> On Jan 15, 2019, at 2:54 PM, Stanislav Fomichev <s...@google.com> wrote:
>
> 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")
> Signed-off-by: Stanislav Fomichev <s...@google.com>
Acked-by: Song Liu <songliubrav...@fb.com>
> ---
> 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 126fc624290d..25f0083a9b2e 100644
> --- a/tools/testing/selftests/bpf/test_progs.c
> +++ b/tools/testing/selftests/bpf/test_progs.c
> @@ -1188,7 +1188,9 @@ 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;
> @@ -1301,6 +1303,19 @@ 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;
> @@ -1341,7 +1356,9 @@ 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;
> @@ -1436,6 +1453,19 @@ 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;
> --
> 2.20.1.97.g81188d93c3-goog
>
