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INFO: rcu detected stall in tc_modify_qdisc (2)

Status: upstream: reported C repro on 2024/11/08 00:04
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+3e756bb26a645ac581b7@syzkaller.appspotmail.com
First crash: 366d, last: 6d02h
▶ ▼ Bug presence (1)
Date Name Commit Repro Result
2024/12/15 upstream (ToT) 2d8308bf5b67 C [report] INFO: rcu detected stall in do_idle
▶ ▼ Similar bugs (11)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 INFO: rcu detected stall in tc_modify_qdisc 1 1 142d 142d 0/2 auto-obsoleted due to no activity on 2025/09/27 23:42
linux-6.1 INFO: rcu detected stall in tc_modify_qdisc 1 3 482d 521d 0/3 auto-obsoleted due to no activity on 2024/10/23 00:42
upstream INFO: rcu detected stall in tc_modify_qdisc net 1 C done 606 10d 1929d 0/29 upstream: reported C repro on 2020/07/29 05:53
linux-5.15 INFO: rcu detected stall in tc_modify_qdisc origin:lts-only 1 C error 18 43m 452d 0/3 upstream: reported C repro on 2024/08/13 15:46
android-6-1 BUG: soft lockup in tc_modify_qdisc 1 C done done 53 712d 744d 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) 1 1 64d 64d 0/2 premoderation: reported on 2025/09/06 05:55
android-5-15 BUG: soft lockup in tc_modify_qdisc origin:lts 1 C done done 254 801d 856d 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 C error 1 890d 890d 0/3 auto-obsoleted due to no activity on 2023/09/11 01:53
linux-6.1 BUG: soft lockup in tc_modify_qdisc origin:upstream 1 C done 1 889d 889d 3/3 fixed on 2023/07/10 11:22
android-5-10 BUG: soft lockup in tc_modify_qdisc 1 C done done 314 803d 856d 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 C 28 6d03h 65d 0/2 upstream: reported C repro on 2025/09/05 07:56
▶ ▼ Fix bisection attempts (6)
Created Duration User Patch Repo Result
2025/09/11 00:33 2h09m bisect fix linux-6.1.y OK (0) job log log
2025/07/06 01:41 2h15m bisect fix linux-6.1.y OK (0) job log log
2025/04/30 06:49 2h03m bisect fix linux-6.1.y OK (0) job log log
2025/03/27 23:48 2h23m bisect fix linux-6.1.y OK (0) job log log
2025/02/23 08:19 1h46m bisect fix linux-6.1.y OK (0) job log log
2025/01/24 04:14 1h42m bisect fix linux-6.1.y OK (0) job log log

Sample crash report:
rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 1-...D } 2688 jiffies s: 2741 root: 0x2/.
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 4444 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:arch_irqs_disabled_flags arch/x86/include/asm/irqflags.h:125 [inline]
RIP: 0010:arch_irqs_disabled arch/x86/include/asm/irqflags.h:132 [inline]
RIP: 0010:lock_acquire+0x1ee/0x490 kernel/locking/lockdep.c:5665
Code: b8 ff ff ff ff 65 0f c1 05 0f 80 9f 7e 83 f8 01 0f 85 f9 00 00 00 48 c7 84 24 80 00 00 00 00 00 00 00 9c 8f 84 24 80 00 00 00 <f6> 84 24 81 00 00 00 02 0f 85 f5 00 00 00 41 f7 c6 00 02 00 00 74
RSP: 0018:ffffc900001e0b60 EFLAGS: 00000046
RAX: 0000000000000001 RBX: 0000000000000000 RCX: d1642fbd968bfa00
RDX: 0000000000000000 RSI: ffffffff8a8c1700 RDI: ffffffff8adef760
RBP: ffffc900001e0c68 R08: dffffc0000000000 R09: fffffbfff215c44a
R10: fffffbfff215c44a R11: 1ffffffff215c449 R12: 0000000000000001
R13: 1ffff9200003c178 R14: 0000000000000046 R15: dffffc0000000000
FS:  0000555593934500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000600 CR3: 0000000074691000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
 _raw_spin_lock_irq+0x9f/0xe0 kernel/locking/spinlock.c:170
 __run_hrtimer kernel/time/hrtimer.c:1751 [inline]
 __hrtimer_run_queues+0x63a/0xd60 kernel/time/hrtimer.c:1811
 hrtimer_interrupt+0x3c5/0x9c0 kernel/time/hrtimer.c:1873
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1107 [inline]
 __sysvec_apic_timer_interrupt+0x153/0x5a0 arch/x86/kernel/apic/apic.c:1124
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
