GRED: Unable to relocate VQ 0x0 after dequeue, screwing up backlog
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 0-...!: (1 GPs behind) idle=411/1/0x4000000000000000 softirq=25473/25475 fqs=299
(detected by 1, t=10504 jiffies, g=37757, q=840)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 11166 Comm: syz.1.2136 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:__preempt_count_add kernel/rcu/tree.c:1119 [inline]
RIP: 0010:rcu_is_watching+0x4/0xa0 kernel/rcu/tree.c:1122
Code: 3b 44 24 70 75 1b 48 8d 65 e8 5b 41 5e 41 5f 5d c3 e8 a0 f9 57 08 41 f7 c7 00 02 00 00 75 bd eb bc e8 80 f9 57 08 41 57 41 56 <53> 65 ff 05 9c 8f 9d 7e e8 7f 09 58 08 89 c3 83 f8 08 73 5c 49 bf
RSP: 0018:ffffc90000007c88 EFLAGS: 00000002
RAX: ffffffff8817178c RBX: 0000000000000001 RCX: ffff888078ae9dc0
RDX: 0000000000010000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffff88807e75c360 R08: ffff88807e75c18f R09: 1ffff1100fceb831
R10: dffffc0000000000 R11: ffffed100fceb832 R12: ffff88807e75c2e8
R13: dffffc0000000000 R14: ffff88807e75c000 R15: 18a93705c7dcf8eb
FS: 00007f011dd896c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f011dd68d58 CR3: 000000001eb49000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
rcu_read_unlock include/linux/rcupdate.h:769 [inline]
advance_sched+0x765/0x940 net/sched/sch_taprio.c:771
__run_hrtimer kernel/time/hrtimer.c:1685 [inline]
__hrtimer_run_queues+0x4f2/0xb70 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
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:__put_user_nocheck_4+0xa/0x11
Code: 0f 01 cb 66 89 01 31 c9 0f 01 ca c3 90 90 90 90 90 48 bb fd ef ff ff ff 7f 00 00 48 39 d9 73 34 0f 01 cb 89 01 31 c9 0f 01 ca 90 90 90 90 90 90 48 bb f9 ef ff ff ff 7f 00 00 48 39 d9 73 14
RSP: 0018:ffffc90002f4f8f8 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000002 RCX: 0000000000000000
RDX: ffffc90002f4fd90 RSI: 0000000000000002 RDI: 00000000ffffffff
RBP: ffffc90002f4fa90 R08: ffffc90002f4f6e7 R09: 1ffff920005e9edc
R10: dffffc0000000000 R11: fffff520005e9edd R12: dffffc0000000000
R13: 00002000003dde80 R14: 0000000000000000 R15: 0000000000000000
____sys_recvmsg+0x399/0x5e0 net/socket.c:2677
___sys_recvmsg+0x21a/0x5c0 net/socket.c:2706
do_recvmmsg+0x382/0x850 net/socket.c:2800
__sys_recvmmsg net/socket.c:2879 [inline]
__do_sys_recvmmsg net/socket.c:2902 [inline]
__se_sys_recvmmsg net/socket.c:2895 [inline]
__x64_sys_recvmmsg+0x195/0x250 net/socket.c:2895
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: 0033:0x7f011fb50dd9
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:00007f011dd89028 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: ffffffffffffffda RBX: 00007f011fdca090 RCX: 00007f011fb50dd9
RDX: 0000000000010106 RSI: 00002000000000c0 RDI: 0000000000000003
RBP: 00007f011fbe6d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f011fdca128 R14: 00007f011fdca090 R15: 00007fffba09de98
rcu: rcu_preempt kthread starved for 9055 jiffies! g37757 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:27384 pid: 15 ppid: 2 flags:0x00004000
Call Trace:
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11ef/0x43c0 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/0x11d0 kernel/rcu/tree.c:1972
rcu_gp_kthread+0x9b/0x370 kernel/rcu/tree.c:2145
kthread+0x436/0x520 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: 4590 Comm: kworker/u4:12 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: writeback wb_workfn (flush-8:0)
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+0x843/0x1120 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+0x4b4/0xb70 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
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_many_cond+0xbb5/0xd90 kernel/smp.c:969
Code: b6 44 05 00 84 c0 0f 85 9d 00 00 00 41 8b 1c 24 89 de 83 e6 01 31 ff e8 b9 62 0b 00 83 e3 01 75 07 e8 4f 5f 0b 00 eb 43 f3 90 <48> b8 00 00 00 00 00 fc ff df 41 0f b6 44 05 00 84 c0 75 11 41 f7
RSP: 0018:ffffc900044be680 EFLAGS: 00000293
RAX: ffffffff816dd568 RBX: 0000000000000001 RCX: ffff888028b53b80
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc900044be7c0 R08: ffff8880b903b407 R09: 1ffff11017207680
R10: dffffc0000000000 R11: ffffed1017207681 R12: ffff8880b9042848
R13: 1ffff11017208509 R14: ffff8880b913b3c0 R15: 0000000000000000
on_each_cpu_cond_mask+0x3b/0x80 kernel/smp.c:1134
__flush_tlb_multi arch/x86/include/asm/paravirt.h:87 [inline]
flush_tlb_multi arch/x86/mm/tlb.c:946 [inline]
flush_tlb_mm_range+0x365/0x580 arch/x86/mm/tlb.c:1034
flush_tlb_page arch/x86/include/asm/tlbflush.h:240 [inline]
ptep_clear_flush+0x112/0x140 mm/pgtable-generic.c:97
page_mkclean_one+0x1eb/0x3e0 mm/rmap.c:938
rmap_walk_file+0x408/0x610 mm/rmap.c:2378
rmap_walk mm/rmap.c:2396 [inline]
page_mkclean+0x2f4/0x400 mm/rmap.c:1006
clear_page_dirty_for_io+0x3f8/0x9f0 mm/page-writeback.c:2749
mpage_submit_page+0x8a/0x210 fs/ext4/inode.c:2095
mpage_process_page_bufs+0x6d8/0x8b0 fs/ext4/inode.c:2229
mpage_prepare_extent_to_map+0xbc2/0xfe0 fs/ext4/inode.c:2657
ext4_writepages+0xa9a/0x2df0 fs/ext4/inode.c:2785
do_writepages+0x476/0x6e0 mm/page-writeback.c:2386
__writeback_single_inode+0x153/0xda0 fs/fs-writeback.c:1657
writeback_sb_inodes+0xa4e/0x1680 fs/fs-writeback.c:1940
__writeback_inodes_wb+0x12a/0x3f0 fs/fs-writeback.c:2011
wb_writeback+0x46f/0xbe0 fs/fs-writeback.c:2116
wb_check_old_data_flush fs/fs-writeback.c:2216 [inline]
wb_do_writeback fs/fs-writeback.c:2269 [inline]
wb_workfn+0xb15/0xf20 fs/fs-writeback.c:2298
process_one_work+0x85f/0x1010 kernel/workqueue.c:2310
worker_thread+0xaa6/0x1290 kernel/workqueue.c:2457
kthread+0x436/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287