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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 4CBE0C433E2 for ; Fri, 28 Aug 2020 08:36:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 15E2E2086A for ; Fri, 28 Aug 2020 08:36:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="L64pBzxB"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="dHNcpQcS" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728614AbgH1Igq (ORCPT ); Fri, 28 Aug 2020 04:36:46 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:43856 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726643AbgH1Ign (ORCPT ); Fri, 28 Aug 2020 04:36:43 -0400 Date: Fri, 28 Aug 2020 10:37:02 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1598603801; 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=pOCz0+m6Q3dzLmGCe/U+1Ir1tkOUWh0lzPLpXP4rESU=; b=L64pBzxBF2X1LhBifpV/LOyayH7sFDp00Gu2jNEB7iQhEapqPAP6NN5ePDUSy/IcSu31k9 khRRwpvPowk1ObbACcrJUlutB7gMeC+IvQXPzWfj6TbnuBAEs51+IiusLM+5X3HsUz3Pz0 Ocb+8mJZxF6tgCey+lOfX1gP3LunL5a3Ny8+pE51UX81Lv5FtI/Vw63RjXLVPiFh0BXTVf yQKJTeub5n848JljZI2aiLusL2A0HmPrZjkzrIA5SWhbWnznJmaxD2emCppVoHSy5Z7Ew7 KP3kNLR77eO74UiwuClJUNWgzkqaIAhI6+6PP7f6dv0k2HsJJITLvwxLrRYPEg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1598603801; 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=pOCz0+m6Q3dzLmGCe/U+1Ir1tkOUWh0lzPLpXP4rESU=; b=dHNcpQcSx5+qWH8EuEM8+ttbRH3Srio3bSru4Zgk3bxanxxJKRKutAKN9sfv1rq8Wrzxl8 lRerVAUk/GRW5wBQ== From: "Ahmed S. Darwish" To: peterz@infradead.org Cc: Ingo Molnar , Will Deacon , Thomas Gleixner , "Sebastian A. Siewior" , "Paul E. McKenney" , Steven Rostedt , LKML Subject: Re: [PATCH v1 3/5] seqlock: seqcount_t: Implement all read APIs as statement expressions Message-ID: <20200828083702.GA7074@lx-t490> References: <20200519214547.352050-1-a.darwish@linutronix.de> <20200828010710.5407-1-a.darwish@linutronix.de> <20200828010710.5407-4-a.darwish@linutronix.de> <20200828083022.GO1362448@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200828083022.GO1362448@hirez.programming.kicks-ass.net> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 28, 2020 at 10:30:22AM +0200, peterz@infradead.org wrote: > On Fri, Aug 28, 2020 at 03:07:08AM +0200, Ahmed S. Darwish wrote: > > #define __read_seqcount_begin(s) \ > > +({ \ > > + unsigned seq; \ > > + \ > > + do { \ > > + seq = __seqcount_sequence(s); \ > > + if (likely(! (seq & 1))) \ > > + break; \ > > + cpu_relax(); \ > > + } while (true); \ > > + \ > > + kcsan_atomic_next(KCSAN_SEQLOCK_REGION_MAX); \ > > + seq; \ > > +}) > > Since we're there anyway, does it make sense to (re)write this like: > > while ((seq = __seqcount_sequence(s)) & 1) > cpu_relax(); > > ? > Yeah, much better of course; will do. Thanks, -- Ahmed S. Darwish Linutronix GmbH