syzbot

map[ReproOpts:{
 "pkg/conf": {
  "EnableCgroups": true,
  "EnableNetDevices": true
 },
 "pkg/repro": {
  "Repeat": true
 }
} ReproSyz:sigaltstack(&(0x7f0000000000)={0x7f0000001000, 0x0, 0x1000}, 0x0)
timer_create(0x1, 0x0, &(0x7f0000000040))
timer_settime(0x0, 0x0, &(0x7f0000000080)={{0x0, 0x1}, {0x0, 0x1}}, 0x0)
 SyzkallerCommit:31e9c887f7dc24e04b3ca70d0d54fc34141844b0]

map[DescriptionFiles:[acpi_thermal_rel.txt aio.txt auto.txt binfmt.txt bpf.txt bpf_prog.txt bpf_trace.txt cgroup.txt damon.txt dev_ashmem.txt dev_bifrost.txt dev_binder.txt dev_binderfs.txt dev_block.txt dev_bsg.txt dev_bus_usb.txt dev_camx.txt dev_cdrom.txt dev_cec.txt dev_char_usb.txt dev_comedi.txt dev_dma_heap.txt dev_dri.txt dev_dsp.txt dev_dvb_demux.txt dev_dvb_dvr.txt dev_dvb_frontend.txt dev_fb.txt dev_floppy.txt dev_hidraw.txt dev_i2c.txt dev_i915.txt dev_img_rogue.txt dev_infiniband_rdma.txt dev_infiniband_rdma_cm.txt dev_input.txt dev_iommu.txt dev_kvm.txt dev_kvm_amd64.txt dev_kvm_arm64.txt dev_kvm_extra.txt dev_kvm_riscv64.txt dev_loop.txt dev_mali.txt dev_media.txt dev_msm.txt dev_msr.txt dev_nbd.txt dev_net_tun.txt dev_panthor.txt dev_ppp.txt dev_ptmx.txt dev_ptp.txt dev_qat_adf_ctl.txt dev_qrtr_tun.txt dev_random.txt dev_rfkill.txt dev_rtc.txt dev_sequencer.txt dev_sg.txt dev_snapshot.txt dev_snd_control.txt dev_snd_hw.txt dev_snd_midi.txt dev_snd_pcm.txt dev_snd_seq.txt dev_snd_timer.txt dev_sr.txt dev_sw_sync.txt dev_tlk_device.txt dev_trusty.txt dev_udmabuf.txt dev_uhid.txt dev_uinput.txt dev_usb_hiddev.txt dev_usbmon.txt dev_userio.txt dev_vfio.txt dev_vga_arbiter.txt dev_vhci.txt dev_video4linux.txt dev_video4linux_vim2m.txt dev_virtual_nci.txt dev_vtpm.txt fanotify.txt filesystem.txt fs_9p.txt fs_fuse.txt fs_incfs.txt fs_ioctl.txt fs_ioctl_autofs.txt fs_ioctl_btrfs.txt fs_ioctl_ext4.txt fs_ioctl_f2fs.txt fs_ioctl_fat.txt fs_ioctl_fscrypt.txt fs_ioctl_fsverity.txt fs_ioctl_xfs.txt futex.txt hafnium.txt inotify.txt io_uring.txt ipc.txt key.txt kfuzztest.txt l2cap.txt landlock.txt lsm.txt namespaces.txt net_80211.txt netfilter.txt netfilter_arp.txt netfilter_bridge.txt netfilter_ipv4.txt netfilter_ipv6.txt netfilter_ipvs.txt netfilter_targets.txt pagemap_ioctl.txt perf.txt prctl.txt quotactl.txt seccomp.txt security_apparmor.txt security_selinux.txt security_smack.txt socket.txt socket_alg.txt socket_ax25.txt socket_bluetooth.txt socket_caif.txt socket_can.txt socket_ieee802154.txt socket_inet.txt socket_inet6.txt socket_inet_dccp.txt socket_inet_icmp.txt socket_inet_igmp.txt socket_inet_l2tp.txt socket_inet_sctp.txt socket_inet_tcp.txt socket_inet_udp.txt socket_ip_tunnel.txt socket_isdn.txt socket_kcm.txt socket_key.txt socket_llc.txt socket_netlink.txt socket_netlink_audit.txt socket_netlink_crypto.txt socket_netlink_generic.txt socket_netlink_generic_80211.txt socket_netlink_generic_batadv.txt socket_netlink_generic_devlink.txt socket_netlink_generic_ethtool.txt socket_netlink_generic_fou.txt socket_netlink_generic_gtp.txt socket_netlink_generic_mptcp.txt socket_netlink_generic_net_dm.txt socket_netlink_generic_netlabel.txt socket_netlink_generic_nfc.txt socket_netlink_generic_seg6.txt socket_netlink_generic_smc.txt socket_netlink_generic_team.txt socket_netlink_generic_wireguard.txt socket_netlink_netfilter.txt socket_netlink_netfilter_acct.txt socket_netlink_netfilter_conntrack.txt socket_netlink_netfilter_conntrack_exp.txt socket_netlink_netfilter_conntrack_helper.txt socket_netlink_netfilter_ipset.txt socket_netlink_netfilter_log.txt socket_netlink_netfilter_nft_compat.txt socket_netlink_netfilter_nftables.txt socket_netlink_netfilter_osf.txt socket_netlink_netfilter_queue.txt socket_netlink_netfilter_timeout.txt socket_netlink_rdma.txt socket_netlink_route.txt socket_netlink_route_sched.txt socket_netlink_route_sched_retired.txt socket_netlink_sock_diag.txt socket_netlink_xfrm.txt socket_netrom.txt socket_nfc.txt socket_nvme_of_tcp.txt socket_packet.txt socket_phonet.txt socket_pppox.txt socket_qipcrtr.txt socket_rds.txt socket_rose.txt socket_rxrpc.txt socket_tipc.txt socket_tipc_netlink.txt socket_unix.txt socket_vnet.txt socket_x25.txt socket_xdp.txt sys.txt uffd.txt usbip.txt vmw_vmci.txt vnet.txt vnet_mptcp.txt vusb.txt watch_queue.txt xattr.txt] SyzkallerCommit:31e9c887f7dc24e04b3ca70d0d54fc34141844b0]

