From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oa1-f79.google.com (mail-oa1-f79.google.com [209.85.160.79]) (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 EE9133C0A0D for ; Mon, 15 Jun 2026 08:05:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.160.79 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781510731; cv=none; b=Aw+28rU8Ntpjmazdcfds1HNEoZ8lXZ19ecvyRJsUcx3vnvH6JMqB6dH0NZWvutiRPj/B3ET+LUI3YVOSyonaan7ZHX+7+9CZHotdZ8AdyhVAJL5lYxLoqg7qApf9eY/NEyE1yD7bYQRi7dOppGDOPRJvwIj4/4/ErJGcQ30M8JY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781510731; c=relaxed/simple; bh=kJKtkYCUSK6/7Ycyn5qaD5nFdvqce34jtbUjzHXOj28=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; b=ON2aqgvSSnvoEGaN+bes5yH1JqpGyU2Hii2P2J7wIZ1XX3jqCdSzC9jBwjuM4ilybJdY3Poe75Dvst4eDGVm7BEL9OxCYKDCdzEvhaa8I0YsYa+3PhyduPbUUWDxpF/Lm7f+xOTNyiYWcQ9ShlKzUnuKb8ZXBBRgeaarRm+vNfs= 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=209.85.160.79 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-f79.google.com with SMTP id 586e51a60fabf-440e6bdc127so4237461fac.2 for ; Mon, 15 Jun 2026 01:05:29 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1781510729; x=1782115529; h=to:from:subject:message-id:in-reply-to:date:mime-version :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=tpIXCQzqfahWYhOAtNF5NHRLKpPfy5+DaDSfJ/OghqU=; b=GQycgv6gick/DDDy2VKRAyVdE9xxvCxi5j6N79S7afUcMgNxIlxB0IorDXBtxMSr3m ziTqkpPHkOvCkvYHJM+ySrltJ4eWiXyY6OgG7BIug/DW6rNpH867dDZnwfiiFhtms32x pxirSHYo4eS8+lNSRuqcUjsRElodlf8hOCImHHtuCaHHRvpFQxliV08iCcwV39LS8dx5 wBO5pBsZFtV0ekttLJ9G23lojHXnKYxEtD35UKLOHEvHbu3hAF65arKK+xCeQ/aUfD6o zXS8AU67+k3uU771/aK9wMzJGXfYQ9bwja+oBkRwlHyQIbJr6VUREd+dO7Yi4chk6pEj cBRA== X-Gm-Message-State: AOJu0YzCopO33m4ZM+aeLnGYEqx0fLsxQ3fXVD1jplLjFh+AaSZ8HpQ6 9Wn2AJwwpDLKcxr//O7xgOWnUczf8YJpKX1yxEC3zwk8PIoucDTEkpjaY1EVv5+7bkUmAAYD5Jc 2Es8TnOMnPDyYbQwpkaUXsiddZmgUSxucGayfr9CR58kiBB5bgUCJasroDBnaBA== Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:221f:b0:69d:f0e8:3223 with SMTP id 006d021491bc7-69edc5e7d8emr8428026eaf.7.1781510728847; Mon, 15 Jun 2026 01:05:28 -0700 (PDT) Date: Mon, 15 Jun 2026 01:05:28 -0700 In-Reply-To: <6a23a4b4.e4db5ad2.3b7dfb.0000.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a2fb248.8812e0fc.3c3fa4.001a.GAE@google.com> Subject: Re: [syzbot] [cgroups?] INFO: task hung in cgroup_subtree_control_write (2) From: syzbot To: cgroups@vger.kernel.org, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, mkoutny@suse.com, syzkaller-bugs@googlegroups.com, tj@kernel.org Content-Type: text/plain; charset="UTF-8" syzbot has found a reproducer for the following issue on: HEAD commit: ec039126b7fa Add linux-next specific files for 20260611 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=178e637a580000 kernel config: https://syzkaller.appspot.com/x/.config?x=d0d1fa2afcbce17c dashboard link: https://syzkaller.appspot.com/bug?extid=bb2e19a1190a556c01b1 compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10b0d4ae580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/be809c32a471/disk-ec039126.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/13ea1053e3b5/vmlinux-ec039126.xz kernel image: https://storage.googleapis.com/syzbot-assets/1bcdab47ddc8/bzImage-ec039126.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+bb2e19a1190a556c01b1@syzkaller.appspotmail.com INFO: task syz.1.18:6037 blocked for more than 143 seconds. Not[ 392.048269][ T39] Not tainted syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz.1.18 state:D stack:27936 pid:6037 tgid:6035 ppid:6000 task_flags:0x400140 flags:0x00080002 Call Trace: context_switch kernel/sched/core.c:5504 [inline] __schedule+0x172b/0x5550 kernel/sched/core.c:7228 __schedule_loop kernel/sched/core.c:7307 [inline] schedule+0x164/0x360 kernel/sched/core.c:7322 cgroup_lock_and_drain_offline+0x516/0x650 kernel/cgroup/cgroup.c:3275 cgroup_kn_lock_live+0x120/0x230 kernel/cgroup/cgroup.c:1715 cgroup_subtree_control_write+0x4b3/0x10a0 kernel/cgroup/cgroup.c:3577 