From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754072AbbIBLyU (ORCPT ); Wed, 2 Sep 2015 07:54:20 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57616 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752778AbbIBLyS (ORCPT ); Wed, 2 Sep 2015 07:54:18 -0400 Date: Wed, 2 Sep 2015 13:54:15 +0200 From: Jiri Olsa To: "Wangnan (F)" Cc: masami.hiramatsu.pt@hitachi.com, acme@redhat.com, Alexei Starovoitov , Jiri Olsa , Namhyung Kim , Zefan Li , pi3orama@163.com, "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] perf tools: Don't write to evsel if parser doesn't collect evsel Message-ID: <20150902115415.GH8598@krava.brq.redhat.com> References: <50399556C9727B4D88A595C8584AAB37525027C2@GSjpTKYDCembx32.service.hitachi.net> <1441176553-116129-1-git-send-email-wangnan0@huawei.com> <55E69D06.4050005@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55E69D06.4050005@huawei.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 On Wed, Sep 02, 2015 at 02:53:58PM +0800, Wangnan (F) wrote: > Sorry, forget to CC kernel mailing list... > > On 2015/9/2 14:49, Wang Nan wrote: > >If parse_events__scanner() collects no entry, perf_evlist__last(evlist) > >is invalid. > > > >Although it shouldn't happen at this point, before calling > >perf_evlist__last(), we should ensure the list is not empty for safety > >reason. > > > >There are 3 places need this checking: > > > > 1. Before setting cmdline_group_boundary; > > 2. Before __perf_evlist__set_leader(); > > 3. In foreach_evsel_in_last_glob. > > > >Signed-off-by: Wang Nan > >Cc: Arnaldo Carvalho de Melo > >Cc: Alexei Starovoitov > >Cc: Jiri Olsa > >Cc: Masami Hiramatsu > >Cc: Namhyung Kim > >Cc: Zefan Li > >Cc: pi3orama@163.com > >--- > > > >Merge all 3 list_empty() test together into one patch. > > > >Add warning messages. > > > >Improve commit message. > > > >--- > > tools/perf/util/parse-events.c | 22 +++++++++++++++++++--- > > 1 file changed, 19 insertions(+), 3 deletions(-) > > > >diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c > >index d826e6f..069848d 100644 > >--- a/tools/perf/util/parse-events.c > >+++ b/tools/perf/util/parse-events.c > >@@ -793,6 +793,11 @@ void parse_events__set_leader(char *name, struct list_head *list) > > { > > struct perf_evsel *leader; > >+ if (list_empty(list)) { > >+ __WARN_printf("WARNING: failed to set leader: empty list"); > >+ return; > >+ } > >+ > > __perf_evlist__set_leader(list); > > leader = list_entry(list->next, struct perf_evsel, node); > > leader->group_name = name ? strdup(name) : NULL; > >@@ -1143,10 +1148,15 @@ int parse_events(struct perf_evlist *evlist, const char *str, > > int entries = data.idx - evlist->nr_entries; > > struct perf_evsel *last; > >+ if (!list_empty(&data.list)) { > >+ last = list_entry(data.list.prev, > >+ struct perf_evsel, node); > >+ last->cmdline_group_boundary = true; > >+ } else > >+ __WARN_printf("WARNING: event parser found nothing"); we need to unify error printing in this object ;-) with this one it's 3 __WARN_printf(... fprintf(stderr,... printf(... WARN_ONCE(... ;-) > >+ > > perf_evlist__splice_list_tail(evlist, &data.list, entries); > > evlist->nr_groups += data.nr_groups; > >- last = perf_evlist__last(evlist); > >- last->cmdline_group_boundary = true; > > return 0; > > } > >@@ -1252,7 +1262,13 @@ foreach_evsel_in_last_glob(struct perf_evlist *evlist, > > struct perf_evsel *last = NULL; > > int err; > >- if (evlist->nr_entries > 0) > >+ /* > >+ * Don't return when list_empty, give func a chance to report > >+ * error when it found last == NULL. > >+ * > >+ * So no need to WARN here, let *func do this. > >+ */ > >+ if (!list_empty(&evlist->entries)) why is it better than to check evlist->nr_entries? evlist->nr_entries is equivalent to !list_empty(&evlist->entries) in here, right? jirka