INFO: rcu detected stall in sys_clock_adjtime (3)

Status: upstream: reported syz repro on 2025/10/14 11:53
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+1e57799e7f3481b8e1bb@syzkaller.appspotmail.com
First crash: 305d, last: 11h41m
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (1)
Date Name Commit Repro Result
2025/10/18 upstream (ToT) 1c64efcb083c syz [report] INFO: rcu detected stall in sys_clock_adjtime
▶ ▼ Similar bugs (6)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: rcu detected stall in sys_clock_adjtime 1 28 789d 1240d 0/3 auto-obsoleted due to no activity on 2024/09/25 13:11
upstream INFO: rcu detected stall in sys_clock_adjtime kernel 1 syz, C done inconclusive 183 5h27m 2230d 0/29 upstream: reported C repro on 2020/07/07 15:13
linux-6.6 INFO: rcu detected stall in sys_clock_adjtime (2) 1 7 18d 93d 0/2 upstream: reported on 2026/05/14 12:23
linux-6.6 INFO: rcu detected stall in sys_clock_adjtime 1 2 269d 281d 0/2 auto-obsoleted due to no activity on 2026/02/26 19:58
linux-5.15 INFO: rcu detected stall in sys_clock_adjtime origin:upstream 1 syz, C error 60 18d 1226d 0/3 upstream: reported C repro on 2023/04/06 18:02
linux-6.1 INFO: rcu detected stall in sys_clock_adjtime (2) 1 3 607d 614d 0/3 auto-obsoleted due to no activity on 2025/03/26 12:12

