On 12/14/22 2:38 AM, xiangxia.m.yue@xxxxxxxxx wrote:
From: Tonghao Zhang <xiangxia.m.yue@xxxxxxxxx>
This testing show how to reproduce deadlock in special case.
Signed-off-by: Tonghao Zhang <xiangxia.m.yue@xxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: Andrii Nakryiko <andrii@xxxxxxxxxx>
Cc: Martin KaFai Lau <martin.lau@xxxxxxxxx>
Cc: Song Liu <song@xxxxxxxxxx>
Cc: Yonghong Song <yhs@xxxxxx>
Cc: John Fastabend <john.fastabend@xxxxxxxxx>
Cc: KP Singh <kpsingh@xxxxxxxxxx>
Cc: Stanislav Fomichev <sdf@xxxxxxxxxx>
Cc: Hao Luo <haoluo@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Hou Tao <houtao1@xxxxxxxxxx>
---
.../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;
No need to have three lines for type 'int' variables. One line
is enough to hold all three variables.
+
+ 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++)
Please add some comments in the above loop to mention the test
expects (hopefully) duriing one of bpf_map_update_elem(), one
perf event might kick to trigger prog bpf_nmi_handle run.
+ 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");
You can use
__type(key, unsigned int);
__type(value, unsigned int);
This is more expressive.
+
+SEC("fentry/nmi_handle")
+int bpf_nmi_handle(struct pt_regs *regs)
Do we need this fentry function? Can be just put
bpf_map_update_elem() into bpf_perf_event program?
Also s390x and aarch64 failed the test due to none/incomplete trampoline
support. See bpf ci https://github.com/kernel-patches/bpf/pull/4211.
You need to add them in their corresponding deny list if this fentry
bpf program is used.
+{
+ 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;
+}
