INFO: rcu detected stall in wait4 (9)

Status: auto-obsoleted due to no activity on 2026/10/08 21:57
Subsystems: kernel
Labels: prio:low
[Documentation on labels]
First crash: 90d, last: 90d
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ID Workflow Result Correct Bug Created Started Finished Revision
8f5d4417 assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ INFO: rcu detected stall in wait4 (9) 2026/07/12 00:51 2026/07/12 00:51 2026/07/12 01:19 d78ea535
▶ ▼ Similar bugs (9)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in wait4 (3) kernel 1 2 1334d 1338d 0/29 auto-obsoleted due to no activity on 2023/05/14 12:43
upstream INFO: rcu detected stall in wait4 kernel 1 2 1951d 2007d 0/29 auto-closed as invalid on 2021/09/04 10:15
upstream INFO: rcu detected stall in wait4 (8) prio:normal fs 1 2 188d 207d 0/29 auto-obsoleted due to no activity on 2026/07/03 08:08
upstream INFO: rcu detected stall in wait4 (5) fs 1 6 707d 738d 0/29 auto-obsoleted due to no activity on 2025/01/30 05:34
upstream INFO: rcu detected stall in wait4 (4) kernel 1 syz, C error done 35 850d 1179d 0/29 auto-obsoleted due to no activity on 2024/09/18 16:22
upstream INFO: rcu detected stall in wait4 (7) kernel 1 1 357d 357d 0/29 auto-obsoleted due to no activity on 2026/01/14 18:39
upstream INFO: rcu detected stall in wait4 (2) kernel 1 2 1535d 1617d 0/29 auto-obsoleted due to no activity on 2022/10/24 16:24
upstream INFO: rcu detected stall in wait4 (6) kernel 1 1 588d 588d 0/29 auto-obsoleted due to no activity on 2025/05/29 01:55
upstream INFO: rcu detected stall in __do_sys_wait4 kernel 1 2 2217d 2248d 0/29 auto-closed as invalid on 2020/12/11 15:32

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (0 ticks this GP) idle=8774/1/0x4000000000000000 softirq=125426/125426 fqs=0
rcu: 	(detected by 1, t=10502 jiffies, g=122753, q=345 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 15416 Comm: syz-executor Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/10/2026
RIP: 0010:hlock_class kernel/locking/lockdep.c:234 [inline]
RIP: 0010:mark_lock+0x52/0xa20 kernel/locking/lockdep.c:4731
Code: 89 d3 83 fa 08 74 6d 41 be 01 00 00 00 89 d9 41 d3 e6 4d 63 f6 41 0f b7 44 24 20 66 25 ff 1f 0f b7 c0 48 0f a3 05 8e df 84 14 <73> 5b 48 8d 04 80 48 8d 04 80 48 8d 04 c5 e0 1d 6a 96 4c 89 f1 48
RSP: 0018:ffffc90000007bb0 EFLAGS: 00000047
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff888023388bc8 RDI: ffff888023388000
RBP: ffffc90000007c48 R08: 0000000000000001 R09: 0000000000000002
R10: 0000000000000000 R11: 0000000000000001 R12: ffff888023388bc8
R13: ffff888023388000 R14: 0000000000000001 R15: 0000000000000001
FS:  0000555565347500(0000) GS:ffff888123deb000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000003000 CR3: 00000000757cf000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 mark_usage kernel/locking/lockdep.c:4639 [inline]
 __lock_acquire+0x10a8/0x1a40 kernel/locking/lockdep.c:5191
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:132 [inline]
 _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:166
 debug_object_deactivate+0x135/0x3b0 lib/debugobjects.c:936
 debug_hrtimer_deactivate kernel/time/hrtimer.c:490 [inline]
 __run_hrtimer kernel/time/hrtimer.c:2000 [inline]
 __hrtimer_run_queues+0x2e9/0x9c0 kernel/time/hrtimer.c:2096
 hrtimer_interrupt+0x3e5/0x940 kernel/time/hrtimer.c:2215
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
 __sysvec_apic_timer_interrupt+0x109/0x470 arch/x86/kernel/apic/apic.c:1068
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
 sysvec_apic_timer_interrupt+0x9e/0xc0 arch/x86/kernel/apic/apic.c:1062
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:179 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0x31/0x80 kernel/locking/spinlock.c:198