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (1 GPs behind) idle=77f4/1/0x4000000000000000 softirq=10108/10109 fqs=2
	(detected by 1, t=10502 jiffies, g=10585, q=11 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4518 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:__kasan_check_read+0x6/0x10 mm/kasan/shadow.c:31
Code: 41 5f 5d c3 48 c7 c7 fa c5 39 8c eb 0a 48 c7 c7 ec 2d 23 8c 48 89 de e8 68 53 34 08 31 ed eb d7 00 00 cc cc 89 f6 48 8b 0c 24 <31> d2 e9 a3 ec ff ff 0f 1f 00 89 f6 48 8b 0c 24 ba 01 00 00 00 e9
RSP: 0018:ffffc90000007b58 EFLAGS: 00000046
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff81630269
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff8dff0e28
RBP: ffffc90000007c68 R08: 0000000000000000 R09: 0000000000000000
R10: ffffed100b6bf65e R11: 1ffff1100b6bf65d R12: 0000000000000000
R13: 1ffff92000000f78 R14: 0000000000000000 R15: dffffc0000000000
FS:  00007fd2e27646c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd2e2763f98 CR3: 000000002b4af000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 instrument_atomic_read include/linux/instrumented.h:72 [inline]
 _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
 cpumask_test_cpu include/linux/cpumask.h:444 [inline]
 cpu_online include/linux/cpumask.h:1030 [inline]
 trace_lock_acquire include/trace/events/lock.h:24 [inline]
 lock_acquire+0xd9/0x490 kernel/locking/lockdep.c:5633
 rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 rcu_read_lock include/linux/rcupdate.h:791 [inline]
 advance_sched+0x6e8/0x970 net/sched/sch_taprio.c:753
 __run_hrtimer kernel/time/hrtimer.c:1747 [inline]
 __hrtimer_run_queues+0x554/0xd60 kernel/time/hrtimer.c:1811
 hrtimer_interrupt+0x3c5/0x9c0 kernel/time/hrtimer.c:1873
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1107 [inline]
 __sysvec_apic_timer_interrupt+0x153/0x5a0 arch/x86/kernel/apic/apic.c:1124
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
 sysvec_apic_timer_interrupt+0x9b/0xc0 arch/x86/kernel/apic/apic.c:1118
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:percpu_down_read include/linux/percpu-rwsem.h:63 [inline]
RIP: 0010:cpus_read_lock+0x97/0x150 kernel/cpu.c:310
Code: cd 33 00 85 db 74 57 e8 17 ca 33 00 eb 05 e8 10 ca 33 00 8b 1d 1a 64 2f 0b 31 ff 89 de e8 61 cd 33 00 85 db 0f 85 88 00 00 00 <e8> f4 c9 33 00 48 8b 05 65 64 2f 0b 65 ff 00 bf 01 00 00 00 e8 c0
RSP: 0018:ffffc900038379b0 EFLAGS: 00000246
RAX: ffffffff814d15cf RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff88801eefd940 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90003837ab0 R08: dffffc0000000000 R09: fffffbfff2119049
R10: fffffbfff2119049 R11: 1ffffffff2119048 R12: 1ffff92000706f60
R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000225c17d03
 clock_was_set+0x165/0x990 kernel/time/hrtimer.c:981
 timekeeping_inject_offset+0x578/0x620 kernel/time/timekeeping.c:1395
 do_adjtimex+0x418/0x9b0 kernel/time/timekeeping.c:2444
 do_clock_adjtime kernel/time/posix-timers.c:1155 [inline]
 __do_sys_clock_adjtime kernel/time/posix-timers.c:1167 [inline]
 __se_sys_clock_adjtime kernel/time/posix-timers.c:1158 [inline]
 __x64_sys_clock_adjtime+0x1f0/0x2a0 kernel/time/posix-timers.c:1158
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fd2e198f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fd2e2764038 EFLAGS: 00000246 ORIG_RAX: 0000000000000131
RAX: ffffffffffffffda RBX: 00007fd2e1be6090 RCX: 00007fd2e198f749
RDX: 0000000000000000 RSI: 0000200000000200 RDI: 0000000000000000
RBP: 00007fd2e1a13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd2e1be6128 R14: 00007fd2e1be6090 R15: 00007fff655e0068
 </TASK>
rcu: rcu_preempt kthread starved for 10498 jiffies! g10585 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:27840 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 schedule_timeout+0x15c/0x280 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x2f2/0x1310 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0x95/0x380 kernel/rcu/tree.c:1905
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 PID: 11 Comm: kworker/u4:1 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: events_unbound toggle_allocation_gate
RIP: 0010:check_kcov_mode kernel/kcov.c:193 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x32/0x60 kernel/kcov.c:216
Code: 64 8f 81 7e 65 8b 15 65 8f 81 7e 81 e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75 35 83 b9 1c 16 00 00 00 74 2c 8b 91 f8 15 00 00 <83> fa 02 75 21 48 8b 91 00 16 00 00 48 8b 32 48 8d 7e 01 8b 89 fc
RSP: 0018:ffffc900001077f8 EFLAGS: 00000246
RAX: ffffffff81760a02 RBX: dffffc0000000000 RCX: ffff88813fe4bb80
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc90000107960 R08: dffffc0000000000 R09: fffffbfff2119049
R10: fffffbfff2119049 R11: 1ffffffff2119048 R12: 1ffff110171c85b5
R13: ffff8880b8f3bb80 R14: 0000000000000000 R15: ffff8880b8e42da8
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c00817e000 CR3: 000000000c68e000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 csd_lock_wait kernel/smp.c:424 [inline]
 smp_call_function_many_cond+0xe92/0x1270 kernel/smp.c:998
 on_each_cpu_cond_mask+0x3b/0x80 kernel/smp.c:1165
 on_each_cpu include/linux/smp.h:71 [inline]
 text_poke_sync arch/x86/kernel/alternative.c:1574 [inline]
 text_poke_bp_batch+0x2b0/0x7d0 arch/x86/kernel/alternative.c:1774
 text_poke_flush arch/x86/kernel/alternative.c:1965 [inline]
 text_poke_finish+0x16/0x30 arch/x86/kernel/alternative.c:1972
 arch_jump_label_transform_apply+0x13/0x20 arch/x86/kernel/jump_label.c:146
 static_key_enable_cpuslocked+0x11f/0x240 kernel/jump_label.c:207
 static_key_enable+0x16/0x20 kernel/jump_label.c:220
 toggle_allocation_gate+0xb4/0x430 mm/kfence/core.c:805
 process_one_work+0x898/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaa2/0x1250 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
hrtimer: interrupt took 109680156274 ns

Crashes (9):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/27 01:22 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_clock_adjtime
2025/10/14 11:52 linux-6.1.y 882efbdd9d34 b6605ba8 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_clock_adjtime
2026/08/15 05:37 linux-6.1.y e4f7d8be268e 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_clock_adjtime
2026/08/04 17:17 linux-6.1.y fb28aa725e05 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_clock_adjtime
2026/08/04 03:01 linux-6.1.y fb28aa725e05 9451e17e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_clock_adjtime
2026/07/23 19:09 linux-6.1.y 090666d3cc90 71a13572 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_clock_adjtime
2026/07/14 04:00 linux-6.1.y 090666d3cc90 2130f682 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_clock_adjtime
2026/07/08 12:15 linux-6.1.y 090666d3cc90 88a4b44c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_clock_adjtime
2026/05/19 06:18 linux-6.1.y c27210688955 9f74d399 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_clock_adjtime
* Struck through repros no longer work on HEAD.