[syzbot] [net?] INFO: rcu detected stall in inet_rtm_newaddr (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 01f95500a162 Merge tag 'uml-for-linux-6.15-rc6' of git://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1347702f980000
kernel config: https://syzkaller.appspot.com/x/.config?x=b39cb28b0a399ed3
dashboard link: https://syzkaller.appspot.com/bug?extid=51cd74c5dfeafd65e488
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16cd49b3980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/18300d795306/disk-01f95500.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6d358d59c6dc/vmlinux-01f95500.xz
kernel image: https://storage.googleapis.com/syzbot-assets/bcdf944974fd/bzImage-01f95500.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+51cd74...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 0-...!: (1 GPs behind) idle=530c/1/0x4000000000000000 softirq=17280/17282 fqs=3
rcu: (detected by 1, t=10506 jiffies, g=8293, q=1787 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 5923 Comm: syz-executor Not tainted 6.15.0-rc5-syzkaller-00022-g01f95500a162 #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/29/2025
RIP: 0010:pv_queued_spin_unlock arch/x86/include/asm/paravirt.h:577 [inline]
RIP: 0010:queued_spin_unlock arch/x86/include/asm/qspinlock.h:57 [inline]
RIP: 0010:do_raw_spin_unlock+0x172/0x230 kernel/locking/spinlock_debug.c:142
Code: 48 ba 00 00 00 00 00 fc ff df 48 c1 e8 03 80 3c 10 00 0f 85 ba 00 00 00 48 83 3d 28 ba 89 0c 00 74 4e 48 89 df e8 0e 15 d7 09 <90> 5b 5d 41 5c c3 cc cc cc cc 48 c7 c6 e0 6c 8d 8b 48 89 df e8 45
RSP: 0018:ffffc90000007ce8 EFLAGS: 00000046
RAX: 0000000000000001 RBX: ffffffff9ad4e378 RCX: ffffffff81985ed3
RDX: dffffc0000000000 RSI: 0000000000000004 RDI: ffffffff9ad4e378
RBP: ffffffff9ad4e380 R08: 0000000000000000 R09: fffffbfff35a9c6f
R10: ffffffff9ad4e37b R11: ffffffff9ad4e378 R12: ffffffff9ad4e388
R13: ffff88807bc05340 R14: dffffc0000000000 R15: 1ffff92000000fa8
FS: 0000555577c53500(0000) GS:ffff8881249df000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555562d75808 CR3: 000000005fb8a000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<IRQ>
__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:150 [inline]
_raw_spin_unlock_irqrestore+0x22/0x80 kernel/locking/spinlock.c:194
debug_object_activate+0x2ec/0x4c0 lib/debugobjects.c:836
debug_hrtimer_activate kernel/time/hrtimer.c:445 [inline]
debug_activate kernel/time/hrtimer.c:484 [inline]
enqueue_hrtimer+0x23/0x3b0 kernel/time/hrtimer.c:1088
__run_hrtimer kernel/time/hrtimer.c:1778 [inline]
__hrtimer_run_queues+0x8ff/0xad0 kernel/time/hrtimer.c:1825
hrtimer_interrupt+0x397/0x8e0 kernel/time/hrtimer.c:1887
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1038 [inline]
__sysvec_apic_timer_interrupt+0x108/0x3f0 arch/x86/kernel/apic/apic.c:1055
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1049 [inline]
sysvec_apic_timer_interrupt+0x9f/0xc0 arch/x86/kernel/apic/apic.c:1049
