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INFO: rcu detected stall in sys_clock_settime (2)

Status: upstream: reported on 2026/06/23 15:18
Reported-by: syzbot+af4540caba043c274f7f@syzkaller.appspotmail.com
First crash: 20h53m, last: 20h51m
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 INFO: rcu detected stall in sys_clock_settime 1 1 197d 197d 0/2 auto-obsoleted due to no activity on 2026/03/19 03:29
linux-6.1 INFO: rcu detected stall in sys_clock_settime origin:lts-only 1 C done 59 33d 1169d 0/3 upstream: reported C repro on 2023/04/11 17:25
linux-5.15 INFO: rcu detected stall in sys_clock_settime 1 43 167d 1077d 0/3 auto-obsoleted due to no activity on 2026/04/17 23:52
upstream INFO: rcu detected stall in sys_clock_settime prio:normal kernel 1 C done inconclusive 540 20h40m 2172d 0/29 upstream: reported C repro on 2020/07/12 17:54
linux-5.15 INFO: rcu detected stall in sys_clock_settime (2) 1 7 26d 49d 0/3 upstream: reported on 2026/05/05 16:49

Sample crash report:
GRED: Unable to relocate VQ 0x0 after dequeue, screwing up backlog
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	1-...!: (1 GPs behind) idle=315c/1/0x4000000000000000 softirq=82320/82321 fqs=1
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P19297/1:b..l
rcu: 	(detected by 0, t=10502 jiffies, g=117389, q=241 ncpus=2)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 19330 Comm: syz.4.3160 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
RIP: 0010:_raw_spin_lock_irqsave+0xa9/0x100 kernel/locking/spinlock.c:162
Code: f8 fa 41 f7 c6 00 02 00 00 74 05 e8 f1 d2 ff f6 bf 01 00 00 00 e8 57 e5 ce f6 48 8d 7b 18 31 f6 31 d2 31 c9 41 b8 01 00 00 00 <45> 31 c9 ff 75 08 e8 1c 80 da f6 48 83 c4 08 48 89 df e8 60 d2 db
RSP: 0018:ffffc900001f0c60 EFLAGS: 00000046
RAX: 0000000000010003 RBX: ffffffff97501530 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff97501548
RBP: ffffc900001f0cf8 R08: 0000000000000001 R09: 0000000000000000
R10: ffff88807bdad340 R11: ffffed100f7b5a6b R12: dffffc0000000000
R13: ffffffff97501528 R14: 0000000000000802 R15: 1ffff9200003e18c
FS:  00007f83f90ad6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa91a32ea10 CR3: 000000006a7cb000 CR4: 00000000003506e0
Call Trace:
 <IRQ>
 debug_object_deactivate+0x67/0x380 lib/debugobjects.c:764
 debug_hrtimer_deactivate kernel/time/hrtimer.c:455 [inline]
 __run_hrtimer kernel/time/hrtimer.c:1722 [inline]
 __hrtimer_run_queues+0x2cc/0xc10 kernel/time/hrtimer.c:1818
 hrtimer_interrupt+0x39d/0x980 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+0x9f/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> 4b e4 ce f6 65 8b 05 1c 33 76 75 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc9000fd47c80 EFLAGS: 00000206
RAX: dffffc0000000004 RBX: 0000000000000a06 RCX: 7ad7a09a98634e00
RDX: dffffc0000000000 RSI: ffffffff8acacb60 RDI: 0000000000000001
RBP: ffffc9000fd47d10 R08: ffffffff8e8ae5ef R09: 1ffffffff1d15cbd
R10: dffffc0000000000 R11: fffffbfff1d15cbe R12: dffffc0000000000
R13: dffffc0000000000 R14: ffffffff8d14b5c0 R15: 1ffff92001fa8f90
 do_settimeofday64+0x591/0x750 kernel/time/timekeeping.c:1342
 __do_sys_clock_settime kernel/time/posix-timers.c:1130 [inline]
 __se_sys_clock_settime kernel/time/posix-timers.c:1114 [inline]
 __x64_sys_clock_settime+0x25e/0x2a0 kernel/time/posix-timers.c:1114
 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: 0033:0x7f83f819ce59
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:00007f83f90ad028 EFLAGS: 00000246 ORIG_RAX: 00000000000000e3
RAX: ffffffffffffffda RBX: 00007f83f8415fa0 RCX: 00007f83f819ce59
RDX: 0000000000000000 RSI: 0000200000000240 RDI: 0000000000000000
RBP: 00007f83f8232e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f83f8416038 R14: 00007f83f8415fa0 R15: 00007ffcd23d5118
 </TASK>
