perf hists: Don't free decayed entries if in the annotation browser

Just let it there till the user exits the annotation browser.

Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-nmaxuzreqhm5k10t2co5sk9a@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
index 50c8fec..9b9d12b 100644
--- a/tools/perf/util/hist.c
+++ b/tools/perf/util/hist.c
@@ -100,6 +100,8 @@
 
 static bool hists__decay_entry(struct hists *hists, struct hist_entry *he)
 {
+	if (he->period == 0)
+		return true;
 	hists->stats.total_period -= he->period;
 	hist_entry__decay(he);
 	hists->stats.total_period += he->period;
@@ -114,8 +116,12 @@
 	while (next) {
 		n = rb_entry(next, struct hist_entry, rb_node);
 		next = rb_next(&n->rb_node);
-
-		if (hists__decay_entry(hists, n)) {
+		/*
+		 * We may be annotating this, for instance, so keep it here in
+		 * case some it gets new samples, we'll eventually free it when
+		 * the user stops browsing and it agains gets fully decayed.
+		 */
+		if (hists__decay_entry(hists, n) && !n->used) {
 			rb_erase(&n->rb_node, &hists->entries);
 
 			if (sort__need_collapse)