syzbot


INFO: rcu detected stall in task_work_run

Status: upstream: reported C repro on 2025/09/04 00:43
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+bd458038ebcbde78a479@syzkaller.appspotmail.com
First crash: 178d, last: 14d
Bug presence (2)
Date Name Commit Repro Result
2026/02/16 linux-6.1.y (ToT) 8ce36b2849ef C [report] INFO: rcu detected stall in corrupted
2026/02/16 upstream (ToT) 0f2acd3148e0 C Didn't crash
Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 INFO: rcu detected stall in task_work_run (3) origin:lts-only 1 syz error 6 12d 168d 0/3 upstream: reported syz repro on 2025/09/13 23:38
linux-5.15 INFO: rcu detected stall in task_work_run (2) origin:lts-only 1 syz error 1 455d 455d 0/3 auto-obsoleted due to no activity on 2025/03/24 21:44
linux-5.15 INFO: rcu detected stall in task_work_run 1 1 705d 705d 0/3 auto-obsoleted due to no activity on 2024/07/04 00:01
upstream INFO: rcu detected stall in task_work_run kernel 1 2 935d 985d 0/29 auto-obsoleted due to no activity on 2023/11/07 12:15
Fix bisection attempts (2)
Created Duration User Patch Repo Result
2026/02/16 07:47 19m fix candidate upstream error job log
2025/10/17 21:38 3h41m fix candidate upstream OK (0) job log

Sample crash report:
rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 0-.... } 2634 jiffies s: 3197 root: 0x1/.
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4498 Comm: syz.0.27 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:rcu_lockdep_current_cpu_online+0xf4/0x120 kernel/rcu/tree.c:780
Code: 48 c7 c7 80 34 b3 8c be 04 00 00 00 e8 c5 ec 66 00 83 3d 2e c0 46 0b 00 74 11 b0 01 65 ff 0d eb fa 95 7e 74 0a 5b 41 5e 41 5f <c3> 31 c0 eb ed e8 4a 0f 94 ff eb ef 48 c7 c7 80 26 b3 8c 48 89 de
RSP: 0018:ffffc90000007328 EFLAGS: 00000002
RAX: 1ffffffff1966501 RBX: 0000000000000000 RCX: 9dae53cd2246c500
RDX: ffff888079c81dc0 RSI: ffffffff8adf0d00 RDI: ffff8880b8e3b9e0
RBP: ffffc90000007470 R08: ffffc900000073f7 R09: ffffc900000073e0
R10: dffffc0000000000 R11: fffff52000000e7f R12: 1ffff92000000e78
R13: ffffc900000074c0 R14: 0000000000000030 R15: ffff888017773c00
FS:  000055557465b500(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b31963fff CR3: 000000002368d000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 rcu_read_lock_held_common kernel/rcu/update.c:112 [inline]
 rcu_read_lock_held+0x1a/0x40 kernel/rcu/update.c:309
 __perf_output_begin kernel/events/ring_buffer.c:170 [inline]
 perf_output_begin_forward+0x1d1/0xa80 kernel/events/ring_buffer.c:272
 __perf_event_output kernel/events/core.c:7732 [inline]
 perf_event_output_forward+0x1ad/0x2f0 kernel/events/core.c:7750
 __perf_event_overflow+0x448/0x610 kernel/events/core.c:9496
 perf_tp_event+0x38c/0xc00 kernel/events/core.c:10029
 perf_trace_run_bpf_submit+0xf3/0x1c0 kernel/events/core.c:10002
 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 92 31 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:ffffc90000007aa0 EFLAGS: 00000206
RAX: 9dae53cd2246c500 RBX: 1ffff92000000f5c RCX: 9dae53cd2246c500
RDX: dffffc0000000000 RSI: ffffffff8a8c1220 RDI: ffffffff8adf0d20
RBP: ffffc90000007b90 R08: ffff8880b8e3580b R09: 1ffff110171c6b01
R10: dffffc0000000000 R11: ffffed10171c6b02 R12: 0000000000000246
R13: dffffc0000000000 R14: ffff8880b8e3b900 R15: 0000000000000001
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
 rcu_read_unlock include/linux/rcupdate.h:823 [inline]
 ieee80211_iterate_active_interfaces_atomic+0x156/0x170 net/mac80211/util.c:826
 mac80211_hwsim_beacon+0xb7/0x1b0 drivers/net/wireless/mac80211_hwsim.c:2147
 __run_hrtimer kernel/time/hrtimer.c:1747 [inline]
 __hrtimer_run_queues+0x560/0xd70 kernel/time/hrtimer.c:1811
 hrtimer_run_softirq+0x183/0x2a0 kernel/time/hrtimer.c:1828
 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:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:160 [inline]
RIP: 0010:_raw_spin_unlock_irq+0x25/0x40 kernel/locking/spinlock.c:202
Code: 00 00 00 66 90 53 48 89 fb 48 83 c7 18 48 8b 74 24 08 e8 9e 12 2e f7 48 89 df e8 e6 da 2e f7 e8 c1 2d 52 f7 fb bf 01 00 00 00 <e8> 86 3b 22 f7 65 8b 05 47 c0 cb 75 85 c0 74 02 5b c3 e8 94 d4 c9
RSP: 0018:ffffc900033c7df0 EFLAGS: 00000286
RAX: 9dae53cd2246c500 RBX: ffff888079c827c0 RCX: 9dae53cd2246c500
RDX: dffffc0000000000 RSI: ffffffff8a8c1220 RDI: 0000000000000001
RBP: ffffc900033c7ec0 R08: ffff8880b8e3580b R09: 1ffff110171c6b01
R10: dffffc0000000000 R11: ffffed10171c6b02 R12: dffffc0000000000
R13: ffff888079ff6500 R14: ffff888079c827c0 R15: ffff888079c82728
 task_work_run+0x193/0x260 kernel/task_work.c:199
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f3b7dd9bf79
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:00007fffbbab6d48 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fffbbab6e30 RCX: 00007f3b7dd9bf79
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 000000000007fc4f R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b30d20000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f3b7e015fac R14: 00007f3b7e015fa8 R15: 00007f3b7e015fa0
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/02/15 20:09 linux-6.1.y 8ce36b2849ef 1e62d198 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in task_work_run
2025/09/04 00:42 linux-6.1.y f89b6e15694c 96a211bc .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in task_work_run
* Struck through repros no longer work on HEAD.