From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 A54C231C58A for ; Wed, 29 Oct 2025 08:26:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761726366; cv=none; b=WGt/XjCIxmrK4yUTKQrTsw1XEH83HbjCVMgDeOqyKm+O1wUG6qmjZkjcc5EXh/Gf/tKnI1WYLsVMawWy1+lj5np3zMA6OVjtjTF4xTn+15S5jzpnbT6WI4oRsQy1xg9dOwmKioBcWci/LzcQvY+NxcyE1xGgtO8TG36QdDzIDuA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761726366; c=relaxed/simple; bh=xgqj5pCdNpa3XGWQgvu4tLTxUw7yCDJ8VB0Ba9N5jEU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=WlV3IJNR3PmrnEksDX1Es255ClVCrA+biH/BD/7AdDNg/jhKXGChldtoRkqGLb/YX2N4+i9lgKWf1t8Y6g4N0EaK3YTDn/0JPLVchDy0mSeas9w3uTH9EMKmBonSt3CfWSI8j6LU1+jmDF4ujfyVzA84xR/DXzUAbEnXTsIlZiM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=CSZ7/u08; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="CSZ7/u08" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1761726363; 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: in-reply-to:in-reply-to:references:references; bh=FLgqPzpwGlfIs1RiLXNE1Fv1B7Pn8WCEkos9O7vhm/s=; b=CSZ7/u08qQzT61nWf25ARHD3/yU0sgSojfPYStyDB8ZuNXe7i8wN5kQJVfavbrSqo8OZqV nBo9YwrtASgqYWujj91TskdysHEqIqWmACoYKF0PXtdMP22UOyKrWmcNmegD4ee4tgk2RO Chb1RyxlC4R3nuFti0TXOEOER6+4vZY= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-326-un4H5XgKPju8loE7Q5Sm_Q-1; Wed, 29 Oct 2025 04:25:57 -0400 X-MC-Unique: un4H5XgKPju8loE7Q5Sm_Q-1 X-Mimecast-MFC-AGG-ID: un4H5XgKPju8loE7Q5Sm_Q_1761726351 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 97F051808997; Wed, 29 Oct 2025 08:25:50 +0000 (UTC) Received: from fedora (unknown [10.72.120.12]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 57CB81800586; Wed, 29 Oct 2025 08:25:41 +0000 (UTC) Date: Wed, 29 Oct 2025 16:25:36 +0800 From: Ming Lei To: Nilay Shroff Cc: Bart Van Assche , David Wei , linux-block@vger.kernel.org, cgroups@vger.kernel.org, hch@lst.de, hare@suse.de, dlemoal@kernel.org, axboe@kernel.dk, tj@kernel.org, josef@toxicpanda.com, gjoyce@ibm.com, lkp@intel.com, oliver.sang@intel.com Subject: Re: [REPORT] Possible circular locking dependency on 6.18-rc2 in blkg_conf_open_bdev_frozen+0x80/0xa0 Message-ID: References: <63c97224-0e9a-4dd8-8706-38c10a1506e9@davidwei.uk> <5b403c7c-67f5-4f42-a463-96aa4a7e6af8@linux.ibm.com> <5c29fa84-3a2c-44be-9842-f0230e7b46dd@acm.org> <544b60be-376c-4891-95a4-361b4a207b8a@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <544b60be-376c-4891-95a4-361b4a207b8a@linux.ibm.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 On Tue, Oct 28, 2025 at 06:36:20PM +0530, Nilay Shroff wrote: > > > On 10/28/25 2:00 AM, Bart Van Assche wrote: > > On 10/23/25 9:54 PM, Nilay Shroff wrote: > >> IMO, we need to make lockdep learn about this differences by assigning separate > >> lockdep key/class for each queue's q->debugfs_mutex to avoid this false positive. > >> As this is another report with the same false-positive lockdep splat, I think we > >> should address this. > >> > >> Any other thoughts or suggestions from others on the list? > > > > Please take a look at lockdep_register_key() and > > lockdep_unregister_key(). I introduced these functions six years ago to > > suppress false positive lockdep complaints like this one. > > > Thanks Bart! I'll send out patch with the above proposed fix. IMO, that may not be a smart approach, here the following dependency should be cut: #4 (&q->q_usage_counter(io)#2){++++}-{0:0}: ... #1 (&q->debugfs_mutex){+.+.}-{4:4}: #0 (&q->rq_qos_mutex){+.+.}-{4:4}: Why is there the dependency between `#1 (&q->debugfs_mutex)` and `#0 (&q->rq_qos_mutex)`? I remember that Yu Kuai is working on remove it: https://lore.kernel.org/linux-block/20251014022149.947800-1-yukuai3@huawei.com/ Thanks, Ming