syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P8929/1:b..l
	(detected by 0, t=10502 jiffies, g=28685, q=211)
task:syz.1.1173      state:R  running task     stack:25008 pid: 8929 ppid:  4184 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11ef/0x43c0 kernel/sched/core.c:6395
 preempt_schedule_irq+0xbb/0x160 kernel/sched/core.c:6799
 irqentry_exit+0x63/0x70 kernel/entry/common.c:432
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:rcu_read_lock include/linux/rcupdate.h:741 [inline]
RIP: 0010:filemap_map_pages+0x193/0x13b0 mm/filemap.c:3313
Code: 48 89 84 24 90 00 00 00 42 0f b6 04 28 84 c0 0f 85 29 0f 00 00 48 89 5c 24 58 8b 03 89 44 24 3c e8 b2 38 c6 ff e8 ad 49 00 00 <e8> 98 f8 1a 08 89 c3 31 ff 89 c6 e8 2d dd d9 ff 85 db 74 10 e8 b4
RSP: 0018:ffffc9000347f760 EFLAGS: 00000282
RAX: e846d26c445db600 RBX: ffff888076dc1814 RCX: e846d26c445db600
RDX: 0000000000000000 RSI: ffffffff8a2b2ea0 RDI: ffffffff8a79e740
RBP: ffffc9000347f8d0 R08: dffffc0000000000 R09: 1ffffffff2036e18
R10: dffffc0000000000 R11: fffffbfff2036e19 R12: ffffc9000347f9a0
R13: dffffc0000000000 R14: ffffc9000347f820 R15: 1ffff9200068ff34
 do_fault_around mm/memory.c:4243 [inline]
 do_read_fault mm/memory.c:4258 [inline]
 do_fault mm/memory.c:4392 [inline]
 handle_pte_fault mm/memory.c:4650 [inline]
 __handle_mm_fault mm/memory.c:4785 [inline]
 handle_mm_fault+0x25bc/0x4410 mm/memory.c:4883
 faultin_page mm/gup.c:976 [inline]
 __get_user_pages+0x94b/0x11e0 mm/gup.c:1197
 populate_vma_page_range+0x213/0x290 mm/gup.c:1529
 __mm_populate+0x275/0x3b0 mm/gup.c:1638
 mm_populate include/linux/mm.h:2646 [inline]
 vm_mmap_pgoff+0x212/0x2d0 mm/util.c:556
 ksys_mmap_pgoff+0x140/0x790 mm/mmap.c:1635
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f2388be9cb9
RSP: 002b:00007f2386e45028 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007f2388e64fa0 RCX: 00007f2388be9cb9
RDX: b635773f06ebbeee RSI: 0000000000b36000 RDI: 0000200000000000
RBP: 00007f2388c57bf7 R08: ffffffffffffffff R09: 0000000000000000
R10: 0000000000008031 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2388e65038 R14: 00007f2388e64fa0 R15: 00007ffe1c9c1df8
 </TASK>
rcu: rcu_preempt kthread starved for 9663 jiffies! g28685 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:27760 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11ef/0x43c0 kernel/sched/core.c:6395
 schedule+0x11b/0x1e0 kernel/sched/core.c:6478
 schedule_timeout+0x184/0x2d0 kernel/time/timer.c:1914
 rcu_gp_fqs_loop+0x2be/0x11d0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0x9b/0x370 kernel/rcu/tree.c:2145
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </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:729