Fix: race with the viewer and readiness of streams

[lttng-tools.git] / src / bin / lttng-relayd / main.c

diff --git a/src/bin/lttng-relayd/main.c b/src/bin/lttng-relayd/main.c
index b46c1628079b05619f564cbfe9f45969674d9a59..7e5733ec8c3253432bd61dbac17b0968fefef21a 100644 (file)
--- a/src/bin/lttng-relayd/main.c
+++ b/src/bin/lttng-relayd/main.c
@@ -1147,6 +1147,70 @@ error:
        return ret;
 }
 
+/*
+ * When we have received all the streams and the metadata for a channel,
+ * we make them visible to the viewer threads.
+ */
+static
+void set_viewer_ready_flag(struct relay_command *cmd)
+{
+       struct relay_stream_recv_handle *node, *tmp_node;
+
+       cds_list_for_each_entry_safe(node, tmp_node, &cmd->recv_head, node) {
+               struct relay_stream *stream;
+
+               rcu_read_lock();
+               stream = relay_stream_find_by_id(node->id);
+               if (!stream) {
+                       /*
+                        * Stream is most probably being cleaned up by the data thread thus
+                        * simply continue to the next one.
+                        */
+                       continue;
+               }
+
+               /*
+                * If any of the streams in the list doesn't have a ctf_trace assigned,
+                * it means that we never received the metadata stream, so we have to
+                * wait until it arrives to make the streams available to the viewer.
+                */
+               if (!stream->ctf_trace) {
+                       goto end;
+               }
+
+               stream->viewer_ready = 1;
+               rcu_read_unlock();
+
+               /* Clean stream handle node. */
+               cds_list_del(&node->node);
+               free(node);
+       }
+
+end:
+       return;
+}
+
+/*
+ * Add a recv handle node to the connection recv list with the given stream
+ * handle. A new node is allocated thus must be freed when the node is deleted
+ * from the list.
+ */
+static void queue_stream_handle(uint64_t handle, struct relay_command *cmd)
+{
+       struct relay_stream_recv_handle *node;
+
+       assert(cmd);
+
+       node = zmalloc(sizeof(*node));
+       if (!node) {
+               PERROR("zmalloc queue stream handle");
+               return;
+       }
+
+       node->id = handle;
+       cds_list_add(&node->node, &cmd->recv_head);
+}
+
 /*
  * relay_add_stream: allocate a new stream for a session
  */
@@ -1239,6 +1303,13 @@ int relay_add_stream(struct lttcomm_relayd_hdr *recv_hdr,
        ctf_trace_assign(cmd->ctf_traces_ht, stream);
        stream->ctf_traces_ht = cmd->ctf_traces_ht;
 
+       /*
+        * Add the stream handle in the recv list of the connection. Once the end
+        * stream message is received, this list is emptied and streams are set
+        * with the viewer ready flag.
+        */
+       queue_stream_handle(stream->stream_handle, cmd);
+
        lttng_ht_node_init_ulong(&stream->stream_n,
                        (unsigned long) stream->stream_handle);
        lttng_ht_add_unique_ulong(relay_streams_ht,
@@ -1987,6 +2058,48 @@ end_no_session:
        return ret;
 }
 
+/*
+ * Receive the streams_sent message.
+ *
+ * Return 0 on success else a negative value.
+ */
+static
+int relay_streams_sent(struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_command *cmd)
+{
+       int ret, send_ret;
+       struct lttcomm_relayd_generic_reply reply;
+
+       assert(cmd);
+
+       DBG("Relay receiving streams_sent");
+
+       if (!cmd->session || cmd->version_check_done == 0) {
+               ERR("Trying to close a stream before version check");
+               ret = -1;
+               goto end_no_session;
+       }
+
+       /*
+        * Flag every pending stream in the connection recv list that they are
+        * ready to be used by the viewer.
+        */
+       set_viewer_ready_flag(cmd);
+
+       reply.ret_code = htobe32(LTTNG_OK);
+       send_ret = cmd->sock->ops->sendmsg(cmd->sock, &reply, sizeof(reply), 0);
+       if (send_ret < 0) {
+               ERR("Relay sending sent_stream reply");
+               ret = send_ret;
+       } else {
+               /* Success. */
+               ret = 0;
+       }
+
+end_no_session:
+       return ret;
+}
+
 /*
  * Process the commands received on the control socket
  */
@@ -2030,6 +2143,9 @@ int relay_process_control(struct lttcomm_relayd_hdr *recv_hdr,
        case RELAYD_SEND_INDEX:
                ret = relay_recv_index(recv_hdr, cmd);
                break;
+       case RELAYD_STREAMS_SENT:
+               ret = relay_streams_sent(recv_hdr, cmd);
+               break;
        case RELAYD_UPDATE_SYNC_INFO:
        default:
                ERR("Received unknown command (%u)", be32toh(recv_hdr->cmd));
@@ -2322,6 +2438,7 @@ int relay_add_connection(int fd, struct lttng_poll_event *events,
                PERROR("read relay cmd pipe");
                goto error_read;
        }
+       CDS_INIT_LIST_HEAD(&relay_connection->recv_head);
 
        /*
         * Only used by the control side and the reference is copied inside each
@@ -2373,8 +2490,17 @@ void relay_del_connection(struct lttng_ht *relay_connections_ht,
        assert(!ret);
 
        if (relay_connection->type == RELAY_CONTROL) {
+               struct relay_stream_recv_handle *node, *tmp_node;
+
                relay_delete_session(relay_connection, sessions_ht);
                lttng_ht_destroy(relay_connection->ctf_traces_ht);
+
+               /* Clean up recv list. */
+               cds_list_for_each_entry_safe(node, tmp_node,
+                               &relay_connection->recv_head, node) {
+                       cds_list_del(&node->node);
+                       free(node);
+               }
        }
 
        call_rcu(&relay_connection->rcu_node, deferred_free_connection);