From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934115AbaKMUIk (ORCPT ); Thu, 13 Nov 2014 15:08:40 -0500 Received: from mail.kernel.org ([198.145.19.201]:58828 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933383AbaKMUIj (ORCPT ); Thu, 13 Nov 2014 15:08:39 -0500 Date: Thu, 13 Nov 2014 17:08:33 -0300 From: Arnaldo Carvalho de Melo To: Andi Kleen Cc: jolsa@redhat.com, linux-kernel@vger.kernel.org, namhyung@kernel.org, Andi Kleen Subject: Re: [PATCH 02/10] perf, tools: Support handling complete branch stacks as histograms Message-ID: <20141113200833.GI3612@kernel.org> References: <1415844328-4884-1-git-send-email-andi@firstfloor.org> <1415844328-4884-3-git-send-email-andi@firstfloor.org> <20141113191417.GC3612@kernel.org> <20141113195208.GS12538@two.firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141113195208.GS12538@two.firstfloor.org> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Thu, Nov 13, 2014 at 08:52:08PM +0100, Andi Kleen escreveu: > On Thu, Nov 13, 2014 at 04:14:17PM -0300, Arnaldo Carvalho de Melo wrote: > > Em Wed, Nov 12, 2014 at 06:05:20PM -0800, Andi Kleen escreveu: > > > +static int remove_loops(struct branch_entry *l, int nr) > > > +{ > > > + int i, j, off; > > > + unsigned char chash[CHASHSZ]; > > > + > > > + memset(chash, NO_ENTRY, sizeof(chash)); > > > + > > > + BUG_ON(nr >= 256); > > > > What is wrong with return -1 and propagating the error, so that the user > > is informed if the data being processed is bogus, stop processing with a > > warning or continue processing if finding the next valid record is > > possible? > > The error doesn't depend on the record. There is a check for the record > being < 127 in front of this. This is merely to catch that > if someone increases PERF_MAX_BRANCH_DEPTH to below 255 they need > to increase the type of the hash table from u8. Ok, so this would be better as a BUILD_BUG_ON? Like: #define CHASHSZ 127 #define CHASHBITS 7 #define NO_ENTRY 0xff #define PERF_MAX_BRANCH_DEPTH 127 /* Remove loops. */ static int remove_loops(struct branch_entry *l, int nr) { int i, j, off; unsigned char chash[CHASHSZ]; memset(chash, NO_ENTRY, sizeof(chash)); /* Change the type of the chash table, u8 is not enough now */ BUILD_BUG_ON(PERF_MAX_BRANCH_DEPTH >= 256); for (i = 0; i < nr; i++) { int h = hash_64(l[i].from, CHASHBITS) % CHASHSZ; ------------------------------------- - Arnaldo