Moving file descriptor blocking to libunit.

The default libunit behavior relies on blocking the recv() call for port file
descriptors, which an application may override if needed.  For external
applications, port file descriptors were toggled to blocking mode before the
exec() call.  If the exec() call failed, descriptor remained blocked, so the
process hanged while trying to read from it.

This patch moves file descriptor mode switch inside libunit.

src/nxt_application.c

@@ -1290,8 +1290,6 @@ nxt_unit_default_init(nxt_task_t *task, nxt_unit_init_t *init)
     init->ready_port.in_fd = -1;
     init->ready_port.out_fd = main_port->pair[1];
 
-    nxt_fd_blocking(task, main_port->pair[1]);
-
     init->ready_stream = my_port->process->stream;
 
     init->router_port.id.pid = router_port->pid;
@@ -1299,15 +1297,11 @@ nxt_unit_default_init(nxt_task_t *task, nxt_unit_init_t *init)
     init->router_port.in_fd = -1;
     init->router_port.out_fd = router_port->pair[1];
 
-    nxt_fd_blocking(task, router_port->pair[1]);
-
     init->read_port.id.pid = my_port->pid;
     init->read_port.id.id = my_port->id;
     init->read_port.in_fd = my_port->pair[0];
     init->read_port.out_fd = -1;
 
-    nxt_fd_blocking(task, my_port->pair[0]);
-
     init->log_fd = 2;
 
     return NXT_OK;

src/nxt_external.c

@@ -52,8 +52,6 @@ nxt_external_fd_no_cloexec(nxt_task_t *task, nxt_socket_t fd)
         return NXT_ERROR;
     }
 
-    nxt_fd_blocking(task, fd);
-
     return NXT_OK;
 }
 

src/nxt_unit.c

@@ -171,6 +171,7 @@ static int nxt_unit_port_queue_recv(nxt_unit_port_t *port,
 static int nxt_unit_app_queue_recv(nxt_unit_port_t *port,
     nxt_unit_read_buf_t *rbuf);
 nxt_inline int nxt_unit_close(int fd);
+static int nxt_unit_fd_blocking(int fd);
 
 static int nxt_unit_port_hash_add(nxt_lvlhsh_t *port_hash,
     nxt_unit_port_t *port);
@@ -413,6 +414,7 @@ nxt_unit_init(nxt_unit_init_t *init)
     }
 
     queue_fd = -1;
+    mem = MAP_FAILED;
 
     if (init->ready_port.id.pid != 0
         && init->ready_stream != 0
@@ -450,6 +452,11 @@ nxt_unit_init(nxt_unit_init_t *init)
 
     ctx = &lib->main_ctx.ctx;
 
+    rc = nxt_unit_fd_blocking(router_port.out_fd);
+    if (nxt_slow_path(rc != NXT_UNIT_OK)) {
+        goto fail;
+    }
+
     lib->router_port = nxt_unit_add_port(ctx, &router_port, NULL);
     if (nxt_slow_path(lib->router_port == NULL)) {
         nxt_unit_alert(NULL, "failed to add router_port");
@@ -473,12 +480,20 @@ nxt_unit_init(nxt_unit_init_t *init)
 
     nxt_port_queue_init(mem);
 
+    rc = nxt_unit_fd_blocking(read_port.in_fd);
+    if (nxt_slow_path(rc != NXT_UNIT_OK)) {
+        goto fail;
+    }
+
     lib->main_ctx.read_port = nxt_unit_add_port(ctx, &read_port, mem);
     if (nxt_slow_path(lib->main_ctx.read_port == NULL)) {
         nxt_unit_alert(NULL, "failed to add read_port");
 
-        munmap(mem, sizeof(nxt_port_queue_t));
+        goto fail;
+    }
 
+    rc = nxt_unit_fd_blocking(ready_port.out_fd);
+    if (nxt_slow_path(rc != NXT_UNIT_OK)) {
         goto fail;
     }
 
@@ -486,8 +501,6 @@ nxt_unit_init(nxt_unit_init_t *init)
     if (nxt_slow_path(rc != NXT_UNIT_OK)) {
         nxt_unit_alert(NULL, "failed to send READY message");
 
-        munmap(mem, sizeof(nxt_port_queue_t));
-
         goto fail;
     }
 
@@ -498,6 +511,10 @@ nxt_unit_init(nxt_unit_init_t *init)
 
 fail:
 
+    if (mem != MAP_FAILED) {
+        munmap(mem, sizeof(nxt_port_queue_t));
+    }
+
     if (queue_fd != -1) {
         nxt_unit_close(queue_fd);
     }
@@ -1064,7 +1081,6 @@ fail:
 static int
 nxt_unit_process_new_port(nxt_unit_ctx_t *ctx, nxt_unit_recv_msg_t *recv_msg)
 {
-    int                      nb;
     void                     *mem;
     nxt_unit_impl_t          *lib;
     nxt_unit_port_t          new_port, *port;
@@ -1103,13 +1119,7 @@ nxt_unit_process_new_port(nxt_unit_ctx_t *ctx, nxt_unit_recv_msg_t *recv_msg)
                    MAP_SHARED, recv_msg->fd2, 0);
 
     } else {
-        nb = 0;
+        if (nxt_slow_path(nxt_unit_fd_blocking(recv_msg->fd) != NXT_UNIT_OK)) {
-
-        if (nxt_slow_path(ioctl(recv_msg->fd, FIONBIO, &nb) == -1)) {
-            nxt_unit_alert(ctx, "#%"PRIu32": new_port: ioctl(%d, FIONBIO, 0) "
-                           "failed: %s (%d)",
-                           recv_msg->stream, recv_msg->fd, strerror(errno), errno);
-
             return NXT_UNIT_ERROR;
         }
 
@@ -5919,6 +5929,24 @@ nxt_unit_close(int fd)
 }
 
 
+static int
+nxt_unit_fd_blocking(int fd)
+{
+    int  nb;
+
+    nb = 0;
+
+    if (nxt_slow_path(ioctl(fd, FIONBIO, &nb) == -1)) {
+        nxt_unit_alert(NULL, "ioctl(%d, FIONBIO, 0) failed: %s (%d)",
+                       fd, strerror(errno), errno);
+
+        return NXT_UNIT_ERROR;
+    }
+
+    return NXT_UNIT_OK;
+}
+
+
 static nxt_int_t
 nxt_unit_port_hash_test(nxt_lvlhsh_query_t *lhq, void *data)
 {