INFO: rcu detected stall in tc_modify_qdisc

Status: upstream: reported C repro on 2024/08/13 15:46
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+6818656ac1d4c60d28ed@syzkaller.appspotmail.com
First crash: 728d, last: 29d
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/08/08 linux-5.15.y (ToT) c79648372d02 C [report] INFO: rcu detected stall in tc_modify_qdisc
2025/08/08 upstream (ToT) 6e64f4580381 C Didn't crash
▶ ▼ Similar bugs (13)
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 418d 418d 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 758d 796d 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 247d 247d 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 665 2d05h 2205d 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 54d 642d 0/3 upstream: reported C repro on 2024/11/08 00:04
android-6-1 BUG: soft lockup in tc_modify_qdisc 1 syz, C done done 53 988d 1019d 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 37 2d08h 171d 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 1077d 1132d 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 1166d 1166d 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 7 47d 159d 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 1164d 1164d 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 1078d 1132d 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 96 10d 340d 0/2 upstream: reported C repro on 2025/09/05 07:56
▶ ▼ Last patch testing requests (10)
Created Duration User Patch Repo Result
2026/07/14 03:05 17m retest repro linux-5.15.y report log
2026/07/14 03:05 21m retest repro linux-5.15.y report log
2026/07/14 03:05 20m retest repro linux-5.15.y report log
2026/06/08 03:08 20m retest repro linux-5.15.y report log
2026/05/19 01:00 20m retest repro linux-5.15.y report log
2026/03/31 20:27 12m retest repro linux-5.15.y report log
2026/03/31 20:27 16m retest repro linux-5.15.y report log
2026/03/15 00:14 5m retest repro linux-5.15.y error
2026/02/28 11:01 11m retest repro linux-5.15.y report log
2026/01/20 18:51 15m retest repro linux-5.15.y report log
▶ ▼ Fix bisection attempts (11)
Created Duration User Patch Repo Result
2026/08/07 14:43 13h11m fix candidate upstream error job log
2026/06/09 13:47 15m fix candidate upstream error job log
2026/03/27 05:32 1m fix candidate upstream error job log
2026/02/24 03:15 7m fix candidate upstream error job log
2026/01/23 17:59 9m fix candidate upstream error job log
2025/07/20 05:34 1m fix candidate upstream error job log
2025/05/16 12:55 10m fix candidate upstream error job log
2025/04/06 19:03 1m fix candidate upstream error job log
2025/02/23 08:17 1m fix candidate upstream error job log
2024/12/13 18:21 1m fix candidate upstream error job log
2024/11/04 08:18 11m fix candidate upstream error job log

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	1-...0: (1 GPs behind) idle=bf7/1/0x4000000000000000 softirq=7252/7253 fqs=2099 
	(detected by 0, t=10502 jiffies, g=8281, q=350)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 4360 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:__lock_acquire+0xfc/0x7d10 kernel/locking/lockdep.c:4882
Code: 84 c0 0f 85 cb 65 00 00 83 3d 43 0f 2d 0c 00 0f 84 a8 27 00 00 83 3d 52 ba c1 0a 00 74 29 48 89 d8 48 c1 e8 03 42 80 3c 00 00 <74> 12 48 89 df e8 ea 36 61 00 49 b8 00 00 00 00 00 fc ff df 48 81
RSP: 0018:ffffc90000dd0900 EFLAGS: 00000046
RAX: 1ffff1100f591d60 RBX: ffff88807ac8eb00 RCX: 1ffff920001ba144
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88807ac8eb00
RBP: ffffc90000dd0b50 R08: dffffc0000000000 R09: 0000000000000001
R10: dffffc0000000000 R11: fffffbfff1b140de R12: 0000000000000001
R13: ffff88807b0f5940 R14: 0000000000000000 R15: 0000000000000001
FS:  000055558afb4500(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00002000000012c0 CR3: 0000000074377000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
 _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
 spin_lock include/linux/spinlock.h:364 [inline]
 advance_sched+0x49/0x920 net/sched/sch_taprio.c:695
 __run_hrtimer kernel/time/hrtimer.c:1685 [inline]
 __hrtimer_run_queues+0x4f2/0xb70 kernel/time/hrtimer.c:1749
 hrtimer_interrupt+0x3bb/0x8d0 kernel/time/hrtimer.c:1811
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
 __sysvec_apic_timer_interrupt+0x137/0x4a0 arch/x86/kernel/apic/apic.c:1114
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0x9b/0xc0 arch/x86/kernel/apic/apic.c:1108
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xbc/0x120 kernel/locking/spinlock.c:194
Code: c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f7 44 24 20 00 02 00 00 41 c6 04 07 f8 75 4b f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> 4f 9d 8b f7 65 8b 05 70 86 3b 76 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc900030cee40 EFLAGS: 00000206
RAX: dffffc0000000004 RBX: 0000000000000a02 RCX: 5aa315ba4aefd100
RDX: dffffc0000000000 RSI: ffffffff8a2b3180 RDI: 0000000000000001
RBP: ffffc900030ceed0 R08: ffffffff901d818f R09: 1ffffffff203b031
R10: dffffc0000000000 R11: fffffbfff203b032 R12: dffffc0000000000
R13: 0000000000008001 R14: ffff88807ac8eae8 R15: 1ffff92000619dc8
 spin_unlock_irqrestore include/linux/spinlock.h:419 [inline]
 taprio_change+0x409d/0x4ef0 net/sched/sch_taprio.c:1589
 qdisc_create+0x7dd/0x1190 net/sched/sch_api.c:1255
 tc_modify_qdisc+0xad0/0x17c0 net/sched/sch_api.c:-1
 rtnetlink_rcv_msg+0x844/0xf30 net/core/rtnetlink.c:5688
 netlink_rcv_skb+0x1f5/0x440 net/netlink/af_netlink.c:2507
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x774/0x920 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x8ba/0xbe0 net/netlink/af_netlink.c:1918
 sock_sendmsg_nosec net/socket.c:706 [inline]
 __sock_sendmsg net/socket.c:718 [inline]
 ____sys_sendmsg+0x5b7/0x8f0 net/socket.c:2445
 ___sys_sendmsg+0x236/0x2e0 net/socket.c:2499
 __sys_sendmsg net/socket.c:2528 [inline]
 __do_sys_sendmsg net/socket.c:2537 [inline]
 __se_sys_sendmsg+0x1af/0x290 net/socket.c:2535
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f412ebcde59
Code: 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 01 48
RSP: 002b:00007fffa068e028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f412ee46fa0 RCX: 00007f412ebcde59
RDX: 0000000000000010 RSI: 00002000000012c0 RDI: 0000000000000005
RBP: 00007f412ec63d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f412ee46fac R14: 00007f412ee46fa0 R15: 00007f412ee46fa0
 </TASK>

