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    Subject[PATCH 5.4 068/388] selftests/bpf: De-flake test_tcpbpf
    Date
    From: Stanislav Fomichev <sdf@google.com>

    [ Upstream commit ef8c84effce3c7a0b8196fcda8f430c815ab511c ]

    It looks like BPF program that handles BPF_SOCK_OPS_STATE_CB state
    can race with the bpf_map_lookup_elem("global_map"); I sometimes
    see the failures in this test and re-running helps.

    Since we know that we expect the callback to be called 3 times (one
    time for listener socket, two times for both ends of the connection),
    let's export this number and add simple retry logic around that.

    Also, let's make EXPECT_EQ() not return on failure, but continue
    evaluating all conditions; that should make potential debugging
    easier.

    With this fix in place I don't observe the flakiness anymore.

    Signed-off-by: Stanislav Fomichev <sdf@google.com>
    Signed-off-by: Alexei Starovoitov <ast@kernel.org>
    Cc: Lawrence Brakmo <brakmo@fb.com>
    Link: https://lore.kernel.org/bpf/20191204190955.170934-1-sdf@google.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    .../selftests/bpf/progs/test_tcpbpf_kern.c | 1 +
    tools/testing/selftests/bpf/test_tcpbpf.h | 1 +
    .../testing/selftests/bpf/test_tcpbpf_user.c | 25 +++++++++++++------
    3 files changed, 20 insertions(+), 7 deletions(-)

    diff --git a/tools/testing/selftests/bpf/progs/test_tcpbpf_kern.c b/tools/testing/selftests/bpf/progs/test_tcpbpf_kern.c
    index 2e233613d1fc0..7fa4595d2b66b 100644
    --- a/tools/testing/selftests/bpf/progs/test_tcpbpf_kern.c
    +++ b/tools/testing/selftests/bpf/progs/test_tcpbpf_kern.c
    @@ -131,6 +131,7 @@ int bpf_testcb(struct bpf_sock_ops *skops)
    g.bytes_received = skops->bytes_received;
    g.bytes_acked = skops->bytes_acked;
    }
    + g.num_close_events++;
    bpf_map_update_elem(&global_map, &key, &g,
    BPF_ANY);
    }
    diff --git a/tools/testing/selftests/bpf/test_tcpbpf.h b/tools/testing/selftests/bpf/test_tcpbpf.h
    index 7bcfa62070056..6220b95cbd02c 100644
    --- a/tools/testing/selftests/bpf/test_tcpbpf.h
    +++ b/tools/testing/selftests/bpf/test_tcpbpf.h
    @@ -13,5 +13,6 @@ struct tcpbpf_globals {
    __u64 bytes_received;
    __u64 bytes_acked;
    __u32 num_listen;
    + __u32 num_close_events;
    };
    #endif
    diff --git a/tools/testing/selftests/bpf/test_tcpbpf_user.c b/tools/testing/selftests/bpf/test_tcpbpf_user.c
    index 716b4e3be5813..3ae127620463d 100644
    --- a/tools/testing/selftests/bpf/test_tcpbpf_user.c
    +++ b/tools/testing/selftests/bpf/test_tcpbpf_user.c
    @@ -16,6 +16,9 @@

    #include "test_tcpbpf.h"

    +/* 3 comes from one listening socket + both ends of the connection */
    +#define EXPECTED_CLOSE_EVENTS 3
    +
    #define EXPECT_EQ(expected, actual, fmt) \
    do { \
    if ((expected) != (actual)) { \
    @@ -23,13 +26,14 @@
    " Actual: %" fmt "\n" \
    " Expected: %" fmt "\n", \
    (actual), (expected)); \
    - goto err; \
    + ret--; \
    } \
    } while (0)

    int verify_result(const struct tcpbpf_globals *result)
    {
    __u32 expected_events;
    + int ret = 0;

    expected_events = ((1 << BPF_SOCK_OPS_TIMEOUT_INIT) |
    (1 << BPF_SOCK_OPS_RWND_INIT) |
    @@ -48,15 +52,15 @@ int verify_result(const struct tcpbpf_globals *result)
    EXPECT_EQ(0x80, result->bad_cb_test_rv, PRIu32);
    EXPECT_EQ(0, result->good_cb_test_rv, PRIu32);
    EXPECT_EQ(1, result->num_listen, PRIu32);
    + EXPECT_EQ(EXPECTED_CLOSE_EVENTS, result->num_close_events, PRIu32);

    - return 0;
    -err:
    - return -1;
    + return ret;
    }

    int verify_sockopt_result(int sock_map_fd)
    {
    __u32 key = 0;
    + int ret = 0;
    int res;
    int rv;

    @@ -69,9 +73,7 @@ int verify_sockopt_result(int sock_map_fd)
    rv = bpf_map_lookup_elem(sock_map_fd, &key, &res);
    EXPECT_EQ(0, rv, "d");
    EXPECT_EQ(1, res, "d");
    - return 0;
    -err:
    - return -1;
    + return ret;
    }

    static int bpf_find_map(const char *test, struct bpf_object *obj,
    @@ -96,6 +98,7 @@ int main(int argc, char **argv)
    int error = EXIT_FAILURE;
    struct bpf_object *obj;
    int cg_fd = -1;
    + int retry = 10;
    __u32 key = 0;
    int rv;

    @@ -134,12 +137,20 @@ int main(int argc, char **argv)
    if (sock_map_fd < 0)
    goto err;

    +retry_lookup:
    rv = bpf_map_lookup_elem(map_fd, &key, &g);
    if (rv != 0) {
    printf("FAILED: bpf_map_lookup_elem returns %d\n", rv);
    goto err;
    }

    + if (g.num_close_events != EXPECTED_CLOSE_EVENTS && retry--) {
    + printf("Unexpected number of close events (%d), retrying!\n",
    + g.num_close_events);
    + usleep(100);
    + goto retry_lookup;
    + }
    +
    if (verify_result(&g)) {
    printf("FAILED: Wrong stats\n");
    goto err;
    --
    2.25.1


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