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INFO: rcu detected stall in lo_ioctl (8)

Status: auto-obsoleted due to no activity on 2026/03/24 20:58
Subsystems: mm block
[Documentation on labels]
First crash: 103d, last: 93d
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ID Workflow Result Correct Bug Created Started Finished Revision Error
a9f7cc85-a5e3-41c2-b6bd-7ec2a6cbd8e6 repro INFO: rcu detected stall in lo_ioctl (8) 2026/03/06 05:48 2026/03/06 05:48 2026/03/06 05:57 31e9c887f7dc24e04b3ca70d0d54fc34141844b0
Similar bugs (10)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 INFO: rcu detected stall in lo_ioctl (2) 1 1 234d 234d 0/3 auto-obsoleted due to no activity on 2025/11/13 16:37
upstream INFO: rcu detected stall in lo_ioctl (4) block 1 2 967d 1023d 0/29 auto-obsoleted due to no activity on 2023/11/02 10:53
linux-5.15 INFO: rcu detected stall in lo_ioctl 1 1 662d 662d 0/3 auto-obsoleted due to no activity on 2024/09/11 22:21
upstream INFO: rcu detected stall in lo_ioctl (2) mm 1 2 2306d 2307d 0/29 closed as invalid on 2019/12/04 14:04
upstream INFO: rcu detected stall in lo_ioctl (3) kernfs 1 2 1550d 1555d 0/29 closed as invalid on 2022/02/08 10:00
upstream INFO: rcu detected stall in lo_ioctl block 1 193 2822d 3022d 0/29 closed as dup on 2018/05/04 17:09
upstream INFO: rcu detected stall in lo_ioctl (5) block 1 7 605d 694d 0/29 auto-obsoleted due to no activity on 2024/10/29 01:08
upstream INFO: rcu detected stall in lo_ioctl (7) mm 1 1 206d 206d 0/29 auto-obsoleted due to no activity on 2025/12/02 00:39
upstream INFO: rcu detected stall in lo_ioctl (6) block 1 4 407d 477d 0/29 auto-obsoleted due to no activity on 2025/05/14 17:06
android-5-15 BUG: soft lockup in lo_ioctl 1 2 677d 698d 0/2 auto-obsoleted due to no activity on 2024/08/18 12:53

Sample crash report:
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P7864/1:b..l
rcu: 	(detected by 0, t=10502 jiffies, g=26129, q=1258 ncpus=2)
task:syz.4.355       state:R  running task     stack:25336 pid:7864  tgid:7863  ppid:7279   task_flags:0x400040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x149b/0x4fd0 kernel/sched/core.c:6863
 preempt_schedule_irq+0x4d/0xa0 kernel/sched/core.c:7190
 irqentry_exit+0x5d8/0x660 kernel/entry/common.c:216
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:rcu_preempt_read_exit kernel/rcu/tree_plugin.h:396 [inline]
RIP: 0010:__rcu_read_unlock+0x33/0xe0 kernel/rcu/tree_plugin.h:435
Code: 55 41 54 53 49 bf 00 00 00 00 00 fc ff df 65 48 8b 3c 25 08 10 80 92 48 8d 9f 84 04 00 00 49 89 dc 49 c1 ec 03 43 0f b6 04 3c <84> c0 75 4f ff 0b 75 1d 4c 8d b7 88 04 00 00 4c 89 f0 48 c1 e8 03
RSP: 0018:ffffc9001f386a08 EFLAGS: 00000217
RAX: 0000000000000000 RBX: ffff88807cfee004 RCX: 0000000000000046
RDX: 0000000000000002 RSI: ffffffff8d975e7a RDI: ffff88807cfedb80
RBP: dffffc0000000000 R08: ffffc9001f387090 R09: ffffc9001f386b58
R10: dffffc0000000000 R11: fffff52003e70d6d R12: 1ffff1100f9fdc00
R13: ffffc9001f380000 R14: ffffc9001f386b08 R15: dffffc0000000000
 rcu_read_unlock include/linux/rcupdate.h:899 [inline]
 class_rcu_destructor include/linux/rcupdate.h:1195 [inline]
 unwind_next_frame+0x1ab6/0x23d0 arch/x86/kernel/unwind_orc.c:695
 arch_stack_walk+0x11c/0x150 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 save_stack+0xf5/0x1f0 mm/page_owner.c:165
 __reset_page_owner+0x71/0x1f0 mm/page_owner.c:320
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1395 [inline]
 __free_frozen_pages+0xbc8/0xd30 mm/page_alloc.c:2943
 discard_slab mm/slub.c:3346 [inline]