 sysvec_apic_timer_interrupt+0x9b/0xc0 arch/x86/kernel/apic/apic.c:1118
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:lockdep_unregister_key+0x4c3/0x530 kernel/locking/lockdep.c:6370
Code: 21 a9 90 48 c7 c6 80 9f 63 81 e8 a8 93 07 00 e8 03 a7 07 00 e9 86 fc ff ff e8 f9 32 b4 08 41 f7 c4 00 02 00 00 74 d1 fb 84 db <75> d0 eb e1 0f 0b eb a1 0f 0b e9 11 ff ff ff 0f 0b e9 5e ff ff ff
RSP: 0018:ffffc90003516ee0 EFLAGS: 00000246
RAX: d1642fbd968bfa00 RBX: 0000000000000000 RCX: d1642fbd968bfa00
RDX: 0000000000000001 RSI: ffffffff8a8c1260 RDI: ffffffff8adef760
RBP: ffffc90003516fc0 R08: dffffc0000000000 R09: fffffbfff21525c5
R10: fffffbfff21525c5 R11: 1ffffffff21525c4 R12: 0000000000000a03
R13: ffff88807dd99299 R14: ffffffff90a92198 R15: 1ffff920006a2de0
 __qdisc_destroy+0x128/0x430 net/sched/sch_generic.c:1078
 taprio_attach+0x26b/0x420 net/sched/sch_taprio.c:1844
 qdisc_graft+0x1165/0x1570 net/sched/sch_api.c:1139
 tc_modify_qdisc+0xe78/0x1cc0 net/sched/sch_api.c:1771
 rtnetlink_rcv_msg+0x79b/0xed0 net/core/rtnetlink.c:6150
 netlink_rcv_skb+0x1de/0x420 net/netlink/af_netlink.c:2511
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x74d/0x8d0 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x89e/0xbc0 net/netlink/af_netlink.c:1872
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg net/socket.c:730 [inline]
 ____sys_sendmsg+0x59b/0x970 net/socket.c:2519
 ___sys_sendmsg+0x21c/0x290 net/socket.c:2573
 __sys_sendmsg net/socket.c:2602 [inline]
 __do_sys_sendmsg net/socket.c:2611 [inline]
 __se_sys_sendmsg+0x19e/0x270 net/socket.c:2609
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fd4acd8efc9
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:00007ffeb59b0098 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fd4acfe5fa0 RCX: 00007fd4acd8efc9
RDX: 0000000000000000 RSI: 00002000000007c0 RDI: 0000000000000004
RBP: 00007fd4ace11f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd4acfe5fa0 R14: 00007fd4acfe5fa0 R15: 0000000000000003
 </TASK>
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	1-...0: (1 ticks this GP) idle=c794/1/0x4000000000000000 softirq=9616/9616 fqs=4592
	(detected by 0, t=10502 jiffies, g=9849, q=636 ncpus=2)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 4444 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:arch_static_branch arch/x86/include/asm/jump_label.h:27 [inline]
RIP: 0010:static_key_false include/linux/jump_label.h:207 [inline]
RIP: 0010:trace_lock_release include/trace/events/lock.h:69 [inline]
RIP: 0010:lock_release+0x7d/0x910 kernel/locking/lockdep.c:5673
Code: 70 c0 79 63 81 4c 8d 7c 24 60 49 c1 ef 03 48 b8 f1 f1 f1 f1 00 f2 f2 f2 4b 89 04 2f 66 43 c7 44 2f 09 f3 f3 43 c6 44 2f 0b f3 <0f> 1f 44 00 00 65 8b 1d 57 9f 9e 7e 48 c7 c0 b0 6c 1f 8e 48 c1 e8
RSP: 0018:ffffc900001e0b60 EFLAGS: 00000806
RAX: f2f2f200f1f1f1f1 RBX: 0000000000000806 RCX: dffffc0000000000
RDX: 0000000000010000 RSI: ffffffff8170fd36 RDI: ffff8880b8f2a598
RBP: ffffc900001e0c70 R08: dffffc0000000000 R09: fffffbfff1c3ed56
R10: fffffbfff1c3ed56 R11: 1ffffffff1c3ed55 R12: dffffc0000000000
R13: dffffc0000000000 R14: ffff8880b8f2a580 R15: 1ffff9200003c178
FS:  0000555593934500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000600 CR3: 0000000074691000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:149 [inline]
 _raw_spin_unlock_irqrestore+0x6d/0x100 kernel/locking/spinlock.c:194
 __run_hrtimer kernel/time/hrtimer.c:1743 [inline]
 __hrtimer_run_queues+0x446/0xd60 kernel/time/hrtimer.c:1811
 hrtimer_interrupt+0x3c5/0x9c0 kernel/time/hrtimer.c:1873
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1107 [inline]
 __sysvec_apic_timer_interrupt+0x153/0x5a0 arch/x86/kernel/apic/apic.c:1124
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