Code: f5 53 48 8b 74 24 10 48 89 fb 48 83 c7 18 e8 16 5f 29 f6 48 89 df e8 9e ae 29 f6 f7 c5 00 02 00 00 75 23 9c 58 f6 c4 02 75 37 <bf> 01 00 00 00 e8 a5 bf 18 f6 65 8b 05 ee 48 a7 08 85 c0 74 16 5b
RSP: 0018:ffffc90005307c40 EFLAGS: 00000246
RAX: 0000000000000006 RBX: ffff888027448ea0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8e1a312a RDI: ffffffff8c400c80
RBP: 0000000000000296 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffffffff81c8052d
R13: ffffc90005307cc8 R14: ffffed100467130e R15: 0000000000000004
 do_wait+0x2f3/0x570 kernel/exit.c:1760
 kernel_wait4+0x16d/0x280 kernel/exit.c:1910
 __do_sys_wait4+0x161/0x170 kernel/exit.c:1938
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb94ff5e68e
Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08
RSP: 002b:00007ffc897ff8f8 EFLAGS: 00000246 ORIG_RAX: 000000000000003d
RAX: ffffffffffffffda RBX: 0000555565347500 RCX: 00007fb94ff5e68e
RDX: 0000000040000001 RSI: 00007ffc897ff99c RDI: ffffffffffffffff
RBP: 00007ffc897ff99c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000001388
R13: 00000000000927c0 R14: 00000000001090a9 R15: 00007ffc897ff9f0
 </TASK>
rcu: rcu_preempt kthread starved for 10502 jiffies! g122753 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:27592 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5510 [inline]
 __schedule+0x125c/0x6730 kernel/sched/core.c:7234
 __schedule_loop kernel/sched/core.c:7311 [inline]
 schedule+0xdd/0x2c0 kernel/sched/core.c:7326
 schedule_timeout+0x127/0x280 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x1a9/0x900 kernel/rcu/tree.c:2123
 rcu_gp_kthread+0x179/0x230 kernel/rcu/tree.c:2325
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 UID: 0 PID: 20719 Comm: syz.1.3416 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/10/2026
RIP: 0010:csd_lock_wait kernel/smp.c:342 [inline]
RIP: 0010:smp_call_function_many_cond+0x58e/0x16c0 kernel/smp.c:892
Code: 00 fc ff df 48 8b 54 24 08 49 89 d5 49 89 d4 49 c1 ed 03 41 83 e4 07 49 01 c5 41 83 c4 03 e8 a9 95 0c 00 f3 90 41 0f b6 45 00 <41> 38 c4 7c 08 84 c0 0f 85 2c 0f 00 00 8b 45 08 31 ff 83 e0 01 41
RSP: 0018:ffffc90003957b40 EFLAGS: 00000202
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff81fd3abd
RDX: ffff888029c60000 RSI: ffffffff81fd3a97 RDI: 0000000000400000
RBP: ffff8880b8443680 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: 000000000007fffc R12: 0000000000000003
R13: ffffed10170886d1 R14: 0000000000000001 R15: ffff8880b853c880
FS:  00007f7aa094c6c0(0000) GS:ffff888123eeb000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2fd06160 CR3: 000000004e5db000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 clock_was_set+0x61c/0x850 kernel/time/hrtimer.c:999
 do_settimeofday64+0x330/0x4d0 kernel/time/timekeeping.c:1684
 do_sys_settimeofday64+0x1dc/0x260 kernel/time/time.c:195
 __do_sys_clock_settime kernel/time/posix-timers.c:1139 [inline]
 __se_sys_clock_settime kernel/time/posix-timers.c:1123 [inline]
 __x64_sys_clock_settime+0x1c1/0x2a0 kernel/time/posix-timers.c:1123
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7a9f99de59
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:00007f7aa094c028 EFLAGS: 00000246 ORIG_RAX: 00000000000000e3
RAX: ffffffffffffffda RBX: 00007f7a9fc25fa0 RCX: 00007f7a9f99de59
RDX: 0000000000000000 RSI: 0000200000000040 RDI: 0000000000000000
RBP: 00007f7a9fa33e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7a9fc26038 R14: 00007f7a9fc25fa0 R15: 00007ffcf1c113d8
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/10 21:46 upstream a635d6748234 99e64375 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in wait4
* Struck through repros no longer work on HEAD.