INFO: rcu detected stall in sys_clock_settime (2)

Status: upstream: reported on 2026/05/05 16:49
Reported-by: syzbot+61069fb15c7f6969fd52@syzkaller.appspotmail.com
First crash: 101d, last: 14d
▶ ▼ 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 249d 249d 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 12d 1221d 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 219d 1129d 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 576 4d23h 2224d 0/29 upstream: reported C repro on 2020/07/12 17:54
linux-6.6 INFO: rcu detected stall in sys_clock_settime (2) 1 6 14d 53d 0/2 upstream: reported on 2026/06/23 15:18

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (1 GPs behind) idle=fe5/1/0x4000000000000000 softirq=70838/70840 fqs=308 
	(detected by 1, t=10505 jiffies, g=100737, q=8811)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 25390 Comm: syz.2.4930 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:__lock_acquire+0xef/0x7b50 kernel/locking/lockdep.c:4882
Code: c0 84 41 8b 8d 48 c1 e8 03 42 0f b6 04 00 84 c0 0f 85 2d 64 00 00 83 3d d2 60 2e 0c 00 0f 84 ee 26 00 00 83 3d e1 00 c2 0a 00 <74> 2a 4c 89 e8 48 c1 e8 03 42 80 3c 00 00 74 12 4c 89 ef e8 99 3e
RSP: 0018:ffffc90000007940 EFLAGS: 00000002
RAX: 0000000000000000 RBX: 0000000000000001 RCX: 1ffff92000000f48
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8880b902a258
RBP: ffffc90000007b70 R08: dffffc0000000000 R09: 0000000000000001
R10: dffffc0000000000 R11: fffffbfff1b161be R12: 0000000000000001
R13: ffff8880b902a258 R14: 0000000000000000 R15: 0000000000000000
FS:  00007f08ae07b6c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f08ae07aff8 CR3: 00000000475e3000 CR4: 00000000003506f0
Call Trace:
 <IRQ>
 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:128 [inline]
 _raw_spin_lock_irq+0xab/0xf0 kernel/locking/spinlock.c:170
 __run_hrtimer kernel/time/hrtimer.c:1689 [inline]
 __hrtimer_run_queues+0x59a/0xb60 kernel/time/hrtimer.c:1749
 hrtimer_interrupt+0x397/0x8b0 kernel/time/hrtimer.c:1811
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
 __sysvec_apic_timer_interrupt+0x137/0x4a0 arch/x86/kernel/apic/apic.c:1114
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0x9b/0xc0 arch/x86/kernel/apic/apic.c:1108
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:finish_lock_switch+0x12f/0x290 kernel/sched/core.c:4804
Code: 83 c7 18 be ff ff ff ff e8 6e cb 6b 08 85 c0 74 46 4d 85 ff 75 62 0f 1f 44 00 00 48 89 df e8 98 3a 75 08 e8 43 d7 2a 00 fb 5b <41> 5c 41 5d 41 5e 41 5f 5d c3 48 89 df e8 2f 0e fe ff 43 80 3c 2c
RSP: 0018:ffffc90004a4f718 EFLAGS: 00000282
RAX: eada5902d0f46a00 RBX: ffff88801efc8000 RCX: eada5902d0f46a00
RDX: dffffc0000000000 RSI: ffffffff8a2b2be0 RDI: ffffffff8a7a4200
RBP: 1ffff11017207613 R08: ffffffff901ee0c7 R09: 1ffffffff203dc18
R10: dffffc0000000000 R11: fffffbfff203dc19 R12: 1ffff110172075c1
R13: dffffc0000000000 R14: ffff8880b903ae08 R15: 0000000000000000
 finish_task_switch+0x12f/0x650 kernel/sched/core.c:4921
 context_switch kernel/sched/core.c:5052 [inline]
 __schedule+0x11cb/0x4350 kernel/sched/core.c:6395
 preempt_schedule_irq+0xbb/0x160 kernel/sched/core.c:6799
 irqentry_exit+0x63/0x70 kernel/entry/common.c:432
