Use per-agent locks and GWeakRefs in callbacks from timeout sources

Work on libnice's bug #1 in Gitlab. This work is composed of multiple
merged parts:

- "Global lock contention removed"
Phabricator D1900: https://phabricator.freedesktop.org/D1900
By @nifigase
Opened in GitLab as Merge Request !12

- "agent: properly handle NiceAgent ref in callbacks from timeout
sources"
Phabricator D1898: https://phabricator.freedesktop.org/D1898
By @mparis
This patch was itself based upon a previous version of the work done in
D1900. After the switch of hosting, it got lost.

On top of these, additions to follow some review comments from @ocrete:
- https://phabricator.freedesktop.org/D1900#40412
- https://phabricator.freedesktop.org/D1898#39332

10 files changed, 281 insertions, 325 deletions

diff --git a/agent/agent-priv.h b/agent/agent-priv.h
index 7269be0..bf67eb5 100644
--- a/agent/agent-priv.h
+++ b/agent/agent-priv.h
@@ -138,6 +138,8 @@ struct _NiceAgent
 {
   GObject parent;                 /* gobject pointer */
 
+  GMutex agent_mutex;             /* Mutex used for thread-safe lib */
+
   gboolean full_mode;             /* property: full-mode */
   gchar *stun_server_ip;          /* property: STUN server IP */
   guint stun_server_port;         /* property: STUN server port */
@@ -208,8 +210,8 @@ NiceStream *agent_find_stream (NiceAgent *agent, guint stream_id);
 void agent_gathering_done (NiceAgent *agent);
 void agent_signal_gathering_done (NiceAgent *agent);
 
-void agent_lock (void);
-void agent_unlock (void);
+void agent_lock (NiceAgent *agent);
+void agent_unlock (NiceAgent *agent);
 void agent_unlock_and_emit (NiceAgent *agent);
 
 void agent_signal_new_selected_pair (
@@ -235,8 +237,14 @@ void agent_signal_initial_binding_request_received (NiceAgent *agent, NiceStream
 
 guint64 agent_candidate_pair_priority (NiceAgent *agent, NiceCandidate *local, NiceCandidate *remote);
 
+typedef gboolean (*NiceTimeoutLockedCallback)(NiceAgent *agent,
+    gpointer user_data);
 void agent_timeout_add_with_context (NiceAgent *agent, GSource **out,
-    const gchar *name, guint interval, GSourceFunc function, gpointer data);
+    const gchar *name, guint interval, NiceTimeoutLockedCallback function,
+    gpointer data);
+void agent_timeout_add_seconds_with_context (NiceAgent *agent, GSource **out,
+    const gchar *name, guint interval, NiceTimeoutLockedCallback function,
+    gpointer data);
 
 StunUsageIceCompatibility agent_to_ice_compatibility (NiceAgent *agent);
 StunUsageTurnCompatibility agent_to_turn_compatibility (NiceAgent *agent);
diff --git a/agent/agent.c b/agent/agent.c
index db3067e..7f444b9 100644
--- a/agent/agent.c
+++ b/agent/agent.c
@@ -140,8 +140,6 @@ enum
 
 static guint signals[N_SIGNALS];
 
-static GMutex agent_mutex;    /* Mutex used for thread-safe lib */
-
 static void priv_stop_upnp (NiceAgent *agent);
 
 static void pseudo_tcp_socket_opened (PseudoTcpSocket *sock, gpointer user_data);
@@ -159,14 +157,14 @@ static void nice_agent_get_property (GObject *object,
 static void nice_agent_set_property (GObject *object,
   guint property_id, const GValue *value, GParamSpec *pspec);
 
-void agent_lock (void)
+void agent_lock (NiceAgent *agent)
 {
-  g_mutex_lock (&agent_mutex);
+  g_mutex_lock (&agent->agent_mutex);
 }
 
-void agent_unlock (void)
+void agent_unlock (NiceAgent *agent)
 {
-  g_mutex_unlock (&agent_mutex);
+  g_mutex_unlock (&agent->agent_mutex);
 }
 
 static GType _nice_agent_stream_ids_get_type (void);
@@ -208,7 +206,7 @@ agent_unlock_and_emit (NiceAgent *agent)
   queue = agent->pending_signals;
   g_queue_init (&agent->pending_signals);
 
-  agent_unlock ();
+  agent_unlock (agent);
 
   while ((sig = g_queue_pop_head (&queue))) {
     g_signal_emitv (sig->params, sig->signal_id, 0, NULL);
@@ -1185,6 +1183,8 @@ nice_agent_init (NiceAgent *agent)
   priv_generate_tie_breaker (agent);
 
   g_queue_init (&agent->pending_signals);
+
+  g_mutex_init (&agent->agent_mutex);
 }
 
 
@@ -1241,7 +1241,7 @@ nice_agent_get_property (
 {
   NiceAgent *agent = NICE_AGENT (object);
 
-  agent_lock();
+  agent_lock (agent);
 
   switch (property_id)
     {
@@ -1441,7 +1441,7 @@ nice_agent_set_property (
 {
   NiceAgent *agent = NICE_AGENT (object);
 
-  agent_lock();
+  agent_lock (agent);
 
   switch (property_id)
     {
@@ -1977,29 +1977,17 @@ pseudo_tcp_socket_write_packet (PseudoTcpSocket *psocket,
 
 
 static gboolean
-notify_pseudo_tcp_socket_clock (gpointer user_data)
+notify_pseudo_tcp_socket_clock_agent_locked (NiceAgent *agent,
+    gpointer user_data)
 {
   NiceComponent *component = user_data;
   NiceStream *stream;
-  NiceAgent *agent;
-
-  agent_lock();
 
   stream = component->stream;
-  agent = component->agent;
-
-  if (g_source_is_destroyed (g_main_current_source ())) {
-    nice_debug ("Source was destroyed. "
-        "Avoided race condition in notify_pseudo_tcp_socket_clock");
-    agent_unlock ();
-    return FALSE;
-  }
 
   pseudo_tcp_socket_notify_clock (component->tcp);
   adjust_tcp_clock (agent, stream, component);
 
-  agent_unlock_and_emit (agent);
-
   return G_SOURCE_CONTINUE;
 }
 
@@ -2023,7 +2011,7 @@ adjust_tcp_clock (NiceAgent *agent, NiceStream *stream, NiceComponent *component
             interval = G_MAXINT;
           agent_timeout_add_with_context (agent, &component->tcp_clock,
               "Pseudo-TCP clock", interval,
-              notify_pseudo_tcp_socket_clock, component);
+              notify_pseudo_tcp_socket_clock_agent_locked, component);
         }
       }
     } else {
@@ -2042,13 +2030,13 @@ _tcp_sock_is_writable (NiceSocket *sock, gpointer user_data)
   NiceAgent *agent = component->agent;
   NiceStream *stream = component->stream;
 
-  agent_lock ();
+  agent_lock (agent);
 
   /* Don't signal writable if the socket that has become writable is not
    * the selected pair */
   if (component->selected_pair.local == NULL ||
       !nice_socket_is_based_on (component->selected_pair.local->sockptr, sock)) {
-    agent_unlock ();
+    agent_unlock (agent);
     return;
   }
 
@@ -2614,7 +2602,7 @@ nice_agent_add_stream (
   g_return_val_if_fail (NICE_IS_AGENT (agent), 0);
   g_return_val_if_fail (n_components >= 1, 0);
 
-  agent_lock();
+  agent_lock (agent);
   stream = nice_stream_new (n_components, agent);
 
   agent->streams = g_slist_append (agent->streams, stream);
@@ -2663,7 +2651,7 @@ nice_agent_set_relay_info(NiceAgent *agent,
   g_return_val_if_fail (password, FALSE);
   g_return_val_if_fail (type <= NICE_RELAY_TYPE_TURN_TLS, FALSE);
 
-  agent_lock();
+  agent_lock (agent);
 
   if (!agent_find_component (agent, stream_id, component_id, &stream,
           &component)) {
@@ -2716,18 +2704,9 @@ nice_agent_set_relay_info(NiceAgent *agent,
 
 static void agent_check_upnp_gathering_done (NiceAgent *agent);
 
-static gboolean priv_upnp_timeout_cb (gpointer user_data)
+static gboolean priv_upnp_timeout_cb_agent_locked (NiceAgent *agent,
+    gpointer user_data)
 {
-  NiceAgent *agent = (NiceAgent*)user_data;
-
-  agent_lock();
-
-  /* If the source has been destroyed, we have already freed all mappings. */
-  if (g_source_is_destroyed (g_main_current_source ())) {
-    agent_unlock ();
-    return FALSE;
-  }
-
   nice_debug ("Agent %p : UPnP port mapping timed out", agent);
 
