syzbot
INFO: rcu detected stall in sys_openat
Status:
upstream: reported C repro on 2025/07/10 07:34
Bug presence:
origin:lts-only
[Documentation on labels]
Reported-by: syzbot+6d93f26ac7a5c42350ec@syzkaller.appspotmail.com
First crash: 392d, last: 7d14h
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Bug presence (2)
| Date |
Name |
Commit |
Repro |
Result |
| 2025/08/20 |
linux-6.6.y (ToT) |
bb9c90ab9c5a |
C
|
[report] INFO: rcu detected stall in corrupted
|
| 2025/08/20 |
upstream (ToT) |
b19a97d57c15 |
C
|
Didn't crash |
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Fix bisection attempts (1)
| Created |
Duration |
User |
Patch |
Repo |
Result |
| 2025/08/28 01:59 |
2h08m
|
fix candidate
|
|
upstream |
OK
(0)
job log
|
Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P5789/1:b..l
rcu: (detected by 1, t=10503 jiffies, g=9613, q=38 ncpus=2)
task:udevd state:R running task stack:26632 pid:5789 ppid:5137 flags:0x00004002
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5381 [inline]
__schedule+0x1553/0x45a0 kernel/sched/core.c:6700
preempt_schedule_irq+0xbf/0x150 kernel/sched/core.c:7010
irqentry_exit+0x67/0x70 kernel/entry/common.c:438
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:lock_acquire+0x208/0x420 kernel/locking/lockdep.c:5758
Code: f7 84 24 80 00 00 00 00 02 00 00 43 c6 44 3c 04 f8 0f 85 f0 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 04 3c 00 00 00 00 43 c7 44 3c 08 00 00 00 00 65 48 8b 04 25
RSP: 0018:ffffc9000458f5a0 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 256779044af82300
RDX: 0000000000000000 RSI: ffffffff8acadb60 RDI: ffffffff8b1c8fa0
RBP: ffffc9000458f6a8 R08: dffffc0000000000 R09: 1ffffffff2238ca0
R10: dffffc0000000000 R11: fffffbfff2238ca1 R12: 1ffff920008b1ec0
R13: ffffffff8d1320e0 R14: 0000000000000246 R15: dffffc0000000000
rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
rcu_read_lock include/linux/rcupdate.h:786 [inline]
get_obj_cgroup_from_current+0xf0/0x280 mm/memcontrol.c:3058
memcg_slab_pre_alloc_hook mm/slab.h:492 [inline]
slab_pre_alloc_hook+0x91/0x310 mm/slab.h:719
slab_alloc_node mm/slub.c:3477 [inline]
slab_alloc mm/slub.c:3503 [inline]
__kmem_cache_alloc_lru mm/slub.c:3510 [inline]
kmem_cache_alloc_lru+0x4d/0x2d0 mm/slub.c:3526
__d_alloc+0x31/0x730 fs/dcache.c:1773
d_alloc fs/dcache.c:1853 [inline]
d_alloc_parallel+0xe0/0x1530 fs/dcache.c:2646
lookup_open fs/namei.c:3421 [inline]
open_last_lookups fs/namei.c:3564 [inline]
path_openat+0x933/0x3230 fs/namei.c:3794
do_filp_open+0x1f5/0x430 fs/namei.c:3824
do_sys_openat2+0x134/0x1d0 fs/open.c:1421
do_sys_open fs/open.c:1436 [inline]
__do_sys_openat fs/open.c:1452 [inline]
__se_sys_openat fs/open.c:1447 [inline]
__x64_sys_openat+0x139/0x160 fs/open.c:1447
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: 0033:0x7fa1337c7407
RSP: 002b:00007ffce6a53390 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fa13319b880 RCX: 00007fa1337c7407
RDX: 0000000000080000 RSI: 00007ffce6a53500 RDI: ffffffffffffff9c
RBP: 0000000000000008 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 00005599cd1647f5
R13: 00005599cd1647f5 R14: 0000000000000001 R15: 00005599cd17f140
</TASK>
rcu: rcu_preempt kthread starved for 10540 jiffies! g9613 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:27656 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:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 5807 Comm: syz-executor298 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:get_current arch/x86/include/asm/current.h:41 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x8/0x60 kernel/kcov.c:215
Code: 00 00 f3 0f 1e fa 53 48 89 fb e8 13 00 00 00 48 8b 3d dc f9 03 0d 48 89 de 5b e9 d3 67 57 00 cc cc cc f3 0f 1e fa 48 8b 04 24 <65> 48 8b 0d b0 93 7c 7e 65 8b 15 b1 93 7c 7e 81 e2 00 01 ff 00 74
RSP: 0018:ffffc90000007d00 EFLAGS: 00000006
RAX: ffffffff8a76c7e6 RBX: ffff8880b8e2b7d0 RCX: ffff88802c983c00
RDX: 0000000000010000 RSI: ffff88802bcee0b0 RDI: ffff8880b8e2c050
RBP: 1ffff1100579dc16 R08: ffffffff9757acdb R09: 1ffffffff2eaf59b
R10: dffffc0000000000 R11: fffffbfff2eaf59c R12: ffff88802bcee0b0
R13: dffffc0000000000 R14: ffff88802bcee0b0 R15: ffff8880b8e2c050
FS: 00005555898253c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000020000006b000 CR3: 000000007b9fa000 CR4: 00000000003506f0
Call Trace:
<IRQ>
timerqueue_del+0x56/0x100 lib/timerqueue.c:55
__remove_hrtimer kernel/time/hrtimer.c:1141 [inline]
__run_hrtimer kernel/time/hrtimer.c:1730 [inline]
__hrtimer_run_queues+0x37f/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_irq include/linux/spinlock_api_smp.h:160 [inline]
RIP: 0010:_raw_spin_unlock_irq+0x29/0x50 kernel/locking/spinlock.c:202
Code: 00 f3 0f 1e fa 53 48 89 fb 48 83 c7 18 48 8b 74 24 08 e8 ea 97 d8 f6 48 89 df e8 a2 6c d9 f6 e8 1d 7f fd f6 fb bf 01 00 00 00 <e8> 82 73 cc f6 65 8b 05 c3 a0 73 75 85 c0 74 02 5b c3 e8 40 88 70
RSP: 0018:ffffc9000467fc78 EFLAGS: 00000286
RAX: d686ec5f7a3d3600 RBX: ffff88802bb3ae40 RCX: d686ec5f7a3d3600
RDX: dffffc0000000000 RSI: ffffffff8acac9e0 RDI: 0000000000000001
RBP: ffff88802bb3b2d8 R08: ffffffff8e8b19af R09: 1ffffffff1d16335
R10: dffffc0000000000 R11: fffffbfff1d16336 R12: 1ffff1100576765b
R13: 0000000000000021 R14: dffffc0000000000 R15: 0000000000000000
spin_unlock_irq include/linux/spinlock.h:401 [inline]
get_signal+0x11f5/0x13f0 kernel/signal.c:2905
arch_do_signal_or_restart+0xc2/0x800 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
do_syscall_64+0x61/0xa0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f417fba761e
Code: 08 0f 85 e5 e1 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 90 41 57 41 56 4d 89 c6 41 55 4d 89 cd 41 54 55 53 48 83 ec 08
RSP: 002b:00007ffc44a80928 EFLAGS: 00000246
RAX: fffffffffffffff7 RBX: 00005555898253c0 RCX: 00007f417fba761e
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003
R13: 00007ffc44a809c0 R14: 00007ffc44a80a00 R15: 0000000000000000
</TASK>
sched: RT throttling activated
Struck through repros no longer work on HEAD.