Fix filter.utils.muxer: NULL dereference in logging statement
[babeltrace.git] / plugins / utils / muxer / muxer.c
index 033a0abb574cb424ce55cbbd9f05f596168c69e4..431530bb08b0ad69098859c520f0af052e6f52b5 100644 (file)
  * SOFTWARE.
  */
 
+#define BT_LOG_TAG "PLUGIN-UTILS-MUXER-FLT"
+#include "logging.h"
+
 #include <babeltrace/babeltrace-internal.h>
+#include <babeltrace/compat/uuid-internal.h>
 #include <babeltrace/ctf-ir/clock-class.h>
 #include <babeltrace/ctf-ir/event.h>
 #include <babeltrace/graph/clock-class-priority-map.h>
 #include <babeltrace/graph/component-filter.h>
 #include <babeltrace/graph/component.h>
+#include <babeltrace/graph/component-internal.h>
 #include <babeltrace/graph/notification-event.h>
 #include <babeltrace/graph/notification-inactivity.h>
 #include <babeltrace/graph/notification-iterator.h>
+#include <babeltrace/graph/notification-iterator-internal.h>
 #include <babeltrace/graph/notification.h>
 #include <babeltrace/graph/port.h>
 #include <babeltrace/graph/private-component-filter.h>
 #include <babeltrace/graph/private-connection.h>
 #include <babeltrace/graph/private-notification-iterator.h>
 #include <babeltrace/graph/private-port.h>
+#include <babeltrace/graph/connection.h>
+#include <babeltrace/graph/connection-internal.h>
+#include <babeltrace/values-internal.h>
 #include <plugins-common.h>
 #include <glib.h>
+#include <stdbool.h>
+#include <inttypes.h>
 #include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define ASSUME_ABSOLUTE_CLOCK_CLASSES_PARAM_NAME       "assume-absolute-clock-classes"
 
 struct muxer_comp {
        /* Array of struct bt_private_notification_iterator * (weak refs) */
@@ -51,14 +66,32 @@ struct muxer_comp {
        size_t available_input_ports;
        bool error;
        bool initializing_muxer_notif_iter;
+       bool assume_absolute_clock_classes;
 };
 
 struct muxer_upstream_notif_iter {
        /* Owned by this, NULL if ended */
        struct bt_notification_iterator *notif_iter;
 
-       /* Owned by this*/
-       struct bt_private_port *priv_port;
+       /*
+        * This flag is true if the upstream notification iterator's
+        * current notification must be considered for the multiplexing
+        * operations. If the upstream iterator returns
+        * BT_NOTIFICATION_ITERATOR_STATUS_AGAIN, then this object
+        * is considered invalid, because its current notification is
+        * still the previous one, but we already took it into account.
+        *
+        * The value of this flag is not important if notif_iter above
+        * is NULL (which means the upstream iterator is finished).
+        */
+       bool is_valid;
+};
+
+enum muxer_notif_iter_clock_class_expectation {
+       MUXER_NOTIF_ITER_CLOCK_CLASS_EXPECTATION_ANY = 0,
+       MUXER_NOTIF_ITER_CLOCK_CLASS_EXPECTATION_ABSOLUTE,
+       MUXER_NOTIF_ITER_CLOCK_CLASS_EXPECTATION_NOT_ABS_SPEC_UUID,
+       MUXER_NOTIF_ITER_CLOCK_CLASS_EXPECTATION_NOT_ABS_NO_UUID,
 };
 
 struct muxer_notif_iter {
@@ -72,11 +105,8 @@ struct muxer_notif_iter {
         */
        GPtrArray *muxer_upstream_notif_iters;
 
-       /* Array of struct muxer_upstream_notif_iter * (weak refs) */
-       GList *muxer_upstream_notif_iters_to_retry;
-
        /*
-        * List of "recently" connected input ports (owned by this) to
+        * List of "recently" connected input ports (weak) to
         * handle by this muxer notification iterator.
         * muxer_port_connected() adds entries to this list, and the
         * entries are removed when a notification iterator is created
@@ -88,10 +118,19 @@ struct muxer_notif_iter {
 
