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=-2.2 required=3.0 tests=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 87397C43603 for ; Mon, 16 Dec 2019 14:44:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 58D822067C for ; Mon, 16 Dec 2019 14:44:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728071AbfLPOoH (ORCPT ); Mon, 16 Dec 2019 09:44:07 -0500 Received: from www62.your-server.de ([213.133.104.62]:44068 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728056AbfLPOoG (ORCPT ); Mon, 16 Dec 2019 09:44:06 -0500 Received: from [2001:1620:665:0:5795:5b0a:e5d5:5944] (helo=localhost) by www62.your-server.de with esmtpsa (TLSv1.2:DHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89_1) (envelope-from ) id 1igrbQ-0001aO-T6; Mon, 16 Dec 2019 15:44:04 +0100 Date: Mon, 16 Dec 2019 15:44:04 +0100 From: Daniel Borkmann To: Andrii Nakryiko Cc: bpf@vger.kernel.org, netdev@vger.kernel.org, ast@fb.com, andrii.nakryiko@gmail.com, kernel-team@fb.com Subject: Re: [PATCH bpf-next 0/4] Fix perf_buffer creation on systems with offline CPUs Message-ID: <20191216144404.GG14887@linux.fritz.box> References: <20191212013521.1689228-1-andriin@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191212013521.1689228-1-andriin@fb.com> User-Agent: Mutt/1.12.1 (2019-06-15) X-Authenticated-Sender: daniel@iogearbox.net X-Virus-Scanned: Clear (ClamAV 0.101.4/25665/Mon Dec 16 10:52:23 2019) Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Wed, Dec 11, 2019 at 05:35:20PM -0800, Andrii Nakryiko wrote: > This patch set fixes perf_buffer__new() behavior on systems which have some of > the CPUs offline/missing (due to difference between "possible" and "online" > sets). perf_buffer will create per-CPU buffer and open/attach to corresponding > perf_event only on CPUs present and online at the moment of perf_buffer > creation. Without this logic, perf_buffer creation has no chances of > succeeding on such systems, preventing valid and correct BPF applications from > starting. Once CPU goes back online and processes BPF events, any attempt to push into perf RB via bpf_perf_event_output() with flag BPF_F_CURRENT_CPU would silently get discarded. Should rather perf API be fixed instead of plain skipping as done here to at least allow creation of ring buffer for BPF to avoid such case? > Andrii Nakryiko (4): > libbpf: extract and generalize CPU mask parsing logic > selftests/bpf: add CPU mask parsing tests > libbpf: don't attach perf_buffer to offline/missing CPUs > selftests/bpf: fix perf_buffer test on systems w/ offline CPUs > > tools/lib/bpf/libbpf.c | 157 ++++++++++++------ > tools/lib/bpf/libbpf_internal.h | 2 + > .../selftests/bpf/prog_tests/cpu_mask.c | 78 +++++++++ > .../selftests/bpf/prog_tests/perf_buffer.c | 29 +++- > 4 files changed, 213 insertions(+), 53 deletions(-) > create mode 100644 tools/testing/selftests/bpf/prog_tests/cpu_mask.c > > -- > 2.17.1 >