syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	(detected by 1, t=10502 jiffies, g=8757, q=42 ncpus=2)
rcu: All QSes seen, last rcu_preempt kthread activity 10502 (4294956047-4294945545), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 10502 jiffies! g8757 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:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0x188/0x2d0 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x313/0x1590 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x9d/0x3b0 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: 5798 Comm: syz-executor295 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:x64_setup_rt_frame+0x149/0xc40 arch/x86/kernel/signal_64.c:175
Code: 00 00 04 31 ff e8 c7 c2 58 00 49 81 e6 00 00 00 04 75 0f e8 79 be 58 00 b8 f2 ff ff ff e9 d7 07 00 00 48 8d 8c 24 00 01 00 00 <ba> b8 01 00 00 4c 89 64 24 38 4c 89 e7 48 89 de e8 c2 ea ff ff 49
RSP: 0018:ffffc9000461fc00 EFLAGS: 00000206
RAX: ffffffff812e5519 RBX: ffffc9000461ff58 RCX: ffffc9000461fd00
RDX: 0000000000000000 RSI: 0000000004000000 RDI: 0000000000000000
RBP: ffffc9000461fd70 R08: ffffffff8e8addaf R09: 1ffffffff1d15bb5
R10: dffffc0000000000 R11: fffffbfff1d15bb6 R12: ffffc9000461fde0
R13: dffffc0000000000 R14: 0000000004000000 R15: 1ffff920008c3f9c
FS:  000055557cb4d3c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000020000006b000 CR3: 000000007bd1e000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 setup_rt_frame arch/x86/kernel/signal.c:223 [inline]
 handle_signal arch/x86/kernel/signal.c:267 [inline]
 arch_do_signal_or_restart+0x42c/0x800 arch/x86/kernel/signal.c:312
 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:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xa0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7ff90e6b27d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 d0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff43bd68a8 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 00007ff90e6b27d9
RDX: 000020000006b000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 00007ff90e689990 R09: 00007ff90e689990
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ff90e72903f
R13: 00007ff90e727172 R14: 00007fff43bd68e0 R15: 0000000000000000
 </TASK>