map[KernelSrc:/usr/local/google/home/dvyukov/syzkaller/agent/workdir/cache/src/9e6908b28e91d9ec5708b9c726ef692ee016f4f7]

map[KernelObj:/usr/local/google/home/dvyukov/syzkaller/agent/workdir/cache/build/e5384555a205a161c0c6677ef857f29073aa396f]

gemini-3-pro-preview

map[ReproOpts:{
 "pkg/conf": {
  "EnableCgroups": true,
  "EnableNetDevices": true
 },
 "pkg/repro": {
  "Repeat": true
 }
}]

You are an expert in linux kernel fuzzing. Your goal is to write a syzkaller program to trigger a specific bug.
Print only the syz program that could be executed directly, without backticks.




Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.

Bug Title: INFO: rcu detected stall in sys_rt_sigreturn

Original Crash Report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5193/2:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=45357, q=755 ncpus=2)
task:udevd           state:R  running task     stack:24368 pid:5193  tgid:5193  ppid:1      task_flags:0x400140 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x149b/0x4fd0 kernel/sched/core.c:6863
 preempt_schedule_common+0x83/0xd0 kernel/sched/core.c:7047
 preempt_schedule_thunk+0x16/0x30 arch/x86/entry/thunk.S:12
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
 _raw_spin_unlock_irqrestore+0x74/0x80 kernel/locking/spinlock.c:194
 spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
 unlock_task_sighand include/linux/sched/signal.h:756 [inline]
 do_send_sig_info kernel/signal.c:1270 [inline]
 group_send_sig_info+0x233/0x260 kernel/signal.c:1419
 kill_pid_info_type+0xf8/0x1f0 kernel/signal.c:1459
 kill_pid_info kernel/signal.c:1473 [inline]
 kill_proc_info+0xd9/0x180 kernel/signal.c:1480
 kill_something_info kernel/signal.c:1577 [inline]
 __do_sys_kill kernel/signal.c:3953 [inline]
 __se_sys_kill+0xc4/0x450 kernel/signal.c:3947
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb61325f357
RSP: 002b:00007ffffa6d6db8 EFLAGS: 00000297 ORIG_RAX: 000000000000003e
RAX: ffffffffffffffda RBX: 00007ffffa6d6dc0 RCX: 00007fb61325f357
RDX: 000055f38480c550 RSI: 000000000000000f RDI: 00000000000025fd
RBP: 0000000000000000 R08: 0000000000000010 R09: 000055f3847b78e0
R10: 0000000000000000 R11: 0000000000000297 R12: 0000000000000000
R13: 000055f345029100 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
rcu: rcu_preempt kthread starved for 10517 jiffies! g45357 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->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:R  running task     stack:27792 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x149b/0x4fd0 kernel/sched/core.c:6863
 __schedule_loop kernel/sched/core.c:6945 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:6960
 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+0x510/0xa50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 10337 Comm: syz.3.742 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:preempt_count_add+0x13/0x190 kernel/sched/core.c:5719