   /* We cannot free priv->upnp here as it may be holding mappings open which
@@ -2737,7 +2716,6 @@ static gboolean priv_upnp_timeout_cb (gpointer user_data)
 
   agent_check_upnp_gathering_done (agent);
 
-  agent_unlock_and_emit (agent);
   return FALSE;
 }
 
@@ -2772,7 +2750,7 @@ static void _upnp_mapped_external_port (GUPnPSimpleIgd *self, gchar *proto,
   NiceCandidateTransport transport;
   GSList *i, *j, *k;
 
-  agent_lock();
+  agent_lock (agent);
 
   if (agent->upnp_timer_source == NULL)
     goto end;
@@ -2842,7 +2820,7 @@ static void _upnp_error_mapping_port (GUPnPSimpleIgd *self, GError *error,
   NiceAddress localaddr;
   GSList *i;
 
-  agent_lock();
+  agent_lock (agent);
 
   nice_debug ("Agent %p : Error mapping %s:%d to %d (%d) : %s", agent, local_ip,
       local_port, external_port, error->domain, error->message);
@@ -2880,7 +2858,7 @@ nice_agent_gather_candidates (
   g_return_val_if_fail (NICE_IS_AGENT (agent), FALSE);
   g_return_val_if_fail (stream_id >= 1, FALSE);
 
-  agent_lock();
+  agent_lock (agent);
 
   stream = agent_find_stream (agent, stream_id);
   if (stream == NULL) {
@@ -3047,7 +3025,8 @@ nice_agent_gather_candidates (
         agent->upnp_mapping = g_slist_prepend (agent->upnp_mapping, base_addr);
 
         agent_timeout_add_with_context (agent, &agent->upnp_timer_source,
-            "UPnP timeout", agent->upnp_timeout, priv_upnp_timeout_cb, agent);
+            "UPnP timeout", agent->upnp_timeout,
+            priv_upnp_timeout_cb_agent_locked, agent);
       }
 #endif
 
@@ -3221,7 +3200,7 @@ nice_agent_remove_stream (
   g_return_if_fail (NICE_IS_AGENT (agent));
   g_return_if_fail (stream_id >= 1);
 
-  agent_lock();
+  agent_lock (agent);
   stream = agent_find_stream (agent, stream_id);
 
   if (!stream) {
@@ -3265,7 +3244,7 @@ nice_agent_set_port_range (NiceAgent *agent, guint stream_id, guint component_id
   g_return_if_fail (stream_id >= 1);
   g_return_if_fail (component_id >= 1);
 
-  agent_lock();
+  agent_lock (agent);
 
   if (agent_find_component (agent, stream_id, component_id, &stream,
           &component)) {
@@ -3288,7 +3267,7 @@ nice_agent_add_local_address (NiceAgent *agent, NiceAddress *addr)
   g_return_val_if_fail (NICE_IS_AGENT (agent), FALSE);
   g_return_val_if_fail (addr != NULL, FALSE);
 
-  agent_lock();
+  agent_lock (agent);
 
   dupaddr = nice_address_dup (addr);
   nice_address_set_port (dupaddr, 0);
@@ -3489,7 +3468,7 @@ nice_agent_set_remote_credentials (
   g_return_val_if_fail (NICE_IS_AGENT (agent), FALSE);
   g_return_val_if_fail (stream_id >= 1, FALSE);
 
-  agent_lock();
+  agent_lock (agent);
 
   stream = agent_find_stream (agent, stream_id);
   /* note: oddly enough, ufrag and pwd can be empty strings */
@@ -3522,7 +3501,7 @@ nice_agent_set_local_credentials (
   g_return_val_if_fail (NICE_IS_AGENT (agent), FALSE);
   g_return_val_if_fail (stream_id >= 1, FALSE);
 
-  agent_lock ();
+  agent_lock (agent);
 
   stream = agent_find_stream (agent, stream_id);
 
@@ -3553,7 +3532,7 @@ nice_agent_get_local_credentials (
   g_return_val_if_fail (NICE_IS_AGENT (agent), FALSE);
   g_return_val_if_fail (stream_id >= 1, FALSE);
 
-  agent_lock();
+  agent_lock (agent);
 
   stream = agent_find_stream (agent, stream_id);
   if (stream == NULL) {
@@ -3623,7 +3602,7 @@ nice_agent_set_remote_candidates (NiceAgent *agent, guint stream_id, guint compo
 
   nice_debug ("Agent %p: set_remote_candidates %d %d", agent, stream_id, component_id);
 
-  agent_lock();
+  agent_lock (agent);
 
   if (!agent_find_component (agent, stream_id, component_id,
           &stream, &component)) {
@@ -4422,7 +4401,7 @@ nice_agent_recv_messages_blocking_or_nonblocking (NiceAgent *agent,
     }
   }
 
-  agent_lock ();
+  agent_lock (agent);
 
   if (!agent_find_component (agent, stream_id, component_id,
           &stream, &component)) {
@@ -4516,9 +4495,9 @@ nice_agent_recv_messages_blocking_or_nonblocking (NiceAgent *agent,
     memcpy (&prev_recv_messages_iter, &component->recv_messages_iter,
         sizeof (NiceInputMessageIter));
 
-    agent_unlock ();
+    agent_unlock (agent);
     g_main_context_iteration (context, blocking);
-    agent_lock ();
+    agent_lock (agent);
 
     if (!agent_find_component (agent, stream_id, component_id,
             &stream, &component)) {
@@ -4709,7 +4688,7 @@ nice_agent_send_messages_nonblocking_internal (
 
   g_assert (n_messages == 1 || !allow_partial);
 
-  agent_lock ();
+  agent_lock (agent);
 
   if (!agent_find_component (agent, stream_id, component_id,
           &stream, &component)) {
@@ -4956,7 +4935,7 @@ nice_agent_get_local_candidates (
   g_return_val_if_fail (stream_id >= 1, NULL);
   g_return_val_if_fail (component_id >= 1, NULL);
 
-  agent_lock();
+  agent_lock (agent);
 
   if (!agent_find_component (agent, stream_id, component_id, NULL, &component)) {
     goto done;
@@ -4990,7 +4969,7 @@ nice_agent_get_remote_candidates (
   g_return_val_if_fail (stream_id >= 1, NULL);
   g_return_val_if_fail (component_id >= 1, NULL);
 
-  agent_lock();
+  agent_lock (agent);
   if (!agent_find_component (agent, stream_id, component_id, NULL, &component))
     {
       goto done;
@@ -5010,7 +4989,7 @@ nice_agent_restart (
 {
   GSList *i;
 
-  agent_lock();
+  agent_lock (agent);
 
   /* step: regenerate tie-breaker value */
   priv_generate_tie_breaker (agent);
@@ -5040,7 +5019,7 @@ nice_agent_restart_stream (
   gboolean res = FALSE;
   NiceStream *stream;
 
-  agent_lock();
+  agent_lock (agent);
 
   stream = agent_find_stream (agent, stream_id);
   if (!stream) {
@@ -5066,6 +5045,8 @@ nice_agent_dispose (GObject *object)
   QueuedSignal *sig;
   NiceAgent *agent = NICE_AGENT (object);
 
+  agent_lock (agent);
+
   /* step: free resources for the binding discovery timers */
   discovery_free (agent);
   g_assert (agent->discovery_list == NULL);
@@ -5131,6 +5112,10 @@ nice_agent_dispose (GObject *object)
     g_main_context_unref (agent->main_context);
   agent->main_context = NULL;
 
+  agent_unlock (agent);
+
+  g_mutex_clear (&agent->agent_mutex);
+
   if (G_OBJECT_CLASS (nice_agent_parent_class)->dispose)
     G_OBJECT_CLASS (nice_agent_parent_class)->dispose (object);
 
@@ -5146,20 +5131,20 @@ component_io_cb (GSocket *gsocket, GIOCondition condition, gpointer user_data)
   gboolean has_io_callback;
   gboolean remove_source = FALSE;
 
-  agent_lock ();
+  component = socket_source->component;
+  agent = component->agent;
+  stream = component->stream;
+
+  agent_lock (agent);
 
   if (g_source_is_destroyed (g_main_current_source ())) {
     /* Silently return FALSE. */
     nice_debug ("%s: source %p destroyed", G_STRFUNC, g_main_current_source ());
 
-    agent_unlock ();
+    agent_unlock (agent);
     return G_SOURCE_REMOVE;
   }
 
-  component = socket_source->component;
-  agent = component->agent;
-  stream = component->stream;
-
   g_object_ref (agent);
 
