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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 657ABC433FE for ; Fri, 3 Sep 2021 08:29:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4504F60FC4 for ; Fri, 3 Sep 2021 08:29:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348332AbhICIaY (ORCPT ); Fri, 3 Sep 2021 04:30:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40656 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348150AbhICIaX (ORCPT ); Fri, 3 Sep 2021 04:30:23 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4FD9BC061575; Fri, 3 Sep 2021 01:29:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=63YjCZz8yI4FKXK+jv7rwHSVADBtiqi5HQcrAte2wY0=; b=ozlT/4knnZ1PqKs/7MNRFQJImq fW+jGTYcx5EzCZpxPjfnL/+TDVNNcAGfYnHChmTZZkLV1iWRNy4eFOzktJ55sJc9rtZ7QPNtp1wdx 0o9yimgl5mP/ynzBxvQY2k23KNN8yLyUnxT+pYxUx87Q6W2klvDsw53pJTl6gU+g0WhQ3jHFoN2pc TTNR+UQO7Kq+ZvPxKm608ugUqpDUt7VKxDeGESG99pbyULGIjimb8xyGM9B17dQN2KVM0r60e//pL acklVuByNpC/Gfy0QuxSbMjRtUZueKyF3KEeDaxhj+9pjc9bvzCbt6F+nj7C7F9/zIlPPCJdToson dveUY/bg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1mM4XV-004HcU-Bx; Fri, 03 Sep 2021 08:27:33 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id E42B130018E; Fri, 3 Sep 2021 10:27:08 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id CDBFC209D9D99; Fri, 3 Sep 2021 10:27:08 +0200 (CEST) Date: Fri, 3 Sep 2021 10:27:08 +0200 From: Peter Zijlstra To: Song Liu Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, acme@kernel.org, mingo@redhat.com, kjain@linux.ibm.com, kernel-team@fb.com Subject: Re: [PATCH v5 bpf-next 1/3] perf: enable branch record for software events Message-ID: References: <20210902165706.2812867-1-songliubraving@fb.com> <20210902165706.2812867-2-songliubraving@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210902165706.2812867-2-songliubraving@fb.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 02, 2021 at 09:57:04AM -0700, Song Liu wrote: > +static int > +intel_pmu_snapshot_branch_stack(struct perf_branch_entry *entries, unsigned int cnt) > +{ > + struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events); > + > + intel_pmu_disable_all(); > + intel_pmu_lbr_read(); > + cnt = min_t(unsigned int, cnt, x86_pmu.lbr_nr); > + > + memcpy(entries, cpuc->lbr_entries, sizeof(struct perf_branch_entry) * cnt); > + intel_pmu_enable_all(0); > + return cnt; > +} Given this disables the PMI from 'random' contexts, should we not add IRQ disabling around this to avoid really bad behaviour?