cgroup_file_write+0x331/0x8f0 kernel/cgroup/cgroup.c:4316 kernfs_fop_write_iter+0x3b0/0x540 fs/kernfs/file.c:345 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x629/0xba0 fs/read_write.c:687 ksys_write+0x156/0x270 fs/read_write.c:739 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f3fb3b0ce59 RSP: 002b:00007f3fb3145028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007f3fb3d86090 RCX: 00007f3fb3b0ce59 RDX: 0000000000000005 RSI: 0000200000000040 RDI: 0000000000000006 RBP: 00007f3fb3ba2d6f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f3fb3d86128 R14: 00007f3fb3d86090 R15: 00007ffe868740f8 INFO: task syz.2.19:6081 blocked for more than 143 seconds. Not tainted syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz.2.19 state:D stack:28344 pid:6081 tgid:6079 ppid:6045 task_flags:0x400140 flags:0x00080002 Call Trace: context_switch kernel/sched/core.c:5504 [inline] __schedule+0x172b/0x5550 kernel/sched/core.c:7228 __schedule_loop kernel/sched/core.c:7307 [inline] schedule+0x164/0x360 kernel/sched/core.c:7322 cgroup_lock_and_drain_offline+0x516/0x650 kernel/cgroup/cgroup.c:3275 cgroup_kn_lock_live+0x120/0x230 kernel/cgroup/cgroup.c:1715 cgroup_subtree_control_write+0x4b3/0x10a0 kernel/cgroup/cgroup.c:3577 cgroup_file_write+0x331/0x8f0 kernel/cgroup/cgroup.c:4316 kernfs_fop_write_iter+0x3b0/0x540 fs/kernfs/file.c:345 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x629/0xba0 fs/read_write.c:687 ksys_write+0x156/0x270 fs/read_write.c:739 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fcd96f6ce59 RSP: 002b:00007fcd965ad028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007fcd971e6090 RCX: 00007fcd96f6ce59 RDX: 0000000000000005 RSI: 0000200000000300 RDI: 0000000000000006 RBP: 00007fcd97002d6f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fcd971e6128 R14: 00007fcd971e6090 R15: 00007ffc255c33a8 INFO: task syz.2.19:6082 blocked for more than 143 seconds. Not tainted syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz.2.19 state:D stack:28920 pid:6082 tgid:6079 ppid:6045 task_flags:0x400040 flags:0x00080002 Call Trace: context_switch kernel/sched/core.c:5504 [inline] __schedule+0x172b/0x5550 kernel/sched/core.c:7228 __schedule_loop kernel/sched/core.c:7307 [inline] rt_mutex_schedule+0x76/0xf0 kernel/sched/core.c:7603 rt_mutex_slowlock_block+0x505/0x670 kernel/locking/rtmutex.c:1669 __rt_mutex_slowlock kernel/locking/rtmutex.c:1746 [inline] __rt_mutex_slowlock_locked kernel/locking/rtmutex.c:1786 [inline] rt_mutex_slowlock+0x2dc/0x780 kernel/locking/rtmutex.c:1826 __rt_mutex_lock kernel/locking/rtmutex.c:1841 [inline] __mutex_lock_common kernel/locking/rtmutex_api.c:560 [inline] mutex_lock_nested+0x168/0x1d0 kernel/locking/rtmutex_api.c:578 fdget_pos+0x252/0x320 fs/file.c:1259 class_fd_pos_constructor include/linux/file.h:85 [inline] ksys_write+0x79/0x270 fs/read_write.c:730 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fcd96f6ce59 RSP: 002b:00007fcd9658c028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007fcd971e6180 RCX: 00007fcd96f6ce59 RDX: 0000000000000005 RSI: 0000200000000040 RDI: 0000000000000006 RBP: 00007fcd97002d6f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fcd971e6218 R14: 00007fcd971e6180 R15: 00007ffc255c33a8 Showing all locks held in the system: 3 locks held by kworker/1:0/32: #0: ffff88813fe57938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x897/0x1630 kernel/workqueue.c:3301 #1: ffffc90000a6fc40 (deferred_process_work){+.+.}-{0:0}, at: process_one_work+0x8be/0x1630 kernel/workqueue.c:3302 #2: ffffffff8f7b0bb8 (rtnl_mutex){+.+.}-{4:4}, at: switchdev_deferred_process_work+0xe/0x20 net/switchdev/switchdev.c:104 1 lock held by khungtaskd/39: #0: ffffffff8e3cb2a0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #0: ffffffff8e3cb2a0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline] #0: ffffffff8e3cb2a0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6777 2 locks held by getty/5366: #0: ffff88802940e0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243 #1: ffffc90003cbe2e0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x465/0x1490 drivers/tty/n_tty.c:2211 3 locks held by kworker/u8:18/5822: #0: ffff888032abd938 ((wq_completion)bat_events){+.