        /* Next thing to return by the "next" method */
        struct bt_notification_iterator_next_return next_next_return;
-       int64_t next_next_return_ts_ns;
 
        /* Last time returned in a notification */
        int64_t last_returned_ts_ns;
+
+       /* Clock class expectation state */
+       enum muxer_notif_iter_clock_class_expectation clock_class_expectation;
+
+       /*
+        * Expected clock class UUID, only valid when
+        * clock_class_expectation is
+        * MUXER_NOTIF_ITER_CLOCK_CLASS_EXPECTATION_NOT_ABS_SPEC_UUID.
+        */
+       unsigned char expected_clock_class_uuid[BABELTRACE_UUID_LEN];
 };
 
 static
@@ -102,8 +141,12 @@ void destroy_muxer_upstream_notif_iter(
                return;
        }
 
+       BT_LOGD("Destroying muxer's upstream notification iterator wrapper: "
+               "addr=%p, notif-iter-addr=%p, is-valid=%d",
+               muxer_upstream_notif_iter,
+               muxer_upstream_notif_iter->notif_iter,
+               muxer_upstream_notif_iter->is_valid);
        bt_put(muxer_upstream_notif_iter->notif_iter);
-       bt_put(muxer_upstream_notif_iter->priv_port);
        g_free(muxer_upstream_notif_iter);
 }
 
@@ -117,47 +160,31 @@ struct muxer_upstream_notif_iter *muxer_notif_iter_add_upstream_notif_iter(
                g_new0(struct muxer_upstream_notif_iter, 1);
 
        if (!muxer_upstream_notif_iter) {
+               BT_LOGE_STR("Failed to allocate one muxer's upstream notification iterator wrapper.");
                goto end;
        }
 
        muxer_upstream_notif_iter->notif_iter = bt_get(notif_iter);
-       muxer_upstream_notif_iter->priv_port = bt_get(priv_port);
+       muxer_upstream_notif_iter->is_valid = false;
        g_ptr_array_add(muxer_notif_iter->muxer_upstream_notif_iters,
                muxer_upstream_notif_iter);
+       BT_LOGD("Added muxer's upstream notification iterator wrapper: "
+               "addr=%p, muxer-notif-iter-addr=%p, notif-iter-addr=%p",
+               muxer_upstream_notif_iter, muxer_notif_iter,
+               notif_iter);
 
 end:
        return muxer_upstream_notif_iter;
 }
 
-static inline
-bool muxer_notif_iter_has_upstream_notif_iter_to_retry(
-               struct muxer_notif_iter *muxer_notif_iter)
-{
-       assert(muxer_notif_iter);
-       return muxer_notif_iter->muxer_upstream_notif_iters_to_retry != NULL;
-}
-
-static
-void muxer_notif_iter_add_upstream_notif_iter_to_retry(
-               struct muxer_notif_iter *muxer_notif_iter,
-               struct muxer_upstream_notif_iter *muxer_upstream_notif_iter)
-{
-       assert(muxer_notif_iter);
-       assert(muxer_upstream_notif_iter);
-       muxer_notif_iter->muxer_upstream_notif_iters_to_retry =
-               g_list_append(
-                       muxer_notif_iter->muxer_upstream_notif_iters_to_retry,
-                       muxer_upstream_notif_iter);
-}
-
 static
-int ensure_available_input_port(struct bt_private_component *priv_comp)
+enum bt_component_status ensure_available_input_port(
+               struct bt_private_component *priv_comp)
 {
        struct muxer_comp *muxer_comp =
                bt_private_component_get_user_data(priv_comp);
-       int ret = 0;
+       enum bt_component_status status = BT_COMPONENT_STATUS_OK;
        GString *port_name = NULL;
-       void *priv_port = NULL;
 
        assert(muxer_comp);
 
