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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 37C54C433DF for ; Fri, 26 Jun 2020 08:54:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 143F320C09 for ; Fri, 26 Jun 2020 08:54:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="BrIGw6n2" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726003AbgFZIyi (ORCPT ); Fri, 26 Jun 2020 04:54:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48252 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725850AbgFZIyi (ORCPT ); Fri, 26 Jun 2020 04:54:38 -0400 Received: from mail-ej1-x631.google.com (mail-ej1-x631.google.com [IPv6:2a00:1450:4864:20::631]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3702FC08C5C1 for ; Fri, 26 Jun 2020 01:54:38 -0700 (PDT) Received: by mail-ej1-x631.google.com with SMTP id o18so4152042eje.7 for ; Fri, 26 Jun 2020 01:54:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=cc:subject:to:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=woJkQIjeb20qDpaTA5AdD32a+Iukxf+56CGseYV3DAk=; b=BrIGw6n20Fu+7T69K5+mye7WKBpJqHvVH5oJxeEGTx1nKAz3IRAoOHbbRMSqCd13/n 0W7NPaebG2umbi8ocAm76J884nRbmN98D/bNTP4ZTtlqSd3oT/wiIK8qrlWTy3Fb45Yw uhTQP+Qly3YNPLKH28dbVL/deEK1bTVCdHmKpmMzPtZOlYdeu/FArLd5jyMNlYEIneeV 2tFDLf/tOkH7TVMjTLMm2zgb42bu2UCquA3Yb3HS3ETpl/ogBpM7N6vVHej4HCMnUQTB kaAJ6uaBP+Doa+yYuIysQPXkkECV31ZRNbonbjK9/8TDnOAez/VHyP1JqAHkj4A4W2fg jDjA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:cc:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=woJkQIjeb20qDpaTA5AdD32a+Iukxf+56CGseYV3DAk=; b=D6ltTjMYj31Oqdojrp8Gf+yUh1/H7qS61n4yRbaee9Y5nkH1G6+eWx02LsxUNzDWdH vZocAD7V80arX/t8Puivk7AtAYJycn9z4fz+eok7KI+P60PpZf/HhbzLLtKylurZvb3u M/ftFgVeRdPDX4BcRWyqyTVJilgiaC4NvXdG0+R0U2kK/1la/i4D7nbWaY/DR0/aieFu AQAVVWkGZHFe0x51ymUyhlui3fidP1DK3TJq1GaVUqDu+9VEuWcm02RamuWd46TE8qBF 6qa+csgl+DT8H5Gh2F0Wy/bl91Z7NLi0eAr+oPnc565dCbaWs9O4sBCjVITezqLKAAw/ fqwA== X-Gm-Message-State: AOAM530riW0gRym6sK+Ct7VPAhywRL6R8A73hDPM3YUjgHmTqBp5CwQC NeWAkhJWJx0IpxrnIw68zuVqBOiw X-Google-Smtp-Source: ABdhPJzjoIhDoNVFchAjNOySRl3Sxz5/hr5QzP6xGwhwi3tNJlE8pfN7QZbPdO+2uGSumzUlj7Lwfg== X-Received: by 2002:a17:906:46cd:: with SMTP id k13mr1605315ejs.312.1593161676821; Fri, 26 Jun 2020 01:54:36 -0700 (PDT) Received: from ?IPv6:2001:a61:253c:8201:b2fb:3ef8:ca:1604? ([2001:a61:253c:8201:b2fb:3ef8:ca:1604]) by smtp.gmail.com with ESMTPSA id sd15sm11109472ejb.66.2020.06.26.01.54.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 26 Jun 2020 01:54:36 -0700 (PDT) Cc: mtk.manpages@gmail.com, Carlos O'Donell , linux-man Subject: Re: POSIX writer locks can't be recursive To: Kumar Kartikeya Dwivedi References: From: "Michael Kerrisk (man-pages)" Message-ID: <8d7edc37-6b5f-1dd9-5f7f-b4e15a9ae39a@gmail.com> Date: Fri, 26 Jun 2020 10:54:35 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-man-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-man@vger.kernel.org Hi Carlos, Could you comment here, as this was your text in pthread_rwlockattr_setkind_np(3)? On 6/25/20 2:32 PM, Kumar Kartikeya Dwivedi wrote: > Hi, > In pthread_rwlockattr_setkind_np(3), the explanation for > PTHREAD_RWLOCK_PREFER_WRITER_NP reads: > >> This is ignored by glibc because the POSIX requirement to support >> recursive writer locks would cause this option to create trivial >> deadlocks; > > I think this should be "reader locks" instead, since it is > undefined[1] for a thread holding a write lock to call > pthread_rwlock_wrlock(3) again (glibc returns EDEADLK, musl simply > deadlocks). There's no such requirement in POSIX either. Please let me > know if I'm missing something. > > [1]: https://pubs.opengroup.org/onlinepubs/007908799/xsh/pthread_rwlock_wrlock.html Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/