Add a create_ust_stream function in ust-app.c

This helps by having a single callsite for ustctl_create_stream and
removes the need for the caller to handle FD reservation. On success,
the function sets the returned handle to the given stream.

Signed-off-by: David Goulet <dgoulet@efficios.com>

diff --git a/src/bin/lttng-sessiond/ust-app.c b/src/bin/lttng-sessiond/ust-app.c
index 22b395773b2efe922ef8f1e579fd71e07161bb04..8f7db8f2ccbda06e5584a93f332576b70a62b9a9 100644 (file)
--- a/src/bin/lttng-sessiond/ust-app.c
+++ b/src/bin/lttng-sessiond/ust-app.c
@@ -748,6 +748,52 @@ error:
        return ret;
 }
 
+/*
+ * Create stream onto the UST tracer for a given channel.
+ *
+ * Return -ENOENT if no more stream is available for this channel.
+ * On success, return 0.
+ * On error, return a negative value.
+ */
+static int create_ust_stream(struct ust_app *app,
+               struct ust_app_channel *ua_chan, struct ltt_ust_stream *stream)
+{
+       int ret;
+
+       assert(app);
+       assert(ua_chan);
+       assert(ua_chan->obj);
+       assert(stream);
+
+       health_code_update(&health_thread_cmd);
+
+       /* We are going to receive 2 fds, we need to reserve them. */
+       ret = lttng_fd_get(LTTNG_FD_APPS, 2);
+       if (ret < 0) {
+               ERR("Exhausted number of available FD on stream creation");
+               /* Just to make sure we never return -ENOENT. */
+               ret = -1;
+               goto error;
+       }
+
+       ret = ustctl_create_stream(app->sock, ua_chan->obj, &stream->obj);
+       if (ret < 0) {
+               lttng_fd_put(LTTNG_FD_APPS, 2);
+               /* Indicates that there is no more stream for that channel. */
+               if (ret != -ENOENT) {
+                       ERR("UST create metadata stream failed (ret: %d)", ret);
+               }
+               goto error;
+       }
+
+       /* Set stream handle with the returned value. */
+       stream->handle = stream->obj->handle;
+
+error:
+       health_code_update(&health_thread_cmd);
+       return ret;
+}
+
 /*
  * Create the specified channel onto the UST tracer for a UST session.
  */
@@ -2307,22 +2353,12 @@ int ust_app_start_trace(struct ltt_ust_session *usess, struct ust_app *app)
                                goto error_rcu_unlock;
                        }
 
-                       /* We are going to receive 2 fds, we need to reserve them. */
-                       ret = lttng_fd_get(LTTNG_FD_APPS, 2);
-                       if (ret < 0) {
-                               ERR("Exhausted number of available FD upon stream create");
-                               free(ustream);
-                               goto error_rcu_unlock;
-                       }
-
                        health_code_update(&health_thread_cmd);
 
-                       ret = ustctl_create_stream(app->sock, ua_chan->obj,
-                                       &ustream->obj);
+                       ret = create_ust_stream(app, ua_chan, ustream);
                        if (ret < 0) {
-                               /* Free unused memory and reset FD states. */
+                               /* Free unused memory after this point. */
                                free(ustream);
-                               lttng_fd_put(LTTNG_FD_APPS, 2);
                                if (ret == -ENOENT) {
                                        /* Got all streams. Continue normal execution. */
                                        break;
@@ -2331,7 +2367,6 @@ int ust_app_start_trace(struct ltt_ust_session *usess, struct ust_app *app)
                                ret = LTTNG_ERR_UST_STREAM_FAIL;
                                goto error_rcu_unlock;
                        }
-                       ustream->handle = ustream->obj->handle;
 
                        health_code_update(&health_thread_cmd);