INFO: rcu detected stall in sys_epoll_wait (8)

Status: auto-obsoleted due to no activity on 2026/03/26 09:15
Subsystems: kernel
[Documentation on labels]
First crash: 226d, last: 226d
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ID Workflow Result Correct Bug Created Started Finished Revision
53082d52 repro ❓ INFO: rcu detected stall in sys_epoll_wait (8) 2026/03/07 11:06 2026/03/07 11:06 2026/03/07 11:16 31e9c887
▶ ▼ Similar bugs (8)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in sys_epoll_wait (6) ext4 1 3 765d 779d 0/29 auto-obsoleted due to no activity on 2024/10/03 13:07
upstream INFO: rcu detected stall in sys_epoll_wait (2) kernel 1 15 2405d 2405d 0/29 closed as invalid on 2020/01/08 05:23
upstream INFO: rcu detected stall in sys_epoll_wait mm cgroups 1 148 2440d 2441d 0/29 closed as invalid on 2019/12/04 14:14
upstream INFO: rcu detected stall in sys_epoll_wait (9) prio:high mm usb input 1 syz, C error error 1 42d 40d 0/29 upstream: reported C repro on 2026/06/29 21:10
upstream INFO: rcu detected stall in sys_epoll_wait (7) fs 1 3 651d 659d 0/29 auto-obsoleted due to no activity on 2025/01/24 21:05
upstream INFO: rcu detected stall in sys_epoll_wait (3) kernel 1 1 2405d 2405d 0/29 closed as invalid on 2020/01/08 05:33
upstream INFO: rcu detected stall in sys_epoll_wait (4) kernel 1 21 2405d 2405d 0/29 closed as invalid on 2020/01/09 08:13
upstream INFO: rcu detected stall in sys_epoll_wait (5) usb fs input 1 syz error 2 1385d 1904d 0/29 closed as dup on 2021/05/25 09:57

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (0 ticks this GP) idle=9b44/1/0x4000000000000000 softirq=200270/200270 fqs=0
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P22860/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=181149, q=271 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 5196 Comm: udevd 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:arch_atomic_try_cmpxchg arch/x86/include/asm/atomic.h:107 [inline]
RIP: 0010:raw_atomic_try_cmpxchg_acquire include/linux/atomic/atomic-arch-fallback.h:2170 [inline]
RIP: 0010:atomic_try_cmpxchg_acquire include/linux/atomic/atomic-instrumented.h:1302 [inline]
RIP: 0010:queued_spin_lock include/asm-generic/qspinlock.h:111 [inline]
RIP: 0010:do_raw_spin_lock+0x121/0x290 kernel/locking/spinlock_debug.c:116
Code: 0f 84 f3 00 00 00 c7 44 24 40 00 00 00 00 48 89 df be 04 00 00 00 e8 1e 89 88 00 48 8d 7c 24 40 be 04 00 00 00 e8 0f 89 88 00 <8b> 44 24 40 b9 01 00 00 00 f0 0f b1 0b 0f 85 dd 00 00 00 65 8b 1d
RSP: 0018:ffffc90000007ba0 EFLAGS: 00000097
RAX: 00000000ffffff01 RBX: ffff88802682b2a8 RCX: ffffffff819e8f81
RDX: 0000000000000001 RSI: 0000000000000004 RDI: ffffc90000007be0
RBP: ffffc90000007c60 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff52000000f7c R12: ffff88802682b2b8
R13: ffff88802682b2b0 R14: 1ffff11004d05657 R15: 1ffff11004d05656
FS:  00007f7a02fd1880(0000) GS:ffff888125e1f000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000480 CR3: 00000000305ff000 CR4: 0000000000350ef0
Call Trace:
 <IRQ>
 spin_lock include/linux/spinlock.h:351 [inline]
 advance_sched+0xc4/0xc90 net/sched/sch_taprio.c:930
 __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:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0x47/0x80 kernel/locking/spinlock.c:194
Code: f7 e8 dd 6a 42 f6 f7 c3 00 02 00 00 74 05 e8 20 95 6c f6 9c 58 a9 00 02 00 00 75 27 f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> 14 85 34 f6 65 8b 05 4d e8 23 07 85 c0 74 18 5b 41 5e e9 1c 19
RSP: 0018:ffffc900036f7a48 EFLAGS: 00000206
RAX: 0000000000000006 RBX: 0000000000000246 RCX: 0000000080000001
RDX: 0000000000000000 RSI: ffffffff8d792008 RDI: 0000000000000001
RBP: 0000000000000001 R08: ffffffff8f822177 R09: 1ffffffff1f0442e
R10: dffffc0000000000 R11: fffffbfff1f0442f R12: ffffc900036f7b50
R13: ffff8880b86282c0 R14: ffff8880b8628240 R15: 0000000000000246
 unlock_hrtimer_base kernel/time/hrtimer.c:1013 [inline]
