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Date: Mon, 23 Sep 2019 09:41:05 -0700 From: Andrii Nakryiko <andrii.nakryiko@...il.com> To: Stanislav Fomichev <sdf@...ichev.me> Cc: Stanislav Fomichev <sdf@...gle.com>, Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>, "David S. Miller" <davem@...emloft.net>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net> Subject: Re: [PATCH bpf] selftests/bpf: test_progs: fix client/server race in tcp_rtt On Mon, Sep 23, 2019 at 8:38 AM Stanislav Fomichev <sdf@...ichev.me> wrote: > > On 09/22, Andrii Nakryiko wrote: > > On Sun, Sep 22, 2019 at 12:10 PM Stanislav Fomichev <sdf@...gle.com> 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@...gle.com> > > > --- > > > 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? > Good point. How about I do the same thing I do in sockopt_inherit tests: > https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/tree/tools/testing/selftests/bpf/prog_tests/sockopt_inherit.c#n73 > > err = listen() > pthread_cond_signal() > if (CHECK_FAIL(err)) { > return; > } > > Should fix the problem of getting stuck forever without any timeouts. > I'll send a v2 later today. Sounds good. > > > > + > > > CHECK_FAIL(run_test(cgroup_fd, server_fd)); > > > close(server_fd); > > > close_cgroup_fd: > > > -- > > > 2.23.0.351.gc4317032e6-goog > > >
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