Code: 0f 1f 80 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 41 57 41 56 53 49 bf 00 00 00 00 00 fc ff df <48> c7 c0 20 54 8b 99 48 c1 e8 03 42 0f b6 04 38 84 c0 0f 85 eb 00
RSP: 0018:ffffc90000007bb8 EFLAGS: 00000096
RAX: b338031c9fd1dd00 RBX: ffff8880593e9e80 RCX: ffffffff81870d04
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000001
RBP: ffff8880593e9e80 R08: ffff8880593e9e87 R09: 1ffff1100b27d3d0
R10: dffffc0000000000 R11: ffffed100b27d3d1 R12: dffffc0000000000
R13: ffff8880306ecc00 R14: 0000000000000000 R15: dffffc0000000000
FS:  00007f9ef358a6c0(0000) GS:ffff888125e1f000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fca75ae8d58 CR3: 000000007b493000 CR4: 0000000000350ef0
Call Trace:
 <IRQ>
 class_preempt_constructor include/linux/preempt.h:468 [inline]
 try_to_wake_up+0x3c/0x12b0 kernel/sched/core.c:4070
 signal_wake_up_state+0xb5/0x120 kernel/signal.c:734
 posixtimer_send_sigqueue+0x404/0xa70 kernel/signal.c:2080
 posix_timer_queue_signal kernel/time/posix-timers.c:364 [inline]
 posix_timer_fn+0x121/0x1c0 kernel/time/posix-timers.c:379
 __run_hrtimer kernel/time/hrtimer.c:1777 [inline]
 __hrtimer_run_queues+0x51c/0xc30 kernel/time/hrtimer.c:1841
 hrtimer_interrupt+0x45b/0xaa0 kernel/time/hrtimer.c:1903
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1045 [inline]
 __sysvec_apic_timer_interrupt+0x102/0x3e0 arch/x86/kernel/apic/apic.c:1062
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline]
 sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1056
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:do_sigaltstack include/linux/sched/signal.h:-1 [inline]
RIP: 0010:restore_altstack+0x1f8/0x4b0 kernel/signal.c:4463
Code: 89 df 4c 89 fe e8 e8 8e 38 00 4c 39 fb 0f 86 72 02 00 00 e8 7a 8c 38 00 eb 0c e8 73 8c 38 00 eb 09 e8 6c 8c 38 00 4c 8b 3c 24 <44> 8b 6c 24 0c 41 81 e5 ff ff ff 7f bf 03 00 00 00 44 89 ee e8 8f
RSP: 0018:ffffc90005327ba0 EFLAGS: 00000293
RAX: ffffffff81886c36 RBX: 00007f9ef3589b40 RCX: ffff8880593e9e80
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00007f9ef3589b40
RBP: ffffc90005327c90 R08: ffffc90005327c17 R09: 1ffff92000a64f82
R10: dffffc0000000000 R11: fffff52000a64f83 R12: 1ffff92000a64f7c
R13: ffff8880593ea828 R14: 0000000000000002 R15: ffff8880593e9e80
 __ia32_sys_rt_sigreturn+0x281/0x860 arch/x86/kernel/signal_64.c:265
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f9ef272b829
Code: 64 c7 00 16 00 00 00 b8 ff ff ff ff c3 0f 1f 40 00 90 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 c7 c0 0f 00 00 00 0f 05 <0f> 1f 80 00 00 00 00 48 81 ec 48 01 00 00 49 89 d0 64 48 8b 04 25
RSP: 002b:00007f9ef3589b40 EFLAGS: 00000206 ORIG_RAX: 000000000000000f
RAX: ffffffffffffffda RBX: 00007f9ef29e6098 RCX: 00007f9ef272b829
RDX: 00007f9ef3589b40 RSI: 00007f9ef3589c70 RDI: 0000000000000021
RBP: 00007f9ef29e6090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007f9ef29e6128 R14: 00007ffd0e6a6570 R15: 00007ffd0e6a6658
 </TASK>


