Em Wed, Sep 02, 2015 at 08:05:54PM +0800, pi3orama escreveu: > 发自我的 iPhone > > 在 2015年9月2日，下午7:54，Jiri Olsa <jo...@redhat.com> 写道： > >> On Wed, Sep 02, 2015 at 02:53:58PM +0800, Wangnan (F) wrote: > >>> @@ -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? > By checking list we won't rely on the assumption that nr_entries reflects the > actual number of elements in that list, makes the logic of this code more > compact. But why would we want to break that assumption? If I see FOO->entries and FOO->nr_entries, it is reasonable to expect that whatever data structure FOO->entries may be has FOO->nr_entries in it, lets not break that assumption. - Arnaldo > Don't you think so? > > At this point they are equivalent, but the whole patch is preventive action. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
