INFO: rcu detected stall in pwq_unbound_release_workfn (2)

Status: upstream: reported on 2026/09/18 21:47
Reported-by: syzbot+b181d989e3353a636db1@syzkaller.appspotmail.com
First crash: 11d, last: 11d
▶ ▼ Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in pwq_unbound_release_workfn kernel 1 1 1765d 1765d 0/29 closed as invalid on 2022/02/08 10:10
upstream INFO: rcu detected stall in pwq_unbound_release_workfn (2) kernel 1 1 1544d 1544d 0/29 auto-closed as invalid on 2022/09/06 17:05
linux-5.15 INFO: rcu detected stall in pwq_unbound_release_workfn 1 1 691d 691d 0/3 auto-obsoleted due to no activity on 2025/02/15 16:46
linux-5.15 INFO: rcu detected stall in pwq_unbound_release_workfn (2) origin:lts-only 1 syz error 3 19d 489d 0/3 upstream: reported syz repro on 2025/05/28 17:46
linux-6.1 INFO: rcu detected stall in pwq_unbound_release_workfn 1 1 781d 781d 0/3 auto-obsoleted due to no activity on 2024/11/17 13:02
upstream INFO: rcu detected stall in pwq_unbound_release_workfn (3) kernel 1 1 1343d 1343d 0/29 auto-obsoleted due to no activity on 2023/04/25 19:12
upstream INFO: rcu detected stall in pwq_unbound_release_workfn (4) kernel 1 2 1177d 1226d 0/29 auto-obsoleted due to no activity on 2023/10/08 15:59

Sample crash report:
rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 0-.... } 2680 jiffies s: 17861 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: 14 Comm: kworker/0:1 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: events pwq_unbound_release_workfn
RIP: 0010:get_current arch/x86/include/asm/current.h:15 [inline]
RIP: 0010:write_comp_data kernel/kcov.c:240 [inline]
RIP: 0010:__sanitizer_cov_trace_const_cmp4+0x4/0x80 kernel/kcov.c:309
Code: 77 22 89 ff 89 f6 49 ff c0 4c 89 01 48 c7 44 11 08 03 00 00 00 48 89 7c 11 10 48 89 74 11 18 48 89 44 11 20 c3 90 48 8b 04 24 <65> 48 8b 15 f4 38 80 7e 65 8b 0d f5 38 80 7e 81 e1 00 01 ff 00 74
RSP: 0018:ffffc900000078d8 EFLAGS: 00000046
RAX: ffffffff818a4c86 RBX: 0000000000000014 RCX: 0000000000007903
RDX: 0000000000000100 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000000001 R08: ffff8880b8e357cb R09: 1ffff110171c6af9
R10: dffffc0000000000 R11: ffffed10171c6afa R12: ffffffff8cb80060
R13: dffffc0000000000 R14: ffffc90000007960 R15: ffffc90000007980
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b30012ff8 CR3: 0000000029c60000 CR4: 00000000003506f0
DR0: 0000200000000300 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 perf_trace_buf_alloc+0x76/0x300 kernel/trace/trace_event_perf.c:415
 perf_trace_preemptirq_template+0x143/0x320 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 32 7b 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:ffffc90000007ae0 EFLAGS: 00000206
RAX: b3de84d275d35100 RBX: 1ffff92000000f64 RCX: b3de84d275d35100
RDX: dffffc0000000000 RSI: ffffffff8a8c18a0 RDI: ffffffff8adf68a0
RBP: ffffc90000007bd0 R08: ffffffff90b0f257 R09: 1ffffffff2161e4a
R10: dffffc0000000000 R11: fffffbfff2161e4b R12: 0000000000000246
R13: dffffc0000000000 R14: ffff8880b8e3bb00 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:2148
 __run_hrtimer kernel/time/hrtimer.c:1751 [inline]
 __hrtimer_run_queues+0x522/0xc90 kernel/time/hrtimer.c:1815
 hrtimer_run_softirq+0x173/0x290 kernel/time/hrtimer.c:1832
 handle_softirqs+0x291/0x910 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:instrument_atomic_read include/linux/instrumented.h:72 [inline]
RIP: 0010:atomic_long_read include/linux/atomic/atomic-instrumented.h:1265 [inline]
RIP: 0010:__mutex_owner kernel/locking/mutex.c:81 [inline]
RIP: 0010:mutex_spin_on_owner+0x26a/0x340 kernel/locking/mutex.c:359
Code: 89 e7 be 08 00 00 00 e8 44 1d 70 00 80 3c 2b 00 74 08 4c 89 e7 e8 a6 1b 70 00 49 f7 04 24 01 00 00 00 0f 85 86 00 00 00 f3 90 <4c> 89 e7 be 08 00 00 00 e8 19 1d 70 00 80 3c 2b 00 0f 84 88 fe ff
RSP: 0018:ffffc90000137520 EFLAGS: 00000246
RAX: 1ffff11027fd63c0 RBX: 1ffffffff196668a RCX: ffffffff81635b3e
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff88813feb1e00
RBP: dffffc0000000000 R08: ffff88813feb1e07 R09: 1ffff11027fd63c0
R10: dffffc0000000000 R11: ffffed1027fd63c1 R12: ffffffff8cb33450
R13: ffffffff8cb334a0 R14: ffffffff8cb334a0 R15: ffff88802fe3da00
 mutex_optimistic_spin kernel/locking/mutex.c:476 [inline]
 __mutex_lock_common kernel/locking/mutex.c:607 [inline]
 __mutex_lock+0x187/0xae0 kernel/locking/mutex.c:747
 exp_funnel_lock kernel/rcu/tree_exp.h:323 [inline]
 synchronize_rcu_expedited+0x3c0/0x890 kernel/rcu/tree_exp.h:962
 synchronize_rcu+0x128/0x3f0 kernel/rcu/tree.c:3580
 lockdep_unregister_key+0x4d2/0x550 kernel/locking/lockdep.c:6390
 wq_unregister_lockdep kernel/workqueue.c:3500 [inline]
 pwq_unbound_release_workfn+0x262/0x2b0 kernel/workqueue.c:3738
 process_one_work+0x8ab/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaf5/0x12a0 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/18 21:46 linux-6.1.y 1a8763b93150 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in pwq_unbound_release_workfn
* Struck through repros no longer work on HEAD.