syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
	(detected by 1, t=10502 jiffies, g=5549, q=27)
rcu: All QSes seen, last rcu_preempt kthread activity 10502 (4294954824-4294944322), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 10502 jiffies! g5549 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:28032 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11bb/0x4390 kernel/sched/core.c:6395
 schedule+0x11b/0x1e0 kernel/sched/core.c:6478
 schedule_timeout+0x15c/0x280 kernel/time/timer.c:1914
 rcu_gp_fqs_loop+0x29e/0x11b0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0x98/0x350 kernel/rcu/tree.c:2145
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
NMI backtrace for cpu 1
CPU: 1 PID: 4193 Comm: syz-executor870 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
 <IRQ>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x397/0x3d0 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:166 [inline]
 rcu_check_gp_kthread_starvation+0x1cd/0x250 kernel/rcu/tree_stall.h:487
 print_other_cpu_stall+0x10c8/0x1220 kernel/rcu/tree_stall.h:592
 check_cpu_stall kernel/rcu/tree_stall.h:745 [inline]
 rcu_pending kernel/rcu/tree.c:3936 [inline]
 rcu_sched_clock_irq+0x831/0x1110 kernel/rcu/tree.c:2619
 update_process_times+0x193/0x200 kernel/time/timer.c:1818
 tick_sched_handle kernel/time/tick-sched.c:254 [inline]
 tick_sched_timer+0x37d/0x560 kernel/time/tick-sched.c:1473
 __run_hrtimer kernel/time/hrtimer.c:1685 [inline]
 __hrtimer_run_queues+0x4fe/0xc40 kernel/time/hrtimer.c:1749
 hrtimer_interrupt+0x3bb/0x8d0 kernel/time/hrtimer.c:1811
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
 __sysvec_apic_timer_interrupt+0x137/0x4a0 arch/x86/kernel/apic/apic.c:1114
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0x9b/0xc0 arch/x86/kernel/apic/apic.c:1108
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:__rcu_read_unlock+0x0/0xd0 kernel/rcu/tree_plugin.h:415
Code: c0 75 11 ff 03 8b 03 3d 00 00 00 40 7d 02 5b c3 0f 0b eb fa 89 d9 80 e1 07 80 c1 03 38 c1 7c e3 48 89 df e8 42 d7 57 00 eb d9 <41> 57 41 56 41 55 41 54 53 49 bf 00 00 00 00 00 fc ff df 65 48 8b
RSP: 0018:ffffc90002ecfed8 EFLAGS: 00000293
RAX: ffffffff814ec8a1 RBX: 000000000000105c RCX: ffff888079588000
RDX: 0000000000000000 RSI: ffffffff8a59a860 RDI: ffffffff8a59a820
RBP: 0000000000000001 R08: dffffc0000000000 R09: fffffbfff1ff7a19
R10: fffffbfff1ff7a19 R11: 1ffffffff1ff7a18 R12: dffffc0000000000
R13: ffff88801f6b0b40 R14: 0000000000000000 R15: ffff88801f6b0c18
 rcu_read_unlock include/linux/rcupdate.h:772 [inline]
 __task_pid_nr_ns+0x34e/0x420 kernel/pid.c:501
 task_tgid_vnr include/linux/sched.h:1585 [inline]
 __ia32_sys_getpid+0x19/0x20 kernel/sys.c:945
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7feed1b98407
Code: 0b e9 68 fe ff ff 48 83 c4 18 48 8d 3d f2 ff 08 00 5b 5d 41 5c 41 5d 41 5e 41 5f e9 03 d8 fd ff 0f 1f 00 b8 27 00 00 00 0f 05 <c3> 0f 1f 84 00 00 00 00 00 31 f6 31 ff e9 87 df 02 00 0f 1f 80 00
RSP: 002b:00007feed1b59b88 EFLAGS: 00000206 ORIG_RAX: 0000000000000027
RAX: ffffffffffffffda RBX: 00007feed1b59cf0 RCX: 00007feed1b98407
RDX: 00007feed1b59bc0 RSI: 00007feed1b59cf0 RDI: 0000000000000021
RBP: 0000000000000000 R08: 00007feed1b5a6c0 R09: 00007feed1b5a6c0
R10: 0000000000000000 R11: 0000000000000206 R12: 00007feed1c2330c
R13: 0000000000000000 R14: 00007ffc41b218c0 R15: 00007ffc41b219a8
 </TASK>