   /* Remove disconnected sockets when we get a HUP */
@@ -5176,7 +5161,7 @@ component_io_cb (GSocket *gsocket, GIOCondition condition, gpointer user_data)
     }
 
     nice_component_remove_socket (component, socket_source->socket);
-    agent_unlock ();
+    agent_unlock (agent);
     g_object_unref (agent);
     return G_SOURCE_REMOVE;
   }
@@ -5349,7 +5334,7 @@ done:
   if (component->n_recv_messages == 0 && component->recv_messages == NULL) {
     agent_unlock_and_emit (agent);
   } else {
-    agent_unlock ();
+    agent_unlock (agent);
   }
 
   g_object_unref (agent);
@@ -5380,7 +5365,7 @@ nice_agent_attach_recv (
   g_return_val_if_fail (stream_id >= 1, FALSE);
   g_return_val_if_fail (component_id >= 1, FALSE);
 
-  agent_lock();
+  agent_lock (agent);
 
   /* attach candidates */
 
@@ -5435,7 +5420,7 @@ nice_agent_set_selected_pair (
   g_return_val_if_fail (lfoundation, FALSE);
   g_return_val_if_fail (rfoundation, FALSE);
 
-  agent_lock();
+  agent_lock (agent);
 
   /* step: check that params specify an existing pair */
   if (!agent_find_component (agent, stream_id, component_id, &stream, &component)) {
@@ -5497,7 +5482,7 @@ nice_agent_get_selected_pair (NiceAgent *agent, guint stream_id,
   g_return_val_if_fail (local != NULL, FALSE);
   g_return_val_if_fail (remote != NULL, FALSE);
 
-  agent_lock();
+  agent_lock (agent);
 
   /* step: check that params specify an existing pair */
   if (!agent_find_component (agent, stream_id, component_id,
@@ -5529,7 +5514,7 @@ nice_agent_get_selected_socket (NiceAgent *agent, guint stream_id,
   g_return_val_if_fail (stream_id >= 1, NULL);
   g_return_val_if_fail (component_id >= 1, NULL);
 
-  agent_lock();
+  agent_lock (agent);
 
   /* Reliable streams are pseudotcp or MUST use RFC 4571 framing */
   if (agent->reliable)
@@ -5560,16 +5545,82 @@ nice_agent_get_selected_socket (NiceAgent *agent, guint stream_id,
   return g_socket;
 }
 
+typedef struct _TimeoutData
+{
+  GWeakRef/*<NiceAgent>*/ agent_ref;
+  NiceTimeoutLockedCallback function;
+  gpointer user_data;
+} TimeoutData;
+
+static void
+timeout_data_destroy (TimeoutData *data)
+{
+  g_weak_ref_clear (&data->agent_ref);
+  g_slice_free (TimeoutData, data);
+}
+
+static TimeoutData *
+timeout_data_new (NiceAgent *agent, NiceTimeoutLockedCallback function,
+    gpointer user_data)
+{
+  TimeoutData *data = g_slice_new0 (TimeoutData);
+
+  g_weak_ref_init (&data->agent_ref, agent);
+  data->function = function;
+  data->user_data = user_data;
+
+  return data;
+}
+
+static gboolean
+timeout_cb (gpointer user_data)
+{
+  TimeoutData *data = user_data;
+  NiceAgent *agent;
+  gboolean ret = G_SOURCE_REMOVE;
+
+  agent = g_weak_ref_get (&data->agent_ref);
+  if (agent == NULL) {
+    return G_SOURCE_REMOVE;
+  }
+
+  agent_lock (agent);
+
+  /* A race condition might happen where the mutex above waits for the lock
+   * and in the meantime another thread destroys the source.
+   * In that case, we don't need to run the function since it should
+   * have been cancelled */
+  if (g_source_is_destroyed (g_main_current_source ())) {
+    nice_debug ("Source was destroyed. Avoided race condition in timeout_cb");
+
+    agent_unlock (agent);
+    goto end;
+  }
+
+  ret = data->function (agent, data->user_data);
+
+  agent_unlock_and_emit (agent);
+
+ end:
+  g_object_unref (agent);
+
+  return ret;
+}
+
 /* Create a new timer GSource with the given @name, @interval, callback
  * @function and @data, and assign it to @out, destroying and freeing any
  * existing #GSource in @out first.
  *
  * This guarantees that a timer won’t be overwritten without being destroyed.
+ *
+ * @interval is given in milliseconds.
  */
-void agent_timeout_add_with_context (NiceAgent *agent, GSource **out,
-    const gchar *name, guint interval, GSourceFunc function, gpointer data)
+static void agent_timeout_add_with_context_internal (NiceAgent *agent,
+    GSource **out, const gchar *name, guint interval, gboolean seconds,
+    NiceTimeoutLockedCallback function, gpointer user_data)
 {
   GSource *source;
+  TimeoutData *data;
 
   g_return_if_fail (function != NULL);
   g_return_if_fail (out != NULL);
@@ -5582,16 +5633,36 @@ void agent_timeout_add_with_context (NiceAgent *agent, GSource **out,
   }
 
   /* Create the new source. */
-  source = g_timeout_source_new (interval);
+  if (seconds)
+    source = g_timeout_source_new_seconds (interval);
+  else
+    source = g_timeout_source_new (interval);
 
   g_source_set_name (source, name);
-  g_source_set_callback (source, function, data, NULL);
+  data = timeout_data_new (agent, function, user_data);
+  g_source_set_callback (source, timeout_cb, data,
+      (GDestroyNotify)timeout_data_destroy);
   g_source_attach (source, agent->main_context);
 
   /* Return it! */
   *out = source;
 }
 
+void agent_timeout_add_with_context (NiceAgent *agent,
+    GSource **out, const gchar *name, guint interval,
+    NiceTimeoutLockedCallback function, gpointer user_data)
+{
+  agent_timeout_add_with_context_internal (agent, out, name, interval, FALSE,
+      function, user_data);
+}
+
+void agent_timeout_add_seconds_with_context (NiceAgent *agent,
+    GSource **out, const gchar *name, guint interval,
+    NiceTimeoutLockedCallback function, gpointer user_data)
+{
+  agent_timeout_add_with_context_internal (agent, out, name, interval, TRUE,
+      function, user_data);
+}
 
 NICEAPI_EXPORT gboolean
 nice_agent_set_selected_remote_candidate (
@@ -5612,7 +5683,7 @@ nice_agent_set_selected_remote_candidate (
   g_return_val_if_fail (component_id != 0, FALSE);
   g_return_val_if_fail (candidate != NULL, FALSE);
 
-  agent_lock();
+  agent_lock (agent);
 
   /* step: check if the component exists*/
   if (!agent_find_component (agent, stream_id, component_id, &stream, &component)) {
@@ -5701,7 +5772,7 @@ nice_agent_set_stream_tos (NiceAgent *agent,
   g_return_if_fail (NICE_IS_AGENT (agent));
   g_return_if_fail (stream_id >= 1);
 
-  agent_lock();
+  agent_lock (agent);
 
   stream = agent_find_stream (agent, stream_id);
   if (stream == NULL)
@@ -5727,7 +5798,7 @@ nice_agent_set_software (NiceAgent *agent, const gchar *software)
 {
   g_return_if_fail (NICE_IS_AGENT (agent));
 
-  agent_lock();
+  agent_lock (agent);
 
   g_free (agent->software_attribute);
   if (software)
@@ -5762,7 +5833,7 @@ nice_agent_set_stream_name (NiceAgent *agent, guint stream_id,
         " are valid", name);
   }
 
-  agent_lock();
+  agent_lock (agent);
 
   for (i = agent->streams; i; i = i->next) {
     NiceStream *stream = i->data;
@@ -5797,7 +5868,7 @@ nice_agent_get_stream_name (NiceAgent *agent, guint stream_id)
   g_return_val_if_fail (NICE_IS_AGENT (agent), NULL);
   g_return_val_if_fail (stream_id >= 1, NULL);
 
-  agent_lock();
+  agent_lock (agent);
 
   stream = agent_find_stream (agent, stream_id);
   if (stream == NULL)
@@ -5871,7 +5942,7 @@ nice_agent_get_default_local_candidate (NiceAgent *agent,
   g_return_val_if_fail (stream_id >= 1, NULL);
   g_return_val_if_fail (component_id >= 1, NULL);
 
-  agent_lock ();
+  agent_lock (agent);
 
   /* step: check if the component exists*/
   if (!agent_find_component (agent, stream_id, component_id,
@@ -6030,7 +6101,7 @@ nice_agent_generate_local_sdp (NiceAgent *agent)
 
   g_return_val_if_fail (NICE_IS_AGENT (agent), NULL);
 
