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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9EF3EC3DA7D for ; Tue, 3 Jan 2023 16:23:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238163AbjACQXV (ORCPT ); Tue, 3 Jan 2023 11:23:21 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46762 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238144AbjACQWW (ORCPT ); Tue, 3 Jan 2023 11:22:22 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id A3FEA6244; Tue, 3 Jan 2023 08:21:47 -0800 (PST) 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 18EE21570; Tue, 3 Jan 2023 08:22:29 -0800 (PST) Received: from [10.32.36.24] (e121896.Emea.Arm.com [10.32.36.24]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8F57E3F882; Tue, 3 Jan 2023 08:21:43 -0800 (PST) Message-ID: <800a1f42-319c-9098-ef1a-cb1e57159d13@arm.com> Date: Tue, 3 Jan 2023 16:21:41 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.2 Subject: Re: [PATCH v2 2/7] perf: Use perf_pmu__open_file() and perf_pmu__scan_file() Content-Language: en-US To: Leo Yan Cc: linux-perf-users@vger.kernel.org, tanmay@marvell.com, sgoutham@marvell.com, gcherian@marvell.com, lcherian@marvell.com, bbhushan2@marvell.com, Mathieu Poirier , Suzuki K Poulose , Mike Leach , John Garry , Will Deacon , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20221222160328.3639989-1-james.clark@arm.com> <20221222160328.3639989-3-james.clark@arm.com> From: James Clark In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 23/12/2022 03:45, Leo Yan wrote: > On Thu, Dec 22, 2022 at 04:03:22PM +0000, James Clark wrote: >> Remove some code that duplicates existing methods. This requires that >> some consts are removed because one of the existing helper methods takes >> a struct perf_pmu instead of a name which has a non const name field. >> But except for the tests, the strings were already non const. >> >> No functional changes. >> >> Signed-off-by: James Clark >> --- >> tools/perf/tests/evsel-roundtrip-name.c | 3 +- >> tools/perf/tests/parse-events.c | 3 +- >> tools/perf/util/cputopo.c | 9 +----- >> tools/perf/util/pmu-hybrid.c | 27 +++------------- >> tools/perf/util/pmu-hybrid.h | 2 +- >> tools/perf/util/pmu.c | 42 +++++++------------------ >> tools/perf/util/pmu.h | 3 +- >> 7 files changed, 24 insertions(+), 65 deletions(-) >> >> diff --git a/tools/perf/tests/evsel-roundtrip-name.c b/tools/perf/tests/evsel-roundtrip-name.c >> index e94fed901992..9bccf177f481 100644 >> --- a/tools/perf/tests/evsel-roundtrip-name.c >> +++ b/tools/perf/tests/evsel-roundtrip-name.c >> @@ -103,8 +103,9 @@ static int test__perf_evsel__roundtrip_name_test(struct test_suite *test __maybe >> int subtest __maybe_unused) >> { >> int err = 0, ret = 0; >> + char cpu_atom[] = "cpu_atom"; >> >> - if (perf_pmu__has_hybrid() && perf_pmu__hybrid_mounted("cpu_atom")) >> + if (perf_pmu__has_hybrid() && perf_pmu__hybrid_mounted(cpu_atom)) > > After change the parameter 'name' to non const type in function > perf_pmu__hybrid_mounted(), at here we still can pass string "cpu_atom" > without warning, right? If so, we don't need to define a local > variable 'cpu_atom'. > > [...] > >> -bool perf_pmu__hybrid_mounted(const char *name) >> +bool perf_pmu__hybrid_mounted(char *name) >> { >> - char path[PATH_MAX]; >> - const char *sysfs; >> - FILE *file; >> - int n, cpu; >> + int cpu; >> + struct perf_pmu pmu = {.name = name}; >> >> if (strncmp(name, "cpu_", 4)) >> return false; >> >> - sysfs = sysfs__mountpoint(); >> - if (!sysfs) >> - return false; >> - >> - snprintf(path, PATH_MAX, CPUS_TEMPLATE_CPU, sysfs, name); >> - if (!file_available(path)) >> - return false; >> - >> - file = fopen(path, "r"); >> - if (!file) >> - return false; >> - >> - n = fscanf(file, "%u", &cpu); >> - fclose(file); >> - if (n <= 0) >> - return false; >> - >> - return true; >> + return perf_pmu__scan_file(&pmu, "cpus", "%u", &cpu) > 0; > > It's not necessarily to change the parameter 'name' to non const type, > we can handle this case in two different ways. > > The first option is to refine the code with using the function > perf_pmu__pathname_scnprintf() which is introduced in patch 01, thus > we can keep using fopen() and fscanf() to read out value from 'cpus' > entry. > > Another option is to define a local array 'pmu_name[PATH_MAX]' and > then copy the input string to this array, something like: > > bool perf_pmu__hybrid_mounted(const char *name) > { > char pmu_name[PATH_MAX]; > struct perf_pmu pmu; > int cpu; > > strncpy(pmu_name, name, sizeof(pmu_name)); > pmu.name = pmu_name; > > return perf_pmu__scan_file(&pmu, "cpus", "%u", &cpu) > 0; > } > > We even can consider to dynamically allocate buffer and copy string from > 'name' to the allocated buffer. > I went with the string copy way and put the consts back in V3. One minor difference is that I had to use strlcpy() instead of strncpy() to avoid a compiler warning about the destination buffer being the same size. James [...] >> -static struct perf_cpu_map *pmu_cpumask(const char *name) >> +static struct perf_cpu_map *pmu_cpumask(char *name) >> { >> - char path[PATH_MAX]; >> struct perf_cpu_map *cpus; >> - const char *sysfs = sysfs__mountpoint(); >> const char *templates[] = { >> - CPUS_TEMPLATE_UNCORE, >> - CPUS_TEMPLATE_CPU, >> + "cpumask", >> + "cpus", >> NULL >> }; >> const char **template; >> - >> - if (!sysfs) >> - return NULL; >> + struct perf_pmu pmu = {.name = name}; > > Here we also can define a local array and copy string from 'name' to > the local array. This can allow us to provide a friendly function and > caller doesn't need to explictly pass non const string. > Done