syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P6431/1:b..l P6380/1:b..l
	(detected by 0, t=10502 jiffies, g=16121, q=331)
task:syz.1.418       state:R  running task     stack:25408 pid: 6380 ppid:  4190 flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11bb/0x4390 kernel/sched/core.c:6395
 preempt_schedule_irq+0xb1/0x150 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:thp_contains+0x3/0x370 include/linux/pagemap.h:448
Code: 8f fd ff ff 89 d9 80 e1 07 80 c1 03 38 c1 7c 8f 48 89 df e8 ef 32 1f 00 eb 85 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 55 41 57 <41> 56 41 55 41 54 53 48 83 ec 18 49 89 f4 49 89 fe 49 bf 00 00 00
RSP: 0018:ffffc90002f4f2a8 EFLAGS: 00000246
RAX: 0000000000008000 RBX: 0000000000000000 RCX: ffff8880187e8000
RDX: 0000000000000000 RSI: 000000000000052e RDI: ffffea00015d8540
RBP: ffffc90002f4f3f0 R08: dffffc0000000000 R09: fffff940002bb0a9
R10: fffff940002bb0a9 R11: 1ffffd40002bb0a8 R12: ffffc90002f4f340
R13: fffffffffffffffe R14: ffffea00015d8540 R15: dffffc0000000000
 find_lock_entries+0x920/0xd50 mm/filemap.c:2106
 shmem_undo_range+0x23a/0x1880 mm/shmem.c:943
 shmem_truncate_range mm/shmem.c:1063 [inline]
 shmem_evict_inode+0x20d/0xa00 mm/shmem.c:1145
 evict+0x485/0x870 fs/inode.c:647
 __dentry_kill+0x431/0x650 fs/dcache.c:586
 dentry_kill+0xb8/0x290 fs/dcache.c:-1
 dput+0xd8/0x1a0 fs/dcache.c:893
 __fput+0x5ee/0x930 fs/file_table.c:319
 task_work_run+0x125/0x1a0 kernel/task_work.c:188
 exit_task_work include/linux/task_work.h:33 [inline]
 do_exit+0x61e/0x20a0 kernel/exit.c:883
 do_group_exit+0x12e/0x300 kernel/exit.c:997
 get_signal+0x6ca/0x12c0 kernel/signal.c:2900
 arch_do_signal_or_restart+0xc1/0x1300 arch/x86/kernel/signal.c:867
 handle_signal_work kernel/entry/common.c:154 [inline]
 exit_to_user_mode_loop+0x9e/0x130 kernel/entry/common.c:178
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fa0cf09efc9
RSP: 002b:00007fa0cd306038 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: 0000000000010106 RBX: 00007fa0cf2f5fa0 RCX: 00007fa0cf09efc9
RDX: 0000000000010106 RSI: 00002000000000c0 RDI: 0000000000000003
RBP: 00007fa0cf121f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa0cf2f6038 R14: 00007fa0cf2f5fa0 R15: 00007ffd515b2fe8
 </TASK>
task:dhcpcd-run-hook state:R  running task     stack:28704 pid: 6431 ppid:  6400 flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11bb/0x4390 kernel/sched/core.c:6395
 preempt_schedule_common+0x82/0xd0 kernel/sched/core.c:6571
 preempt_schedule+0xa7/0xb0 kernel/sched/core.c:6596
 preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:34
 __raw_spin_unlock include/linux/spinlock_api_smp.h:152 [inline]
 _raw_spin_unlock+0x36/0x40 kernel/locking/spinlock.c:186
 spin_unlock include/linux/spinlock.h:403 [inline]
 filemap_map_pages+0x1031/0x1390 mm/filemap.c:3353
 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+0x2580/0x43c0 mm/memory.c:4883
 do_user_addr_fault+0x489/0xc80 arch/x86/mm/fault.c:1357
 handle_page_fault arch/x86/mm/fault.c:1445 [inline]
 exc_page_fault+0x60/0x100 arch/x86/mm/fault.c:1501
 asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:606
RIP: 0033:0x7f6934a3a420
RSP: 002b:00007fffadbcd088 EFLAGS: 00010246
RAX: 00005582c2ce8910 RBX: 00005582c2cea760 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000000000b
RBP: 00005582c2cf04c0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000008 R11: 0000000000000246 R12: 00005582c2ce8910
R13: 00005582c2cf04c0 R14: 0000000000000000 R15: 00007f6934c54460
 </TASK>
rcu: rcu_preempt kthread starved for 9794 jiffies! g16121 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:27808 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11bb/0x4390 kernel/sched/core.c:6395
 schedule+0x11b/0x1e0 kernel/sched/core.c:6478
 schedule_timeout+0x15c/0x280 kernel/time/timer.c:1914
 rcu_gp_fqs_loop+0x29e/0x11b0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0x98/0x350 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