Re: [v6.1] INFO: rcu detected stall in sys_futex

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 1989cd3d56e2 Linux 6.1.167
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11ee3302580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0605c5af04d7603
dashboard link: https://syzkaller.appspot.com/bug?extid=97f2ac670e5e7a3b48e4
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17907bd6580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12091bca580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/3e0cf5574b81/disk-1989cd3d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0c1152de55b1/vmlinux-1989cd3d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3fe87e3166b1/bzImage-1989cd3d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+97f2ac...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 1-.... } 2630 jiffies s: 27637 root: 0x2/.
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 18418 Comm: syz.1.6409 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
RIP: 0010:check_kcov_mode kernel/kcov.c:182 [inline]
RIP: 0010:write_comp_data kernel/kcov.c:245 [inline]
RIP: 0010:__sanitizer_cov_trace_const_cmp8+0x2a/0x80 kernel/kcov.c:320
Code: 48 8b 04 24 65 48 8b 0d c4 f6 7f 7e 65 8b 15 c5 f6 7f 7e 81 e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75 57 83 b9 1c 16 00 00 00 <74> 4e 8b 91 f8 15 00 00 83 fa 03 75 43 48 8b 91 00 16 00 00 44 8b
RSP: 0018:ffffc900001e01b8 EFLAGS: 00000046
RAX: ffffffff813a0f35 RBX: 00000000b8f3b9f0 RCX: ffff88802ababb80
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000001 R08: ffff8880b8f3b9fb R09: 1ffff110171e773f
R10: dffffc0000000000 R11: ffffed10171e7740 R12: 0000000000000000
R13: dffffc0000000001 R14: 000000000000002e R15: 0000000000000000
FS: 00007f39a6c7a6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000037079fec9000 CR3: 000000007d690000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<IRQ>
phys_addr_valid arch/x86/mm/physaddr.h:7 [inline]
__virt_addr_valid+0xb5/0x540 arch/x86/mm/physaddr.c:61
kasan_addr_to_slab+0x9/0xc0 mm/kasan/common.c:36
__kasan_record_aux_stack+0xf/0xc0 mm/kasan/generic.c:471
irq_work_queue_on+0x10f/0x260 kernel/irq_work.c:140
rcu_read_unlock_special+0x3c9/0x510 kernel/rcu/tree_plugin.h:678
__rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
rcu_read_unlock include/linux/rcupdate.h:823 [inline]
__perf_event_output kernel/events/core.c:7741 [inline]
perf_event_output_forward+0x271/0x2f0 kernel/events/core.c:7750
__perf_event_overflow+0x448/0x610 kernel/events/core.c:9496
perf_swevent_overflow kernel/events/core.c:9579 [inline]
perf_swevent_event+0x315/0x570 kernel/events/core.c:9630
perf_tp_event+0x3e7/0xc30 kernel/events/core.c:10064
perf_trace_run_bpf_submit+0xf3/0x1c0 kernel/events/core.c:10032
perf_trace_preemptirq_template+0x268/0x320 include/trace/events/preemptirq.h:14
trace_irq_enable_rcuidle+0xd3/0x140 include/trace/events/preemptirq.h:40
trace_hardirqs_on+0x24/0x40 kernel/trace/trace_preemptirq.c:44
asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:728
RIP: 0010:rcu_read_unlock_special+0x7f/0x510 kernel/rcu/tree_plugin.h:685
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 d2 33 95 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 40 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc900001e0ac0 EFLAGS: 00000206
RAX: 6f28316e77106700 RBX: 1ffff9200003c160 RCX: 6f28316e77106700
RDX: dffffc0000000000 RSI: ffffffff8a8c10a0 RDI: ffffffff8adf0d20
RBP: ffffc900001e0bc0 R08: ffff8880b8f3580b R09: 1ffff110171e6b01
R10: dffffc0000000000 R11: ffffed10171e6b02 R12: 0000000000000246
R13: dffffc0000000000 R14: ffff8880b8f3b900 R15: 0000000000000002
__rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
rcu_read_unlock include/linux/rcupdate.h:823 [inline]
ieee80211_rx_napi+0x221/0x3d0 net/mac80211/rx.c:5339
ieee80211_rx include/net/mac80211.h:4849 [inline]
ieee80211_handle_queued_frames+0x105/0x1b0 net/mac80211/main.c:317
tasklet_action_common+0x2fe/0x4d0 kernel/softirq.c:827
handle_softirqs+0x2a1/0x930 kernel/softirq.c:596
__do_softirq kernel/softirq.c:630 [inline]
invoke_softirq kernel/softirq.c:470 [inline]
__irq_exit_rcu+0x13b/0x230 kernel/softirq.c:679
irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1118
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:finish_task_switch+0x26a/0x8f0 kernel/sched/core.c:5124
Code: 0f 84 3b 01 00 00 48 85 db 0f 85 5a 01 00 00 0f 1f 44 00 00 4c 8b 75 d0 4c 89 e7 e8 00 2c de 08 e8 8b 2c 2f 00 fb 4c 8b 65 c0 <49> 8d bc 24 f8 15 00 00 48 89 f8 48 c1 e8 03 42 0f b6 04 28 84 c0
RSP: 0018:ffffc900048ef8f8 EFLAGS: 00000282
RAX: 6f28316e77106700 RBX: 0000000000000000 RCX: 6f28316e77106700
RDX: dffffc0000000000 RSI: ffffffff8a8c10a0 RDI: ffffffff8adf0d20
RBP: ffffc900048ef950 R08: ffff8880b8f3580b R09: 1ffff110171e6b01
R10: dffffc0000000000 R11: ffffed10171e6b02 R12: ffff88802ababb80
R13: dffffc0000000000 R14: ffff88802e5c9dc0 R15: ffff8880b8f3b5d0
context_switch kernel/sched/core.c:5248 [inline]
__schedule+0x11d9/0x40e0 kernel/sched/core.c:6562
schedule+0xb9/0x180 kernel/sched/core.c:6638
futex_wait_queue+0x134/0x1b0 kernel/futex/waitwake.c:355
futex_wait+0x1e8/0x5e0 kernel/futex/waitwake.c:656
do_futex+0x310/0x320 kernel/futex/syscalls.c:134
__do_sys_futex kernel/futex/syscalls.c:211 [inline]
__se_sys_futex+0x381/0x410 kernel/futex/syscalls.c:192
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f39a5d9c819
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:00007f39a6c7a0e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 00007f39a6015fa8 RCX: 00007f39a5d9c819
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f39a6015fa8
RBP: 00007f39a6015fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f39a6016038 R14: 00007ffdbedf94a0 R15: 00007ffdbedf9588
</TASK>


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