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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 0A0DDC4360F for ; Thu, 4 Apr 2019 05:03:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CCFC8206C0 for ; Thu, 4 Apr 2019 05:03:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="GPduABOZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726656AbfDDFDX (ORCPT ); Thu, 4 Apr 2019 01:03:23 -0400 Received: from mail-qt1-f194.google.com ([209.85.160.194]:34766 "EHLO mail-qt1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726511AbfDDFDX (ORCPT ); Thu, 4 Apr 2019 01:03:23 -0400 Received: by mail-qt1-f194.google.com with SMTP id k2so1835521qtm.1 for ; Wed, 03 Apr 2019 22:03:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=1tBEXosrcvpGtRUaF1KwHY9bzibXQf+KNKFtwMzZlr0=; b=GPduABOZqaHKGD3PKF1ewSBgPwjUG75OUiCi4YyR6w6JdzOqEb0bW/n1H9k7yDAska RDugi4My1V5eBUk5KhBEPDP3v4mk8Da0LmrLcXGPJUsciGLxOUyEqR3T62Fv0Jn5NNeI DQYU7xMdKBd6aIxwHRVMMkNkDLUR0ncEkOHo0hxy3xluWYXixpeb3PL+t/ZAaMboyE42 6sQMOhvHr1A4SR30Cs1sJdRUDbXBiOD2VPxAD4i/InoLFcgCH+VsiT+qJPelgwoj2eh/ JLDeOUDygbrjM1mzNuR/Z5KKlp9Pk0GyDoTgxOoqSWrOVZDJqg69rVtnG3zz3aukq+zc fJnw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=1tBEXosrcvpGtRUaF1KwHY9bzibXQf+KNKFtwMzZlr0=; b=G3uqBFuZackt7P8Ud0l81JJmhjTI+Z5L2tCD095tm15JYKbrNPGW+b6CZCuVDLZSb1 dY2qMT0yen9O+7w9vgFuaoNIzhxV+i2bcmPFAW5aS3g1HfPacVSfvYPFPfAwHY8CkRC/ Kt31kW2GqWhDrlFXnnpVRZE20RA4MrrI/klE4kw7f3htPu3CMIHOpy3tgiMSs3awYJw7 kaE9u2wGi/7/QKALRFXZKnusyrMlvyXJXuHCxLpwOqdREgloFBKmDd73MAswb75gM9xS 1L3CenvIaL1ffmNA86TUqXPbqU/FKgiCko8owTzk/R3X8HKF0Q6wyf57N7DoQPbGSxS3 2+uw== X-Gm-Message-State: APjAAAUB/4SqXVwGsMx9eRSq/KfVTfPapizlNAnUl1Y3NCE4CmfNJqn/ apmHqe6DDDR5ehtFu1TThnbWrl5ssdQEsgfrIH8= X-Google-Smtp-Source: APXvYqxDkjxy/YALYUqnJjSW3g6ZqvNbDu76PKp77sNtbAm90OXwyQtsHGF5pFDcEUwh0YDWATH/CzvMyLoIkHXCIPA= X-Received: by 2002:a0c:ba99:: with SMTP id x25mr3014018qvf.212.1554354202149; Wed, 03 Apr 2019 22:03:22 -0700 (PDT) MIME-Version: 1.0 References: <20190321075725.14054-1-duyuyang@gmail.com> <20190321075725.14054-19-duyuyang@gmail.com> In-Reply-To: <20190321075725.14054-19-duyuyang@gmail.com> From: Yuyang Du Date: Thu, 4 Apr 2019 13:03:10 +0800 Message-ID: Subject: Question on a lockdep test case about mixed read-write ABBA To: peterz@infradead.org, will.deacon@arm.com, mingo@kernel.org Cc: Bart Van Assche , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Peter, I observed this test case you wrote in Commit: e9149858974606 ("locking/lockdep/selftests: Add mixed read-write ABBA"). static void rwsem_ABBA2(void) { RSL(X1); ML(Y1); MU(Y1); RSU(X1); ML(Y1); RSL(X1); RSU(X1); MU(Y1); // should fail } Why should it fail? This is not a deadlock, right? The depencencies would be built by lockdep though; that results in a false positive. Thanks, Yuyang