 sysvec_apic_timer_interrupt+0x9b/0xc0 arch/x86/kernel/apic/apic.c:1118
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:lockdep_unregister_key+0x4c3/0x530 kernel/locking/lockdep.c:6370
Code: 21 a9 90 48 c7 c6 80 9f 63 81 e8 a8 93 07 00 e8 03 a7 07 00 e9 86 fc ff ff e8 f9 32 b4 08 41 f7 c4 00 02 00 00 74 d1 fb 84 db <75> d0 eb e1 0f 0b eb a1 0f 0b e9 11 ff ff ff 0f 0b e9 5e ff ff ff
RSP: 0018:ffffc90003516ee0 EFLAGS: 00000246
RAX: d1642fbd968bfa00 RBX: 0000000000000000 RCX: d1642fbd968bfa00
RDX: 0000000000000001 RSI: ffffffff8a8c1260 RDI: ffffffff8adef760
RBP: ffffc90003516fc0 R08: dffffc0000000000 R09: fffffbfff21525c5
R10: fffffbfff21525c5 R11: 1ffffffff21525c4 R12: 0000000000000a03
R13: ffff88807dd99299 R14: ffffffff90a92198 R15: 1ffff920006a2de0
 __qdisc_destroy+0x128/0x430 net/sched/sch_generic.c:1078
 taprio_attach+0x26b/0x420 net/sched/sch_taprio.c:1844
 qdisc_graft+0x1165/0x1570 net/sched/sch_api.c:1139
 tc_modify_qdisc+0xe78/0x1cc0 net/sched/sch_api.c:1771
 rtnetlink_rcv_msg+0x79b/0xed0 net/core/rtnetlink.c:6150
 netlink_rcv_skb+0x1de/0x420 net/netlink/af_netlink.c:2511
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x74d/0x8d0 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x89e/0xbc0 net/netlink/af_netlink.c:1872
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg net/socket.c:730 [inline]
 ____sys_sendmsg+0x59b/0x970 net/socket.c:2519
 ___sys_sendmsg+0x21c/0x290 net/socket.c:2573
 __sys_sendmsg net/socket.c:2602 [inline]
 __do_sys_sendmsg net/socket.c:2611 [inline]
 __se_sys_sendmsg+0x19e/0x270 net/socket.c:2609
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fd4acd8efc9
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:00007ffeb59b0098 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fd4acfe5fa0 RCX: 00007fd4acd8efc9
RDX: 0000000000000000 RSI: 00002000000007c0 RDI: 0000000000000004
RBP: 00007fd4ace11f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd4acfe5fa0 R14: 00007fd4acfe5fa0 R15: 0000000000000003
 </TASK>

Crashes (15):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/11/03 11:30 linux-6.1.y f6e38ae624cf 2c50b6a9 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/10/03 13:28 linux-6.1.y 882efbdd9d34 49379ee0 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/05/30 18:45 linux-6.1.y da3c5173c55f 3d2f584d .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in tc_modify_qdisc
2024/12/14 12:35 linux-6.1.y e4d90d63d385 7cbfbb3a .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/06/04 09:48 linux-6.1.y da3c5173c55f a30356b7 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/05/30 14:24 linux-6.1.y da3c5173c55f 3d2f584d .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/10/09 08:08 linux-6.1.y 882efbdd9d34 7e2882b3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/10/03 12:04 linux-6.1.y 882efbdd9d34 49379ee0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/10/03 11:01 linux-6.1.y 882efbdd9d34 49379ee0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/08/02 16:40 linux-6.1.y 3594f306da12 7368264b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/08/02 16:37 linux-6.1.y 3594f306da12 7368264b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/08/02 08:08 linux-6.1.y 3594f306da12 7368264b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/08/02 08:06 linux-6.1.y 3594f306da12 7368264b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in tc_modify_qdisc
2024/11/08 00:03 linux-6.1.y 7c15117f9468 867e44df .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/07/11 12:21 linux-6.1.y dfc486ec9cce 3cda49cf .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 BUG: soft lockup in tc_modify_qdisc
* Struck through repros no longer work on HEAD.