syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
	(detected by 0, t=10502 jiffies, g=5697, q=97 ncpus=2)
rcu: All QSes seen, last rcu_preempt kthread activity 10502 (4294955090-4294944588), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 10502 jiffies! g5697 f0x2 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:27464 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10e9/0x40d0 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 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 4282 Comm: syz-executor657 Not tainted 6.1.141-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:lookup_chain_cache kernel/locking/lockdep.c:3718 [inline]
RIP: 0010:lookup_chain_cache_add kernel/locking/lockdep.c:3738 [inline]
RIP: 0010:validate_chain kernel/locking/lockdep.c:3793 [inline]
RIP: 0010:__lock_acquire+0x143f/0x7c50 kernel/locking/lockdep.c:5049
Code: e0 48 c1 e8 03 48 89 84 24 80 00 00 00 42 80 3c 00 00 74 12 4c 89 e7 e8 5f 4b 6f 00 49 b8 00 00 00 00 00 fc ff df 49 8b 1c 24 <48> 85 db 0f 94 c0 48 83 c3 f8 0f 94 c1 08 c1 4c 89 b4 24 90 00 00
RSP: 0018:ffffc90003d87660 EFLAGS: 00000046
RAX: 1ffffffff20a0fa6 RBX: ffffffff9093a088 RCX: ffffffff81630360
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff908b8248
RBP: ffffc90003d878b0 R08: dffffc0000000000 R09: fffffbfff211704a
R10: fffffbfff211704a R11: 1ffffffff2117049 R12: ffffffff90507d30
R13: 00000000f72a9051 R14: 846c99018e5a6e1a R15: ffff88801efca890
FS:  0000555574abe3c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2df85c28e0 CR3: 000000007af17000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662
 seqcount_lockdep_reader_access+0xc6/0x1c0 include/linux/seqlock.h:102
 ktime_get+0x31/0x270 kernel/time/timekeeping.c:846
 common_hrtimer_rearm+0x5d/0x110 kernel/time/posix-timers.c:303
 posixtimer_rearm+0x131/0x340 kernel/time/posix-timers.c:329
 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+0xb1/0x140 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: 0033:0x7f2df85a9169
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 51 1f 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 01 48
RSP: 002b:00007fff26b55678 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 00007f2df85a9169
RDX: 000020000006b000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f2df860027c
R13: 00007f2df85f919a R14: 00007fff26b556b0 R15: 0000000000000000
 </TASK>