@@ -167,88 +194,142 @@ int ensure_available_input_port(struct bt_private_component *priv_comp)
 
        port_name = g_string_new("in");
        if (!port_name) {
-               ret = -1;
+               BT_LOGE_STR("Failed to allocate a GString.");
+               status = BT_COMPONENT_STATUS_NOMEM;
                goto end;
        }
 
        g_string_append_printf(port_name, "%u", muxer_comp->next_port_num);
-       priv_port = bt_private_component_filter_add_input_private_port(
-               priv_comp, port_name->str);
-       if (!priv_port) {
-               ret = -1;
+       status = bt_private_component_filter_add_input_private_port(
+               priv_comp, port_name->str, NULL, NULL);
+       if (status != BT_COMPONENT_STATUS_OK) {
+               BT_LOGE("Cannot add input port to muxer component: "
+                       "port-name=\"%s\", comp-addr=%p, status=%s",
+                       port_name->str, priv_comp,
+                       bt_component_status_string(status));
                goto end;
        }
 
        muxer_comp->available_input_ports++;
        muxer_comp->next_port_num++;
-
+       BT_LOGD("Added one input port to muxer component: "
+               "port-name=\"%s\", comp-addr=%p",
+               port_name->str, priv_comp);
 end:
        if (port_name) {
                g_string_free(port_name, TRUE);
        }
 
-       BT_PUT(priv_port);
-       return ret;
+       return status;
 }
 
 static
-int remove_default_ports(struct bt_private_component *priv_comp)
+enum bt_component_status create_output_port(
+               struct bt_private_component *priv_comp)
 {
-       struct bt_private_port *priv_port;
-       int ret = 0;
+       return bt_private_component_filter_add_output_private_port(
+               priv_comp, "out", NULL, NULL);
+}
 
-       priv_port = bt_private_component_filter_get_default_input_private_port(
-               priv_comp);
-       if (priv_port) {
-               ret = bt_private_port_remove_from_component(priv_port);
-               if (ret) {
-                       goto end;
-               }
+static
+void destroy_muxer_comp(struct muxer_comp *muxer_comp)
+{
+       if (!muxer_comp) {
+               return;
        }
 
-       bt_put(priv_port);
-       priv_port = bt_private_component_filter_get_default_output_private_port(
-               priv_comp);
-       if (priv_port) {
-               ret = bt_private_port_remove_from_component(priv_port);
-               if (ret) {
-                       goto end;
-               }
+       BT_LOGD("Destroying muxer component: muxer-comp-addr=%p, "
+               "muxer-notif-iter-count=%u", muxer_comp,
+               muxer_comp->muxer_notif_iters ?
+                       muxer_comp->muxer_notif_iters->len : 0);
+
+       if (muxer_comp->muxer_notif_iters) {
+               g_ptr_array_free(muxer_comp->muxer_notif_iters, TRUE);
        }
 
-end:
-       bt_put(priv_port);
-       return ret;
+       g_free(muxer_comp);
 }
 
 static
-int create_output_port(struct bt_private_component *priv_comp)
+struct bt_value *get_default_params(void)
 {
-       void *priv_port;
-       int ret = 0;
+       struct bt_value *params;
+       int ret;
 
-       priv_port = bt_private_component_filter_add_output_private_port(
-               priv_comp, "out");
-       if (!priv_port) {
-               ret = -1;
+       params = bt_value_map_create();
+       if (!params) {
+               BT_LOGE_STR("Cannot create a map value object.");
+               goto error;
        }
 
