[tip:perf/core] perf evlist: Make set_maps() more resilient

[tip-bot for Adrian Hunter <tipbot@zytor.com>]

Commit-ID:  934e0f2053ce299893ca48a411bf7fdc8ac6254f
Gitweb:     http://git.kernel.org/tip/934e0f2053ce299893ca48a411bf7fdc8ac6254f
Author:     Adrian Hunter <adrian.hunter@intel.com>
AuthorDate: Tue, 8 Sep 2015 10:58:56 +0300
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Tue, 15 Sep 2015 10:44:22 -0300

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>
---
 tools/perf/util/evlist.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 5bd3b49..78ff52e 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);
 }