Crashes (31):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/14 13:02 linux-5.15.y dc027a595035 1d2f3589 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/11/30 16:39 linux-5.15.y cc5ec8769306 d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/08/02 12:40 linux-5.15.y c79648372d02 7368264b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2024/11/10 16:34 linux-5.15.y 3c17fc483905 6b856513 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 BUG: soft lockup in tc_modify_qdisc
2024/10/27 18:53 linux-5.15.y 74cdd62cb470 65e8686b .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 BUG: soft lockup in tc_modify_qdisc
2026/06/23 02:08 linux-5.15.y eceeec79dbc6 5a630be6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2026/06/23 02:05 linux-5.15.y eceeec79dbc6 5a630be6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2026/06/15 10:06 linux-5.15.y dc027a595035 1d2f3589 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2026/06/15 10:04 linux-5.15.y dc027a595035 1d2f3589 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2026/06/15 06:52 linux-5.15.y dc027a595035 1d2f3589 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2026/06/14 10:33 linux-5.15.y dc027a595035 1d2f3589 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2026/06/14 10:30 linux-5.15.y dc027a595035 1d2f3589 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2026/01/04 17:14 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/12/05 11:00 linux-5.15.y cc5ec8769306 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/12/05 10:57 linux-5.15.y cc5ec8769306 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/12/05 00:58 linux-5.15.y cc5ec8769306 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/11/09 13:18 linux-5.15.y cc5ec8769306 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/11/08 12:28 linux-5.15.y cc5ec8769306 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/10/09 06:42 linux-5.15.y 29e53a5b1c4f 7e2882b3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/10/03 15:30 linux-5.15.y 29e53a5b1c4f 49379ee0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/10/03 15:28 linux-5.15.y 29e53a5b1c4f 49379ee0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/10/03 14:57 linux-5.15.y 29e53a5b1c4f 49379ee0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/09/25 22:59 linux-5.15.y 43bb85222e53 0abd0691 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/08/02 15:12 linux-5.15.y c79648372d02 7368264b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/08/02 08:30 linux-5.15.y c79648372d02 7368264b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/08/02 08:28 linux-5.15.y c79648372d02 7368264b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/02/26 20:07 linux-5.15.y c16c81c81336 d34966d1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/02/10 07:55 linux-5.15.y c16c81c81336 ef44b750 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2024/08/13 15:46 linux-5.15.y 7e89efd3ae1c f21a18ca .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in tc_modify_qdisc
2024/11/22 17:57 linux-5.15.y 0a51d2d4527b 4b25d554 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 BUG: soft lockup in tc_modify_qdisc
2024/09/17 19:58 linux-5.15.y 3a5928702e71 c673ca06 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 BUG: soft lockup in tc_modify_qdisc
* Struck through repros no longer work on HEAD.