-       bt_put(priv_port);
-       return ret;
+       ret = bt_value_map_insert_bool(params,
+               ASSUME_ABSOLUTE_CLOCK_CLASSES_PARAM_NAME, false);
+       if (ret) {
+               BT_LOGE_STR("Cannot add boolean value to map value object.");
+               goto error;
+       }
+
+       goto end;
+
+error:
+       BT_PUT(params);
+
+end:
+       return params;
 }
 
 static
-void destroy_muxer_comp(struct muxer_comp *muxer_comp)
+int configure_muxer_comp(struct muxer_comp *muxer_comp, struct bt_value *params)
 {
-       if (!muxer_comp) {
-               return;
+       struct bt_value *default_params = NULL;
+       struct bt_value *real_params = NULL;
+       struct bt_value *assume_absolute_clock_classes = NULL;
+       int ret = 0;
+       bt_bool bool_val;
+
+       default_params = get_default_params();
+       if (!default_params) {
+               BT_LOGE("Cannot get default parameters: "
+                       "muxer-comp-addr=%p", muxer_comp);
+               goto error;
        }
 
-       if (muxer_comp->muxer_notif_iters) {
-               g_ptr_array_free(muxer_comp->muxer_notif_iters, TRUE);
+       real_params = bt_value_map_extend(default_params, params);
+       if (!real_params) {
+               BT_LOGE("Cannot extend default parameters map value: "
+                       "muxer-comp-addr=%p, def-params-addr=%p, "
+                       "params-addr=%p", muxer_comp, default_params,
+                       params);
+               goto error;
        }
 
-       g_free(muxer_comp);
+       assume_absolute_clock_classes = bt_value_map_get(real_params,
+               ASSUME_ABSOLUTE_CLOCK_CLASSES_PARAM_NAME);
+       if (!bt_value_is_bool(assume_absolute_clock_classes)) {
+               BT_LOGE("Expecting a boolean value for the `%s` parameter: "
+                       "muxer-comp-addr=%p, value-type=%s",
+                       ASSUME_ABSOLUTE_CLOCK_CLASSES_PARAM_NAME, muxer_comp,
+                       bt_value_type_string(
+                               bt_value_get_type(assume_absolute_clock_classes)));
+               goto error;
+       }
+
+       ret = bt_value_bool_get(assume_absolute_clock_classes, &bool_val);
+       assert(ret == 0);
+       muxer_comp->assume_absolute_clock_classes = (bool) bool_val;
+       BT_LOGD("Configured muxer component: muxer-comp-addr=%p, "
+               "assume-absolute-clock-classes=%d",
+               muxer_comp, muxer_comp->assume_absolute_clock_classes);
+       goto end;
+
+error:
+       ret = -1;
+
+end:
+       bt_put(default_params);
+       bt_put(real_params);
+       bt_put(assume_absolute_clock_classes);
+       return ret;
 }
 
 BT_HIDDEN
@@ -260,32 +341,52 @@ enum bt_component_status muxer_init(
        enum bt_component_status status = BT_COMPONENT_STATUS_OK;
        struct muxer_comp *muxer_comp = g_new0(struct muxer_comp, 1);
 
+       BT_LOGD("Initializing muxer component: "
+               "comp-addr=%p, params-addr=%p", priv_comp, params);
+
        if (!muxer_comp) {
+               BT_LOGE_STR("Failed to allocate one muxer component.");
+               goto error;
+       }
+
+       ret = configure_muxer_comp(muxer_comp, params);
+       if (ret) {
+               BT_LOGE("Cannot configure muxer component: "
+                       "muxer-comp-addr=%p, params-addr=%p",
+                       muxer_comp, params);
                goto error;
        }
 
        muxer_comp->muxer_notif_iters = g_ptr_array_new();
        if (!muxer_comp->muxer_notif_iters) {
+               BT_LOGE_STR("Failed to allocate a GPtrArray.");
                goto error;
        }
 
        muxer_comp->priv_comp = priv_comp;
        ret = bt_private_component_set_user_data(priv_comp, muxer_comp);
        assert(ret == 0);
-       ret = remove_default_ports(priv_comp);
-       if (ret) {
+       status = ensure_available_input_port(priv_comp);
+       if (status != BT_COMPONENT_STATUS_OK) {
+               BT_LOGE("Cannot ensure that at least one muxer component's input port is available: "
+                       "muxer-comp-addr=%p, status=%s",
+                       muxer_comp,
+                       bt_component_status_string(status));
                goto error;
        }
 