-  agent_lock();
+  agent_lock (agent);
 
   for (i = agent->streams; i; i = i->next) {
     NiceStream *stream = i->data;
@@ -6054,7 +6125,7 @@ nice_agent_generate_local_stream_sdp (NiceAgent *agent, guint stream_id,
   g_return_val_if_fail (NICE_IS_AGENT (agent), NULL);
   g_return_val_if_fail (stream_id >= 1, NULL);
 
-  agent_lock();
+  agent_lock (agent);
 
   stream = agent_find_stream (agent, stream_id);
   if (stream == NULL)
@@ -6079,7 +6150,7 @@ nice_agent_generate_local_candidate_sdp (NiceAgent *agent,
   g_return_val_if_fail (NICE_IS_AGENT (agent), NULL);
   g_return_val_if_fail (candidate != NULL, NULL);
 
-  agent_lock();
+  agent_lock (agent);
 
   sdp = g_string_new (NULL);
   _generate_candidate_sdp (agent, candidate, sdp);
@@ -6101,7 +6172,7 @@ nice_agent_parse_remote_sdp (NiceAgent *agent, const gchar *sdp)
   g_return_val_if_fail (NICE_IS_AGENT (agent), -1);
   g_return_val_if_fail (sdp != NULL, -1);
 
-  agent_lock();
+  agent_lock (agent);
 
   for (l = agent->streams; l; l = l->next) {
     NiceStream *stream = l->data;
@@ -6193,7 +6264,7 @@ nice_agent_parse_remote_stream_sdp (NiceAgent *agent, guint stream_id,
   g_return_val_if_fail (stream_id >= 1, NULL);
   g_return_val_if_fail (sdp != NULL, NULL);
 
-  agent_lock();
+  agent_lock (agent);
 
   stream = agent_find_stream (agent, stream_id);
   if (stream == NULL) {
@@ -6372,7 +6443,7 @@ nice_agent_get_io_stream (NiceAgent *agent, guint stream_id,
 
   g_return_val_if_fail (agent->reliable, NULL);
 
-  agent_lock ();
+  agent_lock (agent);
 
   if (!agent_find_component (agent, stream_id, component_id, NULL, &component))
     goto done;
@@ -6398,7 +6469,7 @@ nice_agent_forget_relays (NiceAgent *agent, guint stream_id, guint component_id)
   g_return_val_if_fail (stream_id >= 1, FALSE);
   g_return_val_if_fail (component_id >= 1, FALSE);
 
-  agent_lock ();
+  agent_lock (agent);
 
   if (!agent_find_component (agent, stream_id, component_id, NULL, &component)) {
     ret = FALSE;
@@ -6455,12 +6526,12 @@ nice_agent_get_component_state (NiceAgent *agent,
   NiceComponentState state = NICE_COMPONENT_STATE_FAILED;
   NiceComponent *component;
 
-  agent_lock ();
+  agent_lock (agent);
 
   if (agent_find_component (agent, stream_id, component_id, NULL, &component))
     state = component->state;
 
-  agent_unlock ();
+  agent_unlock (agent);
 
   return state;
 }
diff --git a/agent/component.c b/agent/component.c
index 84491e3..dfdba13 100644
--- a/agent/component.c
+++ b/agent/component.c
@@ -894,7 +894,7 @@ nice_component_emit_io_callback (NiceComponent *component,
     agent_unlock_and_emit (agent);
     io_callback (agent, stream_id,
         component_id, buf_len, (gchar *) buf, io_user_data);
-    agent_lock ();
+    agent_lock (agent);
   } else {
     IOCallbackData *data;
 
@@ -1210,7 +1210,7 @@ component_source_prepare (GSource *source, gint *timeout_)
     return FALSE;
 
   /* Needed due to accessing the Component. */
-  agent_lock ();
+  agent_lock (agent);
 
   if (!agent_find_component (agent,
           component_source->stream_id, component_source->component_id, NULL,
diff --git a/agent/conncheck.c b/agent/conncheck.c
index d267429..e2edebd 100644
--- a/agent/conncheck.c
+++ b/agent/conncheck.c
@@ -72,7 +72,8 @@ static size_t priv_create_username (NiceAgent *agent, NiceStream *stream,
     uint8_t *dest, guint dest_len, gboolean inbound);
 static size_t priv_get_password (NiceAgent *agent, NiceStream *stream,
     NiceCandidate *remote, uint8_t **password);
-static void conn_check_free_item (gpointer data);
+static void candidate_check_pair_free (NiceAgent *agent,
+    CandidateCheckPair *pair);
 static CandidateCheckPair *priv_conn_check_add_for_candidate_pair_matched (
     NiceAgent *agent, guint stream_id, NiceComponent *component,
     NiceCandidate *local, NiceCandidate *remote, NiceCheckState initial_state);
@@ -1040,7 +1041,8 @@ conn_check_stop (NiceAgent *agent)
  *
  * @return will return FALSE when no more pending timers.
  */
-static gboolean priv_conn_check_tick_unlocked (NiceAgent *agent)
+static gboolean priv_conn_check_tick_agent_locked (NiceAgent *agent,
+    gpointer user_data)
 {
   CandidateCheckPair *pair = NULL;
   gboolean keep_timer_going = FALSE;
@@ -1150,42 +1152,11 @@ static gboolean priv_conn_check_tick_unlocked (NiceAgent *agent)
   return TRUE;
 }
 
-static gboolean priv_conn_check_tick (gpointer pointer)
-{
-  gboolean ret;
-  NiceAgent *agent = pointer;
-
-  agent_lock();
-  if (g_source_is_destroyed (g_main_current_source ())) {
-    nice_debug ("Source was destroyed. "
-        "Avoided race condition in priv_conn_check_tick");
-    agent_unlock ();
-    return FALSE;
-  }
-
-  ret = priv_conn_check_tick_unlocked (agent);
-  agent_unlock_and_emit (agent);
-
-  return ret;
-}
-
-static gboolean priv_conn_keepalive_retransmissions_tick (gpointer pointer)
+static gboolean priv_conn_keepalive_retransmissions_tick_agent_locked (
+    NiceAgent *agent, gpointer pointer)
 {
   CandidatePair *pair = (CandidatePair *) pointer;
 
-  agent_lock();
-
-  /* A race condition might happen where the mutex above waits for the lock
-   * and in the meantime another thread destroys the source.
-   * In that case, we don't need to run our retransmission tick since it should
-   * have been cancelled */
-  if (g_source_is_destroyed (g_main_current_source ())) {
-    nice_debug ("Source was destroyed. "
-        "Avoided race condition in priv_conn_keepalive_retransmissions_tick");
-    agent_unlock ();
-    return FALSE;
-  }
-
   g_source_destroy (pair->keepalive.tick_source);
   g_source_unref (pair->keepalive.tick_source);
   pair->keepalive.tick_source = NULL;
@@ -1197,12 +1168,11 @@ static gboolean priv_conn_keepalive_retransmissions_tick (gpointer pointer)
         StunTransactionId id;
         NiceComponent *component;
 
-        if (!agent_find_component (pair->keepalive.agent,
+        if (!agent_find_component (agent,
                 pair->keepalive.stream_id, pair->keepalive.component_id,
                 NULL, &component)) {
           nice_debug ("Could not find stream or component in"
               " priv_conn_keepalive_retransmissions_tick");
-          agent_unlock ();
           return FALSE;
         }
 
@@ -1213,11 +1183,11 @@ static gboolean priv_conn_keepalive_retransmissions_tick (gpointer pointer)
         if (pair->keepalive.agent->media_after_tick) {
           nice_debug ("Agent %p : Keepalive conncheck timed out!! "
               "but media was received. Suspecting keepalive lost because of "
-              "network bottleneck", pair->keepalive.agent);
+              "network bottleneck", agent);
         } else {
           nice_debug ("Agent %p : Keepalive conncheck timed out!! "
-              "peer probably lost connection", pair->keepalive.agent);
-          agent_signal_component_state_change (pair->keepalive.agent,
+              "peer probably lost connection", agent);
+          agent_signal_component_state_change (agent,
               pair->keepalive.stream_id, pair->keepalive.component_id,
               NICE_COMPONENT_STATE_FAILED);
         }
@@ -1230,25 +1200,23 @@ static gboolean priv_conn_keepalive_retransmissions_tick (gpointer pointer)
           (gchar *)pair->keepalive.stun_buffer);
 
       nice_debug ("Agent %p : Retransmitting keepalive conncheck",
-          pair->keepalive.agent);
-      agent_timeout_add_with_context (pair->keepalive.agent,
+          agent);
+      agent_timeout_add_with_context (agent,
           &pair->keepalive.tick_source,
           "Pair keepalive", stun_timer_remainder (&pair->keepalive.timer),
-          priv_conn_keepalive_retransmissions_tick, pair);
+          priv_conn_keepalive_retransmissions_tick_agent_locked, pair);
       break;
     case STUN_USAGE_TIMER_RETURN_SUCCESS:
-      agent_timeout_add_with_context (pair->keepalive.agent,
+      agent_timeout_add_with_context (agent,
           &pair->keepalive.tick_source,
           "Pair keepalive", stun_timer_remainder (&pair->keepalive.timer),
-          priv_conn_keepalive_retransmissions_tick, pair);
+          priv_conn_keepalive_retransmissions_tick_agent_locked, pair);
       break;
     default:
       g_assert_not_reached();
       break;
   }
 