 __put_partials+0x146/0x170 mm/slub.c:3886
 __slab_free+0x294/0x320 mm/slub.c:5952
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x97/0x100 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:349
 kasan_slab_alloc include/linux/kasan.h:252 [inline]
 slab_post_alloc_hook mm/slub.c:4953 [inline]
 slab_alloc_node mm/slub.c:5263 [inline]
 __kmalloc_cache_noprof+0x37c/0x700 mm/slub.c:5771
 kmalloc_noprof include/linux/slab.h:957 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 kobject_uevent_env+0x28c/0x9f0 lib/kobject_uevent.c:540
 loop_configure+0xb88/0xe50 drivers/block/loop.c:1093
 lo_ioctl+0x806/0x1c50 drivers/block/loop.c:-1
 blkdev_ioctl+0x60e/0x710 block/ioctl.c:792
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ffb08f8f34b
RSP: 002b:00007ffb09e7edc0 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00007ffb08f8f34b
RDX: 0000000000000003 RSI: 0000000000004c00 RDI: 0000000000000004
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000325
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003
R13: 00007ffb09e7eef0 R14: 00007ffb09e7eeb0 R15: 00007ffafec00000
 </TASK>
rcu: rcu_preempt kthread starved for 3291 jiffies! g26129 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
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:27904 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x149b/0x4fd0 kernel/sched/core.c:6863
 __schedule_loop kernel/sched/core.c:6945 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:6960
 schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2083
 rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2285
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:trace_lock_acquire include/trace/events/lock.h:24 [inline]
RIP: 0010:lock_acquire+0x5f/0x340 kernel/locking/lockdep.c:5831
Code: 89 44 24 58 0f 1f 44 00 00 65 8b 05 1f 22 e2 10 83 f8 08 0f 83 84 01 00 00 89 c0 48 0f a3 05 48 34 e4 0d 73 0d e8 21 0e 09 00 <84> c0 0f 84 cb 01 00 00 83 3d 62 64 e4 0d 00 0f 84 d4 00 00 00 48
RSP: 0018:ffffc90000a07498 EFLAGS: 00000212
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 0000000080000102
RDX: 0000000000000000 RSI: ffffffff8bc083c0 RDI: ffffffff8bc08380
RBP: ffffffff8173fd65 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: ffffffff81acf3a0 R12: 0000000000000002
R13: ffffffff8df41aa0 R14: 0000000000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff888125f1f000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000020000001f000 CR3: 0000000053aa3000 CR4: 0000000000350ef0
Call Trace:
 <IRQ>
 rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 rcu_read_lock include/linux/rcupdate.h:867 [inline]
 class_rcu_constructor include/linux/rcupdate.h:1195 [inline]
 unwind_next_frame+0xc2/0x23d0 arch/x86/kernel/unwind_orc.c:495
 arch_stack_walk+0x11c/0x150 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:56 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:252 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:284
 kasan_slab_free include/linux/kasan.h:234 [inline]
 slab_free_hook mm/slub.c:2540 [inline]
 slab_free mm/slub.c:6670 [inline]
 kmem_cache_free+0x197/0x620 mm/slub.c:6781
 skb_ext_del include/linux/skbuff.h:5057 [inline]
 nf_bridge_info_free net/bridge/br_netfilter_hooks.c:156 [inline]
 br_nf_dev_queue_xmit+0x4ec/0x2560 net/bridge/br_netfilter_hooks.c:851
 NF_HOOK+0x61b/0x6b0 include/linux/netfilter.h:318
 br_nf_post_routing+0xb66/0xfe0 net/bridge/br_netfilter_hooks.c:966
