[v5.15] INFO: rcu detected stall in batadv_nc_worker

Hello,

syzbot found the following issue on:

HEAD commit: 7349e40704a0 Linux 5.15.116
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=12f90c75280000
kernel config: https://syzkaller.appspot.com/x/.config?x=831c3122ac9c9145
dashboard link: https://syzkaller.appspot.com/bug?extid=42b636738d776704a740
compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8c03c3ad4501/disk-7349e407.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/350c3d79bc87/vmlinux-7349e407.xz
kernel image: https://storage.googleapis.com/syzbot-assets/73a4ed3d5438/bzImage-7349e407.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P6072/1:b..l
(detected by 0, t=10502 jiffies, g=138109, q=92)
task:kworker/u4:19 state:R running task stack:20544 pid: 6072 ppid: 2 flags:0x00004000
Workqueue: bat_events batadv_nc_worker
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5026 [inline]
__schedule+0x12c4/0x4590 kernel/sched/core.c:6372
preempt_schedule_irq+0xf7/0x1c0 kernel/sched/core.c:6776
irqentry_exit+0x53/0x80 kernel/entry/common.c:426
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:638
RIP: 0010:lock_acquire+0x252/0x4f0 kernel/locking/lockdep.c:5626
Code: 2b 00 74 08 4c 89 f7 e8 cc e4 66 00 f6 44 24 61 02 0f 85 84 01 00 00 41 f7 c7 00 02 00 00 74 01 fb 48 c7 44 24 40 0e 36 e0 45 <4b> c7 44 25 00 00 00 00 00 43 c7 44 25 09 00 00 00 00 43 c7 44 25
RSP: 0018:ffffc90002dcfa20 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 1ffff920005b9f50 RCX: 1ffff920005b9ef0
RDX: dffffc0000000000 RSI: ffffffff8a8b0f00 RDI: ffffffff8ad86000
RBP: ffffc90002dcfb70 R08: dffffc0000000000 R09: fffffbfff1f79621
R10: 0000000000000000 R11: dffffc0000000001 R12: 1ffff920005b9f4c
R13: dffffc0000000000 R14: ffffc90002dcfa80 R15: 0000000000000246
rcu_lock_acquire+0x2a/0x30 include/linux/rcupdate.h:269
rcu_read_lock include/linux/rcupdate.h:696 [inline]
batadv_nc_process_nc_paths+0xb8/0x350 net/batman-adv/network-coding.c:691
batadv_nc_worker+0x3d4/0x5b0 net/batman-adv/network-coding.c:732
process_one_work+0x8a1/0x10c0 kernel/workqueue.c:2307
worker_thread+0xaca/0x1280 kernel/workqueue.c:2454
kthread+0x3f6/0x4f0 kernel/kthread.c:319
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298
</TASK>
rcu: rcu_preempt kthread timer wakeup didn't happen for 10481 jiffies! g138109 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: Possible timer handling issue on cpu=1 timer-softirq=85349
rcu: rcu_preempt kthread starved for 10482 jiffies! g138109 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->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:I stack:25496 pid: 15 ppid: 2 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5026 [inline]
__schedule+0x12c4/0x4590 kernel/sched/core.c:6372
schedule+0x11b/0x1f0 kernel/sched/core.c:6455
schedule_timeout+0x1b9/0x300 kernel/time/timer.c:1884
rcu_gp_fqs_loop+0x2af/0xf70 kernel/rcu/tree.c:1959
rcu_gp_kthread+0xa4/0x360 kernel/rcu/tree.c:2132
kthread+0x3f6/0x4f0 kernel/kthread.c:319
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298
</TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 23500 Comm: kworker/1:8 Not tainted 5.15.116-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/25/2023
Workqueue: mld mld_ifc_work
RIP: 0010:__list_add include/linux/list.h:73 [inline]
RIP: 0010:list_add_tail include/linux/list.h:100 [inline]
RIP: 0010:list_move_tail include/linux/list.h:228 [inline]
RIP: 0010:fq_pie_qdisc_dequeue+0x495/0xa90 net/sched/sch_fq_pie.c:248
Code: 00 fc ff df 80 3c 08 00 74 08 48 89 df e8 13 2e 60 f9 48 89 2b 48 89 e8 48 c1 e8 03 48 bb 00 00 00 00 00 fc ff df 80 3c 18 00 <74> 08 48 89 ef e8 f1 2d 60 f9 4c 89 75 00 e9 fe fb ff ff e8 43 d2
RSP: 0018:ffffc90002daf470 EFLAGS: 00000246
RAX: 1ffff11008b75c5c RBX: dffffc0000000000 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: ffff888045bae2e0 RDI: ffff88804c658bd0
RBP: ffff888045bae2e0 R08: ffffffff88692394 R09: ffffffff8851a5b8
R10: 0000000000000002 R11: ffff88801eb8bb80 R12: ffff888045bae2f0
R13: ffff888045bae000 R14: ffff88804c658bd0 R15: ffff888045bae2e0
FS: 0000000000000000(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007faf49368718 CR3: 000000005d695000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<NMI>
</NMI>
<TASK>
dequeue_skb net/sched/sch_generic.c:292 [inline]
qdisc_restart net/sched/sch_generic.c:397 [inline]
__qdisc_run+0x253/0x1e90 net/sched/sch_generic.c:415
__dev_xmit_skb net/core/dev.c:3879 [inline]
__dev_queue_xmit+0xf0a/0x3230 net/core/dev.c:4190
neigh_output include/net/neighbour.h:516 [inline]
ip6_finish_output2+0xee4/0x14f0 net/ipv6/ip6_output.c:126
dst_output include/net/dst.h:449 [inline]
NF_HOOK+0x166/0x4f0 include/linux/netfilter.h:307
mld_sendpack+0x70e/0xc10 net/ipv6/mcast.c:1820
mld_send_cr net/ipv6/mcast.c:2121 [inline]
mld_ifc_work+0x7d7/0xc90 net/ipv6/mcast.c:2653
process_one_work+0x8a1/0x10c0 kernel/workqueue.c:2307
worker_thread+0xaca/0x1280 kernel/workqueue.c:2454
kthread+0x3f6/0x4f0 kernel/kthread.c:319
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298
</TASK>


