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: 121d, last: 15d
▶ ▼ 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 317d 317d 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 66 3d08h 1290d 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 288d 1197d 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 592 20h10m 2293d 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 10 1d18h 170d 0/3 upstream: reported on 2026/05/05 16:49

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (0 ticks this GP) idle=0184/1/0x4000000000000000 softirq=117702/117702 fqs=2
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P26631/1:b..l
rcu: 	(detected by 1, t=10506 jiffies, g=160201, q=382 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 26638 Comm: syz.6.6046 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:kasan_check_range+0x0/0x290 mm/kasan/generic.c:186
Code: 48 c1 ee 03 48 01 c6 48 89 c7 e8 fb 5c b3 08 31 c0 c3 0f 0b b8 ea ff ff ff c3 0f 0b b8 ea ff ff ff c3 cc cc cc cc cc cc cc cc <66> 0f 1f 00 b0 01 48 85 f6 0f 84 b4 01 00 00 55 41 57 41 56 41 55
RSP: 0018:ffffc90000007b78 EFLAGS: 00000046
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff81691dc6
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff8e8c6268
RBP: ffffc90000007c88 R08: ffff8881406b515f R09: 1ffff110280d6a2b
R10: dffffc0000000000 R11: ffffed10280d6a2c R12: ffffffff88b98fe7
R13: dffffc0000000000 R14: dffffc0000000000 R15: 1ffff92000000f7c
FS:  00007fdf6398e6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fdf6398dff8 CR3: 000000002d20d000 CR4: 00000000003506f0
DR0: 0000000000010000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 instrument_atomic_read include/linux/instrumented.h:68 [inline]
 _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
 cpumask_test_cpu include/linux/cpumask.h:504 [inline]
 cpu_online include/linux/cpumask.h:1082 [inline]
 trace_lock_release include/trace/events/lock.h:69 [inline]
 lock_release+0xa6/0x8c0 kernel/locking/lockdep.c:5801
 rcu_lock_release include/linux/rcupdate.h:344 [inline]
 rcu_read_unlock include/linux/rcupdate.h:819 [inline]
 advance_sched+0xb07/0xc70 net/sched/sch_taprio.c:1004
 __run_hrtimer kernel/time/hrtimer.c:1754 [inline]
 __hrtimer_run_queues+0x525/0xc10 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> ab 96 c0 f6 65 8b 05 1c 54 67 75 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc9000b4cfbe0 EFLAGS: 00000206
RAX: dffffc0000000004 RBX: 0000000000000a02 RCX: a59e7d4231d84000
RDX: dffffc0000000000 RSI: ffffffff8acacce0 RDI: 0000000000000001
RBP: ffffc9000b4cfc70 R08: ffffffff8e8c626f R09: 1ffffffff1d18c4d
R10: dffffc0000000000 R11: fffffbfff1d18c4e R12: dffffc0000000000
R13: 1ffff92001699f90 R14: ffffffff8d8db158 R15: 1ffff92001699f7c
 spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
 add_device_randomness+0xc6/0x110 drivers/char/random.c:915
 do_settimeofday64+0x66a/0x750 kernel/time/timekeeping.c:1349
 __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: 0033:0x7fdf62b9e199
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:00007fdf6398e028 EFLAGS: 00000246 ORIG_RAX: 00000000000000e3
RAX: ffffffffffffffda RBX: 00007fdf62e25fa0 RCX: 00007fdf62b9e199
RDX: 0000000000000000 RSI: 0000200000000240 RDI: 0000000000000000
RBP: 00007fdf62c358e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdf62e26038 R14: 00007fdf62e25fa0 R15: 00007fff1ba58be8
 </TASK>
task:syz.8.6043      state:R  running task     stack:27560 pid:26631 ppid:23225  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]
 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:1362
 exit_mm+0x23f/0x340 kernel/exit.c:576
 do_exit+0x909/0x2530 kernel/exit.c:877
 do_group_exit+0x22d/0x2f0 kernel/exit.c:1032
 get_signal+0x12a6/0x1390 kernel/signal.c:2915
 arch_do_signal_or_restart+0xc2/0x7b0 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:213
 __syscall_exit_to_user_mode_work kernel/entry/common.c:294 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:305
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7efdc3b9e199
RSP: 002b:00007efdc1df60e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007efdc3e26188 RCX: 00007efdc3b9e199
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007efdc3e26188
RBP: 00007efdc3e26180 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007efdc3e26218 R14: 00007fffa03ae510 R15: 00007fffa03ae5f8
 </TASK>
rcu: rcu_preempt kthread starved for 10495 jiffies! g160201 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:27048 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: 9594 Comm: kworker/u4:54 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
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 01 0b 00 41 83 e6 01 49 be 00 00 00 00 00 fc ff df 75 07 e8 6f 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 53 fd
RSP: 0018:ffffc90003317780 EFLAGS: 00000293
RAX: ffffffff817c935d RBX: 1ffffd1ffff84659 RCX: ffff888030b45a00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc90003317900 R08: ffffffff911f0507 R09: 1ffffffff223e0a0
R10: dffffc0000000000 R11: fffffbfff223e0a1 R12: ffffe8ffffc232c8
R13: ffff8880b8f3d380 R14: dffffc0000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff2b1f037b8 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 (9):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/07 14:14 linux-6.6.y a91a6aa9253c 6520ecdb .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 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.