perf evlist: Make set_maps() more resilient

Make perf_evlist__set_maps() more resilient by allowing for the
possibility that one or another of the maps isn't being changed and
therefore should not be "put".

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@intel.com>
Link: http://lkml.kernel.org/r/1441699142-18905-9-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 15 insertions, 4 deletions

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 5bd3b49452c6..78ff52ee8788 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1155,11 +1155,22 @@ out_delete_threads:
 void perf_evlist__set_maps(struct perf_evlist *evlist, struct cpu_map *cpus,
                            struct thread_map *threads)
 {
-        cpu_map__put(evlist->cpus);
-        evlist->cpus = cpus;
+        /*
+         * Allow for the possibility that one or another of the maps isn't being
+         * changed i.e. don't put it.  Note we are assuming the maps that are
+         * being applied are brand new and evlist is taking ownership of the
+         * original reference count of 1.  If that is not the case it is up to
+         * the caller to increase the reference count.
+         */
+        if (cpus != evlist->cpus) {
+                cpu_map__put(evlist->cpus);
+                evlist->cpus = cpus;
+        }
 
-        thread_map__put(evlist->threads);
-        evlist->threads = threads;
+        if (threads != evlist->threads) {
+                thread_map__put(evlist->threads);
+                evlist->threads = threads;
+        }
 
         perf_evlist__propagate_maps(evlist);
 }