+.}-{0:0}, at: process_one_work+0x897/0x1630 kernel/workqueue.c:3301 #1: ffffc90003db7c40 ((work_completion)(&(&bat_priv->dat.work)->work)){+.+.}-{0:0}, at: process_one_work+0x8be/0x1630 kernel/workqueue.c:3302 #2: ffffffff8e3cb2a0 (rcu_read_lock){....}-{1:3}, at: __local_bh_disable_ip+0x3c/0x420 kernel/softirq.c:163 3 locks held by syz.1.18/6037: #0: ffff88803a43f128 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1259 #1: ffff8880344f2500 (sb_writers#9){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2728 [inline] #1: ffff8880344f2500 (sb_writers#9){.+.+}-{0:0}, at: vfs_write+0x22d/0xba0 fs/read_write.c:683 #2: ffff8880436a3c78 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1df/0x540 fs/kernfs/file.c:336 3 locks held by syz.2.19/6081: #0: ffff88803b865f28 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1259 #1: ffff8880344f2500 (sb_writers#9){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2728 [inline] #1: ffff8880344f2500 (sb_writers#9){.+.+}-{0:0}, at: vfs_write+0x22d/0xba0 fs/read_write.c:683 #2: ffff88803697fc78 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1df/0x540 fs/kernfs/file.c:336 1 lock held by syz.2.19/6082: #0: ffff88803b865f28 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1259 3 locks held by syz.3.20/6122: #0: ffff888037837f28 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1259 #1: ffff8880344f2500 (sb_writers#9){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2728 [inline] #1: ffff8880344f2500 (sb_writers#9){.+.+}-{0:0}, at: vfs_write+0x22d/0xba0 fs/read_write.c:683 #2: ffff888036d05878 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1df/0x540 fs/kernfs/file.c:336 1 lock held by syz.3.20/6123: #0: ffff888037837f28 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1259 3 locks held by syz.4.21/6167: #0: ffff88803bb00d28 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1259 #1: ffff8880344f2500 (sb_writers#9){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2728 [inline] #1: ffff8880344f2500 (sb_writers#9){.+.+}-{0:0}, at: vfs_write+0x22d/0xba0 fs/read_write.c:683 #2: ffff888033038478 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1df/0x540 fs/kernfs/file.c:336 1 lock held by syz.4.21/6168: #0: ffff88803bb00d28 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1259 3 locks held by syz.5.22/6214: #0: ffff88803a467328 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1259 #1: ffff8880344f2500 (sb_writers#9){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2728 [inline] #1: ffff8880344f2500 (sb_writers#9){.+.+}-{0:0}, at: vfs_write+0x22d/0xba0 fs/read_write.c:683 #2: ffff8880408bb078 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1df/0x540 fs/kernfs/file.c:336 1 lock held by syz.5.22/6216: #0: ffff88803a467328 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1259 3 locks held by syz.6.23/6264: #0: ffff888028ed0328 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1259 #1: ffff8880344f2500 (sb_writers#9){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2728 [inline] #1: ffff8880344f2500 (sb_writers#9){.+.+}-{0:0}, at: vfs_write+0x22d/0xba0 fs/read_write.c:683 #2: ffff88803c173c78 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1df/0x540 fs/kernfs/file.c:336 1 lock held by syz.6.23/6265: #0: ffff888028ed0328 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1259 3 locks held by syz.7.24/6310: #0: ffff8880296e8328 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1259 #1: ffff8880344f2500 (sb_writers#9){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2728 [inline] #1: ffff8880344f2500 (sb_writers#9){.+.