From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id A3834244667; Tue, 26 Aug 2025 13:18:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756214311; cv=none; b=f40S7/PlAXseEhVZ+fnvjqINMehJxZkZo6PdT4evswX/q8s9wvK3B7/nyOORNr+B/m1f9z7ssksar0K/YFrzu/15UmK7LOyCtREjS+cAxjdoy+Ycy87UJ2ElgI+8JEpPlcAnVpTgpYQ2er2iTFVlgvk2Mvmky0RerQv+/klFAv8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756214311; c=relaxed/simple; bh=BhQw8k5n2wkINEBiBgIRgXJovOh1V3NCnPs6OwLcw6o=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=TWcH4ucQRlZwOeBOH+JYpfiIClyf+gbmJDsrBBaiHuhZU51CK4P/aqTlopCXCiGRQysM/RSIRJiGuBfW8p8gSxTZYeedTApNGcM5h4siNxXk5Lf3DHrKy3WJ/cSVAeB30QkfBWNTsq6GGc9rjI61iIq3Q2yurE9H4SK2eDgCTUw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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: Precedence: bulk X-Mailing-List: sparclinux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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.