BUG: soft lockup in hsr_announce

Status: upstream: reported C repro on 2026/05/28 20:15
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+275266cebc6586d5795e@syzkaller.appspotmail.com
First crash: 59d, last: 2d05h
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/07/05 linux-6.6.y (ToT) da47cbc25466 C [report] INFO: rcu detected stall in hsr_announce
2026/07/05 upstream (ToT) 7404ce516372 C Didn't crash
▶ ▼ Similar bugs (22)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.19 BUG: soft lockup in hsr_announce (2) 1 7 1377d 1832d 0/1 auto-obsoleted due to no activity on 2023/02/15 11:56
upstream BUG: soft lockup in hsr_announce (2) net 1 3 1032d 1041d 0/29 auto-obsoleted due to no activity on 2023/12/27 12:08
linux-4.14 BUG: soft lockup in hsr_announce 1 C error 1 2396d 2396d 0/1 upstream: reported C repro on 2020/01/03 03:56
linux-4.19 BUG: soft lockup in hsr_announce 1 2 2074d 2100d 0/1 auto-closed as invalid on 2021/03/20 09:02
upstream BUG: soft lockup in hsr_announce (3) prio:normal net 1 syz 38 29d 459d 0/29 upstream: reported syz repro on 2025/04/23 07:51
upstream INFO: rcu detected stall in hsr_announce (7) net 1 30 530d 530d 0/29 closed as invalid on 2025/03/17 11:18
upstream BUG: soft lockup in hsr_announce net 1 2 2431d 2430d 0/29 closed as invalid on 2019/11/30 16:49
linux-6.1 INFO: rcu detected stall in hsr_announce 1 3 591d 691d 0/3 auto-obsoleted due to no activity on 2025/03/22 17:50
linux-6.1 INFO: rcu detected stall in hsr_announce (2) 1 2 239d 266d 0/3 auto-obsoleted due to no activity on 2026/03/09 02:56
upstream INFO: rcu detected stall in hsr_announce (5) net 1 4 1714d 1727d 0/29 closed as invalid on 2022/02/08 10:00
upstream INFO: rcu detected stall in hsr_announce (6) kvm 1 2 1552d 1552d 0/29 auto-closed as invalid on 2022/06/25 07:59
linux-5.15 INFO: rcu detected stall in hsr_announce (3) 1 5 147d 208d 0/3 auto-obsoleted due to no activity on 2026/06/09 03:32
linux-6.1 INFO: rcu detected stall in hsr_announce (3) 1 3 16d 30d 0/3 upstream: reported on 2026/06/26 13:35
linux-6.6 INFO: rcu detected stall in hsr_announce 1 1 222d 222d 0/2 auto-obsoleted due to no activity on 2026/03/26 05:20
linux-5.15 INFO: rcu detected stall in hsr_announce (2) 1 1 340d 340d 0/3 auto-obsoleted due to no activity on 2025/11/28 17:51
linux-5.15 INFO: rcu detected stall in hsr_announce 1 6 664d 710d 0/3 auto-obsoleted due to no activity on 2025/01/08 22:52
upstream INFO: rcu detected stall in hsr_announce (3) net 1 1 2427d 2427d 0/29 closed as invalid on 2019/12/04 14:04
linux-4.14 INFO: rcu detected stall in hsr_announce 1 C error 25 2214d 2413d 0/1 upstream: reported C repro on 2019/12/17 23:42
upstream INFO: rcu detected stall in hsr_announce (4) net 1 1 2053d 2053d 0/29 auto-closed as invalid on 2021/03/11 15:56
upstream INFO: rcu detected stall in hsr_announce net 1 1 2507d 2507d 0/29 auto-closed as invalid on 2019/11/13 18:24
upstream INFO: rcu detected stall in hsr_announce (2) net 1 3 2431d 2431d 0/29 closed as invalid on 2019/11/29 14:24
linux-4.19 INFO: rcu detected stall in hsr_announce 1 1 2126d 2126d 0/1 auto-closed as invalid on 2021/01/27 07:34
▶ ▼ Fix bisection attempts (1)
Created Duration User Patch Repo Result
2026/06/30 03:04 2h26m bisect fix linux-6.6.y OK (0) job log log

