From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oo1-f80.google.com (mail-oo1-f80.google.com [209.85.161.80]) (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 707DF1A680B for ; Sat, 15 Aug 2026 20:30:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.161.80 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786825841; cv=none; b=V9ryfHPCQfTtxin/Pe5pVjeNWhwG6J/MWnVn/m1bee8eMCuTMkCF31CqxHwQHkWrtyZoPIMfvwZHu1/FMdww7yCw+U+HbCw2f3Dg38Kwx8t3bvkvd2OaEY7D2skHVN1WnKfnptmVURNBRr0Ny4cu3+bwQdOXtQbZD095VX94a+Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786825841; c=relaxed/simple; bh=H9U5yuqSbL8TooSh5Cr2MIgx9cHnW+ZOSCBumCtGMJU=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; b=peUQEKPTzpYfHq7b3k9doBpuB3xudfx4q8BezyoGYuFYNHRUuzVoQZOKT4YaIo4Tol1sMdECMuuhBw7u3wC/udowEsADa1MYekjXDBwLyqdcvRmlALN0wOTrqWWFcdnkdNjNGLVN1hpqYiFJ6ad5M7J+Mp5WtiMxUVDBsDtFx68= 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=209.85.161.80 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-f80.google.com with SMTP id 006d021491bc7-6b0fd43eb15so328827eaf.2 for ; Sat, 15 Aug 2026 13:30:39 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786825838; x=1787430638; h=content-type:to:from:subject:message-id:in-reply-to:date :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to:content-type; bh=mVfqNUIyd7+w3J9bAvMSqHMdg1naWR/T8QW7GL8SYTE=; b=l/9DhCaYsR4+XEk4/39dQScx5OgKKwSyQoD5HO/rQC59k0XB8IOwcNXbEFdxYamf9W /ND4lLt+OsHTqaOwrxCrRPtYHnvaKzjamXOKlbZvaZs7fIIoIpLNH6tcvajZXbOT8Rl7 3Ic73dmnDYVn0M/KkVoxpTO3Z3lO2Ilj69FFWPNiG6bFvi30k5P7hdWq8JCVy2MM4gxB jwS0U0ymuRJVNa9lM9sg+9jCiINUv2WaxVbWHPfzrVHrnA5uzYOvjQ5J9xPtS4T8nTxf gWTM/GEcsxSqB36MiPK3c6RYImVWcqlFTs/d7jnTgP2q3r+RkEnT6rv8wHGBtAzG/NPA 2mgA== X-Forwarded-Encrypted: i=1; AHgh+RotXkAwLYerKiiOVjtUY3HjysvqD9Hnb2dQpO5pBJnObrAOhFGk0KvatHrtSsKVkTqz+DMsRQgHHq54SDU=@vger.kernel.org X-Gm-Message-State: AOJu0YyuS1YalSHgIUG8XsdIxc0YN+MRakbkBkVbGTxCH9xp34nwB2ca pxAFwtFRvmcmS1oLA3U7zNlwARy9Cmy9e7jEHv5JIj9jQ+KtLNy5Sypkdkr01ryx5cEOi6BjSrZ fxMN50ngevbRsuL3uQUmPtXl1o1kLKk4weMWPrPp4/tQm/YREuxCeoX7cJPU= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:169e:b0:6aa:d13c:a709 with SMTP id 006d021491bc7-6b0d690f719mr12768172eaf.31.1786825838264; Sat, 15 Aug 2026 13:30:38 -0700 (PDT) Date: Sat, 15 Aug 2026 13:30:38 -0700 In-Reply-To: <6a609a1e.33ea6125.251e5.0008.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a80cc6e.dbb3a75c.20434b.001e.GAE@google.com> Subject: Re: [syzbot] [kernel?] INFO: rcu detected stall in kthread (6) From: syzbot To: bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, linux-kernel@vger.kernel.org, mingo@redhat.com, syzkaller-bugs@googlegroups.com, tglx@kernel.org, x86@kernel.org Content-Type: text/plain; charset="UTF-8" syzbot has found a reproducer for the following issue on: HEAD commit: 15ef2f78c49d Merge tag 'input-for-v7.2-rc7' of git://git.k.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=1279c279580000 kernel config: https://syzkaller.appspot.com/x/.config?x=1d67342c314f228d dashboard link: https://syzkaller.appspot.com/bug?extid=2d47e0896b84fae323c7 compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16de2a25580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11e6b279580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/a93f43b69b22/disk-15ef2f78.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/d4fdb6da0cae/vmlinux-15ef2f78.xz kernel image: https://storage.googleapis.com/syzbot-assets/ef548cd2e0c1/bzImage-15ef2f78.