syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	(detected by 1, t=10502 jiffies, g=6705, q=175 ncpus=2)
rcu: All QSes seen, last rcu_preempt kthread activity 10503 (4294953758-4294943255), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 10504 jiffies! g6705 f0x2 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:27752 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 schedule+0xbd/0x170 kernel/sched/core.c:6773
 schedule_timeout+0x160/0x280 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x99/0x380 kernel/rcu/tree.c:1866
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </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: 5759 Comm: syz-executor347 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:__lock_acquire+0x1bfc/0x7c80 kernel/locking/lockdep.c:5168
Code: 00 00 00 00 42 c7 44 00 17 00 00 00 00 42 c6 44 00 1b 00 65 48 8b 04 25 28 00 00 00 48 3b 84 24 00 02 00 00 0f 85 de 4b 00 00 <44> 89 f0 48 8d 65 d8 5b 41 5c 41 5d 41 5e 41 5f 5d c3 31 db e9 63
RSP: 0018:ffffc90003b27860 EFLAGS: 00000046
RAX: a1c924f46c022c00 RBX: ffff88802e38c6d8 RCX: ffffffff81671100
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff90d94510
RBP: ffffc90003b27aa8 R08: dffffc0000000000 R09: 1ffffffff21b28a2
R10: dffffc0000000000 R11: fffffbfff21b28a3 R12: a32a44b7d318da53
R13: ffff88802e38bc00 R14: 0000000000000001 R15: ffff88802e38c700
FS:  000055556236a380(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f99ae1690d0 CR3: 0000000075299000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
 _raw_spin_lock_irq+0xa3/0xe0 kernel/locking/spinlock.c:170
 spin_lock_irq include/linux/spinlock.h:376 [inline]
 get_signal+0x246/0x1400 kernel/signal.c:2694
 arch_do_signal_or_restart+0x9c/0x7b0 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xf6/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f99ae0f1ce9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 17 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc121d1628 EFLAGS: 00000246 ORIG_RAX: 0000000000000082
RAX: fffffffffffffdfe RBX: 0000200000000100 RCX: 00007f99ae0f1ce9
RDX: 00007f99ae0f1ce9 RSI: 0000000000000008 RDI: 0000200000000040
RBP: 0000200000000108 R08: 00000000000000a0 R09: 00000000000000a0
R10: 00000000000000a0 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007ffc121d1650 R15: 00007ffc121d1640
 </TASK>