0, t=10502 jiffies, g=151861, q=146 ncpus=2)
task:cmp             state:R  running task     stack:24336 pid:18875 ppid:18838  flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5245 [inline]
 __schedule+0x11d1/0x40e0 kernel/sched/core.c:6562
 preempt_schedule_irq+0xbb/0x160 kernel/sched/core.c:6874
 irqentry_exit+0x63/0x70 kernel/entry/common.c:439
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:lock_is_held_type+0x13a/0x190 kernel/locking/lockdep.c:5710
Code: 75 40 48 c7 04 24 00 00 00 00 9c 8f 04 24 f7 04 24 00 02 00 00 75 46 41 f7 c5 00 02 00 00 74 01 fb 65 48 8b 04 25 28 00 00 00 <48> 3b 44 24 08 75 3c 89 e8 48 83 c4 10 5b 41 5c 41 5d 41 5e 41 5f
RSP: 0018:ffffc90004caf658 EFLAGS: 00000206
RAX: 3e374aa81840e300 RBX: ffff888035233b80 RCX: 3e374aa81840e300
RDX: ffff888035233b80 RSI: ffffffff8a8c23a0 RDI: ffffffff8adf0c20
RBP: 0000000000000001 R08: dffffc0000000000 R09: 1ffffffff215e648
R10: dffffc0000000000 R11: fffffbfff215e649 R12: 0000000000000000
R13: 0000000000000246 R14: ffffffff8cb2d620 R15: ffff888035234660
 xa_entry include/linux/xarray.h:1198 [inline]
 xas_descend+0x129/0x490 lib/xarray.c:204
 xas_load+0xba/0x140 lib/xarray.c:242
 filemap_get_read_batch+0x197/0xa90 mm/filemap.c:2444
 filemap_get_pages mm/filemap.c:2661 [inline]
 filemap_read+0x586/0x3020 mm/filemap.c:2759
 generic_file_read_iter+0x136/0x740 mm/filemap.c:2941
 call_read_iter include/linux/fs.h:2259 [inline]
 new_sync_read fs/read_write.c:389 [inline]
 vfs_read+0x4a7/0xa00 fs/read_write.c:470
 ksys_read+0x14c/0x250 fs/read_write.c:613
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fc413980134
RSP: 002b:00007ffcaf4cc018 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007ffcaf4cc090 RCX: 00007fc413980134
RDX: 0000000000000340 RSI: 00007ffcaf4cc2a8 RDI: 0000000000000003
RBP: 00007ffcaf4cc080 R08: 00007ffcaf4cc287 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003
R13: 0000000000000340 R14: 00007ffcaf4cc2a0 R15: 00007ffcaf4cc2a8
 </TASK>
rcu: rcu_preempt kthread starved for 9869 jiffies! g151861 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->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:R  running task     stack:27184 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5245 [inline]
 __schedule+0x11d1/0x40e0 kernel/sched/core.c:6562
 schedule+0xb9/0x180 kernel/sched/core.c:6638
 schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x303/0x1340 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0x99/0x3b0 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