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 [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id A5FF33858C39 for ; Fri, 14 Jan 2022 22:23:53 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org A5FF33858C39 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-593-LLajH0m9OWyn7SXeK3E13g-1; Fri, 14 Jan 2022 17:23:52 -0500 X-MC-Unique: LLajH0m9OWyn7SXeK3E13g-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 30A12196E6C0; Fri, 14 Jan 2022 22:23:51 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.192.49]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2D6466AB99; Fri, 14 Jan 2022 22:23:47 +0000 (UTC) From: Florian Weimer To: Carlos O'Donell Cc: "H.J. Lu" , Carlos O'Donell via Libc-alpha Subject: Re: glibc 2.35 failures in elf/tst-cpu-features-cpuinfo-static. References: <056482b8-d413-2e24-a546-98ea46e68710@redhat.com> <87ee5aqmla.fsf@oldenburg.str.redhat.com> <87tue6p4n6.fsf@oldenburg.str.redhat.com> <51c4a93d-ab7d-f56d-0ac3-0c0a2b287e9a@redhat.com> <87ilumowe8.fsf@oldenburg.str.redhat.com> <5b072214-bd50-9316-536f-4dd9e0ed9d79@redhat.com> Date: Fri, 14 Jan 2022 23:23:45 +0100 In-Reply-To: <5b072214-bd50-9316-536f-4dd9e0ed9d79@redhat.com> (Carlos O'Donell's message of "Fri, 14 Jan 2022 17:10:44 -0500") Message-ID: <87y23ineha.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 10.5.11.16 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-6.4 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_H3, RCVD_IN_MSPIKE_WL, 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: Fri, 14 Jan 2022 22:23:54 -0000 * Carlos O'Donell: > On 1/14/22 16:11, Florian Weimer wrote: >> * Carlos O'Donell: >> >>> Can we make our testing detect this and mark the test XFAIL? >> >> If we treat this as our bug, we'd have to run CPUID on *all* CPUs during >> glibc startup. The bug is visible to applications as well. I don't >> think this is feasible. > > I thought we already ran cpuid at startup for all cpus? > > In cpu-features.c (init_cpu_features) we call __cpuid() unconditionally, and that > is called via ARCH_INIT_CPU_FEATURES() in LIBC_START_MAIN (static), and > DL_PLATFORM_INIT in ld.so (shared). > > In fact we might call cpuid five or six times during startup? It runs on a random CPU. It could be CPU 0 or another CPU. We pretend that it doesn't matter. >>> Or as HJ say, blacklist the CPU from the test e.g. UNSUPPORTED? >> >> I think the bug isn't CPU-specific. > > Could you expand in this a bit more? Maybe I was mistaken. Siddhesh has an i7-8665U. I must have mixed up my timelines. That CPU was released in 2019. > My concern is that testing should be robust and not return false > positives to the extent that we can prevent that. False positives, > regardless of who is at fault, call into question the validity of the > test infrastructure. There is a cost to such prevention of false > positives, for certain, there is a practical limit to the work we can > do. It's a true positive in the sense that the glibc detection (in ) does not work correctly. Now that might not be useful information to us as glibc developers because it's realistically not our problem, but we as Red Hat (or other distributions) should actually work towards fixing this issue. Thanks, Florian