-
-  agent_unlock_and_emit (pair->keepalive.agent);
   return FALSE;
 }
 
@@ -1406,7 +1374,7 @@ static gboolean priv_conn_keepalive_tick_unlocked (NiceAgent *agent)
               agent_timeout_add_with_context (p->keepalive.agent,
                   &p->keepalive.tick_source, "Pair keepalive",
                   stun_timer_remainder (&p->keepalive.timer),
-                  priv_conn_keepalive_retransmissions_tick, p);
+                  priv_conn_keepalive_retransmissions_tick_agent_locked, p);
             } else {
               ++errors;
             }
@@ -1486,19 +1454,11 @@ static gboolean priv_conn_keepalive_tick_unlocked (NiceAgent *agent)
   return ret;
 }
 
-static gboolean priv_conn_keepalive_tick (gpointer pointer)
+static gboolean priv_conn_keepalive_tick_agent_locked (NiceAgent *agent,
+    gpointer pointer)
 {
-  NiceAgent *agent = pointer;
   gboolean ret;
 
-  agent_lock();
-  if (g_source_is_destroyed (g_main_current_source ())) {
-    nice_debug ("Source was destroyed. "
-        "Avoided race condition in priv_conn_keepalive_tick");
-    agent_unlock ();
-    return FALSE;
-  }
-
   ret = priv_conn_keepalive_tick_unlocked (agent);
   if (ret == FALSE) {
     if (agent->keepalive_timer_source) {
@@ -1507,36 +1467,20 @@ static gboolean priv_conn_keepalive_tick (gpointer pointer)
       agent->keepalive_timer_source = NULL;
     }
   }
-  agent_unlock_and_emit (agent);
+
   return ret;
 }
 
 
-static gboolean priv_turn_allocate_refresh_retransmissions_tick (gpointer pointer)
+static gboolean priv_turn_allocate_refresh_retransmissions_tick_agent_locked (
+    NiceAgent *agent, gpointer pointer)
 {
   CandidateRefresh *cand = (CandidateRefresh *) pointer;
-  NiceAgent *agent = NULL;
-
-  agent_lock();
-
-  /* A race condition might happen where the mutex above waits for the lock
-   * and in the meantime another thread destroys the source.
-   * In that case, we don't need to run our retransmission tick since it should
-   * have been cancelled */
-  if (g_source_is_destroyed (g_main_current_source ())) {
-    nice_debug ("Source was destroyed. "
-        "Avoided race condition in priv_turn_allocate_refresh_retransmissions_tick");
-    agent_unlock ();
-    return FALSE;
-  }
-
 
   g_source_destroy (cand->tick_source);
   g_source_unref (cand->tick_source);
   cand->tick_source = NULL;
 
-  agent = g_object_ref (cand->agent);
-
   switch (stun_timer_refresh (&cand->timer)) {
     case STUN_USAGE_TIMER_RETURN_TIMEOUT:
       {
@@ -1556,27 +1500,23 @@ static gboolean priv_turn_allocate_refresh_retransmissions_tick (gpointer pointe
 
       agent_timeout_add_with_context (agent, &cand->tick_source,
           "Candidate TURN refresh", stun_timer_remainder (&cand->timer),
-          priv_turn_allocate_refresh_retransmissions_tick, cand);
+          priv_turn_allocate_refresh_retransmissions_tick_agent_locked, cand);
       break;
     case STUN_USAGE_TIMER_RETURN_SUCCESS:
       agent_timeout_add_with_context (agent, &cand->tick_source,
           "Candidate TURN refresh", stun_timer_remainder (&cand->timer),
-          priv_turn_allocate_refresh_retransmissions_tick, cand);
+          priv_turn_allocate_refresh_retransmissions_tick_agent_locked, cand);
       break;
     default:
       /* Nothing to do. */
       break;
   }
 
-
-  agent_unlock_and_emit (agent);
-
-  g_object_unref (agent);
-
-  return FALSE;
+  return G_SOURCE_REMOVE;
 }
 
-static void priv_turn_allocate_refresh_tick_unlocked (CandidateRefresh *cand)
+static void priv_turn_allocate_refresh_tick_unlocked (NiceAgent *agent,
+    CandidateRefresh *cand)
 {
   uint8_t *username;
   gsize username_len;
@@ -1584,7 +1524,7 @@ static void priv_turn_allocate_refresh_tick_unlocked (CandidateRefresh *cand)
   gsize password_len;
   size_t buffer_len = 0;
   StunUsageTurnCompatibility turn_compat =
-      agent_to_turn_compatibility (cand->agent);
+      agent_to_turn_compatibility (agent);
 
   username = (uint8_t *)cand->candidate->turn->username;
   username_len = (size_t) strlen (cand->candidate->turn->username);
@@ -1610,7 +1550,7 @@ static void priv_turn_allocate_refresh_tick_unlocked (CandidateRefresh *cand)
     g_free (password);
   }
 
-  nice_debug ("Agent %p : Sending allocate Refresh %zd", cand->agent,
+  nice_debug ("Agent %p : Sending allocate Refresh %zd", agent,
       buffer_len);
 
   if (cand->tick_source != NULL) {
@@ -1621,16 +1561,16 @@ static void priv_turn_allocate_refresh_tick_unlocked (CandidateRefresh *cand)
 
   if (buffer_len > 0) {
     stun_timer_start (&cand->timer,
-        cand->agent->stun_initial_timeout,
-        cand->agent->stun_max_retransmissions);
+        agent->stun_initial_timeout,
+        agent->stun_max_retransmissions);
 
     /* send the refresh */
     agent_socket_send (cand->nicesock, &cand->server,
         buffer_len, (gchar *)cand->stun_buffer);
 
-    agent_timeout_add_with_context (cand->agent, &cand->tick_source,
+    agent_timeout_add_with_context (agent, &cand->tick_source,
         "Candidate TURN refresh", stun_timer_remainder (&cand->timer),
-        priv_turn_allocate_refresh_retransmissions_tick, cand);
+        priv_turn_allocate_refresh_retransmissions_tick_agent_locked, cand);
   }
 
 }
@@ -1643,22 +1583,14 @@ static void priv_turn_allocate_refresh_tick_unlocked (CandidateRefresh *cand)
  *
  * @return will return FALSE when no more pending timers.
  */
-static gboolean priv_turn_allocate_refresh_tick (gpointer pointer)
+static gboolean priv_turn_allocate_refresh_tick_agent_locked (NiceAgent *agent,
+    gpointer pointer)
 {
   CandidateRefresh *cand = (CandidateRefresh *) pointer;
 
-  agent_lock();
-  if (g_source_is_destroyed (g_main_current_source ())) {
-    nice_debug ("Source was destroyed. "
-        "Avoided race condition in priv_turn_allocate_refresh_tick");
-    agent_unlock ();
-    return FALSE;
-  }
-
-  priv_turn_allocate_refresh_tick_unlocked (cand);
-  agent_unlock_and_emit (cand->agent);
+  priv_turn_allocate_refresh_tick_unlocked (agent, cand);
 
-  return FALSE;
+  return G_SOURCE_REMOVE;
 }
 
 
@@ -1674,14 +1606,14 @@ void conn_check_schedule_next (NiceAgent *agent)
   if (agent->conncheck_timer_source == NULL) {
     agent_timeout_add_with_context (agent, &agent->conncheck_timer_source,
         "Connectivity check schedule", agent->timer_ta,
-        priv_conn_check_tick, agent);
+        priv_conn_check_tick_agent_locked, NULL);
   }
 
