From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp153-171.sina.com.cn (smtp153-171.sina.com.cn [61.135.153.171]) (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 3EEA61C861A for ; Tue, 8 Jul 2025 01:25:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=61.135.153.171 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751937919; cv=none; b=KczPJKzygopzqEUgROvbUEVN/x/c3sIDLLK2oIrhNi+FYF8UsWF2DnSxgTgdgPcyRghUM2hiCTB414D5O/BpFaAlfq+HA+xLefk7i6im1ISC9PRhqr57rhzyMnf5hVUL8J4LBp6cSxFu8Xc/IRDvoXwcGp+QN7iSbkrqYj1Borc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751937919; c=relaxed/simple; bh=Aoxy5zHDYhuOjLXy/uAfYcRZossxBVN9vBXDcu4IAgo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZPza4qteVWI/Rok5acDuQInJqc4Olb7w+8dr5P6+2qg0dXiggjg3RxXNWojNE/4qM5+8I5hm2CyVTVeWnWepCVj126DQlr2nsrkbGuyHdQSeziZT94yfII4c3Tfkun9hw9sEQlZCSNiqXiDY642t07tak71MZvNN9kbbkqbyias= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=sina.com; spf=pass smtp.mailfrom=sina.com; dkim=pass (1024-bit key) header.d=sina.com header.i=@sina.com header.b=FZCX1bX8; arc=none smtp.client-ip=61.135.153.171 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=sina.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sina.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=sina.com header.i=@sina.com header.b="FZCX1bX8" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sina.com; s=201208; t=1751937911; bh=cwQOjk547Zv2ATJFdaw5csYgtoidNunSGL/zW6G3ct0=; h=From:Subject:Date:Message-ID; b=FZCX1bX87MDFT3FCbXcpj3Izs0N3gdK2TYTFct2oc1TKjfLNy1THHQBl+AVIaa3os FVRSdurcp4RuXdMEzpork3Z7uuN5Nxw17Y8ZcB11zF2s2egqCXP748cz/4MuSp4qV2 KyBoD8hdlR48YP1LWB9fM0BKT3lWyu1t3Ycbp4/g= X-SMAIL-HELO: localhost.localdomain Received: from unknown (HELO localhost.localdomain)([114.249.58.236]) by sina.com (10.54.253.34) with ESMTP id 686C736C00007618; Tue, 8 Jul 2025 09:25:02 +0800 (CST) X-Sender: hdanton@sina.com X-Auth-ID: hdanton@sina.com Authentication-Results: sina.com; spf=none smtp.mailfrom=hdanton@sina.com; dkim=none header.i=none; dmarc=none action=none header.from=hdanton@sina.com X-SMAIL-MID: 2721056291940 X-SMAIL-UIID: 95D3E90001004F7D881C813250BA6C25-20250708-092502-1 From: Hillf Danton To: Tetsuo Handa Cc: Bart Van Assche , axboe@kernel.dk, josef@toxicpanda.com, linux-block@vger.kernel.org, syzbot , Ming Lei , linux-kernel@vger.kernel.org, nbd@other.debian.org, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [nbd?] possible deadlock in nbd_queue_rq Date: Tue, 8 Jul 2025 09:24:49 +0800 Message-ID: <20250708012450.2858-1-hdanton@sina.com> In-Reply-To: References: <20250707005946.2669-1-hdanton@sina.com> <20250708001848.2775-1-hdanton@sina.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Tue, 8 Jul 2025 09:52:18 +0900 Tetsuo Handa wrote: > On 2025/07/08 9:18, Hillf Danton wrote: > > On Mon, 7 Jul 2025 10:39:44 -0700 Bart Van Assche wrote: > >> On 7/6/25 5:59 PM, Hillf Danton wrote: > >>> and given the second one, the report is false positive. > >> > >> Whether or not this report is a false positive, the root cause should be > >> fixed because lockdep disables itself after the first circular locking > >> complaint. From print_usage_bug() in kernel/locking/lockdep.c: > >> > >> if (!debug_locks_off() || debug_locks_silent) > >> return; > >> > > The root cause could be walked around for example by trying not to init > > nbd more than once. > > How did you come to think so? > Based on that nbd_init appears twice in the lock chain syzbot reported. > nbd_init() is already called only once because of module_init(nbd_init). > Ok Bart is misguiding.