perf evlist: Use cpu_map__nr() helper

Use the cpu_map__nr() helper to protect a possible NULL cpu map
dereference.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1362987798-24969-2-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/evlist.c

@@ -228,7 +228,7 @@ void perf_evlist__disable(struct perf_evlist *evlist)
 	int cpu, thread;
 	struct perf_evsel *pos;
 
-	for (cpu = 0; cpu < evlist->cpus->nr; cpu++) {
+	for (cpu = 0; cpu < cpu_map__nr(evlist->cpus); cpu++) {
 		list_for_each_entry(pos, &evlist->entries, node) {
 			if (!perf_evsel__is_group_leader(pos))
 				continue;
@@ -443,7 +443,7 @@ static int perf_evlist__mmap_per_cpu(struct perf_evlist *evlist, int prot, int m
 	struct perf_evsel *evsel;
 	int cpu, thread;
 
-	for (cpu = 0; cpu < evlist->cpus->nr; cpu++) {
+	for (cpu = 0; cpu < cpu_map__nr(evlist->cpus); cpu++) {
 		int output = -1;
 
 		for (thread = 0; thread < evlist->threads->nr; thread++) {
@@ -470,7 +470,7 @@ static int perf_evlist__mmap_per_cpu(struct perf_evlist *evlist, int prot, int m
 	return 0;
 
 out_unmap:
-	for (cpu = 0; cpu < evlist->cpus->nr; cpu++) {
+	for (cpu = 0; cpu < cpu_map__nr(evlist->cpus); cpu++) {
 		if (evlist->mmap[cpu].base != NULL) {
 			munmap(evlist->mmap[cpu].base, evlist->mmap_len);
 			evlist->mmap[cpu].base = NULL;
@@ -725,7 +725,7 @@ int perf_evlist__open(struct perf_evlist *evlist)
 
 	return 0;
 out_err:
-	ncpus = evlist->cpus ? evlist->cpus->nr : 1;
+	ncpus = cpu_map__nr(evlist->cpus);
 	nthreads = evlist->threads ? evlist->threads->nr : 1;
 
 	list_for_each_entry_reverse(evsel, &evlist->entries, node)