Sample crash report:
hrtimer: interrupt took 39149 ns
rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-...!: (1 GPs behind) idle=cefc/1/0x4000000000000000 softirq=12505/12507 fqs=12
rcu: 	(t=10502 jiffies g=9325 q=1023 ncpus=2)
rcu: rcu_preempt kthread starved for 10479 jiffies! g9325 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->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:R  running task     stack:27720 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0x188/0x2d0 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x313/0x1590 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x9d/0x3b0 kernel/rcu/tree.c:1866
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </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: 5965 Comm: syz.3.20 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:get_current arch/x86/include/asm/current.h:41 [inline]
RIP: 0010:rcu_preempt_read_enter kernel/rcu/tree_plugin.h:379 [inline]
RIP: 0010:__rcu_read_lock+0x0/0x60 kernel/rcu/tree_plugin.h:402
Code: b3 6d 00 e9 db fb ff ff 44 89 f1 80 e1 07 38 c1 0f 8c 62 fb ff ff 4c 89 f7 e8 7c b4 6d 00 e9 55 fb ff ff 0f 1f 80 00 00 00 00 <f3> 0f 1e fa 53 65 48 8b 1d a3 fe 91 7e 48 81 c3 3c 04 00 00 48 89
RSP: 0018:ffffc900001efc78 EFLAGS: 00000006
RAX: ffffffff81ae5ac0 RBX: ffff8880318f8000 RCX: ffff888078f43c00
RDX: 0000000000010100 RSI: ffffc900001efe80 RDI: ffff8880318f8000
RBP: ffffc900001efd88 R08: ffff8880318f848b R09: 1ffff1100631f091
R10: dffffc0000000000 R11: ffffed100631f092 R12: dffffc0000000000
R13: ffff8880318f8000 R14: ffffc900001f0338 R15: 1ffff9200003df94
FS:  0000555582a1b500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000001c768 CR3: 000000002f9ea000 CR4: 00000000003506e0
Call Trace:
 <IRQ>
 rcu_read_lock include/linux/rcupdate.h:784 [inline]
 __perf_event_output kernel/events/core.c:7972 [inline]
 perf_event_output_forward+0xb2/0x3e0 kernel/events/core.c:7995
 __perf_event_overflow+0x447/0x630 kernel/events/core.c:9720
 perf_event_overflow kernel/events/core.c:9741 [inline]
 perf_swevent_hrtimer+0x439/0x610 kernel/events/core.c:11230
 __run_hrtimer kernel/time/hrtimer.c:1754 [inline]
 __hrtimer_run_queues+0x4e1/0xc40 kernel/time/hrtimer.c:1818
 hrtimer_interrupt+0x3c9/0x9c0 kernel/time/hrtimer.c:1880
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1077 [inline]
 __sysvec_apic_timer_interrupt+0xfb/0x3b0 arch/x86/kernel/apic/apic.c:1094
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0x51/0xc0 arch/x86/kernel/apic/apic.c:1088
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:seqcount_lockdep_reader_access+0x19a/0x1d0 include/linux/seqlock.h:105
Code: 00 4d 85 e4 75 16 e8 85 c8 0f 00 eb 15 e8 7e c8 0f 00 e8 09 b8 10 09 4d 85 e4 74 ea e8 6f c8 0f 00 fb 48 c7 04 24 0e 36 e0 45 <4b> c7 04 3e 00 00 00 00 43 c7 44 3e 08 00 00 00 00 65 48 8b 04 25
RSP: 0018:ffffc900001f03e0 EFLAGS: 00000246
RAX: ffffffff81776381 RBX: 0000000000000000 RCX: ffff888078f43c00
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc900001f0498 R08: ffffffff911cc5ff R09: 1ffffffff22398bf
R10: dffffc0000000000 R11: fffffbfff22398c0 R12: 0000000000000200
R13: 000001fb6ca015d2 R14: 1ffff9200003e07c R15: dffffc0000000000
 timekeeping_get_delta kernel/time/timekeeping.c:254 [inline]