 asm_sysvec_reschedule_ipi+0x16/0x20 arch/x86/include/asm/idtentry.h:681
RIP: 0010:lock_acquire+0x208/0x400 kernel/locking/lockdep.c:5627
Code: f7 84 24 80 00 00 00 00 02 00 00 43 c6 44 3d 04 f8 0f 85 f1 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 44 3d 00 00 00 00 00 43 c7 44 3d 08 00 00 00 00 65 48 8b 04
RSP: 0018:ffffc90004a4fae0 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: eada5902d0f46a00
RDX: 0000000000000000 RSI: ffffffff8a2b3e80 RDI: ffffffff8a7a4200
RBP: ffffc90004a4fbf8 R08: dffffc0000000000 R09: 1ffffffff203dc18
R10: dffffc0000000000 R11: fffffbfff203dc19 R12: ffffffff8c1bd6f0
R13: 1ffff92000949f68 R14: 0000000000000246 R15: dffffc0000000000
 percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
 cpus_read_lock+0x40/0x150 kernel/cpu.c:309
 clock_was_set+0x109/0x880 kernel/time/hrtimer.c:945
 do_settimeofday64+0x597/0x740 kernel/time/timekeeping.c:1328
 __do_sys_clock_settime kernel/time/posix-timers.c:1125 [inline]
 __se_sys_clock_settime kernel/time/posix-timers.c:1113 [inline]
 __x64_sys_clock_settime+0x25a/0x2a0 kernel/time/posix-timers.c:1113
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f08afe65019
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:00007f08ae07b028 EFLAGS: 00000246 ORIG_RAX: 00000000000000e3
RAX: ffffffffffffffda RBX: 00007f08b00ed180 RCX: 00007f08afe65019
RDX: 0000000000000000 RSI: 0000200000000240 RDI: 0000000000000000
RBP: 00007f08afefc00c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f08b00ed218 R14: 00007f08b00ed180 R15: 00007fff951e7d08
 </TASK>
rcu: rcu_preempt kthread starved for 8965 jiffies! g100737 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:28112 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11c3/0x4350 kernel/sched/core.c:6395
 schedule+0x11b/0x1e0 kernel/sched/core.c:6478
 schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2117
 rcu_gp_fqs_loop+0x2be/0x11f0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0x9a/0x370 kernel/rcu/tree.c:2145
 kthread+0x42e/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
NMI backtrace for cpu 1
CPU: 1 PID: 4749 Comm: kworker/u4:9 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: writeback wb_workfn (flush-8:0)
Call Trace:
 <IRQ>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3a2/0x3d0 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:166 [inline]
 rcu_check_gp_kthread_starvation+0x1cd/0x250 kernel/rcu/tree_stall.h:487
 print_other_cpu_stall+0x1110/0x1270 kernel/rcu/tree_stall.h:592
 check_cpu_stall kernel/rcu/tree_stall.h:745 [inline]
 rcu_pending kernel/rcu/tree.c:3936 [inline]
 rcu_sched_clock_irq+0x845/0x1120 kernel/rcu/tree.c:2619
 update_process_times+0x193/0x200 kernel/time/timer.c:2021
 tick_sched_handle kernel/time/tick-sched.c:254 [inline]
 tick_sched_timer+0x37d/0x560 kernel/time/tick-sched.c:1473
 __run_hrtimer kernel/time/hrtimer.c:1685 [inline]
 __hrtimer_run_queues+0x4b0/0xb60 kernel/time/hrtimer.c:1749
 hrtimer_interrupt+0x397/0x8b0 kernel/time/hrtimer.c:1811
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
 __sysvec_apic_timer_interrupt+0x137/0x4a0 arch/x86/kernel/apic/apic.c:1114
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0x9b/0xc0 arch/x86/kernel/apic/apic.c:1108
