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 D8A67C10F1E for ; Sun, 18 Dec 2022 19:13:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230460AbiLRTNX (ORCPT ); Sun, 18 Dec 2022 14:13:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44246 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230346AbiLRTNS (ORCPT ); Sun, 18 Dec 2022 14:13:18 -0500 Received: from mail-qt1-x829.google.com (mail-qt1-x829.google.com [IPv6:2607:f8b0:4864:20::829]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 28BC1B866 for ; Sun, 18 Dec 2022 11:13:18 -0800 (PST) Received: by mail-qt1-x829.google.com with SMTP id c7so6780110qtw.8 for ; Sun, 18 Dec 2022 11:13:18 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=6wBQIku0dQkyfB58N1D5s2KPLrixlbfwvdwL9dUxK98=; b=lroTRSYT+lpaoGdLTvSe0vNJT4ct3IB3eeOKCL3YQRvVP5j2VrdsOPUcLi8fN4+xcQ tqx9I1ei9F8C2t0E6UYlk4BJAjVqoiJuWOBCAE31g+550nlQkhBhVROKlRx+VoNaGB/1 bWNL2XgieQGjgcDJbwvxzTqS2q3XrhB/3WDXQ= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=6wBQIku0dQkyfB58N1D5s2KPLrixlbfwvdwL9dUxK98=; b=Lt2xvKripCmEaLdiVK03FmFO1/D5LYLeiNibTlzLjUyTtYU+tWX3T/uCIX7MpsPr23 Xg3IqZ2CljPjhTep89zLizpVuplKsfhMgyNKRirUl8xob1Yo8NIXm8C7NwDb38ez87uv pGWhX0//KE4Va/yu7ETS1+bt6rzAX9eqXSO49anBb0TE7t9tc8rd0UoYrmNRBybzjD+t /f98hmJqgQBs6lUGbnajid112lea8RBg3O2YI7xP1idAjv3FtgnnC6fOJj9zD+9FJc3D ZbY5VVPQgimmnc6sRVfRpV2B3qalN5GT5BNilVWPmxmSH35A6GlIPxEp89AFtP0hEcQ6 VklA== X-Gm-Message-State: ANoB5pkjuHVTtbuw258Mv2DFoP274sg9szlbOCr/Nn0wOWXmSoih/zZI fi51NuBLs+b1mAwswJaQBuc3HcsgIc/DuzCtBrY= X-Google-Smtp-Source: AA0mqf7J6UsYdtU3I+7qCCh94ebdBJCmtFyROhsopD/KPQRuOlbhn8h1ckK0lufGxdBXEQVLb6pAww== X-Received: by 2002:ac8:1019:0:b0:39c:da20:683 with SMTP id z25-20020ac81019000000b0039cda200683mr46753016qti.38.1671390796655; Sun, 18 Dec 2022 11:13:16 -0800 (PST) Received: from joelboxx.c.googlers.com.com (48.230.85.34.bc.googleusercontent.com. [34.85.230.48]) by smtp.gmail.com with ESMTPSA id cq8-20020a05622a424800b003a591194221sm4952864qtb.7.2022.12.18.11.13.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 18 Dec 2022 11:13:15 -0800 (PST) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , Josh Triplett , Lai Jiangshan , Mathieu Desnoyers , "Paul E. McKenney" , rcu@vger.kernel.org, Steven Rostedt Subject: [RFC 0/2] srcu: Remove pre-flip memory barrier Date: Sun, 18 Dec 2022 19:13:07 +0000 Message-Id: <20221218191310.130904-1-joel@joelfernandes.org> X-Mailer: git-send-email 2.39.0.314.g84b9a713c41-goog MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, I believe the pre-flip memory barrier is not required. The only reason I can say to remove it, other than the possibility that it is unnecessary, is to not have extra code that does not help. However, since we are issuing a fully memory-barrier after the flip, I cannot say that it hurts to do it anyway. For this reason, please consider these patches as "informational", than a "please merge". :-) Though, feel free to consider merging if you agree! All SRCU scenarios pass with these, with 6 hours of testing. thanks, - Joel Joel Fernandes (Google) (2): srcu: Remove comment about prior read lock counts srcu: Remove memory barrier "E" as it is not required kernel/rcu/srcutree.c | 10 ---------- 1 file changed, 10 deletions(-) -- 2.39.0.314.g84b9a713c41-goog