From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oo1-f77.google.com (mail-oo1-f77.google.com [209.85.161.77]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BBFAB2C0299 for ; Mon, 11 May 2026 06:23:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.161.77 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778480611; cv=none; b=QNhNs5FwYHnC0AwXDVdy5cKkIcAW23V2QahYQRXb/jY3JlmBNc/pIQdLvVu4Z1p8Y9CIXOHQ7QPWw2cpGvTg2eE3u0e1SbUIYXwQrl8OmTyVg+ZgRvT76Tcl4bA+hmSvMHIhgqD6cXPjMmVx2Uw9INqwCbCzmGGLwGlnPQak8xc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778480611; c=relaxed/simple; bh=2/R7v9mNHMjP8cDFOGQ/TPV1slRjThbnyFADaLLiPGo=; h=MIME-Version:Date:Message-ID:Subject:From:To:Content-Type; b=Gu/h3kW5oKlGV8NwVDcXoXCSuUtHutcpVWvA2FkMSTNPIQSwVKLb4fey3RfCj1R4jAuVPQrK4EzSCyS562+NJx8OuNLQiuuIW/GLi2r90B8Ql/8EMH1DJzPY1aseca7KTWqMPywJwrpeBtxg9UezrB35d8odoMfg6uffMGqNZs8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.161.77 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-oo1-f77.google.com with SMTP id 006d021491bc7-679c5ed0942so5651105eaf.1 for ; Sun, 10 May 2026 23:23:29 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1778480609; x=1779085409; h=to:from:subject:message-id:date:mime-version:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=VaFPG7gEHXdorxY3MrBaNDqtO3iWXxWBFIcMFjQggaU=; b=mu4zrjLSpjcnPPpne3qz9G9PiTHGt0lCjDU03uTE6oftdc08RM6g1Igc2T8y5Z5nY8 e2HTcdzXrfeheuFD0QbI+sPQEYF+GO7A+JmVMyyIoZgxptkLUNEJIH64Dsl2EGbqcabJ E3jgxZvqzI+nTzTGou7lcPE9g5s/iPJi0jBKo7mmI+rZj/+HJnsyQ+rl1Gr/KO1p9E47 vMcXEkUbDkLmCiiQghGmWbXoSfZD7xCrLBmlTvIUmpmlIKIzSleAFVgrP7ZfJ6ft0S6p hme6tySHACznAh+mjQYWZwSiFkJFK9aPqrYfm6ERz8fFqBTyYIqhrTC2agY50QlEWBVc WS5A== X-Forwarded-Encrypted: i=1; AFNElJ+uUEkunpjGovT7j7xB2sc2Xvy9Yn9ay9dTJ6eyTQBR3wmiybv6AbaOd6M/Noc4P/T9tfnAXDY=@vger.kernel.org X-Gm-Message-State: AOJu0YzHCNaw9kUYAawNODBp4DMR8uF5gxRRidbw5yVqBKRHsuD3wsBu kB2H6wZvn+74W+3x+8tY1rSVsOWmsXovT5LvqFMdCdRDLlx/TDU1fV2HwAiqFbO3fJm7yPD+yxO RMxYFUI2C23JeVQSMoKBurtT3MYlt/7dCrJ4v5lBV3EHYCmklqa/QV51I/sM= Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:1622:b0:694:980a:2c47 with SMTP id 006d021491bc7-69998bd405bmr12037677eaf.0.1778480608729; Sun, 10 May 2026 23:23:28 -0700 (PDT) Date: Sun, 10 May 2026 23:23:28 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a0175e0.a00a0220.1c3806.0016.GAE@google.com> Subject: [syzbot] [net?] WARNING in qdisc_tree_reduce_backlog (2) From: syzbot To: davem@davemloft.net, edumazet@google.com, horms@kernel.org, jhs@mojatatu.com, jiri@resnulli.us, kuba@kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, pabeni@redhat.com, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 5862221fdded Merge tag 'parisc-for-7.1-rc3' of git://git.k.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=12a4bb26580000 kernel config: https://syzkaller.appspot.com/x/.config?x=f2e8ebfec4636d32 dashboard link: https://syzkaller.appspot.com/bug?extid=9744ccaabe337c6fb123 compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 Unfortunately, I don't have any reproducer for this issue yet. Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/cd9aba7e59bf/disk-5862221f.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/29af9d57e9af/vmlinux-5862221f.xz kernel image: https://storage.googleapis.com/syzbot-assets/02749594fd1e/bzImage-5862221f.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+9744ccaabe337c6fb123@syzkaller.appspotmail.com ------------[ cut here ]------------ parentid != TC_H_ROOT WARNING: net/sched/sch_api.c:797 at qdisc_tree_reduce_backlog+0x3d9/0x480 net/sched/sch_api.c:797, CPU#1: ktimers/1/29 Modules linked in: CPU: 1 UID: 0 PID: 29 Comm: ktimers/1 Tainted: G L syzkaller #0 PREEMPT_{RT,(full)} Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026 RIP: 0010:qdisc_tree_reduce_backlog+0x3d9/0x480 net/sched/sch_api.c:797 Code: ff ff 4c 89 ef e8 b7 85 12 f9 e9 42 ff ff ff e8 4d 7c ab f8 eb 17 e8 46 7c ab f8 eb 10 e8 3f 7c ab f8 eb 09 e8 38 7c ab f8 90 <0f> 0b 90 e8 7f 72 03 02 89 c3 31 ff 89 c6 e8 d4 80 ab f8 85 db 74 RSP: 0018:ffffc90000a3f768 EFLAGS: 00010246 RAX: ffffffff8918f818 RBX: 0000000000000008 RCX: ffff88801daa3d80 RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000100 RBP: dffffc0000000000 R08: 0000000000000000 R09: 0000000000000100 R10: 0000000000000100 R11: 00000000ffffffff R12: 00000000000affe0 R13: dffffc0000000000 R14: ffffc90000a3f8e0 R15: ffff88803d0a7800 FS: 0000000000000000(0000) GS:ffff888126279000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055558bcbda38 CR3: 00000000403d8000 CR4: 00000000003526f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000003e4f DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Call Trace: sfq_rehash net/sched/sch_sfq.c:598 [inline] sfq_perturbation+0x205d/0x22d0 net/sched/sch_sfq.c:615 call_timer_fn+0x192/0x5e0 kernel/time/timer.c:1748 expire_timers kernel/time/timer.c:1799 [inline] __run_timers kernel/time/timer.c:2374 [inline] __run_timer_base+0x6a3/0x9f0 kernel/time/timer.c:2386 run_timer_base kernel/time/timer.c:2395 [inline] run_timer_softirq+0x103/0x170 kernel/time/timer.c:2406 handle_softirqs+0x1de/0x6d0 kernel/softirq.c:622 __do_softirq kernel/softirq.c:656 [inline] run_ktimerd+0x69/0x100 kernel/softirq.c:1151 smpboot_thread_fn+0x541/0xa50 kernel/smpboot.c:160 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. If the report is already addressed, let syzbot know by replying with: #syz fix: exact-commit-title If you want to overwrite report's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the report is a duplicate of another one, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup