syzbot
INFO: rcu detected stall in sys_clock_adjtime (2)
Status:
upstream: reported on 2026/05/14 12:23
Reported-by: syzbot+781e8ba5e868d69673f4@syzkaller.appspotmail.com
First crash: 141d, last: 1d01h
Sample crash report:
net_ratelimit: 24 callbacks suppressed
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 1-...!: (0 ticks this GP) idle=98fc/1/0x4000000000000000 softirq=71900/71900 fqs=2
rcu: (detected by 0, t=10502 jiffies, g=108101, q=192 ncpus=2)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 17081 Comm: syz.0.3309 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:lock_release+0x0/0x8c0 kernel/locking/lockdep.c:5764
Code: 07 80 c1 03 38 c1 0f 8c 5d fa ff ff 4c 89 f7 e8 06 fe 76 00 e9 50 fa ff ff 41 be 2f 00 00 00 e9 66 fa ff ff 66 0f 1f 44 00 00 <f3> 0f 1e fa 55 48 89 e5 41 57 41 56 41 55 41 54 53 48 83 e4 e0 48
RSP: 0018:ffffc900001f0cb8 EFLAGS: 00000092
RAX: f3f3f3f8f1f1f1f1 RBX: 0000000000000802 RCX: 0000000000000002
RDX: ffff88805eb88164 RSI: ffffffff817778dc RDI: ffffffff974f1cd0
RBP: ffffc900001f0d50 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff5200003e17c R12: dffffc0000000000
R13: ffff88802cd2f340 R14: ffffffff974f1cb8 R15: 1ffff9200003e198
FS: 00007f6bb76e56c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f67bee33d58 CR3: 000000005d11a000 CR4: 00000000003506e0
Call Trace:
<IRQ>
__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:149 [inline]
_raw_spin_unlock_irqrestore+0x71/0x120 kernel/locking/spinlock.c:194
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:ktime_mono_to_any+0x53/0x100 kernel/time/timekeeping.c:927
Code: 02 0f 87 b0 00 00 00 e8 db c1 0f 00 49 bc 00 00 00 00 00 fc ff df 4e 8d 34 f5 a0 c6 cc 8a 4c 89 f0 48 c1 e8 03 42 80 3c 20 00 <74> 08 4c 89 f7 e8 d3 4d 68 00 4d 8b 36 4d 89 f5 49 c1 ed 03 e8 a4
RSP: 0018:ffffc90004997918 EFLAGS: 00000246
RAX: 1ffffffff15998d4 RBX: 0000000000000000 RCX: 0000000000080000
RDX: ffffc9000cb9a000 RSI: 00000000000000e2 RDI: 00000000000000e3
RBP: 0000000000000000 R08: ffffffff8e8c316f R09: 1ffffffff1d1862d
R10: dffffc0000000000 R11: fffffbfff1d1862e R12: dffffc0000000000
R13: ffff8880b8f2b740 R14: ffffffff8accc6a0 R15: 0000000000000002
ktime_mono_to_real include/linux/timekeeping.h:149 [inline]
timerfd_clock_was_set+0x20/0x2c0 fs/timerfd.c:99
clock_was_set+0x788/0x800 kernel/time/hrtimer.c:996
timekeeping_inject_offset+0x5d0/0x670 kernel/time/timekeeping.c:1395
do_adjtimex+0x47c/0xa10 kernel/time/timekeeping.c:2450
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+0x244/0x320 kernel/time/posix-timers.c:1163
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: 0033:0x7f6bb679e159
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:00007f6bb76e5028 EFLAGS: 00000246 ORIG_RAX: 0000000000000131
RAX: ffffffffffffffda RBX: 00007f6bb6a25fa0 RCX: 00007f6bb679e159
RDX: 0000000000000000 RSI: 0000200000000000 RDI: 0000000000000000
RBP: 00007f6bb683506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6bb6a26038 R14: 00007f6bb6a25fa0 R15: 00007ffc19bfac48
</TASK>
rcu: rcu_preempt kthread starved for 10498 jiffies! g108101 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:27832 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: 0 PID: 15124 Comm: kworker/u4:7 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 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:ffffc9000d6a7780 EFLAGS: 00000293
RAX: ffffffff817c8dfd RBX: 1ffff110171e83e1 RCX: ffff88802736da00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc9000d6a7900 R08: ffffffff911eb507 R09: 1ffffffff223d6a0
R10: dffffc0000000000 R11: fffffbfff223d6a1 R12: ffff8880b8f41f08
R13: ffff8880b8e3d380 R14: dffffc0000000000 R15: 0000000000000001
FS: 0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2de22ff8 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/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>
* Struck through repros no longer work on HEAD.