syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P4689/1:b..l P7192/1:b..l
	(detected by 0, t=10502 jiffies, g=34109, q=117 ncpus=2)
task:syz.4.656       state:R  running task     stack:24952 pid:7192  ppid:4249   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x143f/0x4570 kernel/sched/core.c:6561
 preempt_schedule_irq+0xf7/0x1c0 kernel/sched/core.c:6873
 irqentry_exit+0x53/0x80 kernel/entry/common.c:439
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:xas_move_index lib/xarray.c:155 [inline]
RIP: 0010:xas_next_offset lib/xarray.c:163 [inline]
RIP: 0010:xas_find+0x407/0xaa0 lib/xarray.c:1260
Code: 0f b6 1f fe c3 88 1f 43 80 3c 37 00 74 08 4c 89 ef e8 3d c4 33 f7 44 0f b6 fb 49 8b 6d 00 48 89 e8 48 c1 e8 03 42 0f b6 04 30 <84> c0 0f 85 b1 05 00 00 44 0f b6 65 00 bf 40 00 00 00 44 89 e6 e8
RSP: 0018:ffffc90004f575a8 EFLAGS: 00000a02
RAX: 0000000000000000 RBX: 000000000000001a RCX: ffffc90004f576d2
RDX: ffffc9000de42000 RSI: 0000000000042178 RDI: ffffc90004f576d2
RBP: ffff888071ffe100 R08: ffffffff8aae46e2 R09: ffffffff8aae44fc
R10: 0000000000000002 R11: ffff888030ffd940 R12: 0000000000000459
R13: ffffc90004f576d8 R14: dffffc0000000000 R15: 000000000000001a
 find_get_entry mm/filemap.c:2031 [inline]
 find_lock_entries+0x24a/0xda0 mm/filemap.c:2123
 shmem_undo_range+0x294/0x2390 mm/shmem.c:925
 shmem_truncate_range mm/shmem.c:1062 [inline]
 shmem_evict_inode+0x265/0xa60 mm/shmem.c:1171
 evict+0x529/0x930 fs/inode.c:705
 __dentry_kill+0x436/0x650 fs/dcache.c:611
 dentry_kill+0xbb/0x290 fs/dcache.c:-1
 dput+0xfb/0x1d0 fs/dcache.c:918
 __fput+0x62e/0x8d0 fs/file_table.c:328
 task_work_run+0x246/0x300 kernel/task_work.c:203
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xde/0x100 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x60/0x270 kernel/entry/common.c:303
 do_syscall_64+0x47/0xb0 arch/x86/entry/common.c:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f4edd18cd6b
RSP: 002b:00007f4ede0d0e10 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: 0000000000000000 RBX: ffffffffffffffff RCX: 00007f4edd18cd6b
RDX: 0000000000000000 RSI: 0000000000004c01 RDI: 0000000000000003
RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000800840
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000016
R13: 00007f4ede0d0eb0 R14: 000000000000968d R15: 0000200000000000
 </TASK>
task:udevd           state:R  running task     stack:24336 pid:4689  ppid:3622   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x143f/0x4570 kernel/sched/core.c:6561
 preempt_schedule_common+0x83/0xd0 kernel/sched/core.c:6730
 preempt_schedule+0xd9/0xe0 kernel/sched/core.c:6754
 preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:34
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
 _raw_spin_unlock_irqrestore+0x128/0x130 kernel/locking/spinlock.c:194
 spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
 __wake_up_common_lock kernel/sched/wait.c:140 [inline]
 __wake_up_sync_key+0x121/0x1c0 kernel/sched/wait.c:208
 sock_def_readable+0x15b/0x280 net/core/sock.c:3308
 unix_dgram_sendmsg+0x153d/0x2060 net/unix/af_unix.c:2058
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg net/socket.c:730 [inline]
 sock_write_iter+0x394/0x4e0 net/socket.c:1143
 call_write_iter include/linux/fs.h:2265 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x857/0xbc0 fs/read_write.c:584
 ksys_write+0x19c/0x2c0 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f20f0516bf2
RSP: 002b:00007fff15a5fab8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f20f0516bf2
RDX: 0000000000000000 RSI: 00007fff15a5fb0f RDI: 000000000000000a
RBP: 00007fff15a5fb0f R08: 0000000000000001 R09: 0000000000000000
R10: 000000000000010f R11: 0000000000000246 R12: 000000000000000a
R13: 00007f20f08d1ae0 R14: 0000000000000000 R15: 000055e7f6da6910
 </TASK>
rcu: rcu_preempt kthread starved for 10567 jiffies! g34109 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:25592 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x143f/0x4570 kernel/sched/core.c:6561
 preempt_schedule_irq+0xf7/0x1c0 kernel/sched/core.c:6873
 irqentry_exit+0x53/0x80 kernel/entry/common.c:439
 asm_sysvec_reschedule_ipi+0x16/0x20 arch/x86/include/asm/idtentry.h:696
RIP: 0010:__free_object+0x9aa/0xa80 lib/debugobjects.c:416
Code: 84 24 80 00 00 00 42 80 3c 2b 00 74 08 4c 89 f7 e8 6b 1c 99 fd f6 84 24 81 00 00 00 02 75 5a f7 44 24 10 00 02 00 00 74 01 fb <48> c7 44 24 60 0e 36 e0 45 48 8b 44 24 40 49 c7 44 05 00 00 00 00
RSP: 0018:ffffc90000157980 EFLAGS: 00000206
RAX: b8b1d258ae69fe00 RBX: 1ffff9200002af44 RCX: ffffffff973c3103
RDX: dffffc0000000000 RSI: ffffffff8b0c1ec0 RDI: ffffffff8b5f7360
RBP: ffffc90000157b58 R08: dffffc0000000000 R09: ffffc90000157a60
R10: 0000000000000000 R11: dffffc0000000001 R12: ffff8880b8f37530
R13: dffffc0000000000 R14: ffffc90000157a20 R15: ffff8880b8f37528
 free_object lib/debugobjects.c:424 [inline]
 debug_object_free+0x2c1/0x460 lib/debugobjects.c:856
 destroy_timer_on_stack kernel/time/timer.c:812 [inline]
 schedule_timeout+0x1d0/0x300 kernel/time/timer.c:1969
 rcu_gp_fqs_loop+0x2d2/0x1150 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0xa3/0x3b0 kernel/rcu/tree.c:1905
 kthread+0x28d/0x320 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:735