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+2d47e0896b84fae323c7@syzkaller.appspotmail.com rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: (detected by 0, t=10502 jiffies, g=13061, q=1051 ncpus=2) rcu: All QSes seen, last rcu_preempt kthread activity 10500 (4294955331-4294944831), jiffies_till_next_fqs=1, root ->qsmask 0x0 rcu: rcu_preempt kthread starved for 10500 jiffies! g13061 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0 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:27592 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000 Call Trace: context_switch kernel/sched/core.c:5510 [inline] __schedule+0x125c/0x6730 kernel/sched/core.c:7234 preempt_schedule_irq+0x50/0x90 kernel/sched/core.c:7556 irqentry_exit_to_kernel_mode_preempt include/linux/irq-entry-common.h:468 [inline] irqentry_exit_to_kernel_mode include/linux/irq-entry-common.h:539 [inline] irqentry_exit+0x205/0xa00 kernel/entry/common.c:167 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674 RIP: 0010:rcu_gp_fqs_loop+0x1a9/0x900 kernel/rcu/tree.c:2123 Code: f6 c5 02 75 42 48 8b 05 fd fc ef 0c 48 85 c0 75 0c 48 8b 05 71 fd ef 0c 48 85 c0 74 2a 48 85 db 74 25 48 89 df e8 87 23 d0 09 <48> 89 c3 ba 02 04 00 00 4c 89 ee 48 c7 c7 98 3a df 8e e8 50 6b f3 RSP: 0018:ffffc90000157ca8 EFLAGS: 00000282 RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000000000 RDX: ffff88801f280000 RSI: ffffffff8bbf5da1 RDI: ffffffff8c600380 RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000000 R12: ffffffff8ea0f280 R13: ffffc90000157d10 R14: 0000000000000000 R15: 1ffff9200002af96 rcu_gp_kthread+0x179/0x230 kernel/rcu/tree.c:2325 kthread+0x370/0x450 kernel/kthread.c:436 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 rcu: Stack dump where RCU GP kthread last ran: CPU: 0 UID: 0 PID: 5954 Comm: syz.0.26 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026 RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:188 [inline] RIP: 0010:_raw_spin_unlock_irq+0x29/0x50 kernel/locking/spinlock.c:206 Code: 90 f3 0f 1e fa 53 48 8b 74 24 08 48 89 fb 48 83 c7 18 e8 fa 90 26 f6 48 89 df e8 82 e0 26 f6 e8 fd 49 53 f6 fb bf 01 00 00 00 32 ee 15 f6 65 8b 05 5b a7 c4 08 85 c0 74 06 5b e9 81 4b 00 00 RSP: 0018:ffffc9000202fc88 EFLAGS: 00000206 RAX: 000000000515ac11 RBX: ffff88802e28ef00 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffffffff8e3aced0 RDI: 0000000000000001 RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000021 R13: ffff88802e28f300 R14: dffffc0000000000 R15: ffff888021f3a540 FS: 00007f8b813fb6c0(0000) GS:ffff888123bde000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000200000000058 CR3: 0000000078326000 CR4: 00000000003526f0 Call Trace: spin_unlock_irq include/linux/spinlock.h:402 [inline] get_signal+0x195a/0x21e0 kernel/signal.c:3049 arch_do_signal_or_restart+0x91/0x7e0 arch/x86/kernel/signal.c:337 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline] exit_to_user_mode_loop+0x139/0x6f0 kernel/entry/common.c:101 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline] syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline] do_syscall_64+0x666/0x870 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f8b8059e0d7 Code: 83 c8 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 RSP: 002b:00007f8b813fb0e8 EFLAGS: 00000246 RAX: 00000000000000ca RBX: 00007f8b80825fa8 RCX: 00007f8b8059e0d9 RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f8b80825fa8 RBP: 00007f8b80825fa0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f8b80826038 R14: 00007fff1b59f550 R15: 00007fff1b59f638 --- If you want syzbot to run the reproducer, reply with: #syz test: git://repo/address.git branch-or-commit-hash If you attach or paste a git patch, syzbot will apply it before testing.