reactor: pass fd opened in blocking mode to spawned process

* pass fds opened in blocking mode to spawned process
* do not tolerate test failures in test_spawn_input

it turns out tools like "cat" expect fd opened blocking mode. while
the pipe fds are always created in non-blocking mode. so in order to
appease these tools, let's set the fds passed to the spawned process
to blocking mode.

Fixes scylladb#1320
Signed-off-by: Jianyong Chen <baluschch@gmail.com>
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>

src/core/reactor.cc

@@ -1986,6 +1986,12 @@ reactor::spawn(std::string_view pathname,
                 std::get<pipefd_read_end>(cin_pipe).spawn_actions_add_close(&actions);
                 std::get<pipefd_write_end>(cout_pipe).spawn_actions_add_close(&actions);
                 std::get<pipefd_write_end>(cerr_pipe).spawn_actions_add_close(&actions);
+                // tools like "cat" expect a fd opened in blocking mode when performing I/O
+                int nonblocking = 0;
+                std::get<pipefd_read_end>(cin_pipe).ioctl(FIONBIO, &nonblocking);
+                std::get<pipefd_write_end>(cout_pipe).ioctl(FIONBIO, &nonblocking);
+                std::get<pipefd_write_end>(cerr_pipe).ioctl(FIONBIO, &nonblocking);
+
                 r = ::posix_spawnattr_init(&attr);
                 throw_pthread_error(r);
                 // make sure the following signals are not ignored by the child process

tests/unit/spawn_test.cc

@@ -92,7 +92,7 @@ SEASTAR_TEST_CASE(test_spawn_echo) {
     });
 }
 
-SEASTAR_TEST_CASE(test_spawn_input, *boost::unit_test::expected_failures(3)) {
+SEASTAR_TEST_CASE(test_spawn_input) {
     static const sstring text = "hello world\n";
     return spawn_process("/bin/cat").then([] (auto process) {
         auto stdin = process.stdin();