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=-5.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS 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 29418FA372C for ; Fri, 8 Nov 2019 10:17:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F27C82178F for ; Fri, 8 Nov 2019 10:17:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="EAaDScY0" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730573AbfKHKR0 (ORCPT ); Fri, 8 Nov 2019 05:17:26 -0500 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:43782 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726103AbfKHKRZ (ORCPT ); Fri, 8 Nov 2019 05:17:25 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1573208244; 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=fIX8vpnWswMFGcn51BSLesh+iewqVLdfIrEKuuDKXaA=; b=EAaDScY0d+mc1XCS1NjlceKveBCCyNWprbFJOJP4xuExjnzb5YpGx5aQGAh0ISurELFSWk KXAYWo003qJBiQtALIgXo4MK8nFxq0K2jiIxWIKM3KnINu4mVK8JqC5crq8+L3aoChj+lE P2T2bm5ooyCcJMDhOr93RXOQ1i9dfFE= 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-118-nk_7zSrSM4OhuQ30hLUp0A-1; Fri, 08 Nov 2019 05:17:21 -0500 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 153791800D7B; Fri, 8 Nov 2019 10:17:20 +0000 (UTC) Received: from oldenburg2.str.redhat.com (dhcp-192-200.str.redhat.com [10.33.192.200]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 47F745C548; Fri, 8 Nov 2019 10:17:18 +0000 (UTC) From: Florian Weimer To: Thomas Gleixner Cc: LKML , Peter Zijlstra , Ingo Molnar , Darren Hart , Yi Wang , Yang Tao , Oleg Nesterov , Carlos O'Donell , Alexander Viro Subject: Re: [patch 00/12] futex: Cure robust/PI futex exit races References: <20191106215534.241796846@linutronix.de> <87zhh78gnf.fsf@oldenburg2.str.redhat.com> <87v9rv8g44.fsf@oldenburg2.str.redhat.com> <87o8xm95rt.fsf@oldenburg2.str.redhat.com> Date: Fri, 08 Nov 2019 11:17:16 +0100 In-Reply-To: (Thomas Gleixner's message of "Fri, 8 Nov 2019 10:18:08 +0100 (CET)") Message-ID: <87o8xm65ar.fsf@oldenburg2.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-MC-Unique: nk_7zSrSM4OhuQ30hLUp0A-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Thomas Gleixner: > On Fri, 8 Nov 2019, Florian Weimer wrote: >> * Florian Weimer: >> > * Florian Weimer: >> >> I ran the glibc upstream test suite (which has some robust futex test= s) >> >> against b21be7e942b49168ee15a75cbc49fbfdeb1e6a97 on x86-64, both nati= ve >> >> and 32-bit/i386 compat mode. >> >> >> >> compat mode seems broken, nptl/tst-thread-affinity-pthread fails. Th= is >> >> is probably *not* due to >> >> because the fa= ilure >> >> is non-sporadic, but reliable fails for thread 253: >> >> >> >> info: Detected CPU set size (in bits): 225 >> >> info: Maximum test CPU: 255 >> >> error: pthread_create for thread 253 failed: Resource temporarily una= vailable >> >> >> >> I'm running this on a large box as root, so ulimits etc. do not apply= . >> >> >> >> I did not see this failure with the x86-64 test. >> >> >> >> You should be able to reproduce with (assuming you've got a multilib = gcc): >> >> >> >> git clone git://sourceware.org/git/glibc.git git >> >> mkdir build >> >> cd build >> >> ../git/configure --prefix=3D/usr CC=3D"gcc -m32" CXX=3D"g++ -m32" --b= uild=3Di686-linux >> >> make -j`nproc` >> >> make test t=3Dnptl/tst-thread-affinity-pthread >> > >> > Sorry, I realized that I didn't actually verify that this is a >> > regression caused by your patches. Maybe I can do that tomorrow. >>=20 >> Confirmed as a regression caused by the patches. Depending on the >> nature of the bug, you need a machine which has or pretends to have many >> CPUs (this one has 256 CPUs). > > Sure I can do that, but I completely fail to see how that's a > regression. > > Unpatched 5.4-rc6: > > FAIL: nptl/tst-thread-affinity-pthread > original exit status 1 > info: Detected CPU set size (in bits): 225 > info: Maximum test CPU: 255 > error: pthread_create for thread 253 failed: Resource temporarily unavail= able Huh. Reverting your patches (at commit 26bc672134241a080a83b2ab9aa8abede8d= 30e1c) fixes the test for me. > TBH, the futex changes have absolutely nothing to do with that resource > fail. I suspect that there are some changes to task exit latency, which triggers the latent resource management bug. Thanks, Florian