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:unwind_next_frame+0x671/0x20a0 arch/x86/kernel/unwind_orc.c:581
Code: 84 f7 0f 85 a4 15 00 00 83 e0 07 38 c2 40 0f 9e c6 84 d2 0f 95 c0 40 84 c6 0f 85 8d 15 00 00 4c 0f bf 31 4d 01 fe 0f b6 41 05 <83> e0 07 3c 03 0f 84 bd 08 00 00 3c 04 0f 84 f6 07 00 00 3c 02 0f
RSP: 0018:ffffc9000477ec48 EFLAGS: 00000292
RAX: 0000000000000002 RBX: 0000000000000001 RCX: ffffffff91275258
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000001
RBP: ffffc9000477ed00 R08: ffffffff9127525c R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000012081 R12: ffffc9000477ed08
R13: ffffc9000477ecb8 R14: ffffc9000477f040 R15: ffffc9000477f018
arch_stack_walk+0x94/0x100 arch/x86/kernel/stacktrace.c:25
stack_trace_save+0x8e/0xc0 kernel/stacktrace.c:122
kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
unpoison_slab_object mm/kasan/common.c:319 [inline]
__kasan_slab_alloc+0x89/0x90 mm/kasan/common.c:345
kasan_slab_alloc include/linux/kasan.h:250 [inline]
slab_post_alloc_hook mm/slub.c:4147 [inline]
slab_alloc_node mm/slub.c:4196 [inline]
kmem_cache_alloc_node_noprof+0x1d5/0x3b0 mm/slub.c:4248
__alloc_skb+0x2b2/0x380 net/core/skbuff.c:658
alloc_skb include/linux/skbuff.h:1340 [inline]
nlmsg_new include/net/netlink.h:1019 [inline]
rtmsg_fib+0x13e/0x520 net/ipv4/fib_semantics.c:552
fib_table_insert+0xbaf/0x1c40 net/ipv4/fib_trie.c:1380
fib_magic+0x4d4/0x5c0 net/ipv4/fib_frontend.c:1133
fib_add_ifaddr+0x3a1/0x580 net/ipv4/fib_frontend.c:1170
fib_inetaddr_event+0x147/0x270 net/ipv4/fib_frontend.c:1469
notifier_call_chain+0xb9/0x410 kernel/notifier.c:85
blocking_notifier_call_chain kernel/notifier.c:380 [inline]
blocking_notifier_call_chain+0x69/0xa0 kernel/notifier.c:368
__inet_insert_ifa+0x925/0xcd0 net/ipv4/devinet.c:567
inet_rtm_newaddr+0xd87/0x1540 net/ipv4/devinet.c:1002
rtnetlink_rcv_msg+0x95b/0xe90 net/core/rtnetlink.c:6955
netlink_rcv_skb+0x16a/0x440 net/netlink/af_netlink.c:2534
netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline]
netlink_unicast+0x53a/0x7f0 net/netlink/af_netlink.c:1339
netlink_sendmsg+0x8d1/0xdd0 net/netlink/af_netlink.c:1883
sock_sendmsg_nosec net/socket.c:712 [inline]
__sock_sendmsg net/socket.c:727 [inline]
__sys_sendto+0x495/0x510 net/socket.c:2180
__do_sys_sendto net/socket.c:2187 [inline]
__se_sys_sendto net/socket.c:2183 [inline]
__x64_sys_sendto+0xe0/0x1c0 net/socket.c:2183
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f87d9f907fc
Code: 2a 5f 02 00 44 8b 4c 24 2c 4c 8b 44 24 20 89 c5 44 8b 54 24 28 48 8b 54 24 18 b8 2c 00 00 00 48 8b 74 24 10 8b 7c 24 08 0f 05 <48> 3d 00 f0 ff ff 77 34 89 ef 48 89 44 24 08 e8 70 5f 02 00 48 8b
RSP: 002b:00007fff248eaf20 EFLAGS: 00000293 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f87dace4620 RCX: 00007f87d9f907fc
RDX: 0000000000000028 RSI: 00007f87dace4670 RDI: 0000000000000003
RBP: 0000000000000000 R08: 00007fff248eaf74 R09: 000000000000000c
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000003
R13: 0000000000000000 R14: 00007f87dace4670 R15: 0000000000000000
