INFO: rcu detected stall in tc_modify_qdisc

Status: auto-obsoleted due to no activity on 2025/09/27 23:42
Reported-by: syzbot+359897f9801d4105d693@syzkaller.appspotmail.com
First crash: 465d, last: 465d
▶ ▼ Similar bugs (13)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: rcu detected stall in tc_modify_qdisc 1 3 805d 844d 0/3 auto-obsoleted due to no activity on 2024/10/23 00:42
linux-6.6 INFO: rcu detected stall in tc_modify_qdisc (2) 1 1 295d 295d 0/2 auto-obsoleted due to no activity on 2026/03/17 12:53
upstream INFO: rcu detected stall in tc_modify_qdisc prio:normal net 1 syz, C done 677 15h30m 2252d 0/29 upstream: reported C repro on 2020/07/29 05:53
linux-6.1 INFO: rcu detected stall in tc_modify_qdisc (2) origin:upstream 1 syz, C error 27 102d 689d 0/3 upstream: reported C repro on 2024/11/08 00:04
linux-5.15 INFO: rcu detected stall in tc_modify_qdisc origin:lts-only 1 syz, C error 31 1d04h 775d 0/3 upstream: reported C repro on 2024/08/13 15:46
android-6-1 BUG: soft lockup in tc_modify_qdisc 1 syz, C done done 53 1035d 1067d 0/2 auto-obsoleted due to no activity on 2024/02/06 04:01
android-5-15 BUG: soft lockup in tc_modify_qdisc (2) origin:lts 1 syz, C 49 8h40m 218d 0/2 upstream: reported C repro on 2026/02/22 06:27
android-5-15 BUG: soft lockup in tc_modify_qdisc origin:lts 1 syz, C done done 254 1124d 1179d 0/2 auto-obsoleted due to no activity on 2023/11/09 01:01
linux-5.15 BUG: soft lockup in tc_modify_qdisc origin:upstream 1 syz, C error 1 1213d 1213d 0/3 auto-obsoleted due to no activity on 2023/09/11 01:53
android-6-1 BUG: soft lockup in tc_modify_qdisc (2) origin:lts 1 syz, C error 10 8d22h 207d 0/2 upstream: reported C repro on 2026/03/05 09:26
linux-6.1 BUG: soft lockup in tc_modify_qdisc origin:upstream 1 syz, C done 1 1212d 1212d 3/3 fixed on 2023/07/10 11:22
android-5-10 BUG: soft lockup in tc_modify_qdisc 1 syz, C done done 314 1126d 1179d 0/2 auto-obsoleted due to no activity on 2023/11/07 07:54
android-5-10 BUG: soft lockup in tc_modify_qdisc (2) 1 syz, C 117 1d07h 388d 0/2 upstream: reported C repro on 2025/09/05 07:56

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	1-...!: (1 ticks this GP) idle=63dc/1/0x4000000000000000 softirq=95709/95709 fqs=0
rcu: 	(detected by 0, t=10505 jiffies, g=126877, q=508 ncpus=2)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 18509 Comm: syz.2.3801 Not tainted 6.6.94-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:check_preemption_disabled+0x37/0x110 lib/smp_processor_id.c:55
Code: 04 25 28 00 00 00 48 89 44 24 08 65 8b 05 6d 6d 9d 75 65 8b 0d 62 6d 9d 75 f7 c1 ff ff ff 7f 74 1f 65 48 8b 0c 25 28 00 00 00 <48> 3b 4c 24 08 0f 85 c4 00 00 00 48 83 c4 10 5b 41 5e 41 5f 5d c3
RSP: 0018:ffffc900001f0b28 EFLAGS: 00000002
RAX: 0000000000000001 RBX: 0000000000000000 RCX: cdb748694e6d2500
RDX: 0000000000000000 RSI: ffffffff8afc68e0 RDI: ffffffff8afc68a0
RBP: ffffc900001f0c88 R08: ffffffff8e49ab2f R09: 1ffffffff1c93565
R10: dffffc0000000000 R11: fffffbfff1c93566 R12: 1ffff9200003e17c
R13: ffff8880b8f2b958 R14: 0000000000000001 R15: dffffc0000000000
FS:  00007f77bf52b6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000056163f182048 CR3: 000000002c90b000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 rcu_dynticks_curr_cpu_in_eqs include/linux/context_tracking.h:122 [inline]