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:csd_lock_wait kernel/smp.c:440 [inline]
RIP: 0010:smp_call_function_many_cond+0xba3/0xd80 kernel/smp.c:969
Code: 0f b6 44 05 00 84 c0 0f 85 9a 00 00 00 41 8b 1e 89 de 83 e6 01 31 ff e8 fb 73 0b 00 83 e3 01 75 07 e8 91 70 0b 00 eb 42 f3 90 <48> b8 00 00 00 00 00 fc ff df 41 0f b6 44 05 00 84 c0 75 10 41 f7
RSP: 0018:ffffc90003456660 EFLAGS: 00000293
RAX: ffffffff816d8c45 RBX: 0000000000000001 RCX: ffff888017ad8000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc900034567a0 R08: ffff8880b903b407 R09: 1ffff11017207680
R10: dffffc0000000000 R11: ffffed1017207681 R12: ffff8880b913b3c0
R13: 1ffff11017208509 R14: ffff8880b9042848 R15: 0000000000000000
 on_each_cpu_cond_mask+0x3b/0x80 kernel/smp.c:1134
 __flush_tlb_multi arch/x86/include/asm/paravirt.h:87 [inline]
 flush_tlb_multi arch/x86/mm/tlb.c:946 [inline]
 flush_tlb_mm_range+0x363/0x570 arch/x86/mm/tlb.c:1034
 flush_tlb_page arch/x86/include/asm/tlbflush.h:240 [inline]
 ptep_clear_flush+0x112/0x140 mm/pgtable-generic.c:97
 page_mkclean_one+0x1eb/0x3e0 mm/rmap.c:938
 rmap_walk_file+0x407/0x610 mm/rmap.c:2378
 rmap_walk mm/rmap.c:2396 [inline]
 page_mkclean+0x2f5/0x400 mm/rmap.c:1006
 clear_page_dirty_for_io+0x3f9/0x9f0 mm/page-writeback.c:2749
 mpage_submit_page+0x8a/0x210 fs/ext4/inode.c:2095
 mpage_process_page_bufs+0x6c6/0x8a0 fs/ext4/inode.c:2229
 mpage_prepare_extent_to_map+0xc48/0x1080 fs/ext4/inode.c:2657
 ext4_writepages+0x9bb/0x2d40 fs/ext4/inode.c:2785
 do_writepages+0x493/0x700 mm/page-writeback.c:2386
 __writeback_single_inode+0x153/0xda0 fs/fs-writeback.c:1657
 writeback_sb_inodes+0xaaa/0x1750 fs/fs-writeback.c:1940
 __writeback_inodes_wb+0x12a/0x3f0 fs/fs-writeback.c:2011
 wb_writeback+0x45e/0xbc0 fs/fs-writeback.c:2116
 wb_check_old_data_flush fs/fs-writeback.c:2216 [inline]
 wb_do_writeback fs/fs-writeback.c:2269 [inline]
 wb_workfn+0xb15/0xf20 fs/fs-writeback.c:2298
 process_one_work+0x867/0xff0 kernel/workqueue.c:2310
 worker_thread+0xad7/0x12a0 kernel/workqueue.c:2457
 kthread+0x42e/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>

Crashes (8):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/31 16:08 linux-5.15.y 6e2fd6534337 7664cf44 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in sys_clock_settime
2026/05/29 03:01 linux-5.15.y 241d66fa280c 4624854e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in sys_clock_settime
2026/05/28 14:23 linux-5.15.y 241d66fa280c 681715f7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in sys_clock_settime
2026/05/28 02:13 linux-5.15.y 241d66fa280c 4c36e7e5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in sys_clock_settime
2026/05/25 16:46 linux-5.15.y 241d66fa280c c69befb3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in sys_clock_settime
2026/05/07 22:23 linux-5.15.y ef251c45f1cd cbf9e0fc .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in sys_clock_settime
2026/05/06 03:27 linux-5.15.y ef251c45f1cd 26da2c66 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in sys_clock_settime
2026/05/05 16:48 linux-5.15.y ef251c45f1cd 06e69a27 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in sys_clock_settime
* Struck through repros no longer work on HEAD.