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=-18.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 6382CC432BE for ; Wed, 1 Sep 2021 18:34:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4942761054 for ; Wed, 1 Sep 2021 18:34:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232312AbhIASe7 (ORCPT ); Wed, 1 Sep 2021 14:34:59 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:59042 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245252AbhIASe6 (ORCPT ); Wed, 1 Sep 2021 14:34:58 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1630521240; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=0CoTPuq9YzYCOqMUWEF6uWhloFZ+Cm12Nm9b+QIj+Jk=; b=QqTH18zOdlgd9V4Y/L5FPFnkQ24fN2suRwcmjSbRDEJbPIUbnaTX5C0Sjoec5Y4G6Ik8G9 0Ha0BxPTLh2YOfYgILk/GCFQyQPGjwqOwrk090gjjKdS9iiCwevnlKwBpzVHCMxMT4kzsP 3B46JxjpUYFB27IdslbaSwgS1TQl89k= Received: from mail-qt1-f200.google.com (mail-qt1-f200.google.com [209.85.160.200]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-25-3ND2Nc7aNLCyhm7eaNdDAA-1; Wed, 01 Sep 2021 14:32:56 -0400 X-MC-Unique: 3ND2Nc7aNLCyhm7eaNdDAA-1 Received: by mail-qt1-f200.google.com with SMTP id f34-20020a05622a1a2200b0029c338949c1so375569qtb.8 for ; Wed, 01 Sep 2021 11:32:56 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:subject:to:cc:references:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=0CoTPuq9YzYCOqMUWEF6uWhloFZ+Cm12Nm9b+QIj+Jk=; b=QgZPCdNRQ4Ecf9MvgnPksO3cOBrgVSCiOQ2byNQBwsd5eSZepj4TVgE88vb/zz8aK5 eGvBcqRMP/TU1BFhcmoHK0jBubqIo8zS1elx0Xcz1shc4XTQ67wrAt896wMyCNgWWUYS flgND5mCiiFLEp9ujuHtItfqkHCJBD9BRz63hz7KpwpWhSd1DbZUETTlUlyRkU92Krrs Jl9gF7Lq4pzz0HuaS8zXP1QSkA1lVy4ZIFEGdat/sumQS2CPfZB15qFgCZReRBP33MO1 RoKLeSY7emnH+6Xzt1cc1fN8f3IapPE7K9XknG4i/jvyK5WYvu8PXysyNvPZ1dgVZHjc IxfQ== X-Gm-Message-State: AOAM531/7v7YpHOlt7jRpyX91PXh+GZ8qJi9S8mZG5hfKOaPkzZnkSB7 zjC7++0dahzcgzGnfM+KYcJ9doxhkgz/ELYV1AjcQcqUNQFcahhcPAQvqjYzE8EJBtA432nJ1UH h+6+WHzV1MC+RFAsUJMziicKe X-Received: by 2002:a05:620a:29c7:: with SMTP id s7mr1043097qkp.186.1630521176302; Wed, 01 Sep 2021 11:32:56 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzwqujBA8w+lcIHJrlFcTQmC4TiAHAd3NMdpbDWMHkLwTtt9aDqUqkAPxwBEyx2V+ulvpz1Gw== X-Received: by 2002:a05:620a:29c7:: with SMTP id s7mr1043072qkp.186.1630521176094; Wed, 01 Sep 2021 11:32:56 -0700 (PDT) Received: from llong.remote.csb ([2601:191:8500:76c0::cdbc]) by smtp.gmail.com with ESMTPSA id a189sm205323qkf.114.2021.09.01.11.32.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 01 Sep 2021 11:32:55 -0700 (PDT) From: Waiman Long X-Google-Original-From: Waiman Long Subject: Re: [PATCH] lockdep: Let lock_is_held_type() detect recursive read as read To: Sebastian Andrzej Siewior , linux-kernel@vger.kernel.org Cc: Peter Zijlstra , Ingo Molnar , Will Deacon , Boqun Feng , Thomas Gleixner References: <20210901162255.u2vhecaxgjsjfdtc@linutronix.de> Message-ID: <9af2b074-9fcf-5aea-f37d-9b2482146489@redhat.com> Date: Wed, 1 Sep 2021 14:32:54 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210901162255.u2vhecaxgjsjfdtc@linutronix.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/1/21 12:22 PM, Sebastian Andrzej Siewior wrote: > lock_is_held_type(, 1) detects acquired read locks. It only recognized > locks acquired with lock_acquire_shared(). Read locks acquired with > lock_acquire_shared_recursive() are not recognized because a `2' is > stored as the read value. > > Rework the check to additionally recognise lock's read value one and two > as a read held lock. > > Fixes: e918188611f07 ("locking: More accurate annotations for read_lock()") > Signed-off-by: Sebastian Andrzej Siewior > --- > > On a related note: What exactly means read_lock_is_recursive() in terms > of recursive locking? The second items mentions QRW locks. Does this > mean that a pending WRITER blocks further READER from acquiring the > lock? > > kernel/locking/lockdep.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c > index f15df3fd7c5a6..39f98454a8827 100644 > --- a/kernel/locking/lockdep.c > +++ b/kernel/locking/lockdep.c > @@ -5366,7 +5366,9 @@ int __lock_is_held(const struct lockdep_map *lock, int read) > struct held_lock *hlock = curr->held_locks + i; > > if (match_held_lock(hlock, lock)) { > - if (read == -1 || hlock->read == read) > + if (read == -1 || > + (read == 0 && hlock->read == 0) || > + (read == 1 && hlock->read > 0)) > return LOCK_STATE_HELD; > > return LOCK_STATE_NOT_HELD; I think the check can be simplified as     if (read == -1 || read == !!hlock->read) Cheers, Longman