Fix: Relay daemon ownership and reference counting

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

diff --git a/src/bin/lttng-relayd/viewer-session.c b/src/bin/lttng-relayd/viewer-session.c
new file mode 100644 (file)
index 0000000..657d3fc
--- /dev/null
+++ b/src/bin/lttng-relayd/viewer-session.c
@@ -0,0 +1,177 @@
+/*
+ * Copyright (C) 2013 - Julien Desfossez <jdesfossez@efficios.com>
+ *                      David Goulet <dgoulet@efficios.com>
+ *               2015 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License, version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc., 51
+ * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#define _GNU_SOURCE
+#define _LGPL_SOURCE
+#include <common/common.h>
+#include <urcu/rculist.h>
+
+#include "lttng-relayd.h"
+#include "ctf-trace.h"
+#include "session.h"
+#include "viewer-session.h"
+#include "viewer-stream.h"
+#include "stream.h"
+
+struct relay_viewer_session *viewer_session_create(void)
+{
+       struct relay_viewer_session *vsession;
+
+       vsession = zmalloc(sizeof(*vsession));
+       if (!vsession) {
+               goto end;
+       }
+       CDS_INIT_LIST_HEAD(&vsession->session_list);
+end:
+       return vsession;
+}
+
+/* The existence of session must be guaranteed by the caller. */
+int viewer_session_attach(struct relay_viewer_session *vsession,
+               struct relay_session *session)
+{
+       int ret = 0;
+
+       /* Will not fail, as per the ownership guarantee. */
+       if (!session_get(session)) {
+               ret = -1;
+               goto end;
+       }
+       pthread_mutex_lock(&session->lock);
+       if (session->viewer_attached) {
+               ret = -1;
+       } else {
+               session->viewer_attached = true;
+       }
+
+       if (!ret) {
+               pthread_mutex_lock(&vsession->session_list_lock);
+               /* Ownership is transfered to the list. */
+               cds_list_add_rcu(&session->viewer_session_node,
+                               &vsession->session_list);
+               pthread_mutex_unlock(&vsession->session_list_lock);
+       } else {
+               /* Put our local ref. */
+               session_put(session);
+       }
+       /* Safe since we know the session exists. */
+       pthread_mutex_unlock(&session->lock);
+end:
+       return ret;
+}
+
+/* The existence of session must be guaranteed by the caller. */
+static int viewer_session_detach(struct relay_viewer_session *vsession,
+               struct relay_session *session)
+{
+       int ret = 0;
+
+       pthread_mutex_lock(&session->lock);
+       if (!session->viewer_attached) {
+               ret = -1;
+       } else {
+               session->viewer_attached = false;
+       }
+
+       if (!ret) {
+               pthread_mutex_lock(&vsession->session_list_lock);
+               cds_list_del_rcu(&session->viewer_session_node);
+               pthread_mutex_unlock(&vsession->session_list_lock);
+               /* Release reference held by the list. */
+               session_put(session);
+       }
+       /* Safe since we know the session exists. */
+       pthread_mutex_unlock(&session->lock);
+       return ret;
+}
+
+void viewer_session_destroy(struct relay_viewer_session *vsession)
+{
+       free(vsession);
+}
+
+void viewer_session_close(struct relay_viewer_session *vsession)
+{
+       struct relay_session *session;
+
+       rcu_read_lock();
+       cds_list_for_each_entry_rcu(session,
+                       &vsession->session_list, viewer_session_node) {
+               struct lttng_ht_iter iter;
+               struct relay_viewer_stream *vstream;
+
+               /*
+                * TODO: improvement: create more efficient list of
+                * vstream per session.
+                */
+               cds_lfht_for_each_entry(viewer_streams_ht->ht, &iter.iter,
+                               vstream, stream_n.node) {
+                       if (!viewer_stream_get(vstream)) {
+                               continue;
+                       }
+                       if (vstream->stream->trace->session != session) {
+                               viewer_stream_put(vstream);
+                               continue;
+                       }
+                       /* Put local reference. */
+                       viewer_stream_put(vstream);
+                       /*
+                        * We have reached one of the viewer stream's lifetime
+                        * end condition.
+                        */
+                       viewer_stream_put(vstream);
+               }
+
+               viewer_session_detach(vsession, session);
+       }
+       rcu_read_unlock();
+}
+
+/*
+ * Check if a connection is attached to a session.
+ * Return 1 if attached, 0 if not attached, a negative value on error.
+ */
+int viewer_session_is_attached(struct relay_viewer_session *vsession,
+               struct relay_session *session)
+{
+       struct relay_session *iter;
+       int found = 0;
+
+       pthread_mutex_lock(&session->lock);
+       if (!vsession) {
+               goto end;
+       }
+       if (!session->viewer_attached) {
+               goto end;
+       }
+       rcu_read_lock();
+       cds_list_for_each_entry_rcu(iter,
+                       &vsession->session_list,
+                       viewer_session_node) {
+               if (session == iter) {
+                       found = 1;
+                       goto end_rcu_unlock;
+               }
+       }
+end_rcu_unlock:
+       rcu_read_unlock();
+end:
+       pthread_mutex_unlock(&session->lock);
+       return found;
+}