[bpf-next 2/2] selftests/bpf: add test cases for htab map

[xiangxia.m.yue@gmail.com]

From: Tonghao Zhang <xiangxia.m.yue@gmail.com>

This testing show how to reproduce deadlock in special case.

Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: Song Liu <song@kernel.org>
Cc: Yonghong Song <yhs@fb.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Stanislav Fomichev <sdf@google.com>
Cc: Hao Luo <haoluo@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Hou Tao <houtao1@huawei.com>
---
 .../selftests/bpf/prog_tests/htab_deadlock.c  | 74 +++++++++++++++++++
 .../selftests/bpf/progs/htab_deadlock.c       | 30 ++++++++
 2 files changed, 104 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/htab_deadlock.c
 create mode 100644 tools/testing/selftests/bpf/progs/htab_deadlock.c

diff --git a/tools/testing/selftests/bpf/prog_tests/htab_deadlock.c b/tools/testing/selftests/bpf/prog_tests/htab_deadlock.c
new file mode 100644
index 000000000000..7dce4c2fe4f5
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/htab_deadlock.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 DiDi Global Inc. */
+#define _GNU_SOURCE
+#include <pthread.h>
+#include <sched.h>
+#include <test_progs.h>
+
+#include "htab_deadlock.skel.h"
+
+static int perf_event_open(void)
+{
+	struct perf_event_attr attr = {0};
+	int pfd;
+
+	/* create perf event */
+	attr.size = sizeof(attr);
+	attr.type = PERF_TYPE_HARDWARE;
+	attr.config = PERF_COUNT_HW_CPU_CYCLES;
+	attr.freq = 1;
+	attr.sample_freq = 1000;
+	pfd = syscall(__NR_perf_event_open, &attr, -1, 0, -1, PERF_FLAG_FD_CLOEXEC);
+
+	return pfd >= 0 ? pfd : -errno;
+}
+
+void test_htab_deadlock(void)
+{
+	unsigned int val = 0, key = 20;
+	struct bpf_link *link = NULL;
+	struct htab_deadlock *skel;
+	cpu_set_t cpus;
+	int err;
+	int pfd;
+	int i;
+
+	skel = htab_deadlock__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
+		return;
+
+	err = htab_deadlock__attach(skel);
+	if (!ASSERT_OK(err, "skel_attach"))
+		goto clean_skel;
+
+	/* NMI events. */
+	pfd = perf_event_open();
+	if (pfd < 0) {
+		if (pfd == -ENOENT || pfd == -EOPNOTSUPP) {
+			printf("%s:SKIP:no PERF_COUNT_HW_CPU_CYCLES\n", __func__);
+			test__skip();
+			goto clean_skel;
+		}
+		if (!ASSERT_GE(pfd, 0, "perf_event_open"))
+			goto clean_skel;
+	}
+
+	link = bpf_program__attach_perf_event(skel->progs.bpf_perf_event, pfd);
+	if (!ASSERT_OK_PTR(link, "attach_perf_event"))
+		goto clean_pfd;
+
+	/* Pinned on CPU 0 */
+	CPU_ZERO(&cpus);
+	CPU_SET(0, &cpus);
+	pthread_setaffinity_np(pthread_self(), sizeof(cpus), &cpus);
+
+	for (i = 0; i < 100000; i++)
+		bpf_map_update_elem(bpf_map__fd(skel->maps.htab),
+				    &key, &val, BPF_ANY);
+
+	bpf_link__destroy(link);
+clean_pfd:
+	close(pfd);
+clean_skel:
+	htab_deadlock__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/htab_deadlock.c b/tools/testing/selftests/bpf/progs/htab_deadlock.c
new file mode 100644
index 000000000000..c4bd1567f882
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/htab_deadlock.c
@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 DiDi Global Inc. */
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(max_entries, 2);
+	__uint(map_flags, BPF_F_ZERO_SEED);
+	__uint(key_size, sizeof(unsigned int));
+	__uint(value_size, sizeof(unsigned int));
+} htab SEC(".maps");
+
+SEC("fentry/nmi_handle")
+int bpf_nmi_handle(struct pt_regs *regs)
+{
+	unsigned int val = 0, key = 4;
+
+	bpf_map_update_elem(&htab, &key, &val, BPF_ANY);
+	return 0;
+}
+
+SEC("perf_event")
+int bpf_perf_event(struct pt_regs *regs)
+{
+	return 0;
+}
-- 
2.27.0