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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 37A5CCA0EFA for ; Tue, 26 Aug 2025 14:53:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=HMGS7IGSOXk5Q1/Q6qxTcm4ZlvzCxxVLFiwmv/SBWY0=; b=0r9I9qu+t0HeiJz46s6OSy1mDk pJRl7qXUiwvAOEmJAoo7f84YgDsU29OA/X8J+skay74PHF2jTTXcoqa522SQgbiqrTeIU3XE8KwmI zTya6hVbQeCRKryYmNCk1UXo9pn4Wt/lvq/xFw6JKJlIIYIMQn0ptq3T/yxbH6nMXM7Ap3lsoZoHZ 4Q+I3UH8K013icIPcxOleGz3IbCfc3N22I03LYceHO6/6hCxM9kfpVo53f/Pk+wmsRWFtrLpDxF9a ewMV++MzZ+dSqYRG9H7y6FKNcu32J+nU1jsxaaad14uw3ZdMpZazLTHEMgIeIK2+vs/tdVYjUv1rM 0t4d0wBA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uqv2y-0000000CKv3-3ZQc; Tue, 26 Aug 2025 14:53:16 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uqtZF-0000000C4ck-3FYB; Tue, 26 Aug 2025 13:18:31 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B0DEB1A25; Tue, 26 Aug 2025 06:18:20 -0700 (PDT) Received: from J2N7QTR9R3 (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E10B23F63F; Tue, 26 Aug 2025 06:18:22 -0700 (PDT) Date: Tue, 26 Aug 2025 14:18:16 +0100 From: Mark Rutland To: Robin Murphy Cc: peterz@infradead.org, mingo@redhat.com, will@kernel.org, acme@kernel.org, namhyung@kernel.org, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, kan.liang@linux.intel.com, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, imx@lists.linux.dev, linux-csky@vger.kernel.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-pm@vger.kernel.org, linux-rockchip@lists.infradead.org, dmaengine@vger.kernel.org, linux-fpga@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, intel-xe@lists.freedesktop.org, coresight@lists.linaro.org, iommu@lists.linux.dev, linux-amlogic@lists.infradead.org, linux-cxl@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-riscv@lists.infradead.org Subject: Re: [PATCH 02/19] perf/hisilicon: Fix group validation Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250826_061829_940885_FC68B2D6 X-CRM114-Status: GOOD ( 23.95 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Aug 26, 2025 at 12:15:23PM +0100, Mark Rutland wrote: > On Wed, Aug 13, 2025 at 06:00:54PM +0100, Robin Murphy wrote: > > The group validation logic shared by the HiSilicon HNS3/PCIe drivers is > > a bit off, in that given a software group leader, it will consider that > > event *in place of* the actual new event being opened. At worst this > > could theoretically allow an unschedulable group if the software event > > config happens to look like one of the hardware siblings. > > > > The uncore framework avoids that particular issue, > > What is "the uncore framework"? I'm not sure exactly what you're > referring to, nor how that composes with the problem described above. > > > but all 3 also share the common issue of not preventing racy access to > > the sibling list, > > Can you please elaborate on this racy access to the silbing list? I'm > not sure exactly what you're referring to. Ah, I think you're referring to the issue in: https://lore.kernel.org/linux-arm-kernel/Zg0l642PgQ7T3a8Z@FVFF77S0Q05N/ ... where when creatign a new event which is its own group leader, lockdep_assert_event_ctx(event) fires in for_each_sibling_event(), because the new event's context isn't locked... > > diff --git a/drivers/perf/hisilicon/hisi_uncore_pmu.c b/drivers/perf/hisilicon/hisi_uncore_pmu.c > > index a449651f79c9..3c531b36cf25 100644 > > --- a/drivers/perf/hisilicon/hisi_uncore_pmu.c > > +++ b/drivers/perf/hisilicon/hisi_uncore_pmu.c > > @@ -101,26 +101,17 @@ static bool hisi_validate_event_group(struct perf_event *event) > > /* Include count for the event */ > > int counters = 1; > > > > - if (!is_software_event(leader)) { > > - /* > > - * We must NOT create groups containing mixed PMUs, although > > - * software events are acceptable > > - */ > > - if (leader->pmu != event->pmu) > > - return false; > > + if (leader == event) > > + return true; ... and hence bailing out here avoids that? It's not strictly "racy access to the sibling list", becuase there's nothing else accessing the list; it's just that this is the simplest way to appease lockdep while avoiding false negatives. It'd probably be better to say something like "the common issue of calling for_each_sibling_event() when initialising a new group leader", and maybe to spell that out a bit. Mark.