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 F0AC2C4332B for ; Fri, 20 Mar 2020 06:56:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C196120724 for ; Fri, 20 Mar 2020 06:56:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="M8wPPWkw" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726820AbgCTG4C (ORCPT ); Fri, 20 Mar 2020 02:56:02 -0400 Received: from mail-qk1-f195.google.com ([209.85.222.195]:38952 "EHLO mail-qk1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726602AbgCTG4C (ORCPT ); Fri, 20 Mar 2020 02:56:02 -0400 Received: by mail-qk1-f195.google.com with SMTP id t17so5843219qkm.6 for ; Thu, 19 Mar 2020 23:56:01 -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:mime-version :content-transfer-encoding; bh=H7qI0J6UdPPMxMo89bJspgFfE6kReY5LFKqgcFnVjEE=; b=M8wPPWkw74OJ30O2RObg0NV3Uqad/cBAquf9jWLlhnwkQWlKMsX15vW5/llQc7ZVma kPOuv5pWfIfh9QqyZlJXrNJB4Ux8KA/twWx2iH39XKFkgXxG/T5IhWKyDHPbqnw2gSVe p1+JNPzVnbVxNJz2extJx7+1rarPEomTnUDRs= 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:mime-version :content-transfer-encoding; bh=H7qI0J6UdPPMxMo89bJspgFfE6kReY5LFKqgcFnVjEE=; b=km14IFrqBA86KWesjFjuJbPR1Ctyv2wvXZOmt1marn8bOu6VJSP0oYnzPA/U5EHYHu eBMeqoqUNmKvKzexL51PeFmuUEotiQ11/aU6mJUsfTwxgWshwmAED7a3FlfHBtr4Nq1E 6+LmpIcO9h8Bl0v4sqBrznmbePS8fKYqgvq96goFZ/FZcUcqjANThHP6ciWEzJeH5WYp bNPtteBeaLy8zB6l+y0kmRI0c8wfztkfJ5PuHSQSlZXVW5+G9iZ/KpQuKYipFtZiCq3Y aGQ4HNyxCkimF7INiGp23EwDNxQNgLt4FJLMJT9CjmoS1kYOT6u8q8p3Exv5O2zlGsE5 6F7Q== X-Gm-Message-State: ANhLgQ0oBBbwyNeo6HiuRECI3Nop9ZWZYvB+heR68zwgjRV3ZMOxihSl uFp5tdtT4LknF9eQuklao4yaGJZnZE0= X-Google-Smtp-Source: ADFU+vvbBbRAvpvItKU3CDLenRkmMnn64zsTki3i6k9ySmu292eqsPkuvXJtQLwlXVDMfaaK0W5jlQ== X-Received: by 2002:a37:6556:: with SMTP id z83mr6558870qkb.381.1584687360401; Thu, 19 Mar 2020 23:56:00 -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.26.2020.03.19.23.55.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Mar 2020 23:55:59 -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 1/3] LKMM: Add litmus test for RCU GP guarantee where updater frees object Date: Fri, 20 Mar 2020 02:55:50 -0400 Message-Id: <20200320065552.253696-1-joel@joelfernandes.org> X-Mailer: git-send-email 2.25.1.696.g5e7596f4ac-goog 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+free.litmus | 40 +++++++++++++++++++ 1 file changed, 40 insertions(+) create mode 100644 tools/memory-model/litmus-tests/RCU+sync+free.litmus diff --git a/tools/memory-model/litmus-tests/RCU+sync+free.litmus b/tools/memory-model/litmus-tests/RCU+sync+free.litmus new file mode 100644 index 0000000000000..c4682502dd296 --- /dev/null +++ b/tools/memory-model/litmus-tests/RCU+sync+free.litmus @@ -0,0 +1,40 @@ +C RCU+sync+free + +(* + * Result: Never + * + * This litmus test demonstrates that an RCU reader can never see a write after + * the grace period, if it saw writes that happen before the grace period. This + * is a typical pattern of RCU usage, where the write before the grace period + * assigns a pointer, and the writes after destroy the object that the pointer + * points to. + * + * This guarantee also implies, an RCU reader can never span a grace period and + * is an important RCU grace period memory ordering guarantee. + *) + +{ +x = 1; +y = x; +z = 1; +} + +P0(int *x, int *z, int **y) +{ + int r0; + int r1; + + rcu_read_lock(); + r0 = rcu_dereference(*y); + r1 = READ_ONCE(*r0); + rcu_read_unlock(); +} + +P1(int *x, int *z, int **y) +{ + rcu_assign_pointer(*y, z); + synchronize_rcu(); + WRITE_ONCE(*x, 0); +} + +exists (0:r0=x /\ 0:r1=0) -- 2.25.1.696.g5e7596f4ac-goog