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: 6d21h, last: 6d08h
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 702d 1154d 0/3 auto-obsoleted due to no activity on 2024/09/25 13:11
linux-6.1 INFO: rcu detected stall in sys_clock_adjtime (3) origin:upstream 1 syz error 3 2d03h 218d 0/3 upstream: reported syz repro on 2025/10/14 11:53
upstream INFO: rcu detected stall in sys_clock_adjtime fs 1 C done inconclusive 153 19h21m 2143d 0/29 upstream: reported C repro on 2020/07/07 15:13
linux-6.6 INFO: rcu detected stall in sys_clock_adjtime 1 2 183d 195d 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 C error 54 26d 1140d 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 520d 527d 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: 	1-...!: (0 ticks this GP) idle=6d4c/1/0x4000000000000000 softirq=105269/105269 fqs=0
rcu: 	(detected by 0, t=10502 jiffies, g=159197, q=212 ncpus=2)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 21405 Comm: syz.0.4023 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:__sanitizer_cov_trace_const_cmp4+0x0/0x90 kernel/kcov.c:314
Code: c0 4c 89 01 48 c7 44 11 08 03 00 00 00 48 89 7c 11 10 48 89 74 11 18 48 89 44 11 20 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 <f3> 0f 1e fa 48 8b 04 24 65 48 8b 15 00 90 7c 7e 65 8b 0d 01 90 7c
RSP: 0018:ffffc900001f0d38 EFLAGS: 00000046
RAX: d27d507e69900200 RBX: ffff8880b8f2b848 RCX: 0000000000000001
RDX: ffff8880b8f2b708 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc900001f0e90 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff5200003e184 R12: ffff88806581c340
R13: dffffc0000000000 R14: 0000000000000001 R15: ffff8880b8f2b800
FS:  00007f8b065bc6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffc023c3f80 CR3: 000000001cb4e000 CR4: 00000000003506e0
Call Trace:
 <IRQ>
 __run_hrtimer kernel/time/hrtimer.c:1765 [inline]
 __hrtimer_run_queues+0x5f0/0xc40 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:ffffc90003937900 EFLAGS: 00000206
RAX: dffffc0000000004 RBX: 0000000000000a02 RCX: d27d507e69900200
RDX: dffffc0000000000 RSI: ffffffff8acac9e0 RDI: 0000000000000001
RBP: ffffc90003937990 R08: ffffffff911c6507 R09: 1ffffffff2238ca0
R10: dffffc0000000000 R11: fffffbfff2238ca1 R12: dffffc0000000000
R13: ffff8880b8e2b700 R14: ffff8880b8e2b700 R15: 1ffff92000726f20
 clock_was_set+0x651/0x7d0 kernel/time/hrtimer.c:993
 timekeeping_inject_offset+0x5d1/0x670 kernel/time/timekeeping.c:1395
 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: 0033:0x7f8b0579ce59
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:00007f8b065bc028 EFLAGS: 00000246 ORIG_RAX: 0000000000000131
RAX: ffffffffffffffda RBX: 00007f8b05a15fa0 RCX: 00007f8b0579ce59
RDX: 0000000000000000 RSI: 0000200000000340 RDI: 0000000000000000
RBP: 00007f8b05832d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8b05a16038 R14: 00007f8b05a15fa0 R15: 00007ffcd9a01888
 </TASK>
rcu: rcu_preempt kthread starved for 10502 jiffies! g159197 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:27080 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: 21404 Comm: syz.0.4023 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
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: 0000:ffffc90004367820 EFLAGS: 00000293
RAX: ffffffff817c3016 RBX: 1ffff110171e826d RCX: ffff88807c019e00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc900043679a0 R08: ffffffff911c6507 R09: 1ffffffff2238ca0
R10: dffffc0000000000 R11: fffffbfff2238ca1 R12: ffff8880b8f41368
R13: dffffc0000000000 R14: ffff8880b8e3d148 R15: 0000000000000001
FS:  00005555751f9500(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8b0654d520 CR3: 000000001cb4e000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 on_each_cpu_cond_mask+0x3f/0x80 kernel/smp.c:1022
 __flush_tlb_multi arch/x86/include/asm/paravirt.h:87 [inline]
 flush_tlb_multi arch/x86/mm/tlb.c:990 [inline]
 flush_tlb_mm_range+0x424/0x6a0 arch/x86/mm/tlb.c:1078
 flush_tlb_page arch/x86/include/asm/tlbflush.h:255 [inline]
 ptep_clear_flush+0x120/0x170 mm/pgtable-generic.c:101
 wp_page_copy mm/memory.c:3162 [inline]
 do_wp_page+0x1dc3/0x35f0 mm/memory.c:3469
 handle_pte_fault mm/memory.c:5063 [inline]
 __handle_mm_fault mm/memory.c:5188 [inline]
 handle_mm_fault+0x135d/0x4c00 mm/memory.c:5353
 do_user_addr_fault+0xac8/0x12c0 arch/x86/mm/fault.c:1322
 handle_page_fault arch/x86/mm/fault.c:1463 [inline]
 exc_page_fault+0x64/0x100 arch/x86/mm/fault.c:1516
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:608
RIP: 0033:0x7f8b057597d4
Code: 0f 92 c7 72 b0 48 8b 44 24 08 48 8d 84 06 00 08 00 00 4c 01 f0 48 21 d8 49 39 c2 72 98 8b 1d db 4f 29 00 31 c0 b9 01 00 00 00 <f0> 0f b1 0d 44 3d df 00 0f 85 ae 09 00 00 c1 e3 02 48 8b 05 54 3d
RSP: 002b:00007ffcd9a01830 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000006 RCX: 0000000000000001
RDX: 000000000000003f RSI: 0000000000000fff RDI: 00007ffcd9a01978
RBP: 0000000000000000 R08: 0000000000000004 R09: 0000000000000032
R10: 0000000000021000 R11: 0000000000020000 R12: 00007ffcd9a01980
R13: ffffffffffffffc0 R14: 0000000000001000 R15: 0000000000000000
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/15 00:36 linux-6.6.y 3b9f64db0496 6ccb967e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_clock_adjtime
2026/05/14 12:23 linux-6.6.y 3b9f64db0496 6ccb967e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_clock_adjtime
* Struck through repros no longer work on HEAD.