syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P4263/1:b..l
	(detected by 1, t=10503 jiffies, g=7701, q=48 ncpus=2)
task:udevd           state:R  running task     stack:27368 pid:4263  ppid:3638   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_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
 _raw_spin_unlock_irqrestore+0xf6/0x100 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+0x11b/0x180 kernel/sched/wait.c:208
 sock_def_readable+0x15b/0x280 net/core/sock.c:3308
 __netlink_sendskb net/netlink/af_netlink.c:1264 [inline]
 netlink_broadcast_deliver net/netlink/af_netlink.c:1399 [inline]
 do_one_broadcast net/netlink/af_netlink.c:1479 [inline]
 netlink_broadcast+0xcea/0x10d0 net/netlink/af_netlink.c:1519
 netlink_sendmsg+0x81e/0xbc0 net/netlink/af_netlink.c:1870
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg net/socket.c:730 [inline]
 ____sys_sendmsg+0x59b/0x970 net/socket.c:2519
 ___sys_sendmsg+0x21c/0x290 net/socket.c:2573
 __sys_sendmsg net/socket.c:2602 [inline]
 __do_sys_sendmsg net/socket.c:2611 [inline]
 __se_sys_sendmsg+0x19e/0x270 net/socket.c:2609
 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: 0033:0x7f7ed98a7407
RSP: 002b:00007ffe939dd410 EFLAGS: 00000202 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f7eda08e880 RCX: 00007f7ed98a7407
RDX: 0000000000000000 RSI: 00007ffe939dd470 RDI: 000000000000000c
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 000000000000008f
R13: 0000562f8923d8a0 R14: 0000000000000000 R15: 0000000000000004
 </TASK>
rcu: rcu_preempt kthread starved for 10515 jiffies! g7701 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
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:26912 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
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 schedule_timeout+0x15c/0x280 kernel/time/timer.c:1965
 rcu_gp_fqs_loop+0x2f2/0x1310 kernel/rcu/tree.c:1706
 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 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4274 Comm: syz-executor168 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:check_wait_context kernel/locking/lockdep.c:4723 [inline]
RIP: 0010:__lock_acquire+0x5a2/0x7c50 kernel/locking/lockdep.c:4999
Code: 7c 24 18 0f 85 40 63 00 00 83 3d 88 94 5b 15 00 0f 84 fd 01 00 00 31 db 48 81 c3 b8 00 00 00 48 89 d8 48 c1 e8 03 0f b6 04 10 <84> c0 0f 85 9e 61 00 00 44 0f b6 33 48 8b 44 24 50 0f b6 04 10 84
RSP: 0018:ffffc90003e17720 EFLAGS: 00000802
RAX: 0000000000000000 RBX: ffffffff9046c2b8 RCX: ffffffff8162fc62
RDX: dffffc0000000000 RSI: 0000000000000008 RDI: ffffffff90ae2240
RBP: ffffc90003e17970 R08: dffffc0000000000 R09: fffffbfff215c449
R10: fffffbfff215c449 R11: 1ffffffff215c448 R12: ffff88807ceb1dc0
R13: 0000000000000000 R14: 0000000000000000 R15: ffff88807ceb28c0
FS:  00007fef4ad486c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000058 CR3: 00000000270e9000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662
 rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 rcu_read_lock include/linux/rcupdate.h:791 [inline]
 __lock_timer+0x55/0x3f0 kernel/time/posix-timers.c:631
 posixtimer_rearm+0x5c/0x340 kernel/time/posix-timers.c:324
 dequeue_signal+0x1b6/0x4b0 kernel/signal.c:704
 get_signal+0x547/0x1350 kernel/signal.c:2751
 arch_do_signal_or_restart+0xb0/0x1230 arch/x86/kernel/signal.c:871
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fef4ad8fe07
Code: 14 25 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 1c 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 <0f> 05 48 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89
RSP: 002b:00007fef4ad48178 EFLAGS: 00000246
RAX: 00000000000000ca RBX: 00007fef4ae12308 RCX: 00007fef4ad8fe09
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007fef4ae12308
RBP: 00007fef4ae12300 R08: 00007fef4ad486c0 R09: 00007fef4ad486c0
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fef4ae1230c
R13: 0000000000000000 R14: 00007ffe6a6b95d0 R15: 00007ffe6a6b96b8
 </TASK>
INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.054 msecs