From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oa1-f80.google.com (mail-oa1-f80.google.com [209.85.160.80]) (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 03FC918CBE1 for ; Tue, 27 Jan 2026 01:07:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.160.80 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769476053; cv=none; b=tF3LnQFS28ae9hA6ySbZiuPTcf9MBeppOei58YXYTnDPlffFD9p9STup35OX2H4MCIhgk54GI+L4Xkbxfw5CTVnDRsYiJ5QGZZHr9lXgM7/vIrpLnTecy49JUa4eUnXZIQu3TgjdEmdALUUAhu+L+F2i3tIh+U/l4vw7+Cf/UHM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769476053; c=relaxed/simple; bh=RR3O277zaj9SyKVVQnBdeaXL5t7VvBo4mEIZxtXViSY=; h=MIME-Version:Date:Message-ID:Subject:From:To:Content-Type; b=N11CKMc6AQnlQL6gc9fs1hMh1LoaTG161gChBA4SBeu2CIIQyRZaLzVPFLUQVozXsmMcAc8QLh6z8kHrFHNJq4bd1J2dHWlYQVaE9jWY/Snet8Msg+E54xGZLuMZBn8DFtS8qc9EtIkIF1HW9psJlJ/8qHY/2PwX0PLeAhGilEU= 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=209.85.160.80 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-oa1-f80.google.com with SMTP id 586e51a60fabf-4042356948fso10152132fac.3 for ; Mon, 26 Jan 2026 17:07:31 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1769476051; x=1770080851; h=to:from:subject:message-id:date:mime-version:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=zGbj0dVfZfXuRnHtd36TSCbucFbRwLCDmK2viXS3NR0=; b=LFLc+bKmXdavG34UCt5OJN0fBF1b9PqOBwlfDI1nNrq67V/7OkHozIuYMPfitJifit Dup9uQaUYAY+1R7mQ9AbDzv5h3bo4A6srB6JEb0lX6gKgwmWMbHw3+I1GoZFRvKyq3Od mziCVLtljG6cJhXo9wO/HfmTzg+1XFedZooK0QiA6RUKF6/5RQjYrjUbq6oamrh2Qy4P KHUGjsMtYbz8ChrcWtNnal+zbmzwLR8A7OaZ673JKL1BHTxEbAMuk3YsNEwNPXn3nrWP nnsuRzu+XU+hwojHa/z6XFrwbjNxGNuDChhBItD+30eUs4DlSQLWsekcIcCzwX5wLtSe xacw== X-Forwarded-Encrypted: i=1; AJvYcCWpxpuF36rvvhq6/kur5FnFXwGYvFJVfHYt7dTDyQ0vdlLNfTjtCPWPEyhgBXBjUFwLvfiHqUeXtXyqHyM=@vger.kernel.org X-Gm-Message-State: AOJu0YxCa2G5FQvWz1GtsHWPc2R3t08BX+BSjLakdldsMynHYBSG2Aln RYy/iZ5C4sTZNhng8vnr1Hn9DAa7eFA1nSDikW04edPeUQeidwxjbakXtR1E8qxtOifVqtBlpEw ypKl7qaGszTUh6Et3pWfNkcNs+UEfBV/UEooGdWgUvJA0X56/x3h7a7dIKmg= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:206:b0:657:5629:2cef with SMTP id 006d021491bc7-662e02c60bcmr3256128eaf.4.1769476050951; Mon, 26 Jan 2026 17:07:30 -0800 (PST) Date: Mon, 26 Jan 2026 17:07:30 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69780fd2.050a0220.c9109.000a.GAE@google.com> Subject: [syzbot] [mm?] INFO: rcu detected stall in schedule_tail (8) From: syzbot To: Liam.Howlett@oracle.com, akpm@linux-foundation.org, david@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, mhocko@suse.com, rppt@kernel.org, surenb@google.com, syzkaller-bugs@googlegroups.com, vbabka@suse.cz Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 12a0094839d0 Merge tag 'timers-urgent-2026-01-24' of git:/.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=105cc05a580000 kernel config: https://syzkaller.appspot.com/x/.config?x=f1fac0919970b671 dashboard link: https://syzkaller.appspot.com/bug?extid=42836f91edd58eb82c6a 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=14557d22580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15d0105a580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/4ede6f8f9210/disk-12a00948.