From: Julien Desfossez <jdesfossez@efficios.com>
Date: Wed, 15 Jan 2014 16:54:38 +0000 (-0500)
Subject: Fix: notify the viewer if new streams got added
X-Git-Tag: v2.5.0-rc1~218
X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=commitdiff_plain;h=4a9daf1745ccbd2aab029206a664f39fcbd640ce

Fix: notify the viewer if new streams got added

As soon as new streams are available, the viewer must start reading
them, otherwise we risk to ignore complete streams.

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

diff --git a/src/bin/lttng-relayd/live.c b/src/bin/lttng-relayd/live.c
index 80c3da57a..1a691a849 100644
--- a/src/bin/lttng-relayd/live.c
+++ b/src/bin/lttng-relayd/live.c
@@ -1142,6 +1142,40 @@ void destroy_viewer_stream(struct relay_viewer_stream *vstream)
 	call_rcu(&vstream->rcu_node, deferred_free_viewer_stream);
 }
 
+/*
+ * Atomically check if new streams got added in the session since the last
+ * check and reset the flag to 0.
+ *
+ * Returns 1 if new streams got added, 0 if nothing changed, a negative value
+ * on error.
+ */
+static
+int check_new_streams(uint64_t session_id, struct lttng_ht *sessions_ht)
+{
+	struct lttng_ht_node_ulong *node;
+	struct lttng_ht_iter iter;
+	struct relay_session *session;
+	unsigned long current_val;
+	int ret;
+
+	lttng_ht_lookup(sessions_ht,
+			(void *)((unsigned long) session_id), &iter);
+	node = lttng_ht_iter_get_node_ulong(&iter);
+	if (node == NULL) {
+		DBG("Relay session %" PRIu64 " not found", session_id);
+		ret = -1;
+		goto error;
+	}
+
+	session = caa_container_of(node, struct relay_session, session_n);
+
+	current_val = uatomic_cmpxchg(&session->new_streams, 1, 0);
+	ret = current_val;
+
+error:
+	return ret;
+}
+
 /*
  * Send the next index for a stream.
  *
@@ -1266,6 +1300,13 @@ int viewer_get_next_index(struct relay_command *cmd,
 		viewer_index.flags |= LTTNG_VIEWER_FLAG_NEW_METADATA;
 	}
 
+	ret = check_new_streams(vstream->session_id, sessions_ht);
+	if (ret < 0) {
+		goto end_unlock;
+	} else if (ret == 1) {
+		viewer_index.flags |= LTTNG_VIEWER_FLAG_NEW_STREAM;
+	}
+
 	pthread_mutex_lock(&vstream->overwrite_lock);
 	if (vstream->abort_flag) {
 		/*
@@ -1354,7 +1395,8 @@ end:
  * Return 0 on success or else a negative value.
  */
 static
-int viewer_get_packet(struct relay_command *cmd)
+int viewer_get_packet(struct relay_command *cmd,
+		struct lttng_ht *sessions_ht)
 {
 	int ret, send_data = 0;
 	char *data = NULL;
@@ -1429,6 +1471,15 @@ int viewer_get_packet(struct relay_command *cmd)
 		goto send_reply;
 	}
 
+	ret = check_new_streams(stream->session_id, sessions_ht);
+	if (ret < 0) {
+		goto end_unlock;
+	} else if (ret == 1) {
+		reply.status = htobe32(VIEWER_GET_PACKET_ERR);
+		reply.flags |= LTTNG_VIEWER_FLAG_NEW_STREAM;
+		goto send_reply;
+	}
+
 	len = be32toh(get_packet_info.len);
 	data = zmalloc(len);
 	if (!data) {
@@ -1663,7 +1714,7 @@ int process_control(struct lttng_viewer_cmd *recv_hdr,
 		ret = viewer_get_next_index(cmd, sessions_ht);
 		break;
 	case VIEWER_GET_PACKET:
-		ret = viewer_get_packet(cmd);
+		ret = viewer_get_packet(cmd, sessions_ht);
 		break;
 	case VIEWER_GET_METADATA:
 		ret = viewer_get_metadata(cmd);
diff --git a/src/bin/lttng-relayd/lttng-relayd.h b/src/bin/lttng-relayd/lttng-relayd.h
index c08c17a4f..ab1ccd410 100644
--- a/src/bin/lttng-relayd/lttng-relayd.h
+++ b/src/bin/lttng-relayd/lttng-relayd.h
@@ -83,6 +83,11 @@ struct relay_session {
 	 */
 	uint64_t minor;
 	uint64_t major;
+	/*
+	 * Flag checked and exchanged with uatomic_cmpxchg to tell the
+	 * viewer-side if new streams got added since the last check.
+	 */
+	unsigned long new_streams;
 };
 
 /*
diff --git a/src/bin/lttng-relayd/main.c b/src/bin/lttng-relayd/main.c
index d8105e405..380b4f833 100644
--- a/src/bin/lttng-relayd/main.c
+++ b/src/bin/lttng-relayd/main.c
@@ -2128,6 +2128,11 @@ int relay_streams_sent(struct lttcomm_relayd_hdr *recv_hdr,
 	 */
 	set_viewer_ready_flag(cmd);
 
+	/*
+	 * Inform the viewer that there are new streams in the session.
+	 */
+	uatomic_set(&cmd->session->new_streams, 1);
+
 	reply.ret_code = htobe32(LTTNG_OK);
 	send_ret = cmd->sock->ops->sendmsg(cmd->sock, &reply, sizeof(reply), 0);
 	if (send_ret < 0) {