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SubjectRe: [PATCH] perf tools: Don't write to evsel if parser doesn't collect evsel
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 <wangnan0@huawei.com>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: Alexei Starovoitov <ast@plumgrid.com>
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Zefan Li <lizefan@huawei.com>
> 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");
> +
> 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))
> last = perf_evlist__last(evlist);
>
> do {




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