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 X-Spam-Level: X-Spam-Status: No, score=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 25C83C4321A for ; Fri, 28 Jun 2019 16:07:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E232C2064A for ; Fri, 28 Jun 2019 16:07:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="vNKzcnEp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726772AbfF1QHx (ORCPT ); Fri, 28 Jun 2019 12:07:53 -0400 Received: from merlin.infradead.org ([205.233.59.134]:44694 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726542AbfF1QHx (ORCPT ); Fri, 28 Jun 2019 12:07:53 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=wPqqFg7p91+r5i4m2+PhArhGPY41i3UB1iDCXb/Pbl4=; b=vNKzcnEpqdst05Grn4tHAHiQJ itngFKqKaInore25YcKuG7VEMm/Oh6NN6oLtKr6+aQtHodvQd/nnsBIYUiB6nPoe6JCbuXzuwNTLC wS/VA6/a4bDbKtUJ3scWkyTo2q3UW1cp/ih0pgXBLHjZtEzCttbmOJ6y+2xmoZtpdG06HTyXzvGuY aCaR7bPk6jwR8EIdA9EhDqgMwkKjTclQbXOYQ4yBgw+8AbdUvMaOR3KElt6hRhw6KZZaGm5ZfjNmA ALvtyIxaSiS6Q82TZzfrnuQ5k6O1YQEw7BwDo537wHP+W4uAbUb4iU5Vdrzmy2SKpf9F3QoqFj4se hVS9ke5JQ==; Received: from [31.161.200.126] (helo=worktop.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92 #3 (Red Hat Linux)) id 1hgtPb-0001gR-5n; Fri, 28 Jun 2019 16:07:43 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id 2BE3E9802C5; Fri, 28 Jun 2019 18:07:40 +0200 (CEST) Date: Fri, 28 Jun 2019 18:07:40 +0200 From: Peter Zijlstra To: John Ogness Cc: linux-kernel@vger.kernel.org, Petr Mladek , Sergey Senozhatsky , Steven Rostedt , Linus Torvalds , Greg Kroah-Hartman , Andrea Parri , Thomas Gleixner , Sergey Senozhatsky Subject: Re: [RFC PATCH v2 1/2] printk-rb: add a new printk ringbuffer implementation Message-ID: <20190628160740.GC8451@worktop.programming.kicks-ass.net> References: <20190607162349.18199-1-john.ogness@linutronix.de> <20190607162349.18199-2-john.ogness@linutronix.de> <20190618114747.GQ3436@hirez.programming.kicks-ass.net> <87k1df28x4.fsf@linutronix.de> <20190626224034.GK2490@worktop.programming.kicks-ass.net> <87mui2ujh2.fsf@linutronix.de> <20190628154435.GZ7905@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190628154435.GZ7905@worktop.programming.kicks-ass.net> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 28, 2019 at 05:44:35PM +0200, Peter Zijlstra wrote: > On Fri, Jun 28, 2019 at 11:50:33AM +0200, John Ogness wrote: > > cmpxchg_release() vs WRITE_ONCE() is not safe?! Can you point me to > > documentation about this? > > Documentation/atomic_t.txt has this, see the SEMANTICS section on > atomic-set. Also see: arch/parisc/lib/bitops.c for one such case.