From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5ED3BC77B7C for ; Wed, 10 May 2023 20:38:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236557AbjEJUi1 (ORCPT ); Wed, 10 May 2023 16:38:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60252 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236451AbjEJUiZ (ORCPT ); Wed, 10 May 2023 16:38:25 -0400 Received: from out-20.mta0.migadu.com (out-20.mta0.migadu.com [91.218.175.20]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 362CE6184 for ; Wed, 10 May 2023 13:38:20 -0700 (PDT) Date: Wed, 10 May 2023 16:38:15 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1683751099; 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=2Fntx7MeicDCqrqkDflloXBJRcdF7P6Ni3sDbF9MNgY=; b=sgO/UEIER2ve69V7tr81qDruo0+4xB0qMuqeM/8cdeT0yaaX6I/u4iRttuOzcQCIkedk7A R06RISg+MM0T5Pweyj+u2fbyUVH8fL50g+G1V7Ab/ISM3Pqn248qKrUvNY6tC1cpnhkhwp hgvyOqVblL24TSKV1xAEptkKxoz3d6s= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Kent Overstreet To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-bcachefs@vger.kernel.org, Ingo Molnar , Will Deacon , Waiman Long , Boqun Feng Subject: Re: [PATCH 03/32] locking/lockdep: lockdep_set_no_check_recursion() Message-ID: References: <20230509165657.1735798-1-kent.overstreet@linux.dev> <20230509165657.1735798-4-kent.overstreet@linux.dev> <20230509193147.GC2148518@hirez.programming.kicks-ass.net> <20230510085905.GJ4253@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230510085905.GJ4253@hirez.programming.kicks-ass.net> X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 10, 2023 at 10:59:05AM +0200, Peter Zijlstra wrote: > On Tue, May 09, 2023 at 04:18:59PM -0400, Kent Overstreet wrote: > > On Tue, May 09, 2023 at 09:31:47PM +0200, Peter Zijlstra wrote: > > > On Tue, May 09, 2023 at 12:56:28PM -0400, Kent Overstreet wrote: > > > > This adds a method to tell lockdep not to check lock ordering within a > > > > lock class - but to still check lock ordering w.r.t. other lock types. > > > > > > > > This is for bcachefs, where for btree node locks we have our own > > > > deadlock avoidance strategy w.r.t. other btree node locks (cycle > > > > detection), but we still want lockdep to check lock ordering w.r.t. > > > > other lock types. > > > > > > > > > > ISTR you had a much nicer version of this where you gave a custom order > > > function -- what happend to that? > > > > Actually, I spoke too soon; this patch and the other series with the > > comparison function solve different problems. > > > > For bcachefs btree node locks, we don't have a defined lock ordering at > > all - we do full runtime cycle detection, so we don't want lockdep > > checking for self deadlock because we're handling that but we _do_ want > > lockdep checking lock ordering of btree node locks w.r.t. other locks in > > the system. > > Have you read the ww_mutex code? If not, please do so, it does similar > things. > > The way it gets around the self-nesting check is by using the nest_lock > annotation, the acquire context itself also has a dep_map for this > purpose. This might work. I was confused for a good bit when reading tho code to figure out how it works - nest_lock seems to be a pretty bad name, it's really not a lock. acquire_ctx?