[PATCH bpf-next 12/13] tools/bpf: add a multithreaded test for map batch operations

[Yonghong Song <yhs@fb.com>]

A multithreaded test is added. Three threads repeatedly did:
  - batch update
  - batch lookup_and_delete
  - batch delete

It is totally possible each batch element operation in kernel
may find that the key, retrieved from bpf_map_get_next_key(),
may fail lookup and/or delete as some other threads in parallel
operates on the same map.

The default mode for new batch APIs is to ignore -ENOENT errors
in case of lookup and delete and move to the next element.
The test would otherwise fail if the kernel reacts as -ENOENT
as a real error and propogates it back to user space.

Signed-off-by: Yonghong Song <yhs@fb.com>
---
 .../selftests/bpf/map_tests/map_batch_mt.c    | 126 ++++++++++++++++++
 1 file changed, 126 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/map_tests/map_batch_mt.c

diff --git a/tools/testing/selftests/bpf/map_tests/map_batch_mt.c b/tools/testing/selftests/bpf/map_tests/map_batch_mt.c
new file mode 100644
index 000000000000..a0e2591d0079
--- /dev/null
+++ b/tools/testing/selftests/bpf/map_tests/map_batch_mt.c
@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <pthread.h>
+
+#include <bpf/bpf.h>
+#include <bpf/libbpf.h>
+
+#include <test_maps.h>
+
+/* Create three threads. Each thread will iteratively do:
+ *   . update constantly
+ *   . lookup and delete constantly
+ *   . delete constantly
+ * So this will make lookup and delete operations
+ * may fail as the elements may be deleted by another
+ * thread.
+ *
+ * By default, we should not see a problem as
+ * -ENOENT for bpf_map_delete_elem() and bpf_map_lookup_elem()
+ * will be ignored. But with flag, BPF_F_ENFORCE_ENOENT
+ * we may see errors.
+ */
+
+static int map_fd;
+static const __u32 max_entries = 10;
+static volatile bool stop = false;
+
+static void do_batch_update()
+{
+	int i, err, keys[max_entries], values[max_entries];
+	__u32 count;
+
+	for (i = 0; i < max_entries; i++) {
+		keys[i] = i + 1;
+		values[i] = i + 2;
+	}
+
+	while (!stop) {
+		count = max_entries;
+		err = bpf_map_update_batch(map_fd, keys, values, &count, 0, 0);
+		CHECK(err, "bpf_map_update_batch()", "error:%s\n",
+		      strerror(errno));
+	}
+}
+
+static void do_batch_delete()
+{
+	__u32 count;
+	int err;
+
+	while (!stop) {
+		count = 0;
+		err = bpf_map_delete_batch(map_fd, NULL, NULL, NULL, &count,
+					   0, 0);
+		CHECK(err, "bpf_map_delete_batch()", "error:%s\n",
+		      strerror(errno));
+	}
+}
+
+static void do_batch_lookup_and_delete()
+{
+	int err, key, keys[max_entries], values[max_entries];
+	__u32 count;
+	void *p_key;
+
+	while (!stop) {
+		p_key = &key;
+		count = max_entries;
+		err = bpf_map_lookup_and_delete_batch(map_fd, NULL, &p_key,
+						      keys, values, &count,
+						      0, 0);
+		CHECK(err, "bpf_map_lookup_and_delete_batch()", "error:%s\n",
+		      strerror(errno));
+	}
+}
+
+static void *do_work(void *arg)
+{
+	int work_index = (int)(long)arg;
+
+	if (work_index == 0)
+		do_batch_update();
+	else if (work_index == 1)
+		do_batch_delete();
+	else
+		do_batch_lookup_and_delete();
+
+	return NULL;
+}
+
+void test_map_batch_mt(void)
+{
+	struct bpf_create_map_attr xattr = {
+		.name = "hash_map",
+		.map_type = BPF_MAP_TYPE_HASH,
+		.key_size = sizeof(int),
+		.value_size = sizeof(int),
+	};
+	const int nr_threads = 3;
+	pthread_t threads[nr_threads];
+	int i, err;
+
+	xattr.max_entries = max_entries;
+	map_fd = bpf_create_map_xattr(&xattr);
+	CHECK(map_fd == -1,
+	      "bpf_create_map_xattr()", "error:%s\n", strerror(errno));
+
+	for (i = 0; i < nr_threads; i++) {
+		err = pthread_create(&threads[i], NULL, do_work,
+				     (void *)(long)i);
+		CHECK(err, "pthread_create", "error: %s\n", strerror(errno));
+	}
+
+	sleep(1);
+	stop = true;
+
+	for (i = 0; i < nr_threads; i++)
+		pthread_join(threads[i], NULL);
+
+	close(map_fd);
+
+	printf("%s:PASS\n", __func__);
+}
-- 
2.17.1