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: 99d, last: 21d
▶ ▼ 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 296d 296d 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 syz, C done 60 58d 1268d 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 266d 1176d 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 syz, C done inconclusive 582 3d00h 2271d 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 9 11d 148d 0/3 upstream: reported on 2026/05/05 16:49

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (1 GPs behind) idle=25ec/1/0x4000000000000000 softirq=81535/81536 fqs=1
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P15913/1:b..l
rcu: 	(detected by 1, t=10505 jiffies, g=105733, q=278 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 17251 Comm: syz.5.2859 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:_raw_spin_unlock_irqrestore+0x60/0x120 kernel/locking/spinlock.c:193
Code: 24 08 9d de 8b 8c 48 c7 44 24 10 30 81 99 8a 49 89 e7 49 c1 ef 03 48 b8 f1 f1 f1 f1 f8 f3 f3 f3 49 bc 00 00 00 00 00 fc ff df <4b> 89 04 27 48 83 c7 18 48 8b 75 08 e8 6f 96 cf f6 4c 89 f7 e8 17
RSP: 0018:ffffc90000007cc0 EFLAGS: 00000802
RAX: f3f3f3f8f1f1f1f1 RBX: 0000000000000802 RCX: 0000000000000002
RDX: ffff888085c45014 RSI: 0000000000000802 RDI: ffffffff975794e8
RBP: ffffc90000007d50 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff52000000f7c R12: dffffc0000000000
R13: ffff8880409d9340 R14: ffffffff975794e8 R15: 1ffff92000000f98
FS:  00007fb95dc456c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb95dc44ff8 CR3: 000000005ed36000 CR4: 00000000003506f0
Call Trace:
 <IRQ>
 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> eb 77 c3 f6 65 8b 05 0c 36 6a 75 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc9000fb3fb60 EFLAGS: 00000206
RAX: dffffc0000000004 RBX: 0000000000000a06 RCX: ea9010867b219700
RDX: dffffc0000000000 RSI: ffffffff8acacce0 RDI: 0000000000000001
RBP: ffffc9000fb3fbf0 R08: ffffffff911ef507 R09: 1ffffffff223dea0
R10: dffffc0000000000 R11: fffffbfff223dea1 R12: dffffc0000000000
R13: ffff8880b8e2b740 R14: ffff8880b8e2b740 R15: 1ffff92001f67f6c
 clock_was_set+0x689/0x800 kernel/time/hrtimer.c:986
 do_settimeofday64+0x59b/0x750 kernel/time/timekeeping.c:1345
 __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: 0033:0x7fb95cd9e159
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:00007fb95dc45028 EFLAGS: 00000246 ORIG_RAX: 00000000000000e3
RAX: ffffffffffffffda RBX: 00007fb95d026090 RCX: 00007fb95cd9e159
RDX: 0000000000000000 RSI: 0000200000000240 RDI: 0000000000000000
RBP: 00007fb95ce3503b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb95d026128 R14: 00007fb95d026090 R15: 00007ffc721c5ca8
 </TASK>
task:syz-executor    state:R  running task     stack:22312 pid:15913 ppid:15899  flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 preempt_schedule_common+0x82/0xc0 kernel/sched/core.c:6868
 preempt_schedule+0xc0/0xd0 kernel/sched/core.c:6892
 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]
 copy_pte_range mm/memory.c:1107 [inline]
 copy_pmd_range mm/memory.c:1168 [inline]
 copy_pud_range mm/memory.c:1205 [inline]
 copy_p4d_range mm/memory.c:1229 [inline]
 copy_page_range+0x2be5/0x3700 mm/memory.c:1323
 dup_mmap kernel/fork.c:769 [inline]
 dup_mm kernel/fork.c:1700 [inline]
 copy_mm+0x1751/0x1e30 kernel/fork.c:1749
 copy_process+0x16c9/0x3da0 kernel/fork.c:2510
 kernel_clone+0x24b/0x8a0 kernel/fork.c:2919
 __do_sys_clone kernel/fork.c:3062 [inline]
 __se_sys_clone kernel/fork.c:3046 [inline]
 __x64_sys_clone+0x1b7/0x230 kernel/fork.c:3046
 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: 0033:0x7f3f005c6bd2
RSP: 002b:00007fffae581a90 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007fffae581a90 RCX: 00007f3f005c6bd2
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 00007fffae581c1c R08: 0000000000000000 R09: 0000000000000001
R10: 000055555fb3b7d0 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000000927c0 R14: 00000000000b5f2e R15: 00007fffae581c70
 </TASK>
rcu: rcu_preempt kthread starved for 10500 jiffies! g105733 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:27384 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 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: 1 PID: 8132 Comm: kworker/u4:17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
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 14 01 0b 00 41 83 e6 01 49 be 00 00 00 00 00 fc ff df 75 07 e8 4f fd 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 33 fd
RSP: 0000:ffffc90003617780 EFLAGS: 00000293
RAX: ffffffff817c853d RBX: 1ffff110171c87a5 RCX: ffff88807ab13c00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc90003617900 R08: ffffffff911ef507 R09: 1ffffffff223dea0
R10: dffffc0000000000 R11: fffffbfff223dea1 R12: ffff8880b8e43d28
R13: ffff8880b8f3d380 R14: dffffc0000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c3dbf46 CR3: 000000000cf32000 CR4: 00000000003506e0
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:2657 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734
 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815
 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 (8):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/09 21:00 linux-6.6.y 8b73de7da85f 4e8b1cc6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_clock_settime
2026/09/09 20:58 linux-6.6.y 8b73de7da85f 4e8b1cc6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_clock_settime
2026/07/31 16:32 linux-6.6.y a1153c0deb44 7664cf44 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_clock_settime
2026/07/11 05:55 linux-6.6.y da47cbc25466 d78ea535 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_clock_settime
2026/07/10 04:05 linux-6.6.y da47cbc25466 4167ee25 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_clock_settime
2026/07/09 16:09 linux-6.6.y da47cbc25466 a0c310a3 .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 15:20 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.