From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754981AbaCMS1s (ORCPT ); Thu, 13 Mar 2014 14:27:48 -0400 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.225]:59470 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754690AbaCMS1r (ORCPT ); Thu, 13 Mar 2014 14:27:47 -0400 Message-ID: <1394735259.26600.14.camel@pippen.local.home> Subject: Re: [PATCH v6 4/7] arm64: Add ftrace support From: Steven Rostedt To: Will Deacon Cc: AKASHI Takahiro , "fweisbec@gmail.com" , "mingo@redhat.com" , Catalin Marinas , "tim.bird@sonymobile.com" , "gkulkarni@caviumnetworks.com" , "dsaxena@linaro.org" , "arndb@arndb.de" , "linux-arm-kernel@lists.infradead.org" , "linaro-kernel@lists.linaro.org" , "linux-kernel@vger.kernel.org" Date: Thu, 13 Mar 2014 14:27:39 -0400 In-Reply-To: <20140313170834.GE25472@mudshark.cambridge.arm.com> References: <1393564724-3966-1-git-send-email-takahiro.akashi@linaro.org> <1394705630-12384-1-git-send-email-takahiro.akashi@linaro.org> <1394705630-12384-5-git-send-email-takahiro.akashi@linaro.org> <20140313170834.GE25472@mudshark.cambridge.arm.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.4.4-4+b1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-RR-Connecting-IP: 107.14.168.142:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2014-03-13 at 17:08 +0000, Will Deacon wrote: > > + /* > > + * Note: > > + * No protection against faulting at *parent, which may be seen > > + * on other archs. It's unlikely on AArch64. > > + */ > > + old = *parent; > > + *parent = return_hooker; > > return_hook? People might take it personally otherwise ;) No, return_hooker is consistent with all the other archs. Hey, it's a rugby position! Note, which I was when I played. ;-) > > > + trace.func = self_addr; > > in kernel/ftrace/ftrace.c there's an smb_wmb() between setting up > tracing_graph_pause and setting the ret_stack with a comment saying: > > /* Make sure the tasks see the -1 first: */ > > Why don't we have a corresponding read-barrier here? The corresponding rmb is in kernel/trace/trace_function_graph ftrace_push_return_trace(). -- Steve