</TASK>
rcu: rcu_preempt kthread starved for 10490 jiffies! g8293 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:27704 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5382 [inline]
__schedule+0x116f/0x5de0 kernel/sched/core.c:6767
__schedule_loop kernel/sched/core.c:6845 [inline]
schedule+0xe7/0x3a0 kernel/sched/core.c:6860
schedule_timeout+0x123/0x290 kernel/time/sleep_timeout.c:99
rcu_gp_fqs_loop+0x1ea/0xb00 kernel/rcu/tree.c:2046
rcu_gp_kthread+0x270/0x380 kernel/rcu/tree.c:2248
kthread+0x3c2/0x780 kernel/kthread.c:464
ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:153
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 UID: 101 PID: 5480 Comm: dhcpcd Not tainted 6.15.0-rc5-syzkaller-00022-g01f95500a162 #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/29/2025
RIP: 0010:write_comp_data+0x8b/0x90 kernel/kcov.c:272
Code: 00 00 4a 8d 34 dd 28 00 00 00 48 39 f2 72 1b 48 83 c7 01 48 89 38 4c 89 44 30 e0 4c 89 4c 30 e8 4c 89 54 30 f0 4a 89 4c d8 20 <c3> cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3
RSP: 0018:ffffc90002ea77b0 EFLAGS: 00000293
RAX: 0000000000000000 RBX: ffff8880b8441720 RCX: ffffffff81af1bb9
RDX: ffff88802577c880 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 0000000000000003 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffffed10170882e5
R13: 0000000000000001 R14: dffffc0000000000 R15: ffff8880b853b040
FS: 00007fe629d36740(0000) GS:ffff888124adf000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055b10a151068 CR3: 0000000025463000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
csd_lock_wait kernel/smp.c:340 [inline]
smp_call_function_many_cond+0x4c9/0x1290 kernel/smp.c:885
on_each_cpu_cond_mask+0x40/0x90 kernel/smp.c:1052
__flush_tlb_multi arch/x86/include/asm/paravirt.h:91 [inline]
flush_tlb_multi arch/x86/mm/tlb.c:1275 [inline]
flush_tlb_mm_range+0x322/0x1780 arch/x86/mm/tlb.c:1365
tlb_flush arch/x86/include/asm/tlb.h:23 [inline]
tlb_flush_mmu_tlbonly include/asm-generic/tlb.h:480 [inline]
tlb_flush_mmu_tlbonly include/asm-generic/tlb.h:470 [inline]
tlb_flush_mmu mm/mmu_gather.c:403 [inline]
tlb_finish_mmu+0x3c9/0x7b0 mm/mmu_gather.c:496
vms_clear_ptes+0x55e/0x770 mm/vma.c:1191
vms_complete_munmap_vmas+0x1ca/0x970 mm/vma.c:1233
do_vmi_align_munmap+0x43b/0x7d0 mm/vma.c:1492
__do_sys_brk+0x8d3/0xaa0 mm/mmap.c:176
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe629e04c7c
Code: 1a 64 c7 03 01 00 00 00 eb 11 64 44 89 23 31 f6 5b 31 ff 5d 41 5c e9 41 ff ff ff 5b 83 c8 ff 5d 41 5c c3 b8 0c 00 00 00 0f 05 <48> 8b 15 d5 61 0d 00 45 31 c0 48 89 02 48 39 c7 76 12 48 8b 05 73
RSP: 002b:00007fffc7ef0748 EFLAGS: 00000206 ORIG_RAX: 000000000000000c
RAX: ffffffffffffffda RBX: fffffffffffdf000 RCX: 00007fe629e04c7c
RDX: 0000558eaa832990 RSI: 0000558eaa6f2010 RDI: 0000558eaa853000
RBP: 0000000000041670 R08: 0000000000000000 R09: ba568e78e099c46f
R10: 00007fffc7ef06a8 R11: 0000000000000206 R12: 0000558eaa874000
R13: 0000558eaa863f20 R14: 00007fe629edbaa0 R15: 00007fffc7ef0978
</TASK>