task:syz.6.3147      state:R  running task     stack:26888 pid:19297 ppid:6497   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6700
 preempt_schedule_common+0x82/0xc0 kernel/sched/core.c:6867
 preempt_schedule+0xc0/0xd0 kernel/sched/core.c:6891
 preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk_64.S:45
 __raw_spin_unlock include/linux/spinlock_api_smp.h:143 [inline]
 _raw_spin_unlock+0x3a/0x40 kernel/locking/spinlock.c:186
 spin_unlock include/linux/spinlock.h:391 [inline]
 zap_pte_range mm/memory.c:1523 [inline]
 zap_pmd_range mm/memory.c:1571 [inline]
 zap_pud_range mm/memory.c:1600 [inline]
 zap_p4d_range mm/memory.c:1621 [inline]
 unmap_page_range+0x2577/0x32f0 mm/memory.c:1642
 unmap_vmas+0x286/0x3f0 mm/memory.c:1732
 exit_mmap+0x238/0xb90 mm/mmap.c:3302
 __mmput+0x118/0x3a0 kernel/fork.c:1357
 exit_mm+0x23f/0x340 kernel/exit.c:570
 do_exit+0x909/0x2530 kernel/exit.c:871
 do_group_exit+0x22d/0x2f0 kernel/exit.c:1026
 get_signal+0x12a6/0x1390 kernel/signal.c:2903
 arch_do_signal_or_restart+0xc2/0x7b0 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f26a719ce59
RSP: 002b:00007f26a7f9d028 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: 0000000000010106 RBX: 00007f26a7416090 RCX: 00007f26a719ce59
RDX: 0000000000010106 RSI: 00002000000000c0 RDI: 0000000000000003
RBP: 00007f26a7232e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f26a7416128 R14: 00007f26a7416090 R15: 00007ffd3b1c2368
 </TASK>
rcu: rcu_preempt kthread starved for 10500 jiffies! g117389 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
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:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x15ae/0x4660 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+0x30d/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:
CPU: 0 PID: 16425 Comm: kworker/u4:3 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Workqueue: events_unbound toggle_allocation_gate
RIP: 0010:csd_lock_wait kernel/smp.c:311 [inline]
RIP: 0010:smp_call_function_many_cond+0xd85/0x1190 kernel/smp.c:855
Code: 45 8b 34 24 44 89 f6 83 e6 01 31 ff e8 34 f1 0a 00 41 83 e6 01 49 be 00 00 00 00 00 fc ff df 75 07 e8 6f ed 0a 00 eb 38 f3 90 <42> 0f b6 04 33 84 c0 75 11 41 f7 04 24 01 00 00 00 74 1e e8 53 ed
RSP: 0018:ffffc9000c8a7780 EFLAGS: 00000293
RAX: ffffffff817bf7fd RBX: 1ffff110171e82bd RCX: ffff88801a7a9e00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc9000c8a7900 R08: ffffffff911bc507 R09: 1ffffffff22378a0
R10: dffffc0000000000 R11: fffffbfff22378a1 R12: ffff8880b8f415e8
R13: ffff8880b8e3d3c0 R14: dffffc0000000000 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa91a6063f0 CR3: 000000000cf32000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 on_each_cpu_cond_mask+0x3f/0x80 kernel/smp.c:1022
 on_each_cpu include/linux/smp.h:71 [inline]
 text_poke_sync arch/x86/kernel/alternative.c:2222 [inline]
 text_poke_bp_batch+0x31e/0x980 arch/x86/kernel/alternative.c:2432
 text_poke_flush arch/x86/kernel/alternative.c:2623 [inline]
 text_poke_finish+0x30/0x50 arch/x86/kernel/alternative.c:2630
 arch_jump_label_transform_apply+0x1c/0x30 arch/x86/kernel/jump_label.c:146
 static_key_enable_cpuslocked+0x123/0x240 kernel/jump_label.c:207
 static_key_enable+0x1a/0x20 kernel/jump_label.c:220
 toggle_allocation_gate+0xa8/0x260 mm/kfence/core.c:847
 process_one_work kernel/workqueue.c:2653 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2730
 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2811
 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>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/23 15:20 linux-6.6.y d1cfde2d5d15 4b1d8f01 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_clock_settime
2026/06/23 15:18 linux-6.6.y d1cfde2d5d15 4b1d8f01 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_clock_settime
* Struck through repros no longer work on HEAD.