rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: 0-...!: (3 ticks this GP) idle=d45/1/0x4000000000000000 softirq=6573/6573 fqs=314 (detected by 1, t=10502 jiffies, g=6997, q=3478) Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 4197 Comm: syz-executor Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026 RIP: 0010:match_held_lock+0x0/0xb0 kernel/locking/lockdep.c:5070 Code: db 85 c0 74 d8 83 3d 16 28 cb 03 00 75 cf 48 c7 c7 80 2a 2b 8a 48 c7 c6 c0 2a 2b 8a e8 49 10 f5 ff 0f 0b eb b6 e8 f0 fa ff ff 01 00 00 00 48 39 77 10 74 6c 53 81 7f 20 00 00 10 00 72 5f 48 RSP: 0018:ffffc90000007c80 EFLAGS: 00000083 RAX: 0000000000000003 RBX: ffff88801a395940 RCX: 0000000000000000 RDX: 0000000000010000 RSI: ffff88805f60a300 RDI: ffff88801a396458 RBP: 00000000ffffffff R08: 0000000000000003 R09: 0000000000000004 R10: dffffc0000000000 R11: fffff52000000f88 R12: 0000000000000001 R13: 0000000000000046 R14: ffff88805f60a300 R15: ffff88801a396458 FS: 0000555568dd2500(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000110c3429cf CR3: 0000000063199000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __lock_is_held kernel/locking/lockdep.c:5366 [inline] lock_is_held_type+0xa6/0x190 kernel/locking/lockdep.c:5666 lock_is_held include/linux/lockdep.h:287 [inline] advance_sched+0x13f/0x920 net/sched/sch_taprio.c:701 __run_hrtimer kernel/time/hrtimer.c:1685 [inline] __hrtimer_run_queues+0x4ea/0xb60 kernel/time/hrtimer.c:1749 hrtimer_interrupt+0x397/0x8b0 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 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676 RIP: 0010:get_current arch/x86/include/asm/current.h:15 [inline] RIP: 0010:need_resched include/linux/sched.h:2118 [inline] RIP: 0010:mutex_spin_on_owner+0x143/0x370 kernel/locking/mutex.c:364 Code: 39 c4 0f 85 3a 02 00 00 48 8b 44 24 40 0f b6 04 18 84 c0 0f 85 65 01 00 00 49 8d 44 24 34 83 38 00 0f 84 bb 01 00 00 49 89 ef <65> 48 8b 2d 05 58 a6 7e 48 89 ef be 08 00 00 00 e8 08 0e 62 00 48 RSP: 0018:ffffc90002eff468 EFLAGS: 00000202 RAX: ffff888027f81df4 RBX: dffffc0000000000 RCX: ffffffff815c18ef RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff8d44d420 RBP: ffffffff8d44d470 R08: ffffffff8d44d427 R09: 1ffffffff1a89a84 R10: dffffc0000000000 R11: fffffbfff1a89a85 R12: ffff888027f81dc0 R13: ffffffff8d44d420 R14: 1ffffffff1a89a84 R15: ffffffff8d44d470 mutex_optimistic_spin+0x38/0x300 kernel/locking/mutex.c:469 __mutex_lock_common+0x20f/0x2400 kernel/locking/mutex.c:599 __mutex_lock kernel/locking/mutex.c:729 [inline] mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743 rtnl_lock net/core/rtnetlink.c:72 [inline] rtnetlink_rcv_msg+0x79f/0xf10 net/core/rtnetlink.c:5695 netlink_rcv_skb+0x1e9/0x430 net/netlink/af_netlink.c:2519 netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline] netlink_unicast+0x78f/0x940 net/netlink/af_netlink.c:1340 netlink_sendmsg+0x8ba/0xbe0 net/netlink/af_netlink.c:1919 sock_sendmsg_nosec net/socket.c:706 [inline] __sock_sendmsg net/socket.c:718 [inline] __sys_sendto+0x46d/0x620 net/socket.c:2073 __do_sys_sendto net/socket.c:2085 [inline] __se_sys_sendto net/socket.c:2081 [inline] __x64_sys_sendto+0xda/0xf0 net/socket.c:2081 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: 