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 9B1F6C433F5 for ; Fri, 11 Feb 2022 21:05:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353650AbiBKVFM (ORCPT ); Fri, 11 Feb 2022 16:05:12 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:58178 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229596AbiBKVFL (ORCPT ); Fri, 11 Feb 2022 16:05:11 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 26B742D2 for ; Fri, 11 Feb 2022 13:05:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=djDzuW0cps2g7Kw8gzqN7GELDrjwVHlIZPy10UxJRYI=; b=i5yDxCAwbRqf/kSNqOJ4w3Mb4m zb4rrO/PBj9ceJFio1tJmUpAbdI3K2pKriEmbNS0J6aTZ6l8yJUfnwUo3bMchFF4j1TxHQzWgexDm +zi2taLh7aKe6OKERTeuNkNGOnDR41OOtuFo9zo3adt1ZX4X5ibbv9vyvbnau6B/afpbg5wolvSvq 3tI1eFyH5nXIwqmrP85XGG80Jw+YGffPrWrt7U4z61Q42w+HtJiUixk70usmWS9TfyX+k+8Fe4gUu LCV3N3T/a1hIg4smJQLMyf4fwVGGP9+rvRi56XAH41l0sU3K4e5W0fS+2DLNpdhNf0gWEL87uJlrz hhVmaLSg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1nId67-00Ajgv-53; Fri, 11 Feb 2022 21:04:55 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id E9C1530022C; Fri, 11 Feb 2022 22:04:48 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id A3E11264E6612; Fri, 11 Feb 2022 22:04:48 +0100 (CET) Date: Fri, 11 Feb 2022 22:04:48 +0100 From: Peter Zijlstra To: Steven Rostedt Cc: John Ogness , Petr Mladek , Sergey Senozhatsky , Thomas Gleixner , linux-kernel@vger.kernel.org, Andrew Morton , Marco Elver , Stephen Boyd , Alexander Potapenko , Randy Dunlap , Nicholas Piggin Subject: Re: [PATCH printk v1 01/13] printk: rename cpulock functions Message-ID: References: <20220207194323.273637-1-john.ogness@linutronix.de> <20220207194323.273637-2-john.ogness@linutronix.de> <87fsopcvnj.fsf@jogness.linutronix.de> <20220211155727.49ab86f5@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220211155727.49ab86f5@gandalf.local.home> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 11, 2022 at 03:57:27PM -0500, Steven Rostedt wrote: > On Fri, 11 Feb 2022 15:48:08 +0106 > John Ogness wrote: > > > It is because (as in the example above), taking this "lock" does not > > provide synchronization to data. It is only synchronizing between > > CPUs. It was Steven's suggestion to call the thing a cpu_sync object and > > nobody in the RT Track seemed to disagree. > > I love causing trouble ;-) > > Actually, it wasn't just my suggestion. IIRC, I believe Peter Zijlstra was > against calling it a lock (Peter, you can use lore to see the context here). All I remember is that it was in a room and I was late, I can't even remember what City we were all in at the time. Was this Lisbon? Anyway, as Steve said, it isn't really a strict exclusion thing, it only avoids the most egregious inter-cpu interleaving. I'm down with goldi-locks, something has to have that name :-)