   /* step: also start the keepalive timer */
   if (agent->keepalive_timer_source == NULL) {
     agent_timeout_add_with_context (agent, &agent->keepalive_timer_source,
         "Connectivity keepalive timeout", NICE_AGENT_TIMER_TR_DEFAULT,
-        priv_conn_keepalive_tick, agent);
+        priv_conn_keepalive_tick_agent_locked, NULL);
   }
 }
 
@@ -1753,7 +1685,8 @@ void conn_check_remote_credentials_set(NiceAgent *agent, NiceStream *stream)
  * in ICE spec section 5.7.3 (ID-19). See also 
  * conn_check_add_for_candidate().
  */
-static GSList *priv_limit_conn_check_list_size (GSList *conncheck_list, guint upper_limit)
+static GSList *priv_limit_conn_check_list_size (NiceAgent *agent,
+    GSList *conncheck_list, guint upper_limit)
 {
   guint valid = 0;
   guint cancelled = 0;
@@ -1765,7 +1698,7 @@ static GSList *priv_limit_conn_check_list_size (GSList *conncheck_list, guint up
 
     valid++;
     if (valid > upper_limit) {
-        conn_check_free_item (pair);
+        candidate_check_pair_free (agent, pair);
         conncheck_list = g_slist_delete_link (conncheck_list, item);
         cancelled++;
     }
@@ -1859,7 +1792,6 @@ static void priv_update_check_list_failed_components (NiceAgent *agent, NiceStre
     for (i = stream->conncheck_list; i; i = i->next) {
       CandidateCheckPair *p = i->data;
 
-      g_assert (p->agent == agent);
       g_assert (p->stream_id == stream->id);
 
       if (p->component_id == (c + 1)) {
@@ -2055,7 +1987,6 @@ static CandidateCheckPair *priv_add_new_check_pair (NiceAgent *agent,
   stream = agent_find_stream (agent, stream_id);
   pair = g_slice_new0 (CandidateCheckPair);
 
-  pair->agent = agent;
   pair->stream_id = stream_id;
   pair->component_id = component->id;;
   pair->local = local;
@@ -2095,7 +2026,7 @@ static CandidateCheckPair *priv_add_new_check_pair (NiceAgent *agent,
   /* implement the hard upper limit for number of
      checks (see sect 5.7.3 ICE ID-19): */
   if (agent->compatibility == NICE_COMPATIBILITY_RFC5245) {
-    stream->conncheck_list = priv_limit_conn_check_list_size (
+    stream->conncheck_list = priv_limit_conn_check_list_size (agent,
         stream->conncheck_list, agent->max_conn_checks);
   }
 
@@ -2271,12 +2202,10 @@ int conn_check_add_for_local_candidate (NiceAgent *agent, guint stream_id, NiceC
  * Frees the CandidateCheckPair structure pointer to 
  * by 'user data'. Compatible with GDestroyNotify.
  */
-static void conn_check_free_item (gpointer data)
+static void candidate_check_pair_free (NiceAgent *agent,
+    CandidateCheckPair *pair)
 {
-  CandidateCheckPair *pair = data;
-
-  if (pair->agent)
-    priv_remove_pair_from_triggered_check_queue (pair->agent, pair);
+  priv_remove_pair_from_triggered_check_queue (agent, pair);
   priv_free_all_stun_transactions (pair, NULL);
   g_slice_free (CandidateCheckPair, pair);
 }
@@ -2291,9 +2220,13 @@ void conn_check_free (NiceAgent *agent)
     NiceStream *stream = i->data;
 
     if (stream->conncheck_list) {
+      GSList *item;
+
       nice_debug ("Agent %p, freeing conncheck_list of stream %p", agent,
           stream);
-      g_slist_free_full (stream->conncheck_list, conn_check_free_item);
+      for (item = stream->conncheck_list; item; item = item->next)
+        candidate_check_pair_free (agent, item->data);
+      g_slist_free (stream->conncheck_list);
       stream->conncheck_list = NULL;
     }
   }
@@ -2313,9 +2246,13 @@ void conn_check_prune_stream (NiceAgent *agent, NiceStream *stream)
   gboolean keep_going = FALSE;
 
   if (stream->conncheck_list) {
+    GSList *item;
+
     nice_debug ("Agent %p, freeing conncheck_list of stream %p", agent, stream);
 
-    g_slist_free_full (stream->conncheck_list, conn_check_free_item);
+    for (item = stream->conncheck_list; item; item = item->next)
+      candidate_check_pair_free (agent, item->data);
+    g_slist_free (stream->conncheck_list);
     stream->conncheck_list = NULL;
   }
 
@@ -2725,7 +2662,7 @@ static guint priv_prune_pending_checks (NiceAgent *agent, NiceStream *stream, gu
     if (p->component_id == component_id) {
       if (p->state == NICE_CHECK_FROZEN || p->state == NICE_CHECK_WAITING) {
         nice_debug ("Agent %p : pair %p removed.", agent, p);
-	conn_check_free_item (p);
+        candidate_check_pair_free (agent, p);
         stream->conncheck_list = g_slist_delete_link(stream->conncheck_list, i);
       }
 
@@ -2972,7 +2909,6 @@ static CandidateCheckPair *priv_add_peer_reflexive_pair (NiceAgent *agent, guint
   CandidateCheckPair *pair = g_slice_new0 (CandidateCheckPair);
   NiceStream *stream = agent_find_stream (agent, stream_id);
 
-  pair->agent = agent;
   pair->stream_id = stream_id;
   pair->component_id = component->id;;
   pair->local = local_cand;
@@ -3480,9 +3416,10 @@ priv_add_new_turn_refresh (CandidateDiscovery *cdisco, NiceCandidate *relay_cand
 
   /* step: also start the refresh timer */
   /* refresh should be sent 1 minute before it expires */
-  agent_timeout_add_with_context (agent, &cand->timer_source,
+  agent_timeout_add_seconds_with_context (agent, &cand->timer_source,
       "Candidate TURN refresh",
-      (lifetime - 60) * 1000, priv_turn_allocate_refresh_tick, cand);
+      lifetime - 60, priv_turn_allocate_refresh_tick_agent_locked,
+      cand);
 
   nice_debug ("timer source is : %p", cand->timer_source);
 
@@ -3791,9 +3728,10 @@ static gboolean priv_map_reply_to_relay_refresh (NiceAgent *agent, StunMessage *
             agent, cand, (int)res);
         if (res == STUN_USAGE_TURN_RETURN_RELAY_SUCCESS) {
           /* refresh should be sent 1 minute before it expires */
-          agent_timeout_add_with_context (cand->agent, &cand->timer_source,
-              "Candidate TURN refresh", (lifetime - 60) * 1000,
-              priv_turn_allocate_refresh_tick, cand);
+          agent_timeout_add_seconds_with_context (cand->agent,
+              &cand->timer_source,
+              "Candidate TURN refresh", lifetime - 60,
+              priv_turn_allocate_refresh_tick_agent_locked, cand);
 
           g_source_destroy (cand->tick_source);
           g_source_unref (cand->tick_source);
@@ -3827,7 +3765,7 @@ static gboolean priv_map_reply_to_relay_refresh (NiceAgent *agent, StunMessage *
                   stun_message_length (resp));
               cand->stun_resp_msg.buffer = cand->stun_resp_buffer;
               cand->stun_resp_msg.buffer_len = sizeof(cand->stun_resp_buffer);
-              priv_turn_allocate_refresh_tick_unlocked (cand);
+              priv_turn_allocate_refresh_tick_unlocked (agent, cand);
             } else {
               /* case: a real unauthorized error */
               refresh_cancel (cand);
@@ -4352,7 +4290,7 @@ conn_check_prune_socket (NiceAgent *agent, NiceStream *stream, NiceComponent *co
       nice_debug ("Agent %p : Retransmissions failed, giving up on pair %p",
           agent, p);
       candidate_check_pair_fail (stream, agent, p);
-      conn_check_free_item (p);
+      candidate_check_pair_free (agent, p);
       stream->conncheck_list = g_slist_delete_link (stream->conncheck_list, l);
     }
 
diff --git a/agent/conncheck.h b/agent/conncheck.h
index 8cfe2d6..2e4bc45 100644
--- a/agent/conncheck.h
+++ b/agent/conncheck.h
@@ -83,7 +83,6 @@ struct _StunTransaction
 
 struct _CandidateCheckPair
 {
-  NiceAgent *agent;         /* back pointer to owner */
   guint stream_id;
   guint component_id;
   NiceCandidate *local;
diff --git a/agent/discovery.c b/agent/discovery.c
index 30a9539..ef27346 100644
--- a/agent/discovery.c
+++ b/agent/discovery.c
@@ -998,10 +998,9 @@ NiceCandidate *discovery_learn_remote_peer_reflexive_candidate (
  *
  * @return will return FALSE when no more pending timers.
  */
-static gboolean priv_discovery_tick_unlocked (gpointer pointer)
+static gboolean priv_discovery_tick_unlocked (NiceAgent *agent)
 {
   CandidateDiscovery *cand;
-  NiceAgent *agent = pointer;
   GSList *i;
   int not_done = 0; /* note: track whether to continue timer */
   size_t buffer_len = 0;
@@ -1183,20 +1182,12 @@ static gboolean priv_discovery_tick_unlocked (gpointer pointer)
   return TRUE;
 }
 