 hrtimer_try_to_cancel+0x3be/0x420 kernel/time/hrtimer.c:1360
 hrtimer_cancel+0x16/0x50 kernel/time/hrtimer.c:1481
 schedule_hrtimeout_range_clock+0x144/0x2f0 kernel/time/sleep_timeout.c:218
 ep_poll fs/eventpoll.c:2028 [inline]
 do_epoll_wait+0xca7/0xf30 fs/eventpoll.c:2461
 __do_sys_epoll_wait fs/eventpoll.c:2469 [inline]
 __se_sys_epoll_wait fs/eventpoll.c:2464 [inline]
 __x64_sys_epoll_wait+0x1be/0x210 fs/eventpoll.c:2464
 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: 0033:0x7f7a028a7407
Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007ffc133070c0 EFLAGS: 00000202 ORIG_RAX: 00000000000000e8
RAX: ffffffffffffffda RBX: 00007f7a02fd1880 RCX: 00007f7a028a7407
RDX: 0000000000000008 RSI: 00007ffc13307220 RDI: 000000000000000b
RBP: 0000564551303520 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000bb8 R11: 0000000000000202 R12: 0000000000000000
R13: 00005645456ae100 R14: 0000000000000007 R15: 0000000000000000
 </TASK>
task:udevd           state:R  running task     stack:23608 pid:22860 tgid:22860 ppid:5196   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]
 __wake_up_common_lock+0x190/0x1f0 kernel/sched/wait.c:127
 sock_def_readable+0x1eb/0x530 net/core/sock.c:3611
 unix_dgram_sendmsg+0xdfb/0x1840 net/unix/af_unix.c:2286
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg+0x21c/0x270 net/socket.c:742
 sock_write_iter+0x279/0x360 net/socket.c:1195
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x5c9/0xb30 fs/read_write.c:686
 ksys_write+0x145/0x250 fs/read_write.c:738
 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: 0033:0x7f7a028a7407
RSP: 002b:00007ffc13306ed0 EFLAGS: 00000202 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f7a02fd1880 RCX: 00007f7a028a7407
RDX: 0000000000000000 RSI: 00007ffc13306f77 RDI: 000000000000000a
RBP: 000000000000000a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 00007f7a02fd16e8
R13: 0000000000000000 R14: 0000000000000000 R15: 00005645512e7f20
 </TASK>
rcu: rcu_preempt kthread starved for 10502 jiffies! g181149 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:27584 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:
CPU: 1 UID: 0 PID: 62 Comm: kworker/u8:4 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: events_unbound toggle_allocation_gate
RIP: 0010:csd_lock_wait kernel/smp.c:342 [inline]
RIP: 0010:smp_call_function_many_cond+0xcca/0x1260 kernel/smp.c:877
Code: 89 ee 83 e6 01 31 ff e8 d4 95 0b 00 41 83 e5 01 49 bd 00 00 00 00 00 fc ff df 75 07 e8 7f 91 0b 00 eb 38 f3 90 42 0f b6 04 2b <84> c0 75 11 41 f7 04 24 01 00 00 00 74 1e e8 63 91 0b 00 eb e4 44
RSP: 0018:ffffc9000213f6a0 EFLAGS: 00000293
RAX: 0000000000000000 RBX: 1ffff110170c856d RCX: ffff88801ab3db80
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc9000213f7e0 R08: ffffffff8f822177 R09: 1ffffffff1f0442e
R10: dffffc0000000000 R11: fffffbfff1f0442f R12: ffff8880b8642b68
R13: dffffc0000000000 R14: ffff8880b873bb00 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff888125f1f000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c489ba5 CR3: 000000000dd3a000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 on_each_cpu_cond_mask+0x3f/0x80 kernel/smp.c:1043
 on_each_cpu include/linux/smp.h:71 [inline]
 smp_text_poke_sync_each_cpu arch/x86/kernel/alternative.c:2711 [inline]
 smp_text_poke_batch_finish+0x5f9/0x1130 arch/x86/kernel/alternative.c:2921
 arch_jump_label_transform_apply+0x1c/0x30 arch/x86/kernel/jump_label.c:146
 static_key_enable_cpuslocked+0x128/0x240 kernel/jump_label.c:210
 static_key_enable+0x1a/0x20 kernel/jump_label.c:223
 toggle_allocation_gate+0xad/0x240 mm/kfence/core.c:874
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421
 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>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/26 09:09 upstream ccd1cdca5cd4 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in sys_epoll_wait
* Struck through repros no longer work on HEAD.