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 E72B1C54EBD for ; Mon, 9 Jan 2023 20:49:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234895AbjAIUtM (ORCPT ); Mon, 9 Jan 2023 15:49:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57992 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231258AbjAIUs6 (ORCPT ); Mon, 9 Jan 2023 15:48:58 -0500 Received: from mail-pj1-x102d.google.com (mail-pj1-x102d.google.com [IPv6:2607:f8b0:4864:20::102d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F1D5E1A3AD; Mon, 9 Jan 2023 12:48:57 -0800 (PST) Received: by mail-pj1-x102d.google.com with SMTP id o7-20020a17090a0a0700b00226c9b82c3aso11069976pjo.3; Mon, 09 Jan 2023 12:48:57 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:from:to:cc:subject:date:message-id :reply-to; bh=ozgtWXStaifDCNgxslV51L9a9hMuGEd0/nehBJs5fnk=; b=T8qovgWlSZC8V8Nu5uttH59MXaChBsCI/gnRaGKVGLwOPQP6JFSyxkip3cXJyVVf4C D1lTIpYnSayynxqxocTY1T9GjZ27L5IL4oJMha83QTPliGYrb2NIimWL6HTbDgeUukF/ sw/ucV9zAwNXGqArc4hctwBhSUSyZrb4DqBbm8HFR9xoVIQQrlNeNe+0R/rQ2eiV+b39 uLqnlqmESQe7kw1/Q/CxwryGKiaibMv18//JGsUPhnCBmehCTomfIZzKXC7hWb82tDwz YygbLAukH01JVtMnE5vf1+hVqAXXYtj/7AOMvBRR4dQczyc1rQJMtMaqy1qDIpwXwjMc 9nng== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=ozgtWXStaifDCNgxslV51L9a9hMuGEd0/nehBJs5fnk=; b=zTdNcrGvo/50YGE/05ws8RQVjrXDRuXOdLdNrNcZfGV9UUUtfUbbP+VWI6ZoQzm9T4 GVbTckOBz9ooIfPqLhlBS/rPaAzbSrldQGL/6ldZ0fvMebMac5DcY9VYWZ+5AgGEN8st Ve6N4SS4S1NOG9dJxMmpczhK/BF3KC5q2hdmNiHmKpmBgeqF1ZDpo0vtNKcd1sf7Y5oc v+1meQWj8wPmEdHmYdeyDR3Nbxo/NXYtY1ppz/o0FZF2VqSR4HhiXxK/gU0Vyi0dRwHZ B2DtkJe79rCMgr4UA/tl3R2PUwNQBo94pv74DeBKEhfLWOVEMViHL46gnmzbxQ0t/Pl6 h3SA== X-Gm-Message-State: AFqh2ko4Ox7d6l6fDZy64GKlrF6LfDmG/np6sf4SHBXYRNDQ7qp1dd/E 2N1MrTMsk36DC+eKek5d0lM= X-Google-Smtp-Source: AMrXdXudu3zGX1Bk6RQEqbaxea7o8PBKNte85xa8wTy0U7BSYdzI3mqcMO0/sha5+LEP8Yr+76tpJA== X-Received: by 2002:a17:902:7583:b0:189:4bf4:2cfc with SMTP id j3-20020a170902758300b001894bf42cfcmr66193787pll.31.1673297337405; Mon, 09 Jan 2023 12:48:57 -0800 (PST) Received: from localhost (2603-800c-1a02-1bae-a7fa-157f-969a-4cde.res6.spectrum.com. [2603:800c:1a02:1bae:a7fa:157f:969a:4cde]) by smtp.gmail.com with ESMTPSA id a16-20020a170902ecd000b001868ed86a95sm6526556plh.174.2023.01.09.12.48.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Jan 2023 12:48:57 -0800 (PST) Sender: Tejun Heo Date: Mon, 9 Jan 2023 10:48:55 -1000 From: Tejun Heo To: Christoph Hellwig Cc: axboe@kernel.dk, josef@toxicpanda.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/4] blkcg: Drop unnecessary RCU read [un]locks from blkg_conf_prep/finish() Message-ID: References: <20230105212432.289569-1-tj@kernel.org> <20230105212432.289569-2-tj@kernel.org> <20230108170240.GA19165@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230108170240.GA19165@lst.de> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Christoph. On Sun, Jan 08, 2023 at 06:02:40PM +0100, Christoph Hellwig wrote: > On Thu, Jan 05, 2023 at 11:24:29AM -1000, Tejun Heo wrote: > > Holding the queue lock now implies RCU read lock, so no need to use > > rcu_read_[un]lock() explicitly. This shouldn't cause any behavior changes. > > How so? Now that all RCU flavors have been combined, holding a spin lock, disabling irq, disabling preemption all imply RCU read lock. > > While at it, drop __acquires() annotation on the queue lock too. The > > __acquires() part was already out of sync and it doesn't catch anything that > > lockdep can't. > > This makes sparse even more unhappy than it was before. For now > please keep the annotation. I can drop the changes but this actually bothers me. The annotation has been broken for a *long* time and nobody noticed. Furthermore, I can't remember a time when __acquires/__releases notation caught anything that lockdep couldn't trivially and can't even think of a way how it could. AFAICS, these annotations don't contribute anything other than preservation of themselves. I don't see why we would want to keep them. Thanks. -- tejun