Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753187AbbHEQAr (ORCPT ); Wed, 5 Aug 2015 12:00:47 -0400 Received: from mail-pa0-f43.google.com ([209.85.220.43]:36481 "EHLO mail-pa0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752170AbbHEQAp (ORCPT ); Wed, 5 Aug 2015 12:00:45 -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> <20150805101506.GY18673@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: <55C2332B.3010708@plumgrid.com> Date: Wed, 5 Aug 2015 09:00:43 -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: <20150805101506.GY18673@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: 707 Lines: 18 On 8/5/15 3:15 AM, Peter Zijlstra wrote: > On Wed, Aug 05, 2015 at 12:04:25PM +0200, Peter Zijlstra wrote: >> On Tue, Aug 04, 2015 at 08:58:15AM +0000, Kaixu Xia wrote: > >>> + event->ctx->task != current) > > Strictly speaking we should hold rcu_read_lock around dereferencing > event->ctx (or have IRQs disabled -- although I know Paul doesn't like > us relying on that). programs are always executing under rcu_read_lock, so we should be good here too. -- 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/