From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 17A2BC55178 for ; Tue, 27 Oct 2020 14:34:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C5247207BB for ; Tue, 27 Oct 2020 14:34:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760209AbgJ0Od7 (ORCPT ); Tue, 27 Oct 2020 10:33:59 -0400 Received: from foss.arm.com ([217.140.110.172]:41964 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2897650AbgJ0OcA (ORCPT ); Tue, 27 Oct 2020 10:32:00 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 23C8013D5; Tue, 27 Oct 2020 07:31:59 -0700 (PDT) Received: from arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 775DC3F719; Tue, 27 Oct 2020 07:31:57 -0700 (PDT) Date: Tue, 27 Oct 2020 14:31:54 +0000 From: Dave Martin To: Leo Yan Cc: Arnaldo Carvalho de Melo , Andre Przywara , Peter Zijlstra , Ingo Molnar , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Wei Li , James Clark , Al Grant , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v4 06/21] perf arm-spe: Refactor printing string to buffer Message-ID: <20201027143153.GF27285@arm.com> References: <20201027030917.15404-1-leo.yan@linaro.org> <20201027030917.15404-7-leo.yan@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201027030917.15404-7-leo.yan@linaro.org> User-Agent: Mutt/1.5.23 (2014-03-12) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 27, 2020 at 03:09:02AM +0000, Leo Yan wrote: > When outputs strings to the decoding buffer with function snprintf(), > SPE decoder needs to detects if any error returns from snprintf() and if > so needs to directly bail out. If snprintf() returns success, it needs > to update buffer pointer and reduce the buffer length so can continue to > output the next string into the consequent memory space. > > This complex logics are spreading in the function arm_spe_pkt_desc() so > there has many duplicate codes for handling error detecting, increment > buffer pointer and decrement buffer size. > > To avoid the duplicate code, this patch introduces a new helper function > arm_spe_pkt_snprintf() which is used to wrap up the complex logics, and > the caller arm_spe_pkt_desc() will call it and simply check the returns > value. > > This patch also moves the variable 'blen' as the function's local > variable, this allows to remove the unnecessary braces and improve the > readability. > > Suggested-by: Dave Martin > Signed-off-by: Leo Yan > Reviewed-by: Andre Przywara > --- > .../arm-spe-decoder/arm-spe-pkt-decoder.c | 247 ++++++++++-------- > 1 file changed, 135 insertions(+), 112 deletions(-) > > diff --git a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c > index 04fd7fd7c15f..b400636e6da2 100644 > --- a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c > +++ b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c > @@ -9,6 +9,7 @@ > #include > #include > #include > +#include > > #include "arm-spe-pkt-decoder.h" > > @@ -258,192 +259,214 @@ int arm_spe_get_packet(const unsigned char *buf, size_t len, > return ret; > } > > +static int arm_spe_pkt_snprintf(char **buf_p, size_t *blen, > + const char *fmt, ...) > +{ > + va_list ap; > + int ret; > + > + va_start(ap, fmt); > + ret = vsnprintf(*buf_p, *blen, fmt, ap); > + va_end(ap); > + > + if (ret < 0) > + return ret; > + > + *buf_p += ret; > + *blen -= ret; > + return ret; > +} > + This approach seems OK, though I wonder whether all the "if (ret < 0) return;" logic is really needed. In case of failure, it probably doesn't matter what ends up in buf. If not, we could just implement a cumulative error: static int arm_spe_pkt_snprintf(int *err, char **buf_p, size_t *blen, { /* ... */ if (ret < 0) { if (err && !*err) *err = ret; } else { *buf_p += ret; *blen -= ret; } return err ? *err : ret; } and just return the final value of err. > int arm_spe_pkt_desc(const struct arm_spe_pkt *packet, char *buf, > size_t buf_len) > { > int ret, ns, el, idx = packet->index; > unsigned long long payload = packet->payload; > const char *name = arm_spe_pkt_name(packet->type); > + size_t blen = buf_len; > > switch (packet->type) { > case ARM_SPE_BAD: > case ARM_SPE_PAD: > case ARM_SPE_END: > - return snprintf(buf, buf_len, "%s", name); > - case ARM_SPE_EVENTS: { > - size_t blen = buf_len; > - > - ret = 0; > - ret = snprintf(buf, buf_len, "EV"); > - buf += ret; > - blen -= ret; > + return arm_spe_pkt_snprintf(&buf, &blen, "%s", name); > + case ARM_SPE_EVENTS: > + ret = arm_spe_pkt_snprintf(&buf, &blen, "EV"); > + if (ret < 0) > + return ret; > + ... Then this becomes case ARM_SPE_END: return arm_spe_pkt_snprintf(&err, &buf, &blen, "%s", name); case ARM_SPE_EVENTS: arm_spe_pkt_snprintf(&ret, &buf, &blen, "%s", name); if (payload & 0x1) arm_spe_pkt_snprintf(&err, &buf, &blen, " EXCEPTION-GEN"); if (payload & 0x2) arm_spe_pkt_snprintf(&err, &buf, &blen, " RETIRED"); /* ... */ This might be over-engineering, but it does help to condense the code. [...] Cheers ---Dave