 timekeeping_get_ns kernel/time/timekeeping.c:388 [inline]
 ktime_get_with_offset+0x103/0x330 kernel/time/timekeeping.c:891
 ktime_get_real include/linux/timekeeping.h:79 [inline]
 netif_rx_internal+0x344/0x4e0 net/core/dev.c:5153
 __netif_rx+0x78/0xc0 net/core/dev.c:5196
 veth_forward_skb drivers/net/veth.c:325 [inline]
 veth_xmit+0x550/0x9f0 drivers/net/veth.c:378
 __netdev_start_xmit include/linux/netdevice.h:4943 [inline]
 netdev_start_xmit include/linux/netdevice.h:4957 [inline]
 xmit_one net/core/dev.c:3644 [inline]
 dev_hard_start_xmit+0x246/0x740 net/core/dev.c:3660
 __dev_queue_xmit+0x19a3/0x3660 net/core/dev.c:4454
 dev_queue_xmit include/linux/netdevice.h:3113 [inline]
 hsr_xmit net/hsr/hsr_forward.c:382 [inline]
 hsr_forward_do net/hsr/hsr_forward.c:473 [inline]
 hsr_forward_skb+0x1335/0x2140 net/hsr/hsr_forward.c:626
 send_hsr_supervision_frame+0x5fb/0xb90 net/hsr/hsr_device.c:346
 hsr_announce+0x198/0x350 net/hsr/hsr_device.c:402
 call_timer_fn+0x189/0x540 kernel/time/timer.c:1701
 expire_timers kernel/time/timer.c:1752 [inline]
 __run_timers+0x542/0x800 kernel/time/timer.c:2023
 run_timer_softirq+0x67/0xf0 kernel/time/timer.c:2036
 handle_softirqs+0x280/0x820 kernel/softirq.c:578
 __do_softirq kernel/softirq.c:612 [inline]
 invoke_softirq kernel/softirq.c:452 [inline]
 __irq_exit_rcu+0xd3/0x190 kernel/softirq.c:661
 irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:check_kcov_mode kernel/kcov.c:184 [inline]
RIP: 0010:write_comp_data kernel/kcov.c:245 [inline]
RIP: 0010:__sanitizer_cov_trace_const_cmp8+0x30/0x80 kernel/kcov.c:320
Code: 04 24 65 48 8b 0d 80 85 7c 7e 65 8b 15 81 85 7c 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 89 fc
RSP: 0018:ffffc9000376fc90 EFLAGS: 00000246
RAX: ffffffff813ca4e1 RBX: 00000000295da500 RCX: ffff888078f43c00
RDX: 0000000000000000 RSI: 00000000295da500 RDI: 00003fffffffffff
RBP: ffffc9000376fda8 R08: ffff8880295da55f R09: 1ffff110052bb4ab
R10: dffffc0000000000 R11: ffffed10052bb4ac R12: 0000000000000000
R13: ffff888078f43c00 R14: 000000000000002e R15: 0000000000000000
 pfn_valid include/linux/mmzone.h:2008 [inline]
 __virt_addr_valid+0xe1/0x540 arch/x86/mm/physaddr.c:65
 kasan_addr_to_slab+0xd/0xc0 mm/kasan/common.c:36
 __kasan_record_aux_stack+0xf/0xc0 mm/kasan/generic.c:477
 task_work_add+0xd9/0x470 kernel/task_work.c:82
 fput+0xdd/0x1a0 fs/file_table.c:440
 filp_close+0x10f/0x150 fs/open.c:1547
 __range_close fs/file.c:698 [inline]
 __close_range+0x368/0x660 fs/file.c:755
 __do_sys_close_range fs/open.c:1599 [inline]
 __se_sys_close_range fs/open.c:1596 [inline]
 __x64_sys_close_range+0x7a/0x90 fs/open.c:1596
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f102e59ce59
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:00007ffc422167b8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: ffffffffffffffda RBX: 00007ffc422168a0 RCX: 00007f102e59ce59
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 000000000001c768 R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b2d020000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f102e815fac R14: 00007f102e815fa8 R15: 00007f102e815fa0
 </TASK>
CPU: 0 PID: 5961 Comm: syz.2.19 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:should_resched arch/x86/include/asm/preempt.h:104 [inline]