+}-{0:0}, at: vfs_write+0x22d/0xba0 fs/read_write.c:683 #2: ffff88803e05a878 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1df/0x540 fs/kernfs/file.c:336 1 lock held by syz.7.24/6311: #0: ffff8880296e8328 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1259 3 locks held by syz.8.25/6356: #0: ffff8880257b2728 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1259 #1: ffff8880344f2500 (sb_writers#9){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2728 [inline] #1: ffff8880344f2500 (sb_writers#9){.+.+}-{0:0}, at: vfs_write+0x22d/0xba0 fs/read_write.c:683 #2: ffff888031468078 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1df/0x540 fs/kernfs/file.c:336 1 lock held by syz.8.25/6357: #0: ffff8880257b2728 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1259 3 locks held by syz.9.26/6407: #0: ffff888028ea4528 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1259 #1: ffff8880344f2500 (sb_writers#9){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2728 [inline] #1: ffff8880344f2500 (sb_writers#9){.+.+}-{0:0}, at: vfs_write+0x22d/0xba0 fs/read_write.c:683 #2: ffff888032e47078 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1df/0x540 fs/kernfs/file.c:336 1 lock held by syz.9.26/6408: #0: ffff888028ea4528 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1259 3 locks held by syz-executor/6411: #0: ffffffff8f7b0bb8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline] #0: ffffffff8f7b0bb8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock net/core/rtnetlink.c:341 [inline] #0: ffffffff8f7b0bb8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0x883/0x1bb0 net/core/rtnetlink.c:4150 #1: ffffffff8e3cb2a0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #1: ffffffff8e3cb2a0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline] #1: ffffffff8e3cb2a0 (rcu_read_lock){....}-{1:3}, at: ib_device_get_by_netdev+0x81/0x4f0 drivers/infiniband/core/device.c:2357 #2: ffff8880b8724540 (psi_seq){-...}-{0:0}, at: psi_task_change+0xd4/0x340 kernel/sched/psi.c:919 ============================================= NMI backtrace for cpu 0 CPU: 0 UID: 0 PID: 39 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 nmi_cpu_backtrace+0x274/0x2d0 lib/nmi_backtrace.c:122 nmi_trigger_cpumask_backtrace+0x17a/0x380 lib/nmi_backtrace.c:65 trigger_all_cpu_backtrace include/linux/nmi.h:162 [inline] __sys_info lib/sys_info.c:157 [inline] sys_info+0x135/0x170 lib/sys_info.c:165 check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline] watchdog+0xfd3/0x1030 kernel/hung_task.c:561 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 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 UID: 0 PID: 29 Comm: rcuc/1 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026 RIP: 0010:mark_lock+0x9a/0x190 kernel/locking/lockdep.c:4776 Code: 0e 00 75 13 48 8d 3d e5 1a 31 0e 48 c7 c6 51 2b a9 8d 67 48 0f b9 3a 90 31 c9 4c 89 fe 4c 89 f7 b8 01 00 00 00 85 69 60 74 10 <5b> 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc 49 89 fe 49 89 f7 RSP: 0018:ffffc90000a3f970 EFLAGS: 00000006 RAX: 0000000000000001 RBX: 0000000000000009 RCX: ffffffff93640d68 RDX: 0000000000000008 RSI: ffff88801e694a30 RDI: ffff88801e693e00 RBP: 0000000000000200 R08: ffffffff81883dac R09: ffffffff8e3cb2a0 R10: dffffc0000000000 R11: fffffbfff1f9e71f R12: 0000000000000003 R13: ffff88801e694a30 R14: ffff88801e693e00 R15: 0000000000000001 FS: 0000000000000000(0000) GS:ffff888125b6b000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f2e59a3b6b0 CR3: 000000003ef78000 CR4: 00000000003526f0 Call Trace: mark_usage kernel/locking/lockdep.c:4676 [inline] __lock_acquire+0x6b5/0x2d10 kernel/locking/lockdep.c:5193 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5870 rcu_lock_acquire include/linux/rcupdate.h:300 [inline] rcu_read_lock include/linux/rcupdate.h:840 [inline] __local_bh_disable_ip+0x205/0x420 kernel/softirq.c:174 local_bh_disable include/linux/bottom_half.h:20 [inline] rcu_cpu_kthread+0x214/0x1470 kernel/rcu/tree.c:2978 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 --- 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.