1 files changed, 48 insertions, 1 deletions

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 3cebc9a8d52e..3c9e77d6b4c2 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1003,6 +1003,7 @@ int perf_evlist__create_maps(struct perf_evlist *evlist, struct target *target)
 
 out_delete_threads:
         thread_map__delete(evlist->threads);
+        evlist->threads = NULL;
         return -1;
 }
 
@@ -1175,11 +1176,51 @@ void perf_evlist__close(struct perf_evlist *evlist)
         }
 }
 
+static int perf_evlist__create_syswide_maps(struct perf_evlist *evlist)
+{
+        int err = -ENOMEM;
+
+        /*
+         * Try reading /sys/devices/system/cpu/online to get
+         * an all cpus map.
+         *
+         * FIXME: -ENOMEM is the best we can do here, the cpu_map
+         * code needs an overhaul to properly forward the
+         * error, and we may not want to do that fallback to a
+         * default cpu identity map :-\
+         */
+        evlist->cpus = cpu_map__new(NULL);
+        if (evlist->cpus == NULL)
+                goto out;
+
+        evlist->threads = thread_map__new_dummy();
+        if (evlist->threads == NULL)
+                goto out_free_cpus;
+
+        err = 0;
+out:
+        return err;
+out_free_cpus:
+        cpu_map__delete(evlist->cpus);
+        evlist->cpus = NULL;
+        goto out;
+}
+
 int perf_evlist__open(struct perf_evlist *evlist)
 {
         struct perf_evsel *evsel;
         int err;
 
+        /*
+         * Default: one fd per CPU, all threads, aka systemwide
+         * as sys_perf_event_open(cpu = -1, thread = -1) is EINVAL
+         */
+        if (evlist->threads == NULL && evlist->cpus == NULL) {
+                err = perf_evlist__create_syswide_maps(evlist);
+                if (err < 0)
+                        goto out_err;
+        }
+
         perf_evlist__update_id_pos(evlist);
 
         evlist__for_each(evlist, evsel) {
@@ -1276,8 +1317,14 @@ int perf_evlist__prepare_workload(struct perf_evlist *evlist, struct target *tar
                 sigaction(SIGUSR1, &act, NULL);
         }
 
-        if (target__none(target))
+        if (target__none(target)) {
+                if (evlist->threads == NULL) {
+                        fprintf(stderr, "FATAL: evlist->threads need to be set at this point (%s:%d).\n",
+                                __func__, __LINE__);
+                        goto out_close_pipes;
+                }
                 evlist->threads->map[0] = evlist->workload.pid;
+        }
 
         close(child_ready_pipe[1]);
         close(go_pipe[0]);