perf tools: Add evlist__add_sched_switch()

Add a help to create a system-wide sched_switch event. One merit is
that it sets the system-wide bit before adding it to evlist so that
the libperf can handle the cpu and thread maps correctly.

Reviewed-by: Adrian Hunter <[e-mail]>
Signed-off-by: Namhyung Kim <[e-mail]>
Cc: Ian Rogers <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Leo Yan <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/arch/x86/util/intel-pt.c

···
 #include <linux/bitops.h>
 #include <linux/log2.h>
 #include <linux/zalloc.h>
+#include <linux/err.h>
 #include <cpuid.h>
 
 #include "../../../util/session.h"
···
 	if (!evlist__can_select_event(evlist, sched_switch))
 		return -EPERM;
 
-	err = parse_event(evlist, sched_switch);
-	if (err) {
-		pr_debug2("%s: failed to parse %s, error %d\n",
+	evsel = evlist__add_sched_switch(evlist, true);
+	if (IS_ERR(evsel)) {
+		err = PTR_ERR(evsel);
+		pr_debug2("%s: failed to create %s, error = %d\n",
 			  __func__, sched_switch, err);
 		return err;
 	}
 
-	evsel = evlist__last(evlist);
-
-	evsel__set_sample_bit(evsel, CPU);
-	evsel__set_sample_bit(evsel, TIME);
-
-	evsel->core.system_wide = true;
-	evsel->no_aux_samples = true;
 	evsel->immediate = true;
 
 	return 0;

tools/perf/tests/switch-tracking.c

···
 #include <time.h>
 #include <stdlib.h>
 #include <linux/zalloc.h>
+#include <linux/err.h>
 #include <perf/cpumap.h>
 #include <perf/evlist.h>
 #include <perf/mmap.h>
···
 		goto out;
 	}
 
-	err = parse_event(evlist, sched_switch);
-	if (err) {
-		pr_debug("Failed to parse event %s\n", sched_switch);
+	switch_evsel = evlist__add_sched_switch(evlist, true);
+	if (IS_ERR(switch_evsel)) {
+		err = PTR_ERR(switch_evsel);
+		pr_debug("Failed to create event %s\n", sched_switch);
 		goto out_err;
 	}
 
-	switch_evsel = evlist__last(evlist);
-
-	evsel__set_sample_bit(switch_evsel, CPU);
-	evsel__set_sample_bit(switch_evsel, TIME);
-
-	switch_evsel->core.system_wide = true;
-	switch_evsel->no_aux_samples = true;
 	switch_evsel->immediate = true;
 
 	/* Test moving an event to the front */

tools/perf/util/evlist.c

···
 	return evsel;
 }
 
+struct evsel *evlist__add_sched_switch(struct evlist *evlist, bool system_wide)
+{
+	struct evsel *evsel = evsel__newtp_idx("sched", "sched_switch", 0);
+
+	if (IS_ERR(evsel))
+		return evsel;
+
+	evsel__set_sample_bit(evsel, CPU);
+	evsel__set_sample_bit(evsel, TIME);
+
+	evsel->core.system_wide = system_wide;
+	evsel->no_aux_samples = true;
+
+	evlist__add(evlist, evsel);
+	return evsel;
+};
+
 int evlist__add_attrs(struct evlist *evlist, struct perf_event_attr *attrs, size_t nr_attrs)
 {
 	struct evsel *evsel, *n;

tools/perf/util/evlist.h

···
 {
 	return evlist__add_aux_dummy(evlist, true);
 }
+struct evsel *evlist__add_sched_switch(struct evlist *evlist, bool system_wide);
 
 int evlist__add_sb_event(struct evlist *evlist, struct perf_event_attr *attr,
 			 evsel__sb_cb_t cb, void *data);