The list of existing description files:
acpi_thermal_rel.txt
aio.txt
auto.txt
binfmt.txt
bpf.txt
bpf_prog.txt
bpf_trace.txt
cgroup.txt
damon.txt
dev_ashmem.txt
dev_bifrost.txt
dev_binder.txt
dev_binderfs.txt
dev_block.txt
dev_bsg.txt
dev_bus_usb.txt
dev_camx.txt
dev_cdrom.txt
dev_cec.txt
dev_char_usb.txt
dev_comedi.txt
dev_dma_heap.txt
dev_dri.txt
dev_dsp.txt
dev_dvb_demux.txt
dev_dvb_dvr.txt
dev_dvb_frontend.txt
dev_fb.txt
dev_floppy.txt
dev_hidraw.txt
dev_i2c.txt
dev_i915.txt
dev_img_rogue.txt
dev_infiniband_rdma.txt
dev_infiniband_rdma_cm.txt
dev_input.txt
dev_iommu.txt
dev_kvm.txt
dev_kvm_amd64.txt
dev_kvm_arm64.txt
dev_kvm_extra.txt
dev_kvm_riscv64.txt
dev_loop.txt
dev_mali.txt
dev_media.txt
dev_msm.txt
dev_msr.txt
dev_nbd.txt
dev_net_tun.txt
dev_panthor.txt
dev_ppp.txt
dev_ptmx.txt
dev_ptp.txt
dev_qat_adf_ctl.txt
dev_qrtr_tun.txt
dev_random.txt
dev_rfkill.txt
dev_rtc.txt
dev_sequencer.txt
dev_sg.txt
dev_snapshot.txt
dev_snd_control.txt
dev_snd_hw.txt
dev_snd_midi.txt
dev_snd_pcm.txt
dev_snd_seq.txt
dev_snd_timer.txt
dev_sr.txt
dev_sw_sync.txt
dev_tlk_device.txt
dev_trusty.txt
dev_udmabuf.txt
dev_uhid.txt
dev_uinput.txt
dev_usb_hiddev.txt
dev_usbmon.txt
dev_userio.txt
dev_vfio.txt
dev_vga_arbiter.txt
dev_vhci.txt
dev_video4linux.txt
dev_video4linux_vim2m.txt
dev_virtual_nci.txt
dev_vtpm.txt
fanotify.txt
filesystem.txt
fs_9p.txt
fs_fuse.txt
fs_incfs.txt
fs_ioctl.txt
fs_ioctl_autofs.txt
fs_ioctl_btrfs.txt
fs_ioctl_ext4.txt
fs_ioctl_f2fs.txt
fs_ioctl_fat.txt
fs_ioctl_fscrypt.txt
fs_ioctl_fsverity.txt
fs_ioctl_xfs.txt
futex.txt
hafnium.txt
inotify.txt
io_uring.txt
ipc.txt
key.txt
kfuzztest.txt
l2cap.txt
landlock.txt
lsm.txt
namespaces.txt
net_80211.txt
netfilter.txt
netfilter_arp.txt
netfilter_bridge.txt
netfilter_ipv4.txt
netfilter_ipv6.txt
netfilter_ipvs.txt
netfilter_targets.txt
pagemap_ioctl.txt
perf.txt
prctl.txt
quotactl.txt
seccomp.txt
security_apparmor.txt
security_selinux.txt
security_smack.txt
socket.txt
socket_alg.txt
socket_ax25.txt
socket_bluetooth.txt
socket_caif.txt
socket_can.txt
socket_ieee802154.txt
socket_inet.txt
socket_inet6.txt
socket_inet_dccp.txt
socket_inet_icmp.txt
socket_inet_igmp.txt
socket_inet_l2tp.txt
socket_inet_sctp.txt
socket_inet_tcp.txt
socket_inet_udp.txt
socket_ip_tunnel.txt
socket_isdn.txt
socket_kcm.txt
socket_key.txt
socket_llc.txt
socket_netlink.txt
socket_netlink_audit.txt
socket_netlink_crypto.txt
socket_netlink_generic.txt
socket_netlink_generic_80211.txt
socket_netlink_generic_batadv.txt
socket_netlink_generic_devlink.txt
socket_netlink_generic_ethtool.txt
socket_netlink_generic_fou.txt
socket_netlink_generic_gtp.txt
socket_netlink_generic_mptcp.txt
socket_netlink_generic_net_dm.txt
socket_netlink_generic_netlabel.txt
socket_netlink_generic_nfc.txt
socket_netlink_generic_seg6.txt
socket_netlink_generic_smc.txt
socket_netlink_generic_team.txt
socket_netlink_generic_wireguard.txt
socket_netlink_netfilter.txt
socket_netlink_netfilter_acct.txt
socket_netlink_netfilter_conntrack.txt
socket_netlink_netfilter_conntrack_exp.txt
socket_netlink_netfilter_conntrack_helper.txt
socket_netlink_netfilter_ipset.txt
socket_netlink_netfilter_log.txt
socket_netlink_netfilter_nft_compat.txt
socket_netlink_netfilter_nftables.txt
socket_netlink_netfilter_osf.txt
socket_netlink_netfilter_queue.txt
socket_netlink_netfilter_timeout.txt
socket_netlink_rdma.txt
socket_netlink_route.txt
socket_netlink_route_sched.txt
socket_netlink_route_sched_retired.txt
socket_netlink_sock_diag.txt
socket_netlink_xfrm.txt
socket_netrom.txt
socket_nfc.txt
socket_nvme_of_tcp.txt
socket_packet.txt
socket_phonet.txt
socket_pppox.txt
socket_qipcrtr.txt
socket_rds.txt
socket_rose.txt
socket_rxrpc.txt
socket_tipc.txt
socket_tipc_netlink.txt
socket_unix.txt
socket_vnet.txt
socket_x25.txt
socket_xdp.txt
sys.txt
uffd.txt
usbip.txt
vmw_vmci.txt
vnet.txt
vnet_mptcp.txt
vusb.txt
watch_queue.txt
xattr.txt

