Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753702AbbHEQIh (ORCPT ); Wed, 5 Aug 2015 12:08:37 -0400 Received: from mail-pd0-f174.google.com ([209.85.192.174]:35973 "EHLO mail-pd0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753639AbbHEQIe (ORCPT ); Wed, 5 Aug 2015 12:08:34 -0400 Subject: Re: [PATCH v6 3/4] bpf: Implement function bpf_perf_event_read() that get the selected hardware PMU conuter To: Peter Zijlstra , Kaixu Xia References: <1438678696-88289-1-git-send-email-xiakaixu@huawei.com> <1438678696-88289-4-git-send-email-xiakaixu@huawei.com> <20150805100425.GZ25159@twins.programming.kicks-ass.net> <20150805135317.GZ18673@twins.programming.kicks-ass.net> Cc: davem@davemloft.net, acme@kernel.org, mingo@redhat.com, masami.hiramatsu.pt@hitachi.com, jolsa@kernel.org, daniel@iogearbox.net, wangnan0@huawei.com, linux-kernel@vger.kernel.org, pi3orama@163.com, hekuang@huawei.com, netdev@vger.kernel.org From: Alexei Starovoitov Message-ID: <55C23500.1000207@plumgrid.com> Date: Wed, 5 Aug 2015 09:08:32 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: <20150805135317.GZ18673@twins.programming.kicks-ass.net> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 747 Lines: 22 On 8/5/15 6:53 AM, Peter Zijlstra wrote: > + /* > + * If the event is currently on this CPU, its either a per-task event, > + * or local to this CPU. Furthermore it means its ACTIVE (otherwise > + * oncpu == -1). > + */ > + if (event->oncpu == smp_processor_id()) > + event->pmu->read(event); > + > + val = local64_read(&event->count); > + local_irq_restore(flags); > + nice! cleaner and faster. so raw_spin_lock(&ctx->lock) is not needed, because update_*(event) methods are not called, right? -- 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/