---
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[Hillf Danton]

On Tue, 06 May 2025 07:06:40 -0700

Shedding light on adding a couple of debug lines of code to catch
hrtimer CPU hog like this one is welcome, given long running raprio [1,2,3].

[1] Subject: [syzbot] [kernel?] INFO: rcu detected stall in kthread_worker_fn (2)
https://lore.kernel.org/lkml/67d2a576.050a022...@google.com/
[2] Subject: [syzbot] [wireguard?] INFO: rcu detected stall in wg_packet_handshake_receive_worker (3)
https://lore.kernel.org/lkml/6817bba9.050a022...@google.com/
[3] Subject: [syzbot] [batman?] INFO: rcu detected stall in rtnl_newlink (5)
https://lore.kernel.org/lkml/67fc8e73.050a022...@google.com/

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 18a7e218cfcd Merge tag 'net-6.18-rc1' of git://git.kernel...
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12504dcd980000
kernel config: https://syzkaller.appspot.com/x/.config?x=61ab7fa743df0ec1
dashboard link: https://syzkaller.appspot.com/bug?extid=51cd74c5dfeafd65e488
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14d2a542580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=142149e2580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7a01e6dce97e/disk-18a7e218.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5e1b7e41427f/vmlinux-18a7e218.xz
kernel image: https://storage.googleapis.com/syzbot-assets/69b558601209/bzImage-18a7e218.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+51cd74...@syzkaller.appspotmail.com

sched: DL replenish lagged too much

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:

rcu: 0-...!: (2 GPs behind) idle=7754/1/0x4000000000000000 softirq=15464/15465 fqs=1
rcu: (detected by 1, t=10502 jiffies, g=11321, q=371 ncpus=2)

Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0

CPU: 0 UID: 0 PID: 5948 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:rb_insert_color_cached include/linux/rbtree.h:113 [inline]
RIP: 0010:rb_add_cached include/linux/rbtree.h:183 [inline]
RIP: 0010:timerqueue_add+0x1a8/0x200 lib/timerqueue.c:40
Code: e7 31 f6 e8 6a 0c de f6 42 80 3c 2b 00 74 08 4c 89 f7 e8 7b 0a de f6 4d 89 26 4d 8d 7e 08 4c 89 f8 48 c1 e8 03 42 80 3c 28 00 <74> 08 4c 89 ff e8 5e 0a de f6 4d 89 27 4d 85 e4 40 0f 95 c5 eb 07
RSP: 0018:ffffc90000007cf0 EFLAGS: 00000046
RAX: 1ffff110170c4f83 RBX: 1ffff110170c4f82 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88805de72358
RBP: 0000000000000000 R08: ffff88805de72357 R09: 0000000000000000
R10: ffff88805de72340 R11: ffffed100bbce46b R12: ffff88805de72340
R13: dffffc0000000000 R14: ffff8880b8627c10 R15: ffff8880b8627c18
FS: 000055557c657500(0000) GS:ffff888125d0f000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000200000000600 CR3: 000000002ee76000 CR4: 00000000003526f0
Call Trace:
<IRQ>
__run_hrtimer kernel/time/hrtimer.c:1794 [inline]
__hrtimer_run_queues+0x656/0xc60 kernel/time/hrtimer.c:1841
hrtimer_interrupt+0x45b/0xaa0 kernel/time/hrtimer.c:1903
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1041 [inline]
__sysvec_apic_timer_interrupt+0x108/0x410 arch/x86/kernel/apic/apic.c:1058
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1052 [inline]
sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1052

