From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 43FDB279DC3; Fri, 22 Aug 2025 16:20:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755879646; cv=none; b=njM/abb9UciWRjdDsqaA48fj8W72s5xPIDZakasq5AjImq67gmfCsUB7R2PBo5EXOErT8TY/9OIzc8CdFhNFz3y0uFwfcXsq/XhwuSqzLNRyX6Y/KGOiwyRmWmzpSXqPLwBqBlM5S/ZTWKh1szjBgtw22FOqzViRuS6vZzUBKTk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755879646; c=relaxed/simple; bh=pUefhvtx3fa9NKd7t7x8qj/cQQxg+Sux7Educwfd/bI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=hy0KI4rtAvOOW1U22qs/lj03E3tQIwkn9faiR8KzJfNmmAwcr3A/3mmT4bgFADdUiuv8KqNI+5CbHh2qk0aDNNAcUK1dIeqGF5VzPlCCwizThVinxG4X0QqmjzMwDRxqcNV62YQ5zKIcbKCe4qjllcM70m8Z4FPChHc99BifLBE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=w5HR0ADz; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=t8eHg1iS; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="w5HR0ADz"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="t8eHg1iS" Date: Fri, 22 Aug 2025 18:20:41 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1755879643; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=AtQFGIIZgwtLl5kOnn6MiSKJx7hARPjf03xjlGYheR0=; b=w5HR0ADzMEB1gfQs/FxLabGL0IVBvCgZa4l5SuQsyDFRdOPQx+ZhKiqJI34Wuj3hVmGW06 hQUEDXb8L3M7t2jUIhXFFH/hjM17MRMoc4Kopg+FHAMWPmBW7NXiFLa+RdBquNMoXzAfsW UpJCcUEzYibM2RtnROSzOdl8Aec92GC3w5PvTONy6O6laAF7hZNei5od2tj7DkomsFNgk3 Klz4WEA/ytY8c78nOd6bpPXZV+elMG8zSoYJ56J0RXGp+KB79bdHrhWQKF9taPQ79DW+fy p5aDZ6WrsELON3+KwZN9UAtQuOyYEQssQnIqeyABWgdGook1WhCrDuZAjn9MUA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1755879643; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=AtQFGIIZgwtLl5kOnn6MiSKJx7hARPjf03xjlGYheR0=; b=t8eHg1iSaaYcDhGsPl+SqXNKwRd9lmq9DvOkVx/LQLla7fm/FVfwAYbPCLYQOTXimi7WmX yQ9e7cWWtwYKCiDA== From: Sebastian Andrzej Siewior To: syzbot Cc: brauner@kernel.org, jack@suse.cz, linkinjeon@kernel.org, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, sj1557.seo@samsung.com, syzkaller-bugs@googlegroups.com, tglx@linutronix.de, viro@zeniv.linux.org.uk Subject: Re: [syzbot] [exfat?] [ext4?] WARNING in __rt_mutex_slowlock_locked Message-ID: <20250822162041.gXcLgwIW@linutronix.de> References: <68a72860.050a0220.3d78fd.002a.GAE@google.com> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: <68a72860.050a0220.3d78fd.002a.GAE@google.com> On 2025-08-21 07:08:32 [-0700], syzbot wrote: > dashboard link: https://syzkaller.appspot.com/bug?extid=3Da725ab460fc1def= 9896f =E2=80=A6 > The issue was bisected to: >=20 > commit d2d6422f8bd17c6bb205133e290625a564194496 > Author: Sebastian Andrzej Siewior > Date: Fri Sep 6 10:59:04 2024 +0000 >=20 > x86: Allow to enable PREEMPT_RT. >=20 =E2=80=A6 > exFAT-fs (loop0): Medium has reported failures. Some data may be lost. > exFAT-fs (loop0): failed to load upcase table (idx : 0x00010000, chksum := 0xe5674ec2, utbl_chksum : 0xe619d30d) > ------------[ cut here ]------------ > rtmutex deadlock detected > WARNING: CPU: 0 PID: 6000 at kernel/locking/rtmutex.c:1674 rt_mutex_handl= e_deadlock kernel/locking/rtmutex.c:1674 [inline] > WARNING: CPU: 0 PID: 6000 at kernel/locking/rtmutex.c:1674 __rt_mutex_slo= wlock kernel/locking/rtmutex.c:1734 [inline] > WARNING: CPU: 0 PID: 6000 at kernel/locking/rtmutex.c:1674 __rt_mutex_slo= wlock_locked+0xed2/0x25e0 kernel/locking/rtmutex.c:1760 RT detected a deadlock and complained. The same testcase on !RT results in: | [ 15.363878] loop0: detected capacity change from 0 to 256 | [ 15.367981] exFAT-fs (loop0): Volume was not properly unmounted. Some = data may be corrupt. Please run fsck. | [ 15.373808] exFAT-fs (loop0): Medium has reported failures. Some data = may be lost. | [ 15.380396] exFAT-fs (loop0): failed to load upcase table (idx : 0x000= 10000, chksum : 0xe5674ec2, utbl_chksum : 0xe619d30d) | [ 62.668182] INFO: task exfat-repro:2155 blocked for more than 30 secon= ds. | [ 62.669405] Not tainted 6.17.0-rc2+ #10 | [ 62.670181] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disable= s this message. | [ 62.671612] task:exfat-repro state:D stack:0 pid:2155 tgid:21= 55 ppid:1 task_flags:0x400140 flags:0x00004006 | [ 62.673557] Call Trace: | [ 62.674008] | [ 62.674400] __schedule+0x4ef/0xbb0 | [ 62.675069] schedule+0x22/0xd0 | [ 62.675656] schedule_preempt_disabled+0x10/0x20 | [ 62.676495] rwsem_down_write_slowpath+0x1e2/0x6c0 | [ 62.679028] down_write+0x66/0x70 | [ 62.679645] vfs_rename+0x5c6/0xc30 | [ 62.681734] do_renameat2+0x3c4/0x570 | [ 62.682395] __x64_sys_renameat2+0x7b/0xc0 | [ 62.683187] do_syscall_64+0x7f/0x290 | [ 62.695576] entry_SYSCALL_64_after_hwframe+0x76/0x7e After ctrl+c that testcase terminates but one thread remains in D state. This is from=20 | lock_new_subdir =3D new_dir !=3D old_dir || !(flags & RENAME_EXCH= ANGE); | if (is_dir) { | if (lock_old_subdir) | inode_lock_nested(source, I_MUTEX_CHILD); ^^^ | 5 locks held by exfat-repro/2156: | #0: ffff888113b69400 (sb_writers#11){.+.+}-{0:0}, at: do_renameat2+0x1c8= /0x580 | #1: ffff888113b69710 (&type->s_vfs_rename_key){+.+.}-{4:4}, at: do_renam= eat2+0x24d/0x580 | #2: ffff88810fb79b88 (&sb->s_type->i_mutex_key#16/1){+.+.}-{4:4}, at: lo= ck_two_directories+0x6c/0x110 | #3: ffff88810fb7a1c0 (&sb->s_type->i_mutex_key#17/5){+.+.}-{4:4}, at: lo= ck_two_directories+0x82/0x110 | #4: ffffffff82f618a0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_loc= ks+0x3d/0x184 #2 and #3 are from the "(r =3D=3D p1)" case. The lock it appears to acquire is #2. Could an exfat take a look, please? Sebastian