[RFC PATCH 3/4] selftests/rseq: Implement sched state test program

[Mathieu Desnoyers <mathieu.desnoyers@efficios.com>]

This is a small test program with can be altered to show whether the
target thread is on-cpu or not, dependending on whether it loops on
poll() or does a busy-loop.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---
 tools/testing/selftests/rseq/.gitignore       |  1 +
 tools/testing/selftests/rseq/Makefile         |  2 +-
 .../testing/selftests/rseq/sched_state_test.c | 71 +++++++++++++++++++
 3 files changed, 73 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/rseq/sched_state_test.c

diff --git a/tools/testing/selftests/rseq/.gitignore b/tools/testing/selftests/rseq/.gitignore
index 16496de5f6ce..a8db9f7a7cec 100644
--- a/tools/testing/selftests/rseq/.gitignore
+++ b/tools/testing/selftests/rseq/.gitignore
@@ -9,3 +9,4 @@ param_test_compare_twice
 param_test_mm_cid
 param_test_mm_cid_benchmark
 param_test_mm_cid_compare_twice
+sched_state_test
diff --git a/tools/testing/selftests/rseq/Makefile b/tools/testing/selftests/rseq/Makefile
index b357ba24af06..7c8f4f2be74c 100644
--- a/tools/testing/selftests/rseq/Makefile
+++ b/tools/testing/selftests/rseq/Makefile
@@ -14,7 +14,7 @@ OVERRIDE_TARGETS = 1
 
 TEST_GEN_PROGS = basic_test basic_percpu_ops_test basic_percpu_ops_mm_cid_test param_test \
 		param_test_benchmark param_test_compare_twice param_test_mm_cid \
-		param_test_mm_cid_benchmark param_test_mm_cid_compare_twice
+		param_test_mm_cid_benchmark param_test_mm_cid_compare_twice sched_state_test
 
 TEST_GEN_PROGS_EXTENDED = librseq.so
 
diff --git a/tools/testing/selftests/rseq/sched_state_test.c b/tools/testing/selftests/rseq/sched_state_test.c
new file mode 100644
index 000000000000..47aeee6d980f
--- /dev/null
+++ b/tools/testing/selftests/rseq/sched_state_test.c
@@ -0,0 +1,71 @@
+// SPDX-License-Identifier: LGPL-2.1
+
+#define _GNU_SOURCE
+#include <assert.h>
+#include <sched.h>
+#include <signal.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/time.h>
+#include <poll.h>
+
+#include "rseq.h"
+
+static struct rseq_abi *target_thread;
+
+//TODO:
+//Use rseq c.s. and rseq fence to protect access to remote thread's rseq_abi.
+
+static
+void show_sched_state(struct rseq_abi *rseq_thread)
+{
+	uint32_t state;
+
+	state = rseq_thread->sched_state;
+	printf("Target thread: ON_CPU=%d\n", !!(state & RSEQ_SCHED_STATE_ON_CPU));
+}
+
+
+static
+void *test_thread(void *arg)
+{
+	int i;
+
+	for (i = 0; i < 1000; i++) {
+		show_sched_state(target_thread);
+		(void) poll(NULL, 0, 100);
+	}
+	return NULL;
+}
+
+int main(int argc, char **argv)
+{
+	pthread_t test_thread_id;
+	int i;
+
+	if (rseq_register_current_thread()) {
+		fprintf(stderr, "Error: rseq_register_current_thread(...) failed(%d): %s\n",
+			errno, strerror(errno));
+		goto init_thread_error;
+	}
+	target_thread = rseq_get_abi();
+
+	pthread_create(&test_thread_id, NULL, test_thread, NULL);
+
+	for (i = 0; i < 1000000000; i++)
+		rseq_barrier();
+	//for (i = 0; i < 10000; i++)
+	//	(void) poll(NULL, 0, 75);
+
+	pthread_join(test_thread_id, NULL);
+
+	if (rseq_unregister_current_thread()) {
+		fprintf(stderr, "Error: rseq_unregister_current_thread(...) failed(%d): %s\n",
+			errno, strerror(errno));
+		goto init_thread_error;
+	}
+	return 0;
+
+init_thread_error:
+	return -1;
+}
-- 
2.25.1