From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by sourceware.org (Postfix) with ESMTPS id BAB183857C7E for ; Thu, 11 Nov 2021 17:41:22 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org BAB183857C7E Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-106-_qAHqxHVMKqHss8qCXGoIw-1; Thu, 11 Nov 2021 12:41:19 -0500 X-MC-Unique: _qAHqxHVMKqHss8qCXGoIw-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 16123871810; Thu, 11 Nov 2021 17:41:18 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.192.82]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0A8E35D6D7; Thu, 11 Nov 2021 17:41:16 +0000 (UTC) From: Florian Weimer To: Adhemerval Zanella Cc: Adhemerval Zanella via Libc-alpha , leonardo.macchia@gmail.com Subject: Re: [PATCH 1/3] inet: Fix getnameinfo (NI_NOFQDN) race condition (BZ#28566) References: <20211110185832.1931688-1-adhemerval.zanella@linaro.org> <20211110185832.1931688-2-adhemerval.zanella@linaro.org> <87r1bn150g.fsf@oldenburg.str.redhat.com> <27605b2b-cde0-9b1a-fc97-882d30e30b49@linaro.org> <87czn6yf0d.fsf@oldenburg.str.redhat.com> <87lf1uwzkr.fsf@oldenburg.str.redhat.com> <8dee4235-b730-dad4-6497-2ba13d9c4f8d@linaro.org> Date: Thu, 11 Nov 2021 18:41:14 +0100 In-Reply-To: <8dee4235-b730-dad4-6497-2ba13d9c4f8d@linaro.org> (Adhemerval Zanella's message of "Thu, 11 Nov 2021 11:17:11 -0300") Message-ID: <878rxuwpxh.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-6.7 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H2, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 11 Nov 2021 17:41:25 -0000 * Adhemerval Zanella: > On 11/11/2021 11:12, Florian Weimer wrote: >> * Adhemerval Zanella: >> >>> I meant H.J internal lock optimization [1], where the lll_lock int this >>> case will be mostly a relaxed load instead of a CAS (since once 'domain' >>> is properly initialized, there is no need to take the lock). >>> >>> [1] https://sourceware.org/pipermail/libc-alpha/2021-November/132899.html >> >> It doesn't work this way. It still does a CAS. > > Yeah, it helps only on contended case. Do you think we need to keep the > double-check optimization here? I would say yes. It also helps with fork safety. After the first call, concurrent forks won't get a bad lock state. Thanks, Florian