</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702

RIP: 0010:pv_vcpu_is_preempted arch/x86/include/asm/paravirt.h:579 [inline]
RIP: 0010:vcpu_is_preempted arch/x86/include/asm/qspinlock.h:63 [inline]
RIP: 0010:owner_on_cpu include/linux/sched.h:2282 [inline]
RIP: 0010:mutex_spin_on_owner+0x189/0x360 kernel/locking/mutex.c:361
Code: b6 04 30 84 c0 0f 85 59 01 00 00 48 8b 44 24 08 8b 18 48 8b 44 24 48 42 80 3c 30 00 74 0c 48 c7 c7 90 8c fa 8d e8 a7 cd 88 00 <48> 83 3d ff 27 5e 0c 00 0f 84 b9 01 00 00 48 89 df e8 41 e0 d5 ff
RSP: 0018:ffffc900034c7428 EFLAGS: 00000246
RAX: 1ffffffff1bf5192 RBX: 0000000000000001 RCX: ffffffff819c6588
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff8f4df8a0
RBP: 1ffffffff1e9bf14 R08: ffffffff8f4df8a7 R09: 1ffffffff1e9bf14
R10: dffffc0000000000 R11: fffffbfff1e9bf15 R12: ffffffff8f4df8a0
R13: ffffffff8f4df8f0 R14: dffffc0000000000 R15: ffff8880267a9e40
mutex_optimistic_spin kernel/locking/mutex.c:464 [inline]
__mutex_lock_common kernel/locking/mutex.c:602 [inline]
__mutex_lock+0x311/0x1350 kernel/locking/mutex.c:760
rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
inet_rtm_newaddr+0x3b0/0x18b0 net/ipv4/devinet.c:978
rtnetlink_rcv_msg+0x7cf/0xb70 net/core/rtnetlink.c:6954
netlink_rcv_skb+0x205/0x470 net/netlink/af_netlink.c:2552
netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
netlink_unicast+0x82f/0x9e0 net/netlink/af_netlink.c:1346
netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1896
sock_sendmsg_nosec net/socket.c:727 [inline]
__sock_sendmsg+0x21c/0x270 net/socket.c:742
__sys_sendto+0x3bd/0x520 net/socket.c:2244
__do_sys_sendto net/socket.c:2251 [inline]
__se_sys_sendto net/socket.c:2247 [inline]
__x64_sys_sendto+0xde/0x100 net/socket.c:2247
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7faade790d5c

Code: 2a 5f 02 00 44 8b 4c 24 2c 4c 8b 44 24 20 89 c5 44 8b 54 24 28 48 8b 54 24 18 b8 2c 00 00 00 48 8b 74 24 10 8b 7c 24 08 0f 05 <48> 3d 00 f0 ff ff 77 34 89 ef 48 89 44 24 08 e8 70 5f 02 00 48 8b

RSP: 002b:00007ffdd2e3b670 EFLAGS: 00000293 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007faadf514620 RCX: 00007faade790d5c
RDX: 0000000000000028 RSI: 00007faadf514670 RDI: 0000000000000003
RBP: 0000000000000000 R08: 00007ffdd2e3b6c4 R09: 000000000000000c

R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000003

R13: 0000000000000000 R14: 00007faadf514670 R15: 0000000000000000
</TASK>
rcu: rcu_preempt kthread timer wakeup didn't happen for 10499 jiffies! g11321 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: Possible timer handling issue on cpu=0 timer-softirq=4286
rcu: rcu_preempt kthread starved for 10500 jiffies! g11321 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->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:I stack:27224 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5325 [inline]
__schedule+0x1798/0x4cc0 kernel/sched/core.c:6929
__schedule_loop kernel/sched/core.c:7011 [inline]
schedule+0x165/0x360 kernel/sched/core.c:7026
schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99
rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2083
rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2285
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>


---

[Eric Dumazet]

Yet another taprio report.

If taprio can not be fixed, perhaps we should remove it from the
kernel, or clearly marked as broken.
(Then ask syzbot to no longer include it)