[PATCH AUTOSEL 4.20 091/105] selftests/bpf: retry tests that expect build-id

Sasha Levin
2019-02-13T02:36:32Z

From: Stanislav Fomichev <sdf@google.com>

[ Upstream commit f67ad87ab3120e82845521b18a2b99273a340308 ]

While running test_progs in a loop I found out that I'm sometimes hitting
"Didn't find expected build ID from the map" error.

Looking at stack_map_get_build_id_offset() it seems that it is racy (by
design) and can sometimes return BPF_STACK_BUILD_ID_IP (i.e. can't trylock
current->mm->mmap_sem).

Let's retry this test a single time.

Fixes: 13790d1cc72c ("bpf: add selftest for stackmap with build_id in NMI context")
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/testing/selftests/bpf/test_progs.c | 30 ++++++++++++++++++++++++
1 file changed, 30 insertions(+)

diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c
index 2d3c04f45530..998b6cc77ed6 100644
--- a/tools/testing/selftests/bpf/test_progs.c
+++ b/tools/testing/selftests/bpf/test_progs.c
@@ -1136,7 +1136,9 @@ static void test_stacktrace_build_id(void)
int i, j;
struct bpf_stack_build_id id_offs[PERF_MAX_STACK_DEPTH];
int build_id_matches = 0;
+ int retry = 1;

+retry:
err = bpf_prog_load(file, BPF_PROG_TYPE_TRACEPOINT, &obj, &prog_fd);
if (CHECK(err, "prog_load", "err %d errno %d\n", err, errno))
goto out;
@@ -1249,6 +1251,19 @@ static void test_stacktrace_build_id(void)
previous_key = key;
} while (bpf_map_get_next_key(stackmap_fd, &previous_key, &key) == 0);

+ /* stack_map_get_build_id_offset() is racy and sometimes can return
+ * BPF_STACK_BUILD_ID_IP instead of BPF_STACK_BUILD_ID_VALID;
+ * try it one more time.
+ */
+ if (build_id_matches < 1 && retry--) {
+ ioctl(pmu_fd, PERF_EVENT_IOC_DISABLE);
+ close(pmu_fd);
+ bpf_object__close(obj);
+ printf("%s:WARN:Didn't find expected build ID from the map, retrying\n",
+ __func__);
+ goto retry;
+ }
+
if (CHECK(build_id_matches < 1, "build id match",
"Didn't find expected build ID from the map\n"))
goto disable_pmu;
@@ -1289,7 +1304,9 @@ static void test_stacktrace_build_id_nmi(void)
int i, j;
struct bpf_stack_build_id id_offs[PERF_MAX_STACK_DEPTH];
int build_id_matches = 0;
+ int retry = 1;

+retry:
err = bpf_prog_load(file, BPF_PROG_TYPE_PERF_EVENT, &obj, &prog_fd);
if (CHECK(err, "prog_load", "err %d errno %d\n", err, errno))
return;
@@ -1384,6 +1401,19 @@ static void test_stacktrace_build_id_nmi(void)
previous_key = key;
} while (bpf_map_get_next_key(stackmap_fd, &previous_key, &key) == 0);

+ /* stack_map_get_build_id_offset() is racy and sometimes can return
+ * BPF_STACK_BUILD_ID_IP instead of BPF_STACK_BUILD_ID_VALID;
+ * try it one more time.
+ */
+ if (build_id_matches < 1 && retry--) {
+ ioctl(pmu_fd, PERF_EVENT_IOC_DISABLE);
+ close(pmu_fd);
+ bpf_object__close(obj);
+ printf("%s:WARN:Didn't find expected build ID from the map, retrying\n",
+ __func__);
+ goto retry;
+ }
+
if (CHECK(build_id_matches < 1, "build id match",
"Didn't find expected build ID from the map\n"))
goto disable_pmu;
--
2.19.1