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/47f57ac656a5/vmlinux-12a00948.xz kernel image: https://storage.googleapis.com/syzbot-assets/22586c0d39b7/bzImage-12a00948.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+42836f91edd58eb82c6a@syzkaller.appspotmail.com rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P6967/1:b..l rcu: (detected by 0, t=10503 jiffies, g=14029, q=726 ncpus=2) task:syz-executor state:R running task stack:29456 pid:6967 tgid:6967 ppid:6192 task_flags:0x400040 flags:0x00080000 Call Trace: context_switch kernel/sched/core.c:5260 [inline] __schedule+0xfe4/0x5e10 kernel/sched/core.c:6867 preempt_schedule_irq+0x50/0x90 kernel/sched/core.c:7194 irqentry_exit+0x17b/0x670 kernel/entry/common.c:216 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697 RIP: 0010:ptlock_ptr include/linux/mm.h:3240 [inline] RIP: 0010:pte_lockptr include/linux/mm.h:3264 [inline] RIP: 0010:pte_offset_map_rw_nolock+0xbd/0x1c0 mm/pgtable-generic.c:330 Code: 80 3c 10 00 0f 85 bb 00 00 00 48 03 1d 5c 91 92 0b 48 b8 00 00 00 00 00 fc ff df 48 8d 7b 28 48 89 fa 48 c1 ea 03 80 3c 02 00 <0f> 85 c0 00 00 00 4c 89 e2 48 8b 5b 28 48 b8 00 00 00 00 00 fc ff RSP: 0018:ffffc9000bba7ad8 EFLAGS: 00000246 RAX: dffffc0000000000 RBX: ffffea0001ee7580 RCX: ffffffff825bf480 RDX: 1ffffd40003dceb5 RSI: ffffffff825bf3de RDI: ffffea0001ee75a8 RBP: ffff88807b9d60c8 R08: 0000000000000007 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffffc9000bba7c38 R13: 000000007b9d6067 R14: 0000000000000067 R15: 0000000000000001 handle_pte_fault mm/memory.c:6261 [inline] __handle_mm_fault+0xc0e/0x2b50 mm/memory.c:6414 handle_mm_fault+0x36d/0xa20 mm/memory.c:6583 do_user_addr_fault+0x74c/0x12f0 arch/x86/mm/fault.c:1385 handle_page_fault arch/x86/mm/fault.c:1474 [inline] exc_page_fault+0x6f/0xd0 arch/x86/mm/fault.c:1527 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 RIP: 0010:__put_user_4+0xd/0x20 arch/x86/lib/putuser.S:94 Code: 66 89 01 31 c9 0f 01 ca c3 cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 48 89 cb 48 c1 fb 3f 48 09 d9 0f 01 cb <89> 01 31 c9 0f 01 ca e9 07 ba 03 00 0f 1f 80 00 00 00 00 90 90 90 RSP: 0018:ffffc9000bba7e78 EFLAGS: 00050202 RAX: 000000000000001b RBX: 0000000000000000 RCX: 0000555562a197d0 RDX: dffffc0000000000 RSI: ffffffff8dc45476 RDI: ffff888025b2a944 RBP: ffff888025b2aba0 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000001 R11: 1ffffffff1cbde81 R12: 1ffff92001774fd6 R13: ffffc9000bba7f48 R14: 0000000000000000 R15: dffffc0000000000 schedule_tail+0x9e/0xd0 kernel/sched/core.c:5193 ret_from_fork+0x79/0xaf0 arch/x86/kernel/process.c:154 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 rcu: rcu_preempt kthread starved for 10518 jiffies! g14029 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->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:I stack:27368 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000 Call Trace: context_switch kernel/sched/core.c:5260 [inline] __schedule+0xfe4/0x5e10 kernel/sched/core.c:6867 preempt_schedule_irq+0x50/0x90 