sigaltstack(&(0x7f0000000000)={0x7f0000001000, 0x0, 0x1000}, 0x0)
timer_create(0x1, 0x0, &(0x7f0000000040))
timer_settime(0x0, 0x0, &(0x7f0000000080)={{0x0, 0x1}, {0x0, 0x1}}, 0x0)

gemini-3-pro-preview

							input: 5849
							output: 62
							thoughts: 15004
						

**RCU Stall in sys_rt_sigreturn: Reproduction Attempt**

Okay, so the goal is to trigger this "INFO: rcu detected stall in sys_rt_sigreturn" bug. The crash report points to an RCU stall on CPU 0, specifically during the `sys_rt_sigreturn` system call. The stack traces reveal a timer interrupt is occurring within `restore_altstack`, which is part of `rt_sigreturn`, while `udevd` is also present and appears to be blocked. It seems like a race between signal handling and timers is the culprit, potentially causing lock contention or a very tight loop that starves other processes and prevents RCU quiescent states from being reported.

The core of the problem seems to be the interaction between `rt_sigreturn` (called after a signal handler) and the timer interrupt.  I need to reproduce this. A good starting point involves creating a timer with a very short interval and setting up a signal handler, then repeatedly calling `rt_sigreturn`, either implicitly by triggering a signal, or potentially directly through a crafted program if syzkaller allows (but it looks like direct `rt_sigreturn` is difficult to generate, so a signal handler is the way to go).

To reproduce, I think I need to construct a syzkaller program that:

1.  Sets up an alternate signal stack using `sigaltstack` (important because `restore_altstack` is in the trace).
2.  Creates a timer using `timer_create` with a very small interval (e.g., 1 nanosecond) via `timer_settime`.
3.  Establishes a signal handler using `rt_sigaction`. The executor *already* sets up default handlers including SA\_ONSTACK, so I don't need a custom `rt_sigaction` call.
4.  Loop, which will happen automatically with the fast timer.

The `restore_altstack` function is key. It's called from `sys_rt_sigreturn` and accesses user memory. The crash is happening within it. The NMI backtrace showed that code. The timer interrupt is interrupting `restore_altstack`. This strongly suggests that a timer is firing, sending a signal, and the signal handler is being executed, which then *returns* from the handler which triggers `rt_sigreturn` which in turn calls `restore_altstack`. The small interval leads to a very tight loop, which blocks and stalls RCU.

The stalled `udevd` process suggests an overload issue where `udevd` is not able to get scheduled. The culprit is CPU 0 (the syzkaller program's CPU), which is stuck.

The syzkaller program should look something like:

```
sigaltstack(&(0x20000000)={0x20001000, 0x0, 0x1000}, 0x0)
timer_create(0x1, 0x0, &(0x20000100))
timer_settime(0x0, 0x0, &(0x20000200)={{0x0, 0x1}, {0x0, 0x1}}, 0x0)
```

I'm making the following assumptions in this code:

*   The timer ID returned by `timer_create` is 0 (first timer).
*   The addresses used for the data structures are valid and mapped.
*   The syzkaller executor sets up a signal handler with `SA_ONSTACK`, so the signal will run on the alternate stack.

This program should generate a very tight signal loop, causing an RCU stall as CPU 0 is overwhelmed by signal processing and `udevd` is unable to complete a RCU read side section due to starvation. This should reproduce the crash.

map[ReproOpts:{
 "pkg/conf": {
  "EnableCgroups": true,
  "EnableNetDevices": true
 },
 "pkg/repro": {
  "Repeat": true
 }
}]

map[ReproOpts:{
 "pkg/conf": {
  "EnableCgroups": true,
  "EnableNetDevices": true
 },
 "pkg/repro": {
  "Repeat": true
 }
}]

gemini-3-pro-preview

							input: 21812
							output: 140
							thoughts: 0