Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754084Ab3JGVpq (ORCPT ); Mon, 7 Oct 2013 17:45:46 -0400 Received: from mga02.intel.com ([134.134.136.20]:17210 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751489Ab3JGVpp (ORCPT ); Mon, 7 Oct 2013 17:45:45 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.90,1051,1371106800"; d="scan'208";a="406852933" From: Andi Kleen To: Stephane Eranian Cc: LKML , Peter Zijlstra , "mingo\@elte.hu" , Arnaldo Carvalho de Melo , Jiri Olsa , "Yan\, Zheng" Subject: Re: [PATCH v1 1/2] perf,x86: add Intel RAPL PMU support References: <1381162158-24329-1-git-send-email-eranian@google.com> <1381162158-24329-2-git-send-email-eranian@google.com> <20131007175542.GB3363@tassilo.jf.intel.com> Date: Mon, 07 Oct 2013 14:45:44 -0700 In-Reply-To: (Stephane Eranian's message of "Mon, 7 Oct 2013 22:58:44 +0200") Message-ID: <87pprgzref.fsf@tassilo.jf.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2368 Lines: 73 Stephane Eranian writes: > >>> + goto again; >>> + >>> + struct rapl_pmu *pmu = __get_cpu_var(rapl_pmu); >>> + >>> + if (WARN_ON_ONCE(!(event->hw.state & PERF_HES_STOPPED))) >>> + return; >>> + >>> + event->hw.state = 0; >>> + >>> + local64_set(&event->hw.prev_count, rapl_read_counter(event)); >>> + >>> + pmu->n_active++; >> >> What lock protects this add? >> > None. I will add one. Bu then I am wondering about if it is really > necessary given > that RAPL event are system-wide and this pinned to a CPU. If the call came > from another CPU, then it IPI there, and that means that CPU is executing that > code. Any other CPU will need IPI too, and that interrupt will be kept pending. > Am I missing a test case here? Are IPI reentrant? they can be if interrupts are enabled (likely here) > >>> +} >>> + >>> +static ssize_t rapl_get_attr_cpumask(struct device *dev, >>> + struct device_attribute *attr, char *buf) >>> +{ >>> + int n = cpulist_scnprintf(buf, PAGE_SIZE - 2, &rapl_cpu_mask); >> >> Check n here in case it overflowed >> > But isn't that what the -2 and the below \n\0 are for? I know it's very unlikely and other stuff would break, but Assuming you have a system with some many CPUs that they don't fit into a page. Then the scnprintf would fail, but you would corrupt random data because you write before the buffer. >> Doesn't this need a lock of some form? AFAIK we can do parallel >> CPU startup now. >> > Did not know about this change? But then that means all the other > perf_event *_starting() and maybe even _*prepare() routines must also > use locks. I can add that to RAPL. Yes may be broken everywhere. >>> + /* check supported CPU */ >>> + switch (boot_cpu_data.x86_model) { >>> + case 42: /* Sandy Bridge */ >>> + case 58: /* Ivy Bridge */ >>> + case 60: /* Haswell */ >> >> Need more model numbers for Haswell (see the main perf driver) >> > Don't have all the models to test... It should be all the same. -Andi -- ak@linux.intel.com -- Speaking for myself only -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/