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=-11.4 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=no 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 86835C433E1 for ; Sat, 22 Aug 2020 17:30:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5FEC6206C0 for ; Sat, 22 Aug 2020 17:30:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="dyCpYQrx" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728449AbgHVRau (ORCPT ); Sat, 22 Aug 2020 13:30:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40212 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728132AbgHVRas (ORCPT ); Sat, 22 Aug 2020 13:30:48 -0400 Received: from mail-yb1-xb2f.google.com (mail-yb1-xb2f.google.com [IPv6:2607:f8b0:4864:20::b2f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 57C48C061573 for ; Sat, 22 Aug 2020 10:30:48 -0700 (PDT) Received: by mail-yb1-xb2f.google.com with SMTP id e187so2817408ybc.5 for ; Sat, 22 Aug 2020 10:30:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=uDk1uTkzBrobW1w/NKB0oMWkQcelQXY/S6aVRrAX0ZA=; b=dyCpYQrxZN93H1AZy0Svu15URVWoPeG7t+Bjh405njPSC+q6aqdkS/8H/dJChB+kxX whnTVWTCOFzgZGQ3lqwsivukNlwOwYS10yIBa2iCcpKlqlifHV+hF3o+tpuxP8m1Vez9 tt2xfKXXvTYFk6sNGaCwM5y/XWvyLTsrrXwfBQjtWT2euwkPyLLi2XzVljG7somyHg44 HI4vV/ZXhA6msoH0Uj0HOQdA7SivMo2hPfjMRFq12ND1Qd6I9YI8uPsCTsct6dD1MlSN PSAQdI1+dqSmrDRRhWgDkOkGdCsVYXynn3H1xBiKuC3dsVM5FN/yeh0g7yU6lnIbIa5y YV6Q== 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=uDk1uTkzBrobW1w/NKB0oMWkQcelQXY/S6aVRrAX0ZA=; b=Zc+7x2zw7Ifl3F5AsCz3Zd6YTc0wQVdJYMzy/GMqI5w/U82XsNNqamvjD69dz0D9Vs oxSRw3n7+Uypo88idakH+K7NKmPodoTxF/EB1B9QWcmWQfYJxVwOaW/4sy9gGe2qVc3P 5ZkzVqBI7HwZGdPJsOTS7hytEwNm8RJNNeAsc9fZOykQneFgATMjcpoKHP1KZrUnqN6z j+sn7coct3bitGq7p/k91Sq3WErMiY+M49kQGJqgPKGzrkUG2JLu51EnyWg4sSwXQ1um GNwYj4UWFn9HlUaNEVw/wkYgTo6Qb4dqcjULZ7Z7hzBnP+hZaSAHmCBsBnzX3+Csrsnx e2ww== X-Gm-Message-State: AOAM530DFcU3AKB6XH52FhbvTYmmntpOebKavoPE/SplRAt1OmH5gU4E f6sYae/EojoqNHHBDzzvaigtGcmdMctFtlnavRA3Aw== X-Google-Smtp-Source: ABdhPJx6OI5qEcfI3wAi2qnLIinIWm8ZhOM7frPW9ne8dpaYB3ssb0hlJOW/CYwILyYDgT8yZDdMqrVimTKgGB+5hAo= X-Received: by 2002:a25:c4c5:: with SMTP id u188mr10605839ybf.162.1598117446875; Sat, 22 Aug 2020 10:30:46 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Michel Lespinasse Date: Sat, 22 Aug 2020 10:30:34 -0700 Message-ID: Subject: Re: Lockdep question regarding two-level locks To: Peter Zijlstra , Ingo Molnar , Will Deacon , Davidlohr Bueso Cc: LKML 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 On Sat, Aug 22, 2020 at 9:04 AM Michel Lespinasse wrote: > - B's implementation could, when lockdep is enabled, always release > lock A before acquiring lock B. This is not ideal though, since this > would hinder testing of the not-blocked code path in the acquire > sequence. Actually, this may be an acceptable way to handle my issue. In the non-blocking case, B's implementation does not have to actually release A, but it could tell lockdep that it's released A, acquired B and acquired A again. Kinda ugly but should work... -- Michel "Walken" Lespinasse A program is never fully debugged until the last user dies.