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_slow+0xc5/0x220 net/netfilter/core.c:623
 nf_hook include/linux/netfilter.h:273 [inline]
 NF_HOOK+0x215/0x3c0 include/linux/netfilter.h:316
 br_forward_finish+0xd3/0x130 net/bridge/br_forward.c:66
 br_nf_hook_thresh net/bridge/br_netfilter_hooks.c:-1 [inline]
 br_nf_forward_finish+0xa40/0xe60 net/bridge/br_netfilter_hooks.c:662
 NF_HOOK+0x61b/0x6b0 include/linux/netfilter.h:318
 br_nf_forward_ip+0x647/0x7e0 net/bridge/br_netfilter_hooks.c:716
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_slow+0xc5/0x220 net/netfilter/core.c:623
 nf_hook include/linux/netfilter.h:273 [inline]
 NF_HOOK+0x215/0x3c0 include/linux/netfilter.h:316
 __br_forward+0x397/0x540 net/bridge/br_forward.c:115
 deliver_clone net/bridge/br_forward.c:131 [inline]
 maybe_deliver+0xb5/0x160 net/bridge/br_forward.c:191
 br_flood+0x31a/0x6a0 net/bridge/br_forward.c:238
 br_handle_frame_finish+0x15a3/0x1c90 net/bridge/br_input.c:229
 br_nf_hook_thresh+0x3c6/0x4a0 net/bridge/br_netfilter_hooks.c:-1
 br_nf_pre_routing_finish_ipv6+0x999/0xd60 net/bridge/br_netfilter_ipv6.c:-1
 NF_HOOK include/linux/netfilter.h:318 [inline]
 br_nf_pre_routing_ipv6+0x37e/0x6b0 net/bridge/br_netfilter_ipv6.c:184
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_bridge_pre net/bridge/br_input.c:291 [inline]
 br_handle_frame+0x96e/0x14f0 net/bridge/br_input.c:442
 __netif_receive_skb_core+0x95f/0x2f90 net/core/dev.c:6024
 __netif_receive_skb_one_core net/core/dev.c:6135 [inline]
 __netif_receive_skb+0x72/0x380 net/core/dev.c:6250
 process_backlog+0x54f/0x1340 net/core/dev.c:6602
 __napi_poll+0xae/0x320 net/core/dev.c:7666
 napi_poll net/core/dev.c:7729 [inline]
 net_rx_action+0x64a/0xe00 net/core/dev.c:7881
 handle_softirqs+0x22b/0x7c0 kernel/softirq.c:622
 __do_softirq kernel/softirq.c:656 [inline]
 invoke_softirq kernel/softirq.c:496 [inline]
 __irq_exit_rcu+0x60/0x150 kernel/softirq.c:723
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:739
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1056
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:pv_native_safe_halt+0x13/0x20 arch/x86/kernel/paravirt.c:82
Code: 3e b4 b6 f5 cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 73 c1 0e 00 f3 0f 1e fa fb f4 <e9> 13 b4 b6 f5 cc cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc90000197e20 EFLAGS: 000002c2
RAX: 0000000000dc58e3 RBX: ffffffff819713be RCX: 0000000080000001
RDX: 0000000000000001 RSI: ffffffff8d791fea RDI: ffffffff8bc083e0
RBP: ffffc90000197f10 R08: ffff8880b87336db R09: 1ffff110170e66db
R10: dffffc0000000000 R11: ffffed10170e66dc R12: ffffffff8f822270
R13: 1ffff110038dbb70 R14: 0000000000000001 R15: 0000000000000001
 arch_safe_halt arch/x86/include/asm/paravirt.h:107 [inline]
 default_idle+0x13/0x20 arch/x86/kernel/process.c:767
 default_idle_call+0x73/0xb0 kernel/sched/idle.c:122
 cpuidle_idle_call kernel/sched/idle.c:191 [inline]
 do_idle+0x1be/0x4d0 kernel/sched/idle.c:332
 cpu_startup_entry+0x44/0x60 kernel/sched/idle.c:430
 start_secondary+0x101/0x110 arch/x86/kernel/smpboot.c:312
 common_startup_64+0x13e/0x147
 </TASK>
net_ratelimit: 13655 callbacks suppressed
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:22:1f:50:c9:01:fd, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/24 20:51 upstream b927546677c8 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in lo_ioctl
2025/12/15 04:02 upstream 8f0b4cce4481 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in lo_ioctl
* Struck through repros no longer work on HEAD.