perf test: Add 'thloop' test workload

The thloop is similar to noploop but runs in two threads.  This is
needed to verify perf record --per-thread to handle multi-threaded
programs properly.

  $ perf test -w thloop

It also takes an optional argument to specify runtime in seconds
(default: 1).

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Cc: German Gomez <german.gomez@arm.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Zhengjun Xing <zhengjun.xing@linux.intel.com>
Link: https://lore.kernel.org/r/20221116233854.1596378-4-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/builtin-test.c

@@ -120,6 +120,7 @@ static struct test_suite **tests[] = {
 
 static struct test_workload *workloads[] = {
 	&workload__noploop,
+	&workload__thloop,
 };
 
 static int num_subtests(const struct test_suite *t)

tools/perf/tests/tests.h

@@ -201,5 +201,6 @@ struct test_workload workload__##work = {	\
 
 /* The list of test workloads */
 DECLARE_WORKLOAD(noploop);
+DECLARE_WORKLOAD(thloop);
 
 #endif /* TESTS_H */

tools/perf/tests/workloads/Build

@@ -1,3 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0
 
 perf-y += noploop.o
+perf-y += thloop.o

tools/perf/tests/workloads/thloop.c

@@ -0,0 +1,53 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <pthread.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <unistd.h>
+#include <linux/compiler.h>
+#include "../tests.h"
+
+static volatile sig_atomic_t done;
+static volatile unsigned count;
+
+/* We want to check this symbol in perf report */
+noinline void test_loop(void);
+
+static void sighandler(int sig __maybe_unused)
+{
+	done = 1;
+}
+
+noinline void test_loop(void)
+{
+	while (!done)
+		count++;
+}
+
+static void *thfunc(void *arg)
+{
+	void (*loop_fn)(void) = arg;
+
+	loop_fn();
+	return NULL;
+}
+
+static int thloop(int argc, const char **argv)
+{
+	int sec = 1;
+	pthread_t th;
+
+	if (argc > 0)
+		sec = atoi(argv[0]);
+
+	signal(SIGINT, sighandler);
+	signal(SIGALRM, sighandler);
+	alarm(sec);
+
+	pthread_create(&th, NULL, thfunc, test_loop);
+	test_loop();
+	pthread_join(th, NULL);
+
+	return 0;
+}
+
+DEFINE_WORKLOAD(thloop);