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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id CF8FAD149F0 for ; Fri, 25 Oct 2024 20:44:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type:MIME-Version: References:Message-ID:In-Reply-To:Subject:cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=ePBCrXDkYFx/2MDEBoHUpjfoxbGRLqNpKAELJMFiw1s=; b=ZT/efOV+CGeqfF+9vfGQIJ5NOg Q1M+VjhKvntmMoJ4Jz2IfB10dT/gN6HIj3Ual12QAFg9wukW5QL2FLKd/hBvJpabYFagS3S9w1RcZ NDU+lgaNwyatnVjLoMUKYyE4xeowdC/ltRnfHznx4+EYPdRbH2F5fQtIqX0Y7GDhbOacyM4uAivmv o4Dz5te7FrpV7tiNpjMi3bYJINV5/uqMYhtzblZaGqvvIMSxr4KC6KOFzUuME0awMuU7svCKqOOzW 8rRBSt/WRLUndXTLeoX+j7BrZKK11AmuWG8FjuXPedLHaSk+gIvSUBMTT8SpqsJdBH+ew8DwUtjv6 z16E87tQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1t4RAI-000000059fr-3Wmb; Fri, 25 Oct 2024 20:44:10 +0000 Received: from gentwo.org ([62.72.0.81]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1t4R7T-000000058L6-44BF for linux-arm-kernel@lists.infradead.org; Fri, 25 Oct 2024 20:41:17 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gentwo.org; s=default; t=1729884632; bh=ePBCrXDkYFx/2MDEBoHUpjfoxbGRLqNpKAELJMFiw1s=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=tKnIU9yLNT99wXsnGjwNZKVelKMhdVUWjq8L2OltJ89liNws7uTd5XHNZ/dh7Rdtg +Zr9Z+y8LnEli7a/gbrQJZYA2kf7gb6EO0kEY37+chasBXZ/XiOFFk3TAxP8V6lETj dTN0G6HxplP2egvSeFaopp1BBhME+m3fnTR0OwS4= Received: by gentwo.org (Postfix, from userid 1003) id 38560409C6; Fri, 25 Oct 2024 12:30:32 -0700 (PDT) Received: from localhost (localhost [127.0.0.1]) by gentwo.org (Postfix) with ESMTP id 3716240681; Fri, 25 Oct 2024 12:30:32 -0700 (PDT) Date: Fri, 25 Oct 2024 12:30:32 -0700 (PDT) From: "Christoph Lameter (Ampere)" To: Peter Zijlstra cc: Linus Torvalds , Will Deacon , Thomas Gleixner , Catalin Marinas , Ingo Molnar , Waiman Long , Boqun Feng , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org Subject: Re: [PATCH v3] Avoid memory barrier in read_seqcount() through load acquire In-Reply-To: <20241025074244.GB14555@noisy.programming.kicks-ass.net> Message-ID: <797cf697-83b2-7f45-4865-2ee394887dc8@gentwo.org> References: <20240912-seq_optimize-v3-1-8ee25e04dffa@gentwo.org> <20240917071246.GA27290@willie-the-truck> <4b546151-d5e1-22a3-a6d5-167a82c5724d@gentwo.org> <20241023194543.GD11151@noisy.programming.kicks-ass.net> <20241025074244.GB14555@noisy.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241025_134116_104402_EF11242B X-CRM114-Status: UNSURE ( 9.14 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, 25 Oct 2024, Peter Zijlstra wrote: > > atomic_inc_release(&seqcount) > > It would not be, making the increment itself atomic would make the whole > thing far more expensive. True. I was too much taken by a cool hw feature on ARM.