[v6.6] INFO: rcu detected stall in sys_clock_adjtime (2)

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May 14, 2026, 8:23:26 AM (2 days ago) May 14
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Hello,

syzbot found the following issue on:

HEAD commit: 3b9f64db0496 Linux 6.6.138
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16ab8950580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c5b35c4db8465904
dashboard link: https://syzkaller.appspot.com/bug?extid=781e8ba5e868d69673f4
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9e5afbe648d5/disk-3b9f64db.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c3607dd9b93c/vmlinux-3b9f64db.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f0392d8b3ded/bzImage-3b9f64db.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+781e8b...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 1-...!: (1 GPs behind) idle=622c/1/0x4000000000000000 softirq=11568/11569 fqs=2
rcu: (detected by 0, t=10506 jiffies, g=11945, q=380 ncpus=2)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 5980 Comm: syz.2.33 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:kasan_check_range+0x0/0x290 mm/kasan/generic.c:186
Code: 48 c1 ee 03 48 01 c6 48 89 c7 e8 5b f8 a7 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:ffffc900001f0a18 EFLAGS: 00000046
RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffffffff81682ae7
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff8e8b19a8
RBP: ffffc900001f0b28 R08: 0000000000000001 R09: 0000000000000000
R10: dffffc0000000000 R11: fffff5200003e184 R12: 1ffff9200003e150
R13: ffffffff8d7d9560 R14: 0000000000000001 R15: dffffc0000000000
FS: 00007f3bad1406c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c456059 CR3: 000000007f9b9000 CR4: 00000000003506e0
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_acquire include/trace/events/lock.h:24 [inline]
lock_acquire+0xb7/0x420 kernel/locking/lockdep.c:5725
debug_objects_fill_pool+0xab/0x730 lib/debugobjects.c:615
debug_object_activate+0x36/0x4f0 lib/debugobjects.c:705
debug_hrtimer_activate kernel/time/hrtimer.c:450 [inline]
debug_activate kernel/time/hrtimer.c:505 [inline]
enqueue_hrtimer+0x30/0x370 kernel/time/hrtimer.c:1108
__run_hrtimer kernel/time/hrtimer.c:1767 [inline]
__hrtimer_run_queues+0x63a/0xc40 kernel/time/hrtimer.c:1814
hrtimer_interrupt+0x3c9/0x9c0 kernel/time/hrtimer.c:1876
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> 0b 74 cc f6 65 8b 05 4c a1 73 75 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc900051d7a20 EFLAGS: 00000206
RAX: dffffc0000000004 RBX: 0000000000000a06 RCX: f8a317e7c998bf00
RDX: dffffc0000000000 RSI: ffffffff8acac9e0 RDI: 0000000000000001
RBP: ffffc900051d7ab0 R08: ffffffff8e8b19af R09: 1ffffffff1d16335
R10: dffffc0000000000 R11: fffffbfff1d16336 R12: dffffc0000000000
R13: dffffc0000000000 R14: ffffffff8d14b800 R15: 1ffff92000a3af44
timekeeping_inject_offset+0x5c7/0x670 kernel/time/timekeeping.c:1392
do_adjtimex+0x47c/0xa10 kernel/time/timekeeping.c:2444
do_clock_adjtime kernel/time/posix-timers.c:1160 [inline]
__do_sys_clock_adjtime kernel/time/posix-timers.c:1172 [inline]
__se_sys_clock_adjtime kernel/time/posix-timers.c:1163 [inline]
__x64_sys_clock_adjtime+0x246/0x320 kernel/time/posix-timers.c:1163
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f3bac19ce59
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:00007f3bad140028 EFLAGS: 00000246 ORIG_RAX: 0000000000000131
RAX: ffffffffffffffda RBX: 00007f3bac415fa0 RCX: 00007f3bac19ce59
RDX: 0000000000000000 RSI: 0000200000000380 RDI: 0000000000000000
RBP: 00007f3bac232d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f3bac416038 R14: 00007f3bac415fa0 R15: 00007ffc2d60a698
</TASK>
rcu: rcu_preempt kthread starved for 10495 jiffies! g11945 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:27344 pid:17 ppid:2 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5381 [inline]
__schedule+0x1553/0x45a0 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+0x313/0x1590 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: 313 Comm: kworker/u4:5 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: events_unbound toggle_allocation_gate
RIP: 0010:csd_lock_wait kernel/smp.c:311 [inline]
RIP: 0010:smp_call_function_many_cond+0xdfe/0x1140 kernel/smp.c:855
Code: 45 8b 2c 24 44 89 ee 83 e6 01 31 ff e8 cb f5 0a 00 41 83 e5 01 49 bd 00 00 00 00 00 fc ff df 75 07 e8 06 f2 0a 00 eb 38 f3 90 <42> 0f b6 04 2b 84 c0 75 11 41 f7 04 24 01 00 00 00 74 1e e8 ea f1
RSP: 0018:ffffc900031c7780 EFLAGS: 00000293
RAX: ffffffff817c3016 RBX: 1ffff110171e826d RCX: ffff88801cbdda00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc900031c7900 R08: ffffffff911c6507 R09: 1ffffffff2238ca0
R10: dffffc0000000000 R11: fffffbfff2238ca1 R12: ffff8880b8f41368
R13: dffffc0000000000 R14: ffff8880b8e3d148 R15: 0000000000000001
FS: 0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbf5d810000 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/0x990 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+0xa5d/0x15d0 kernel/workqueue.c:2730
worker_thread+0xa55/0xfc0 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>


---
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