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=-9.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham 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 E1797C4332D for ; Fri, 20 Mar 2020 06:56:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B002720724 for ; Fri, 20 Mar 2020 06:56:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="OGS30BXK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726892AbgCTG4E (ORCPT ); Fri, 20 Mar 2020 02:56:04 -0400 Received: from mail-qv1-f68.google.com ([209.85.219.68]:44758 "EHLO mail-qv1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726232AbgCTG4D (ORCPT ); Fri, 20 Mar 2020 02:56:03 -0400 Received: by mail-qv1-f68.google.com with SMTP id w5so2418840qvp.11 for ; Thu, 19 Mar 2020 23:56:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=lZktbxS0i0oIpqeQrOD+jHQIgM5+6wOIwrhIyNa/H6M=; b=OGS30BXKvOOsiK6bD9IHOQ/GNBieNsiIIavZuTQRPmaN+dLmHB72W7AG9FSAKiF68g QRPpdBrWYryk/9Q4y39ZNGQ9DEhRzN2NNMESkxWC+20ZItrbfMAM4eIWJclNOKm1WtD8 MbAR5IBjM8/daadm5FSS1NRGtu7/JG+3gQ9w0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=lZktbxS0i0oIpqeQrOD+jHQIgM5+6wOIwrhIyNa/H6M=; b=KXxLEF13tOFmlx6X2vUXSjs/TydlOXQtm44L5fm7m7fl/nXM3SLIKGrcn6n4+pEEzy oC5M98BIfbv22A83+FMkSUA2LVcDBAW5i5kBVV0xoBcjJWdyqp0eckWBJf/1bhS6etmE UuZeFZRNsuTZ2MZLWbW/r23Jzq4xMHPEM675+jmoKVOUs8DXXFvBJCz5Ve3DZJWBsZ26 Yl3emjyssbriP4BxphWR5yDXPYfjFEv+wzXdJk+uSHrpAU6JHSt5dstQAkF8NV/qV6KY vaAQMUWNWoAMVhWxrW1k9ZUdCHr5nflPvqDYJcmfd+ras1SZG/rDra1h/h5dPGUheSkL L17w== X-Gm-Message-State: ANhLgQ0IK4kih66G/qPzsnIUGnbgFzPCeOiaYL0h4dNPne8x00zGDxhK csZcMCWc98S+BEwpHmUVkLlNzgqBX8A= X-Google-Smtp-Source: ADFU+vsBfhVA6txgEV2FXFv04i7OnbCf4MVeIQfB2DE8puxWcSZZqD9MC2EXp6EPoVIRkmczAddJfg== X-Received: by 2002:a0c:eeca:: with SMTP id h10mr6656674qvs.206.1584687361491; Thu, 19 Mar 2020 23:56:01 -0700 (PDT) Received: from joelaf.cam.corp.google.com ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id m15sm419985qkk.26.2020.03.19.23.56.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Mar 2020 23:56:01 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , Akira Yokosawa , Alan Stern , Andrea Parri , Boqun Feng , Daniel Lustig , David Howells , Jade Alglave , linux-arch@vger.kernel.org, Luc Maranget , Nicholas Piggin , "Paul E. McKenney" , Peter Zijlstra , Will Deacon Subject: [PATCH 2/3] LKMM: Add litmus test for RCU GP guarantee where reader stores Date: Fri, 20 Mar 2020 02:55:51 -0400 Message-Id: <20200320065552.253696-2-joel@joelfernandes.org> X-Mailer: git-send-email 2.25.1.696.g5e7596f4ac-goog In-Reply-To: <20200320065552.253696-1-joel@joelfernandes.org> References: <20200320065552.253696-1-joel@joelfernandes.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This adds an example for the important RCU grace period guarantee, which shows an RCU reader can never span a grace period. Signed-off-by: Joel Fernandes (Google) --- .../litmus-tests/RCU+sync+read.litmus | 37 +++++++++++++++++++ 1 file changed, 37 insertions(+) create mode 100644 tools/memory-model/litmus-tests/RCU+sync+read.litmus diff --git a/tools/memory-model/litmus-tests/RCU+sync+read.litmus b/tools/memory-model/litmus-tests/RCU+sync+read.litmus new file mode 100644 index 0000000000000..73557772e2a32 --- /dev/null +++ b/tools/memory-model/litmus-tests/RCU+sync+read.litmus @@ -0,0 +1,37 @@ +C RCU+sync+read + +(* + * Result: Never + * + * This litmus test demonstrates that after a grace period, an RCU updater always + * sees all stores done in prior RCU read-side critical sections. Such + * read-side critical sections would have ended before the grace period ended. + * + * This guarantee also implies, an RCU reader can never span a grace period and + * is an important RCU grace period memory ordering guarantee. + *) + +{ +x = 0; +y = 0; +} + +P0(int *x, int *y) +{ + rcu_read_lock(); + WRITE_ONCE(*x, 1); + WRITE_ONCE(*y, 1); + rcu_read_unlock(); +} + +P1(int *x, int *y) +{ + int r0; + int r1; + + r0 = READ_ONCE(*x); + synchronize_rcu(); + r1 = READ_ONCE(*y); +} + +exists (1:r0=1 /\ 1:r1=0) -- 2.25.1.696.g5e7596f4ac-goog