syzbot
INFO: rcu detected stall in rt_sigreturn (2)
Status: auto-obsoleted due to no activity on 2026/09/28 12:08
Subsystems:
kernel
Labels:
prio:high
[Documentation on labels]
First crash: 98d, last: 98d
Sample crash report:
IPVS: wrr: UDP 224.0.0.2:0 - no destination available
IPVS: wrr: UDP 224.0.0.2:0 - no destination available
IPVS: wrr: UDP 224.0.0.2:0 - no destination available
IPVS: wrr: UDP 224.0.0.2:0 - no destination available
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: (detected by 1, t=10502 jiffies, g=77349, q=141 ncpus=2)
rcu: All QSes seen, last rcu_preempt kthread activity 10499 (4295010574-4295000075), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 10499 jiffies! g77349 f0x2 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:27592 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5510 [inline]
__schedule+0x125c/0x6730 kernel/sched/core.c:7234
__schedule_loop kernel/sched/core.c:7311 [inline]
schedule+0xdd/0x2c0 kernel/sched/core.c:7326
schedule_timeout+0x127/0x280 kernel/time/sleep_timeout.c:99
rcu_gp_fqs_loop+0x1a9/0x900 kernel/rcu/tree.c:2123
rcu_gp_kthread+0x179/0x230 kernel/rcu/tree.c:2325
kthread+0x370/0x450 kernel/kthread.c:436
ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 13031 Comm: syz.1.1906 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:__kasan_check_byte+0x13/0x50 mm/kasan/common.c:573
Code: 2a 00 00 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 0f 1f 40 d6 41 54 49 89 f4 55 48 89 fd 53 e8 7d 1e 00 00 <89> c3 84 c0 74 0b 89 d8 5b 5d 41 5c e9 bc 41 26 09 4c 89 e1 48 89
RSP: 0018:ffffc90000007d00 EFLAGS: 00000097
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8b9fc44a RDI: fffffbfff36da080
RBP: ffffffff9b6d0400 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffffffff8b9fc44a
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000000
FS: 00007fad8d6ac6c0(0000) GS:ffff8881240e0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f122cc09250 CR3: 0000000075eaa000 CR4: 00000000003526f0
Call Trace:
<IRQ>
kasan_check_byte include/linux/kasan.h:402 [inline]
lock_acquire kernel/locking/lockdep.c:5842 [inline]
lock_acquire+0x132/0x370 kernel/locking/lockdep.c:5825
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:132 [inline]
_raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:166
debug_object_deactivate+0x135/0x3b0 lib/debugobjects.c:936
debug_hrtimer_deactivate kernel/time/hrtimer.c:490 [inline]
__run_hrtimer kernel/time/hrtimer.c:2000 [inline]
__hrtimer_run_queues+0x2e9/0x9c0 kernel/time/hrtimer.c:2096
hrtimer_interrupt+0x3e5/0x940 kernel/time/hrtimer.c:2215
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
__sysvec_apic_timer_interrupt+0x109/0x470 arch/x86/kernel/apic/apic.c:1068
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0x9e/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:lock_acquire+0x5e/0x370 kernel/locking/lockdep.c:5872
Code: 05 bb ef 4e 12 83 f8 07 0f 87 da 00 00 00 48 0f a3 05 06 a2 16 0f 0f 82 ac 02 00 00 8b 35 ce d5 16 0f 85 f6 0f 85 c7 00 00 00 <48> 8b 44 24 30 65 48 2b 05 5d ef 4e 12 0f 85 ec 02 00 00 48 83 c4
RSP: 0018:ffffc9000da07a38 EFLAGS: 00000206
RAX: 0000000000000046 RBX: 0000000000000000 RCX: edbc7214ceca522d
RDX: 0000000000000000 RSI: ffffffff8e137c0e RDI: ffffffff8c3e9b80
RBP: ffff88813fe55038 R08: 00000000ffffffff R09: 00000000000001c8
R10: 0000000000000200 R11: 0000000000000000 R12: 0000000000000001
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000000
__might_fault+0xde/0x140 mm/memory.c:7292
__copy_from_user include/linux/uaccess.h:115 [inline]
check_xstate_in_sigframe arch/x86/kernel/fpu/signal.c:35 [inline]
__fpu_restore_sig+0xee/0x13b0 arch/x86/kernel/fpu/signal.c:340
fpu__restore_sig+0x151/0x190 arch/x86/kernel/fpu/signal.c:485
restore_sigcontext+0x4cb/0x6a0 arch/x86/kernel/signal_64.c:95
__do_sys_rt_sigreturn+0x229/0x2c0 arch/x86/kernel/signal_64.c:268
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fad8c79ce57
Code: 83 c8 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
RSP: 002b:00007fad8d6ac0e8 EFLAGS: 00000246
RAX: 00000000000000ca RBX: 00007fad8ca16188 RCX: 00007fad8c79ce59
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007fad8ca16188
RBP: 00007fad8ca16180 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fad8ca16218 R14: 00007ffd6841d9a0 R15: 00007ffd6841da88
</TASK>
IPVS: wrr: UDP 224.0.0.2:0 - no destination available
IPVS: wrr: UDP 224.0.0.2:0 - no destination available
IPVS: wrr: UDP 224.0.0.2:0 - no destination available
IPVS: wrr: UDP 224.0.0.2:0 - no destination available
IPVS: wrr: UDP 224.0.0.2:0 - no destination available
IPVS: wrr: UDP 224.0.0.2:0 - no destination available
IPVS: wrr: UDP 224.0.0.2:0 - no destination available
IPVS: wrr: UDP 224.0.0.2:0 - no destination available
IPVS: wrr: UDP 224.0.0.2:0 - no destination available
Struck through repros no longer work on HEAD.