-static gboolean priv_discovery_tick (gpointer pointer)
+static gboolean priv_discovery_tick_agent_locked (NiceAgent *agent,
+    gpointer pointer)
 {
-  NiceAgent *agent = pointer;
   gboolean ret;
 
-  agent_lock();
-  if (g_source_is_destroyed (g_main_current_source ())) {
-    nice_debug ("Source was destroyed. "
-        "Avoided race condition in priv_discovery_tick");
-    agent_unlock ();
-    return FALSE;
-  }
-
-  ret = priv_discovery_tick_unlocked (pointer);
+  ret = priv_discovery_tick_unlocked (agent);
   if (ret == FALSE) {
     if (agent->discovery_timer_source != NULL) {
       g_source_destroy (agent->discovery_timer_source);
@@ -1204,7 +1195,6 @@ static gboolean priv_discovery_tick (gpointer pointer)
       agent->discovery_timer_source = NULL;
     }
   }
-  agent_unlock_and_emit (agent);
 
   return ret;
 }
@@ -1227,7 +1217,7 @@ void discovery_schedule (NiceAgent *agent)
       if (res == TRUE) {
         agent_timeout_add_with_context (agent, &agent->discovery_timer_source,
             "Candidate discovery tick", agent->timer_ta,
-            priv_discovery_tick, agent);
+            priv_discovery_tick_agent_locked, NULL);
       }
     }
   }
diff --git a/agent/inputstream.c b/agent/inputstream.c
index 58a4a0d..eafac1b 100644
--- a/agent/inputstream.c
+++ b/agent/inputstream.c
@@ -341,7 +341,7 @@ nice_input_stream_close (GInputStream *stream, GCancellable *cancellable,
   if (agent == NULL)
     return TRUE;
 
-  agent_lock ();
+  agent_lock (agent);
 
   /* Shut down the read side of the pseudo-TCP stream, if it still exists. */
   if (agent_find_component (agent, priv->stream_id, priv->component_id,
@@ -350,7 +350,7 @@ nice_input_stream_close (GInputStream *stream, GCancellable *cancellable,
     pseudo_tcp_socket_shutdown (component->tcp, PSEUDO_TCP_SHUTDOWN_RD);
   }
 
-  agent_unlock ();
+  agent_unlock (agent);
 
   g_object_unref (agent);
 
@@ -376,7 +376,7 @@ nice_input_stream_is_readable (GPollableInputStream *stream)
   if (agent == NULL)
     return FALSE;
 
-  agent_lock ();
+  agent_lock (agent);
 
   if (!agent_find_component (agent, priv->stream_id, priv->component_id,
           &_stream, &component)) {
@@ -405,7 +405,7 @@ nice_input_stream_is_readable (GPollableInputStream *stream)
   }
 
 done:
-  agent_unlock ();
+  agent_unlock (agent);
 
   g_object_unref (agent);
 
diff --git a/agent/outputstream.c b/agent/outputstream.c
index 391ab33..7fae413 100644
--- a/agent/outputstream.c
+++ b/agent/outputstream.c
@@ -485,7 +485,7 @@ nice_output_stream_close (GOutputStream *stream, GCancellable *cancellable,
   if (agent == NULL)
     return TRUE;
 
-  agent_lock ();
+  agent_lock (agent);
 
   /* Shut down the write side of the pseudo-TCP stream. */
   if (agent_find_component (agent, priv->stream_id, priv->component_id,
@@ -494,7 +494,7 @@ nice_output_stream_close (GOutputStream *stream, GCancellable *cancellable,
     pseudo_tcp_socket_shutdown (component->tcp, PSEUDO_TCP_SHUTDOWN_WR);
   }
 
-  agent_unlock ();
+  agent_unlock (agent);
 
   g_object_unref (agent);
 
@@ -519,7 +519,7 @@ nice_output_stream_is_writable (GPollableOutputStream *stream)
   if (agent == NULL)
     return FALSE;
 
-  agent_lock ();
+  agent_lock (agent);
 
   if (!agent_find_component (agent, priv->stream_id, priv->component_id,
           &_stream, &component)) {
@@ -540,7 +540,7 @@ nice_output_stream_is_writable (GPollableOutputStream *stream)
   }
 
 done:
-  agent_unlock ();
+  agent_unlock (agent);
 
   g_object_unref (agent);
 
@@ -618,7 +618,7 @@ nice_output_stream_create_source (GPollableOutputStream *stream,
   if (agent == NULL)
     return component_source;
 
-  agent_lock ();
+  agent_lock (agent);
 
   /* Grab the socket for this component. */
   if (!agent_find_component (agent, priv->stream_id, priv->component_id,
@@ -638,7 +638,7 @@ nice_output_stream_create_source (GPollableOutputStream *stream,
   }
 
 done:
-  agent_unlock ();
+  agent_unlock (agent);
 
   g_object_unref (agent);
 
diff --git a/socket/tcp-bsd.c b/socket/tcp-bsd.c
index 285d323..d5dd633 100644
--- a/socket/tcp-bsd.c
+++ b/socket/tcp-bsd.c
@@ -60,6 +60,7 @@
 #define TCP_NODELAY 1
 
 typedef struct {
+  GMutex mutex;
   NiceAddress remote_addr;
   GQueue send_queue;
   GMainContext *context;
@@ -101,6 +102,7 @@ nice_tcp_bsd_socket_new_from_gsock (GMainContext *ctx, GSocket *gsock,
 
   if (ctx == NULL)
     ctx = g_main_context_default ();
+  g_mutex_init (&priv->mutex);
   priv->context = g_main_context_ref (ctx);
   priv->remote_addr = *remote_addr;
   priv->error = FALSE;
@@ -227,6 +229,8 @@ socket_close (NiceSocket *sock)
   if (priv->context)
     g_main_context_unref (priv->context);
 
+  g_mutex_clear (&priv->mutex);
+
   g_slice_free(TcpPriv, sock->priv);
 }
 
@@ -424,12 +428,12 @@ socket_send_more (
   NiceSocket *sock = (NiceSocket *) data;
   TcpPriv *priv = sock->priv;
 
-  agent_lock ();
+  g_mutex_lock (&priv->mutex);
 
   if (g_source_is_destroyed (g_main_current_source ())) {
     nice_debug ("Source was destroyed. "
         "Avoided race condition in tcp-bsd.c:socket_send_more");
-    agent_unlock ();
+    g_mutex_unlock (&priv->mutex);
     return FALSE;
   }
 
@@ -441,7 +445,7 @@ socket_send_more (
     g_source_unref (priv->io_source);
     priv->io_source = NULL;
 
-    agent_unlock ();
+    g_mutex_unlock (&priv->mutex);
 
     if (priv->writable_cb)
       priv->writable_cb (sock, priv->writable_data);
@@ -449,6 +453,6 @@ socket_send_more (
     return FALSE;
   }
 
-  agent_unlock ();
+  g_mutex_unlock (&priv->mutex);
   return TRUE;
 }
diff --git a/socket/udp-turn.c b/socket/udp-turn.c
index c6bd803..466ec32 100644
--- a/socket/udp-turn.c
+++ b/socket/udp-turn.c
@@ -71,6 +71,7 @@ typedef struct {
 } ChannelBinding;
 
 typedef struct {
+  GMutex mutex;
   GMainContext *ctx;
   StunAgent agent;
   GList *channels;
@@ -144,7 +145,7 @@ static gboolean priv_send_channel_bind (UdpTurnPriv *priv,
     const NiceAddress *peer);
 static gboolean priv_add_channel_binding (UdpTurnPriv *priv,
     const NiceAddress *peer);
-static gboolean priv_forget_send_request (gpointer pointer);
+static gboolean priv_forget_send_request_agent_locked (gpointer pointer);
 static void priv_clear_permissions (UdpTurnPriv *priv);
 
 static guint
@@ -209,6 +210,7 @@ nice_udp_turn_socket_new (GMainContext *ctx, NiceAddress *addr,
         STUN_AGENT_USAGE_NO_ALIGNED_ATTRIBUTES);
   }
 