---
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#syz undup

syzbot has found a reproducer for the following issue on:

HEAD commit: c16c81c81336 Linux 5.15.178
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16eec9b0580000
kernel config: https://syzkaller.appspot.com/x/.config?x=d302c69e93fb6774
dashboard link: https://syzkaller.appspot.com/bug?extid=42b636738d776704a740
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=158c14e4580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17c57718580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/267e46ee7273/disk-c16c81c8.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/944e289206cf/vmlinux-c16c81c8.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f8cadf62458e/bzImage-c16c81c8.xz
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P154/1:b..l
(detected by 1, t=10502 jiffies, g=6517, q=381)
task:kworker/u4:2 state:R running task stack:23832 pid: 154 ppid: 2 flags:0x00004000
context_switch kernel/sched/core.c:5027 [inline]
__schedule+0x12c4/0x45b0 kernel/sched/core.c:6373
preempt_schedule_irq+0xf7/0x1c0 kernel/sched/core.c:6777
irqentry_exit+0x53/0x80 kernel/entry/common.c:432
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:rcu_is_watching+0x63/0xa0 kernel/rcu/tree.c:1124
Code: 89 f7 e8 30 34 5f 00 48 c7 c3 c8 b2 03 00 49 03 1e 48 89 d8 48 c1 e8 03 42 0f b6 04 38 84 c0 75 1a 8b 03 65 ff 0d e5 35 97 7e <74> 08 24 01 5b 41 5e 41 5f c3 e8 c6 52 95 ff eb f1 89 d9 80 e1 07
RSP: 0018:ffffc90001eb7a60 EFLAGS: 00000286
RAX: 00000000000067b7 RBX: ffff8880b8e3b2c8 RCX: ffffffff8162cdec
RDX: 0000000000000000 RSI: ffffffff8af9f2a0 RDI: ffffffff8af9f260
RBP: ffffc90001eb7bd8 R08: dffffc0000000000 R09: fffffbfff1c150ee
R10: 0000000000000000 R11: dffffc0000000001 R12: 1ffff920003d6f58
R13: dffffc0000000000 R14: ffffffff8c5cc810 R15: dffffc0000000000
trace_lock_acquire include/trace/events/lock.h:13 [inline]
lock_acquire+0xdd/0x4f0 kernel/locking/lockdep.c:5594
rcu_lock_acquire+0x2a/0x30 include/linux/rcupdate.h:312
rcu_read_lock include/linux/rcupdate.h:739 [inline]
batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:412 [inline]
batadv_nc_worker+0xc1/0x5b0 net/batman-adv/network-coding.c:723
process_one_work+0x8a1/0x10c0 kernel/workqueue.c:2310
worker_thread+0xaca/0x1280 kernel/workqueue.c:2457
kthread+0x3f6/0x4f0 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>
rcu: rcu_preempt kthread starved for 10528 jiffies! g6517 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
task:rcu_preempt state:R running task stack:26144 pid: 15 ppid: 2 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5027 [inline]
__schedule+0x12c4/0x45b0 kernel/sched/core.c:6373
schedule+0x11b/0x1f0 kernel/sched/core.c:6456
schedule_timeout+0x1b9/0x300 kernel/time/timer.c:1914
rcu_gp_fqs_loop+0x2bf/0x1080 kernel/rcu/tree.c:1972
rcu_gp_kthread+0xa4/0x360 kernel/rcu/tree.c:2145
kthread+0x3f6/0x4f0 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
CPU: 1 PID: 4231 Comm: syz-executor185 Not tainted 5.15.178-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2d0 lib/dump_stack.c:106
