perf evsel: Add a backpointer to the evlist a evsel is in

So that functions that deal primarily with an evsel to access
information that concerns the whole evlist it is in.

Cc: Adrian Hunter <[e-mail]>
Cc: Andi Kleen <[e-mail]>
Cc: Andy Lutomirski <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Stephane Eranian <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Kan Liang <[e-mail]>
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/evlist.c

···
 
 	evlist__for_each_safe(evlist, n, pos) {
 		list_del_init(&pos->node);
+		pos->evlist = NULL;
 		perf_evsel__delete(pos);
 	}
 
···
 
 void perf_evlist__add(struct perf_evlist *evlist, struct perf_evsel *entry)
 {
+	entry->evlist = evlist;
 	list_add_tail(&entry->node, &evlist->entries);
 	entry->idx = evlist->nr_entries;
 	entry->tracking = !entry->idx;

tools/perf/util/evsel.c

···
 	evsel->leader	   = evsel;
 	evsel->unit	   = "";
 	evsel->scale	   = 1.0;
+	evsel->evlist	   = NULL;
 	INIT_LIST_HEAD(&evsel->node);
 	INIT_LIST_HEAD(&evsel->config_terms);
 	perf_evsel__object.init(evsel);
···
 void perf_evsel__exit(struct perf_evsel *evsel)
 {
 	assert(list_empty(&evsel->node));
+	assert(evsel->evlist == NULL);
 	perf_evsel__free_fd(evsel);
 	perf_evsel__free_id(evsel);
 	perf_evsel__free_config_terms(evsel);

tools/perf/util/evsel.h

···
 
 /** struct perf_evsel - event selector
  *
+ * @evlist - evlist this evsel is in, if it is in one.
+ * @node - To insert it into evlist->entries or in other list_heads, say in
+ *         the event parsing routines.
  * @name - Can be set to retain the original event name passed by the user,
  *         so that when showing results in tools such as 'perf stat', we
  *         show the name used, not some alias.
···
  */
 struct perf_evsel {
 	struct list_head	node;
+	struct perf_evlist	*evlist;
 	struct perf_event_attr	attr;
 	char			*filter;
 	struct xyarray		*fd;