On Sun, Sep 22, 2019 at 12:10 PM Stanislav Fomichev <sdf@xxxxxxxxxx> wrote:
>
> This is the same problem I found earlier in test_sockopt_inherit:
> there is a race between server thread doing accept() and client
> thread doing connect(). Let's explicitly synchronize them via
> pthread conditional variable.
>
> Fixes: b55873984dab ("selftests/bpf: test BPF_SOCK_OPS_RTT_CB")
> Signed-off-by: Stanislav Fomichev <sdf@xxxxxxxxxx>
> ---
> tools/testing/selftests/bpf/prog_tests/tcp_rtt.c | 16 +++++++++++++++-
> 1 file changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/tcp_rtt.c b/tools/testing/selftests/bpf/prog_tests/tcp_rtt.c
> index fdc0b3614a9e..e64058906bcd 100644
> --- a/tools/testing/selftests/bpf/prog_tests/tcp_rtt.c
> +++ b/tools/testing/selftests/bpf/prog_tests/tcp_rtt.c
> @@ -203,6 +203,9 @@ static int start_server(void)
> return fd;
> }
>
> +static pthread_mutex_t server_started_mtx = PTHREAD_MUTEX_INITIALIZER;
> +static pthread_cond_t server_started = PTHREAD_COND_INITIALIZER;
> +
> static void *server_thread(void *arg)
> {
> struct sockaddr_storage addr;
> @@ -215,6 +218,10 @@ static void *server_thread(void *arg)
> return NULL;
> }
>
> + pthread_mutex_lock(&server_started_mtx);
> + pthread_cond_signal(&server_started);
> + pthread_mutex_unlock(&server_started_mtx);
> +
> client_fd = accept(fd, (struct sockaddr *)&addr, &len);
> if (CHECK_FAIL(client_fd < 0)) {
> perror("Failed to accept client");
> @@ -248,7 +255,14 @@ void test_tcp_rtt(void)
> if (CHECK_FAIL(server_fd < 0))
> goto close_cgroup_fd;
>
> - pthread_create(&tid, NULL, server_thread, (void *)&server_fd);
> + if (CHECK_FAIL(pthread_create(&tid, NULL, server_thread,
> + (void *)&server_fd)))
> + goto close_cgroup_fd;
> +
> + pthread_mutex_lock(&server_started_mtx);
> + pthread_cond_wait(&server_started, &server_started_mtx);
> + pthread_mutex_unlock(&server_started_mtx);
If the server fails to listen, then we'll never get a signal, right?
Let's use timedwait instead to avoid test getting stuck forever in
such cases?
> +
> CHECK_FAIL(run_test(cgroup_fd, server_fd));
> close(server_fd);
> close_cgroup_fd:
> --
> 2.23.0.351.gc4317032e6-goog
>