nmi_cpu_backtrace+0x46a/0x4a0 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x181/0x2a0 lib/nmi_backtrace.c:62
trigger_single_cpu_backtrace include/linux/nmi.h:166 [inline]
rcu_check_gp_kthread_starvation+0x1d2/0x240 kernel/rcu/tree_stall.h:487
print_other_cpu_stall+0x137a/0x14d0 kernel/rcu/tree_stall.h:592
check_cpu_stall kernel/rcu/tree_stall.h:745 [inline]
rcu_pending kernel/rcu/tree.c:3932 [inline]
rcu_sched_clock_irq+0xa38/0x1150 kernel/rcu/tree.c:2619
update_process_times+0x196/0x200 kernel/time/timer.c:1818
tick_sched_handle kernel/time/tick-sched.c:254 [inline]
tick_sched_timer+0x386/0x550 kernel/time/tick-sched.c:1473
__run_hrtimer kernel/time/hrtimer.c:1688 [inline]
__hrtimer_run_queues+0x55b/0xcf0 kernel/time/hrtimer.c:1752
hrtimer_interrupt+0x392/0x980 kernel/time/hrtimer.c:1814
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
__sysvec_apic_timer_interrupt+0x13b/0x4b0 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:lock_acquire+0x252/0x4f0 kernel/locking/lockdep.c:5627
Code: 2b 00 74 08 4c 89 f7 e8 9c 9e 67 00 f6 44 24 61 02 0f 85 84 01 00 00 41 f7 c7 00 02 00 00 74 01 fb 48 c7 44 24 40 0e 36 e0 45 <4b> c7 44 25 00 00 00 00 00 43 c7 44 25 09 00 00 00 00 43 c7 44 25
RSP: 0018:ffffc9000303f9c0 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 1ffff92000607f44 RCX: ffffffff816389a2
RDX: dffffc0000000000 RSI: ffffffff8aab3e20 RDI: ffffffff8af9f2c0
RBP: ffffc9000303fb18 R08: dffffc0000000000 R09: fffffbfff2131827
R10: 0000000000000000 R11: dffffc0000000001 R12: 1ffff92000607f40
R13: dffffc0000000000 R14: ffffc9000303fa20 R15: 0000000000000246
__might_fault+0xb4/0x110 mm/memory.c:5355
rseq_get_rseq_cs kernel/rseq.c:131 [inline]
rseq_ip_fixup kernel/rseq.c:244 [inline]
__rseq_handle_notify_resume+0x11b/0x1250 kernel/rseq.c:292
rseq_handle_notify_resume include/linux/sched.h:2204 [inline]
rseq_signal_deliver include/linux/sched.h:2213 [inline]
setup_rt_frame arch/x86/kernel/signal.c:769 [inline]
handle_signal arch/x86/kernel/signal.c:824 [inline]
arch_do_signal_or_restart+0x27d/0x1890 arch/x86/kernel/signal.c:869
handle_signal_work kernel/entry/common.c:154 [inline]
exit_to_user_mode_loop+0x97/0x130 kernel/entry/common.c:178
exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:214
__syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
syscall_exit_to_user_mode+0x5d/0x240 kernel/entry/common.c:307
do_syscall_64+0x47/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f25d2d4e627
Code: 14 25 28 00 00 00 75 05 48 83 c4 28 c3 e8 91 1a 00 00 90 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 b0 ff ff ff f7 d8 64 89
RSP: 002b:00007f25d2d08218 EFLAGS: 00000246
RAX: 00000000000000ca RBX: 00007f25d2dd63e8 RCX: 00007f25d2d4e629
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f25d2dd63e8
RBP: 00007f25d2dd63e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f25d2da2600
R13: 0000400000000100 R14: 0000400000000680 R15: 000040000006b000
</TASK>
sched: RT throttling activated


---
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