 rcu_is_watching+0x15/0xb0 kernel/rcu/tree.c:700
 trace_lock_acquire include/trace/events/lock.h:24 [inline]
 lock_acquire+0xcb/0x410 kernel/locking/lockdep.c:5725
 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
 _raw_spin_lock_irq+0xa3/0xe0 kernel/locking/spinlock.c:170
 __run_hrtimer kernel/time/hrtimer.c:1759 [inline]
 __hrtimer_run_queues+0x5e3/0xc40 kernel/time/hrtimer.c:1819
 hrtimer_interrupt+0x3c9/0x9c0 kernel/time/hrtimer.c:1881
 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:lockdep_unregister_key+0x4e6/0x580 kernel/locking/lockdep.c:6490
Code: 54 d3 90 48 c7 c6 80 a3 67 81 e8 35 09 08 00 e8 f0 1b 08 00 e9 67 fc ff ff e8 76 94 fe 08 41 f7 c4 00 02 00 00 74 d1 fb 84 db <75> d0 eb e1 0f 0b 31 db eb a1 0f 0b e9 fd fe ff ff e8 54 93 fe 08
RSP: 0018:ffffc90004faede0 EFLAGS: 00000246
RAX: cdb748694e6d2500 RBX: 0000000000000000 RCX: cdb748694e6d2500
RDX: 0000000000000001 RSI: ffffffff8aaabfa0 RDI: ffffffff8afc6900
RBP: ffffc90004faeeb0 R08: ffffffff90d37c8f R09: 1ffffffff21a6f91
R10: dffffc0000000000 R11: fffffbfff21a6f92 R12: 0000000000000a02
R13: ffffffff907982b0 R14: ffff88807ebc6a99 R15: 1ffff920009f5dc0
 __qdisc_destroy+0x128/0x3c0 net/sched/sch_generic.c:1078
 taprio_attach+0x25e/0x380 net/sched/sch_taprio.c:2172
 qdisc_graft+0x1169/0x1570 net/sched/sch_api.c:1146
 tc_modify_qdisc+0xe54/0x1be0 net/sched/sch_api.c:1768
 rtnetlink_rcv_msg+0x7c7/0xf10 net/core/rtnetlink.c:6475
 netlink_rcv_skb+0x216/0x480 net/netlink/af_netlink.c:2537
 netlink_unicast_kernel net/netlink/af_netlink.c:1323 [inline]
 netlink_unicast+0x750/0x8c0 net/netlink/af_netlink.c:1349
 netlink_sendmsg+0x8c1/0xbe0 net/netlink/af_netlink.c:1891
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 ____sys_sendmsg+0x5bf/0x950 net/socket.c:2595
 ___sys_sendmsg+0x220/0x290 net/socket.c:2649
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2687 [inline]
 __se_sys_sendmsg+0x1a5/0x270 net/socket.c:2685
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f77be78e929
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f77bf52b038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f77be9b5fa0 RCX: 00007f77be78e929
RDX: 0000000000000000 RSI: 00002000000007c0 RDI: 0000000000000004
RBP: 00007f77be810b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f77be9b5fa0 R15: 00007ffd0d896fc8
 </TASK>
rcu: rcu_preempt kthread timer wakeup didn't happen for 10504 jiffies! g126877 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=1 timer-softirq=58547
rcu: rcu_preempt kthread starved for 10505 jiffies! g126877 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->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:I stack:26728 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x14e2/0x4580 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0x160/0x280 kernel/time/timer.c:2167
 rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x99/0x380 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 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 18509 Comm: syz.2.3801 Not tainted 6.6.94-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:__lock_acquire+0x210/0x7c80 kernel/locking/lockdep.c:5041