+  g_mutex_init (&priv->mutex);
   priv->channels = NULL;
   priv->current_binding = NULL;
   priv->base_socket = base_socket;
@@ -420,18 +422,16 @@ socket_recv_messages (NiceSocket *sock,
   return i;
 }
 
+/* interval is given in milliseconds */
 static GSource *
 priv_timeout_add_with_context (UdpTurnPriv *priv, guint interval,
-    gboolean seconds, GSourceFunc function, gpointer data)
+    GSourceFunc function, gpointer data)
 {
-  GSource *source;
+  GSource *source = NULL;
 
   g_return_val_if_fail (function != NULL, NULL);
 
-  if (seconds)
-    source = g_timeout_source_new_seconds (interval);
-  else
-    source = g_timeout_source_new (interval);
+  source = g_timeout_source_new (interval);
 
   g_source_set_callback (source, function, data, NULL);
   g_source_attach (source, priv->ctx);
@@ -825,7 +825,7 @@ socket_send_message (NiceSocket *sock, const NiceAddress *to,
       req->priv = priv;
       stun_message_id (&msg, req->id);
       req->source = priv_timeout_add_with_context (priv,
-          STUN_END_TIMEOUT, FALSE, priv_forget_send_request, req);
+          STUN_END_TIMEOUT, priv_forget_send_request_agent_locked, req);
       g_queue_push_tail (priv->send_requests, req);
     }
   }
@@ -962,19 +962,10 @@ socket_is_based_on (NiceSocket *sock, NiceSocket *other)
 }
 
 static gboolean
-priv_forget_send_request (gpointer pointer)
+priv_forget_send_request_agent_locked (gpointer pointer)
 {
   SendRequest *req = pointer;
 
-  agent_lock ();
-
-  if (g_source_is_destroyed (g_main_current_source ())) {
-    nice_debug ("Source was destroyed. "
-        "Avoided race condition in turn.c:priv_forget_send_request");
-    agent_unlock ();
-    return FALSE;
-  }
-
   stun_agent_forget_transaction (&req->priv->agent, req->id);
 
   g_queue_remove (req->priv->send_requests, req);
@@ -983,8 +974,6 @@ priv_forget_send_request (gpointer pointer)
   g_source_unref (req->source);
   req->source = NULL;
 
-  agent_unlock ();
-
   g_slice_free (SendRequest, req);
 
   return FALSE;
@@ -997,11 +986,11 @@ priv_permission_timeout (gpointer data)
 
   nice_debug ("Permission is about to timeout, schedule renewal");
 
-  agent_lock ();
+  g_mutex_lock (&priv->mutex);
   /* remove all permissions for this agent (the permission for the peer
      we are sending to will be renewed) */
   priv_clear_permissions (priv);
-  agent_unlock ();
+  g_mutex_unlock (&priv->mutex);
 
   return TRUE;
 }
@@ -1015,16 +1004,6 @@ priv_binding_expired_timeout (gpointer data)
 
   nice_debug ("Permission expired, refresh failed");
 
-  agent_lock ();
-
-  source = g_main_current_source ();
-  if (g_source_is_destroyed (source)) {
-    nice_debug ("Source was destroyed. "
-        "Avoided race condition in turn.c:priv_binding_expired_timeout");
-    agent_unlock ();
-    return FALSE;
-  }
-
   /* find current binding and destroy it */
   for (i = priv->channels ; i; i = i->next) {
     ChannelBinding *b = i->data;
@@ -1061,8 +1040,6 @@ priv_binding_expired_timeout (gpointer data)
     }
   }
 
-  agent_unlock ();
-
   return FALSE;
 }
 
@@ -1075,16 +1052,6 @@ priv_binding_timeout (gpointer data)
 
   nice_debug ("Permission is about to timeout, sending binding renewal");
 
-  agent_lock ();
-
-  source = g_main_current_source ();
-  if (g_source_is_destroyed (source)) {
-    nice_debug ("Source was destroyed. "
-        "Avoided race condition in turn.c:priv_binding_timeout");
-    agent_unlock ();
-    return FALSE;
-  }
-
   /* find current binding and mark it for renewal */
   for (i = priv->channels ; i; i = i->next) {
     ChannelBinding *b = i->data;
@@ -1099,7 +1066,7 @@ priv_binding_timeout (gpointer data)
 
       /* Install timer to expire the permission */
       b->timeout_source = priv_timeout_add_with_context (priv,
-          STUN_EXPIRE_TIMEOUT, TRUE, priv_binding_expired_timeout, priv);
+          STUN_EXPIRE_TIMEOUT * 1000, priv_binding_expired_timeout, priv);
 
       /* Send renewal */
       if (!priv->current_binding_msg)
@@ -1108,8 +1075,6 @@ priv_binding_timeout (gpointer data)
     }
   }
 
-  agent_unlock ();
-
   return FALSE;
 }
 
@@ -1372,8 +1337,8 @@ nice_udp_turn_socket_parse_recv (NiceSocket *sock, NiceSocket **from_sock,
                 }
                 /* Install timer to schedule refresh of the permission */
                 binding->timeout_source =
-                    priv_timeout_add_with_context (priv, STUN_BINDING_TIMEOUT,
-                        TRUE, priv_binding_timeout, priv);
+                    priv_timeout_add_with_context (priv,
+                    STUN_BINDING_TIMEOUT * 1000, priv_binding_timeout, priv);
               }
               priv_process_pending_bindings (priv);
             }
@@ -1463,8 +1428,9 @@ nice_udp_turn_socket_parse_recv (NiceSocket *sock, NiceSocket **from_sock,
             if (stun_message_get_class (&msg) == STUN_RESPONSE &&
                 !priv->permission_timeout_source) {
               priv->permission_timeout_source =
-                  priv_timeout_add_with_context (priv, STUN_PERMISSION_TIMEOUT,
-                      TRUE, priv_permission_timeout, priv);
+                  priv_timeout_add_with_context (priv,
+                      STUN_PERMISSION_TIMEOUT * 1000, priv_permission_timeout,
+                      priv);
             }
 
             /* send enqued data */
@@ -1721,14 +1687,6 @@ priv_retransmissions_tick (gpointer pointer)
 {
   UdpTurnPriv *priv = pointer;
 
-  agent_lock ();
-  if (g_source_is_destroyed (g_main_current_source ())) {
-    nice_debug ("Source was destroyed. "
-        "Avoided race condition in turn.c:priv_retransmissions_tick");
-    agent_unlock ();
-    return FALSE;
-  }
-
   if (priv_retransmissions_tick_unlocked (priv) == FALSE) {
     if (priv->tick_source_channel_bind != NULL) {
       g_source_destroy (priv->tick_source_channel_bind);
@@ -1736,7 +1694,6 @@ priv_retransmissions_tick (gpointer pointer)
       priv->tick_source_channel_bind = NULL;
     }
   }
-  agent_unlock ();
 
   return FALSE;
 }
@@ -1746,21 +1703,11 @@ priv_retransmissions_create_permission_tick (gpointer pointer)
 {
   UdpTurnPriv *priv = pointer;
 
-  agent_lock ();
-  if (g_source_is_destroyed (g_main_current_source ())) {
-    nice_debug ("Source was destroyed. Avoided race condition in "
-                "turn.c:priv_retransmissions_create_permission_tick");
-    agent_unlock ();
-    return FALSE;
-  }
-
   /* This will call priv_retransmissions_create_permission_tick_unlocked() for
    * every pending permission with an expired timer and will create a new timer
    * if there are pending permissions that require it */
   priv_schedule_tick (priv);
 
-  agent_unlock ();
-
   return FALSE;
 }
 
@@ -1781,7 +1728,7 @@ priv_schedule_tick (UdpTurnPriv *priv)
     guint timeout = stun_timer_remainder (&priv->current_binding_msg->timer);
     if (timeout > 0) {
       priv->tick_source_channel_bind =
-          priv_timeout_add_with_context (priv, timeout, FALSE,
+          priv_timeout_add_with_context (priv, timeout,
               priv_retransmissions_tick, priv);
     } else {
       priv_retransmissions_tick_unlocked (priv);
@@ -1819,8 +1766,7 @@ priv_schedule_tick (UdpTurnPriv *priv)
   /* We create one timer for the minimal timeout we need */
   if (min_timeout != G_MAXUINT) {
     priv->tick_source_create_permission =
-        priv_timeout_add_with_context (priv, FALSE,
-            min_timeout,
+        priv_timeout_add_with_context (priv, min_timeout,
             priv_retransmissions_create_permission_tick,
             priv);
   }