RIP: 0010:__local_bh_enable_ip+0x142/0x1c0 kernel/softirq.c:413
Code: 8a e8 12 c6 35 09 65 66 8b 05 4a 4a b1 7e 66 85 c0 75 54 bf 01 00 00 00 e8 8b 22 0a 00 e8 b6 32 3b 00 fb 65 8b 05 16 4a b1 7e <85> c0 75 05 e8 95 31 ae ff 48 c7 04 24 0e 36 e0 45 4b c7 04 37 00
RSP: 0018:ffffc90000007880 EFLAGS: 00000282
RAX: 0000000000000302 RBX: 0000000000000201 RCX: 18c28050e2fc8300
RDX: dffffc0000000000 RSI: ffffffff8acacbe0 RDI: ffffffff8b1c9a20
RBP: ffffc90000007900 R08: ffffffff911cc5ff R09: 1ffffffff22398bf
R10: dffffc0000000000 R11: fffffbfff22398c0 R12: ffffffff8a640b93
R13: dffffc0000000000 R14: dffffc0000000000 R15: 1ffff92000000f10
FS:  0000555587d6c500(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2db63fff CR3: 000000007ac0c000 CR4: 00000000003506f0
Call Trace:
 <IRQ>
 spin_unlock_bh include/linux/spinlock.h:396 [inline]
 hsr_register_frame_out+0x263/0x3a0 net/hsr/hsr_framereg.c:-1
 hsr_forward_do net/hsr/hsr_forward.c:443 [inline]
 hsr_forward_skb+0xdfb/0x2140 net/hsr/hsr_forward.c:626
 send_hsr_supervision_frame+0x5fb/0xb90 net/hsr/hsr_device.c:346
 hsr_announce+0x198/0x350 net/hsr/hsr_device.c:402
 call_timer_fn+0x189/0x540 kernel/time/timer.c:1701
 expire_timers kernel/time/timer.c:1752 [inline]
 __run_timers+0x542/0x800 kernel/time/timer.c:2023
 run_timer_softirq+0x67/0xf0 kernel/time/timer.c:2036
 handle_softirqs+0x280/0x820 kernel/softirq.c:578
 __do_softirq kernel/softirq.c:612 [inline]
 invoke_softirq kernel/softirq.c:452 [inline]
 __irq_exit_rcu+0xd3/0x190 kernel/softirq.c:661
 irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xc0/0x120 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> ab c8 ca f6 65 8b 05 3c f0 71 75 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc9000378fca0 EFLAGS: 00000206
RAX: dffffc0000000004 RBX: 0000000000000a06 RCX: 18c28050e2fc8300
RDX: dffffc0000000000 RSI: ffffffff8acacbe0 RDI: 0000000000000001
RBP: ffffc9000378fd30 R08: ffffffff911cc60f R09: 1ffffffff22398c1
R10: dffffc0000000000 R11: fffffbfff22398c2 R12: dffffc0000000000
R13: 1ffff920006f1fb8 R14: ffff8880258f6c00 R15: 1ffff920006f1f94
 __do_sys_perf_event_open kernel/events/core.c:12958 [inline]
 __se_sys_perf_event_open+0x183e/0x1c50 kernel/events/core.c:12609
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f1f46d9ce59
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:00007fff243e66c8 EFLAGS: 00000246 ORIG_RAX: 000000000000012a
RAX: ffffffffffffffda RBX: 00007f1f47015fa0 RCX: 00007f1f46d9ce59
RDX: ffffffffffffffff RSI: 0000000000000000 RDI: 0000200000000140
RBP: 00007f1f46e32d6f R08: 0000000000000002 R09: 0000000000000000
R10: ffffffffffffffff R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1f47015fac R14: 00007f1f47015fa0 R15: 00007f1f47015fa0
 </TASK>

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/30 23:57 linux-6.6.y 0a40c6fbd105 6b4a8443 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in hsr_announce
2026/07/24 19:16 linux-6.6.y da47cbc25466 dd737a83 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf BUG: soft lockup in hsr_announce
2026/05/28 20:14 linux-6.6.y 0a40c6fbd105 681715f7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf BUG: soft lockup in hsr_announce
* Struck through repros no longer work on HEAD.