0033:0x7f54052f06ce Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08 RSP: 002b:00007ffc65b85aa8 EFLAGS: 00000246 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 0000555568dd2500 RCX: 00007f54052f06ce RDX: 0000000000000028 RSI: 00007f54060e6670 RDI: 0000000000000003 RBP: 0000000000000001 R08: 00007ffc65b85b24 R09: 000000000000000c R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003 R13: 0000000000000000 R14: 00007f54060e6670 R15: 0000000000000000 rcu: rcu_preempt kthread starved for 9869 jiffies! g6997 f0x0 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:27440 pid: 15 ppid: 2 flags:0x00004000 Call Trace: context_switch kernel/sched/core.c:5049 [inline] __schedule+0x11c3/0x4350 kernel/sched/core.c:6395 schedule+0x11b/0x1e0 kernel/sched/core.c:6478 schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2117 rcu_gp_fqs_loop+0x2be/0x11f0 kernel/rcu/tree.c:1972 rcu_gp_kthread+0x9a/0x370 kernel/rcu/tree.c:2145 kthread+0x42e/0x520 kernel/kthread.c:334 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 rcu: Stack dump where RCU GP kthread last ran: NMI backtrace for cpu 1 CPU: 1 PID: 4277 Comm: syz.2.9 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026 Call Trace: dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106 nmi_cpu_backtrace+0x3a2/0x3d0 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+0x1110/0x1270 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+0x845/0x1120 kernel/rcu/tree.c:2619 update_process_times+0x193/0x200 kernel/time/timer.c:2021 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+0x4b0/0xb60 kernel/time/hrtimer.c:1749 hrtimer_interrupt+0x397/0x8b0 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 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676 RIP: 0010:csd_lock_wait kernel/smp.c:440 [inline] RIP: 0010:smp_call_function_single+0x232/0x4c0 kernel/smp.c:758 Code: 48 44 89 f6 83 e6 01 31 ff e8 aa 89 0b 00 41 83 e6 01 49 bc 00 00 00 00 00 fc ff df 75 0a e8 35 86 0b 00 e9 a3 00 00 00 f3 90 44 24 48 01 00 00 00 0f 84 8e 00 00 00 e8 1b 86 0b 00 eb e9 e8 RSP: 0018:ffffc900031ff8c0 EFLAGS: 00000246 RAX: ffffffff816d7b65 RBX: 0000000000000000 RCX: 0000000000080000 RDX: ffffc900044a5000 RSI: 000000000007ffff RDI: 0000000000080000 RBP: ffffc900031ff9b0 R08: ffff8880b903b407 R09: 1ffff11017207680 R10: dffffc0000000000 R11: ffffed1017207681 R12: dffffc0000000000 R13: 0000000000000001 R14: 0000000000000001 R15: 1ffff9200063ff1c rcu_barrier+0x25d/0x4c0 kernel/rcu/tree.c:4082 nfsd_file_cache_shutdown+0xe7/0x4f0 fs/nfsd/filecache.c:905 nfsd_svc+0x3a5/0x9e0 fs/nfsd/nfssvc.c:816 write_threads+0x2ea/0x350 fs/nfsd/nfsctl.c:426 nfsctl_transaction_write+0x105/0x150 fs/nfsd/nfsctl.c:114 vfs_write+0x304/0xd70 fs/read_write.c:592 ksys_write+0x153/0x260 fs/read_write.c:647 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: 0033:0x7f3715e7ae99 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 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f37140d3028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007f3716102fa0 RCX: 00007f3715e7ae99 RDX: 0000000000000002 RSI: 0000200000000240 RDI: 0000000000000005 RBP: 00007f3715f10eaf R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f3716103038 R14: 00007f3716102fa0 R15: 00007ffd48cfb958