kernel/sched/core.c:7194 irqentry_exit+0x17b/0x670 kernel/entry/common.c:216 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697 RIP: 0010:debug_object_assert_init+0x7b/0x300 lib/debugobjects.c:1000 Code: f1 f1 f1 c7 40 04 f1 f1 00 00 c7 40 08 00 00 00 f3 c7 40 0c f3 f3 f3 f3 65 48 8b 05 17 95 f4 0e 48 89 84 24 b8 00 00 00 31 c0 <80> 3d 7e bc c7 0b 00 48 89 7c 24 68 48 c7 44 24 60 00 00 00 00 48 RSP: 0018:ffffc90000157910 EFLAGS: 00000246 RAX: 0000000000000000 RBX: ffffc90000157b58 RCX: 0000000000000000 RDX: ffff88801e290000 RSI: ffffffff8b92b940 RDI: ffffc90000157b58 RBP: ffffc90000157a00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: dffffc0000000000 R13: 0000000000000004 R14: ffff88801e290000 R15: 1ffff9200002af26 debug_timer_assert_init kernel/time/timer.c:803 [inline] debug_assert_init kernel/time/timer.c:848 [inline] __mod_timer+0xad/0xca0 kernel/time/timer.c:1025 add_timer+0x62/0x90 kernel/time/timer.c:1249 schedule_timeout+0x122/0x280 kernel/time/sleep_timeout.c:98 rcu_gp_fqs_loop+0x1a9/0xb00 kernel/rcu/tree.c:2083 rcu_gp_kthread+0x21e/0x320 kernel/rcu/tree.c:2285 kthread+0x3b3/0x730 kernel/kthread.c:463 ret_from_fork+0x754/0xaf0 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 rcu: Stack dump where RCU GP kthread last ran: CPU: 0 UID: 0 PID: 6972 Comm: syz.8.313 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/13/2026 RIP: 0010:__get_user_nocheck_4+0x8/0x20 arch/x86/lib/getuser.S:142 Code: c3 cc cc cc cc 66 66 2e 0f 1f 84 00 00 00 00 00 66 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 0f 01 cb 0f ae e8 8b 10 <31> c0 0f 01 ca c3 cc cc cc cc 66 66 2e 0f 1f 84 00 00 00 00 00 0f RSP: 0018:ffffc9000546fad8 EFLAGS: 00040202 RAX: 00007f4f28dcf040 RBX: ffff888021280000 RCX: 1ffff1100425033a RDX: 0000000046505845 RSI: 00007f4f28dce5c0 RDI: ffff888021281a04 RBP: 0000000000000000 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 00007f4f28dce5c0 R13: ffffc9000546fb90 R14: 0000000000000000 R15: ffff888021281a00 FS: 00007f4f28dcf6c0(0000) GS:ffff8881245dc000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000555562a197d0 CR3: 0000000028f6b000 CR4: 00000000003526f0 Call Trace: check_xstate_in_sigframe arch/x86/kernel/fpu/signal.c:46 [inline] __fpu_restore_sig+0x836/0x12f0 arch/x86/kernel/fpu/signal.c:335 fpu__restore_sig+0x151/0x190 arch/x86/kernel/fpu/signal.c:480 restore_sigcontext+0x4cb/0x6a0 arch/x86/kernel/signal_64.c:95 __do_sys_rt_sigreturn+0x229/0x2c0 arch/x86/kernel/signal_64.c:268 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xc9/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f4f27f9acb7 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:00007f4f28dcf0e8 EFLAGS: 00000246 RAX: 00000000000000ca RBX: 00007f4f28215fa8 RCX: 00007f4f27f9acb9 RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f4f28215fa8 RBP: 00007f4f28215fa0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f4f28216038 R14: 00007ffd840d3410 R15: 00007ffd840d34f8 --- 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 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. 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