Code: 00 00 48 89 5c 24 40 8b 5d 30 44 8b 7d 20 48 c7 c0 e0 d3 6e 90 49 29 c5 49 c1 fd 04 48 b9 c5 4e ec c4 4e ec c4 4e 49 0f af cd <41> 89 cd 85 db 0f 85 2c 01 00 00 83 7c 24 60 00 0f 84 21 01 00 00
RSP: 0018:ffffc900001f0880 EFLAGS: 00000803
RAX: ffffffff906ed3e0 RBX: 0000000000000000 RCX: 0000000000000001
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff9705a058
RBP: ffffc900001f0ac8 R08: dffffc0000000000 R09: 0000000000000001
R10: dffffc0000000000 R11: fffffbfff1c93566 R12: 0000000000000001
R13: 000000000000000d R14: ffffffff9705a060 R15: 0000000000000000
FS:  00007f77bf52b6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000056163f182048 CR3: 000000002c90b000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0xa8/0xf0 kernel/locking/spinlock.c:162
 debug_object_deactivate+0x67/0x350 lib/debugobjects.c:764
 debug_hrtimer_deactivate kernel/time/hrtimer.c:455 [inline]
 debug_deactivate+0x1d/0x1d0 kernel/time/hrtimer.c:511
 __run_hrtimer kernel/time/hrtimer.c:1723 [inline]
 __hrtimer_run_queues+0x2bf/0xc40 kernel/time/hrtimer.c:1819
 hrtimer_interrupt+0x3c9/0x9c0 kernel/time/hrtimer.c:1881
 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:lockdep_unregister_key+0x4e6/0x580 kernel/locking/lockdep.c:6490
Code: 54 d3 90 48 c7 c6 80 a3 67 81 e8 35 09 08 00 e8 f0 1b 08 00 e9 67 fc ff ff e8 76 94 fe 08 41 f7 c4 00 02 00 00 74 d1 fb 84 db <75> d0 eb e1 0f 0b 31 db eb a1 0f 0b e9 fd fe ff ff e8 54 93 fe 08
RSP: 0018:ffffc90004faede0 EFLAGS: 00000246
RAX: cdb748694e6d2500 RBX: 0000000000000000 RCX: cdb748694e6d2500
RDX: 0000000000000001 RSI: ffffffff8aaabfa0 RDI: ffffffff8afc6900
RBP: ffffc90004faeeb0 R08: ffffffff90d37c8f R09: 1ffffffff21a6f91
R10: dffffc0000000000 R11: fffffbfff21a6f92 R12: 0000000000000a02
R13: ffffffff907982b0 R14: ffff88807ebc6a99 R15: 1ffff920009f5dc0
 __qdisc_destroy+0x128/0x3c0 net/sched/sch_generic.c:1078
 taprio_attach+0x25e/0x380 net/sched/sch_taprio.c:2172
 qdisc_graft+0x1169/0x1570 net/sched/sch_api.c:1146
 tc_modify_qdisc+0xe54/0x1be0 net/sched/sch_api.c:1768
 rtnetlink_rcv_msg+0x7c7/0xf10 net/core/rtnetlink.c:6475
 netlink_rcv_skb+0x216/0x480 net/netlink/af_netlink.c:2537
 netlink_unicast_kernel net/netlink/af_netlink.c:1323 [inline]
 netlink_unicast+0x750/0x8c0 net/netlink/af_netlink.c:1349
 netlink_sendmsg+0x8c1/0xbe0 net/netlink/af_netlink.c:1891
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 ____sys_sendmsg+0x5bf/0x950 net/socket.c:2595
 ___sys_sendmsg+0x220/0x290 net/socket.c:2649
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2687 [inline]
 __se_sys_sendmsg+0x1a5/0x270 net/socket.c:2685
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f77be78e929
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f77bf52b038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f77be9b5fa0 RCX: 00007f77be78e929
RDX: 0000000000000000 RSI: 00002000000007c0 RDI: 0000000000000004
RBP: 00007f77be810b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f77be9b5fa0 R15: 00007ffd0d896fc8
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/06/19 23:41 linux-6.6.y 6282921b6825 ed3e87f7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in tc_modify_qdisc
* Struck through repros no longer work on HEAD.