[v5.15] INFO: rcu detected stall in sys_wait4 (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: b9d57c40a767 Linux 5.15.203
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1018e2ce580000
kernel config: https://syzkaller.appspot.com/x/.config?x=353ae28c40b35af5
dashboard link: https://syzkaller.appspot.com/bug?extid=4837511a1b851eda355e
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/1b2ee9aebbe3/disk-b9d57c40.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e5742bf875d7/vmlinux-b9d57c40.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5175fafcf12a/bzImage-b9d57c40.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+483751...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 0-....: (1 GPs behind) idle=65f/1/0x4000000000000002 softirq=7422/7423 fqs=5207
(detected by 1, t=10502 jiffies, g=7877, q=5184)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4185 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:rcu_is_watching+0x63/0xa0 kernel/rcu/tree.c:1124
Code: 89 f7 e8 00 73 59 00 48 c7 c3 08 b3 03 00 49 03 1e 48 89 d8 48 c1 e8 03 42 0f b6 04 38 84 c0 75 2b 8b 03 65 ff 0d 45 8f 9d 7e <74> 08 24 01 5b 41 5e 41 5f c3 e8 a6 9c 9b ff eb f1 48 c7 c7 a0 37
RSP: 0018:ffffc90000007a08 EFLAGS: 00000002
RAX: 000000000000765f RBX: ffff8880b903b308 RCX: 1a1d0dff7fbdff00
RDX: 0000000000000000 RSI: ffffffff8a79fe20 RDI: ffffffff8a79fde0
RBP: 0000000000000000 R08: ffffffff8d89f06f R09: 1ffffffff1b13e0d
R10: dffffc0000000000 R11: fffffbfff1b13e0e R12: 0000000000000000
R13: 0000000000000000 R14: ffffffff8be33820 R15: dffffc0000000000
FS: 00005555838ca500(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000005c00000000 CR3: 0000000064af1000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
<IRQ>
trace_irq_work_exit arch/x86/include/asm/trace/irq_vectors.h:64 [inline]
__sysvec_irq_work+0xcf/0x240 arch/x86/kernel/irq_work.c:23
instr_sysvec_irq_work arch/x86/kernel/irq_work.c:17 [inline]
sysvec_irq_work+0x4a/0xc0 arch/x86/kernel/irq_work.c:17
asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:713
RIP: 0010:rcu_read_unlock_special+0x7f/0x4a0 kernel/rcu/tree_plugin.h:674
Code: eb 03 48 b8 f1 f1 f1 f1 f8 f2 f2 f2 4a 89 04 2b 42 c7 44 2b 08 f8 f3 f3 f3 65 44 8b 35 32 e1 9c 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 20 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc90000007b00 EFLAGS: 00000206
RAX: 1a1d0dff7fbdff00 RBX: 1ffff92000000f64 RCX: 1a1d0dff7fbdff00
RDX: dffffc0000000000 RSI: ffffffff8a2b2800 RDI: ffffffff8a79fe40
RBP: ffffc90000007bd8 R08: ffff8880b903b30b R09: 1ffff11017207661
R10: dffffc0000000000 R11: ffffed1017207662 R12: ffffffff8c323000
R13: dffffc0000000000 R14: 0000000000000246 R15: 0000000000000001
__rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:422
rcu_read_unlock include/linux/rcupdate.h:772 [inline]
ieee80211_iterate_active_interfaces_atomic+0x132/0x140 net/mac80211/util.c:831
mac80211_hwsim_beacon+0x9b/0x180 drivers/net/wireless/mac80211_hwsim.c:1865
__run_hrtimer kernel/time/hrtimer.c:1685 [inline]
__hrtimer_run_queues+0x4f2/0xb70 kernel/time/hrtimer.c:1749
hrtimer_run_softirq+0x176/0x240 kernel/time/hrtimer.c:1766
handle_softirqs+0x339/0x830 kernel/softirq.c:576
__do_softirq kernel/softirq.c:610 [inline]
invoke_softirq kernel/softirq.c:450 [inline]
__irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659
irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
sysvec_apic_timer_interrupt+0xa0/0xc0 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:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xbc/0x120 kernel/locking/spinlock.c:194
Code: c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f7 44 24 20 00 02 00 00 41 c6 04 07 f8 75 4b f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> 5f 29 8c f7 65 8b 05 f0 26 3c 76 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc90002effb40 EFLAGS: 00000206
RAX: dffffc0000000004 RBX: 0000000000000a06 RCX: 1a1d0dff7fbdff00
RDX: dffffc0000000000 RSI: ffffffff8a2b2800 RDI: 0000000000000001
RBP: ffffc90002effbc0 R08: ffff8880b903b30b R09: 1ffff11017207661
R10: dffffc0000000000 R11: ffffed1017207662 R12: dffffc0000000000
R13: ffffc90002effcc8 R14: ffff8880217bc120 R15: 1ffff920005dff68
do_wait+0x8ff/0xac0 kernel/exit.c:1614
kernel_wait4+0x22b/0x2b0 kernel/exit.c:1752
__do_sys_wait4 kernel/exit.c:1780 [inline]
__se_sys_wait4 kernel/exit.c:1776 [inline]
__x64_sys_wait4+0x163/0x230 kernel/exit.c:1776
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: 0033:0x7f61b197460e
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 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08
RSP: 002b:00007ffe676fcea8 EFLAGS: 00000246 ORIG_RAX: 000000000000003d
RAX: ffffffffffffffda RBX: 00005555838ca500 RCX: 00007f61b197460e
RDX: 0000000040000001 RSI: 00007ffe676fcf4c RDI: ffffffffffffffff
RBP: 00007ffe676fcf4c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000001388
R13: 00000000000927c0 R14: 00000000000168d9 R15: 00007ffe676fcfa0
</TASK>


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