-       ret = ensure_available_input_port(priv_comp);
-       if (ret) {
+       status = create_output_port(priv_comp);
+       if (status) {
+               BT_LOGE("Cannot create muxer component's output port: "
+                       "muxer-comp-addr=%p, status=%s",
+                       muxer_comp,
+                       bt_component_status_string(status));
                goto error;
        }
 
-       ret = create_output_port(priv_comp);
-       if (ret) {
-               goto error;
-       }
+       BT_LOGD("Initialized muxer component: "
+               "comp-addr=%p, params-addr=%p, muxer-comp-addr=%p",
+               priv_comp, params, muxer_comp);
 
        goto end;
 
@@ -293,7 +394,10 @@ error:
        destroy_muxer_comp(muxer_comp);
        ret = bt_private_component_set_user_data(priv_comp, NULL);
        assert(ret == 0);
-       status = BT_COMPONENT_STATUS_ERROR;
+
+       if (status == BT_COMPONENT_STATUS_OK) {
+               status = BT_COMPONENT_STATUS_ERROR;
+       }
 
 end:
        return status;
@@ -305,6 +409,8 @@ void muxer_finalize(struct bt_private_component *priv_comp)
        struct muxer_comp *muxer_comp =
                bt_private_component_get_user_data(priv_comp);
 
+       BT_LOGD("Finalizing muxer component: comp-addr=%p",
+               priv_comp);
        destroy_muxer_comp(muxer_comp);
 }
 
@@ -315,28 +421,35 @@ struct bt_notification_iterator *create_notif_iter_on_input_port(
        struct bt_port *port = bt_port_from_private_port(priv_port);
        struct bt_notification_iterator *notif_iter = NULL;
        struct bt_private_connection *priv_conn = NULL;
+       enum bt_connection_status conn_status;
 
        assert(ret);
        *ret = 0;
        assert(port);
-
        assert(bt_port_is_connected(port));
        priv_conn = bt_private_port_get_private_connection(priv_port);
-       if (!priv_conn) {
-               *ret = -1;
-               goto end;
-       }
+       assert(priv_conn);
 
        // TODO: Advance the iterator to >= the time of the latest
        //       returned notification by the muxer notification
        //       iterator which creates it.
-       notif_iter = bt_private_connection_create_notification_iterator(
-               priv_conn);
-       if (!notif_iter) {
+       conn_status = bt_private_connection_create_notification_iterator(
+               priv_conn, NULL, &notif_iter);
+       if (conn_status != BT_CONNECTION_STATUS_OK) {
+               BT_LOGE("Cannot create upstream notification iterator on input port's connection: "
+                       "port-addr=%p, port-name=\"%s\", conn-addr=%p, "
+                       "status=%s",
+                       port, bt_port_get_name(port), priv_conn,
+                       bt_connection_status_string(conn_status));
                *ret = -1;
                goto end;
        }
 
+       BT_LOGD("Created upstream notification iterator on input port's connection: "
+               "port-addr=%p, port-name=\"%s\", conn-addr=%p, "
+               "notif-iter-addr=%p",
+               port, bt_port_get_name(port), priv_conn, notif_iter);
+
 end:
        bt_put(port);
        bt_put(priv_conn);
@@ -344,81 +457,78 @@ end:
 }
 
 static
-int muxer_upstream_notif_iter_next(struct muxer_notif_iter *muxer_notif_iter,
+enum bt_notification_iterator_status muxer_upstream_notif_iter_next(
                struct muxer_upstream_notif_iter *muxer_upstream_notif_iter)
 {
-       int ret = 0;
-       enum bt_notification_iterator_status next_status;
+       enum bt_notification_iterator_status status;
 
-       next_status = bt_notification_iterator_next(
+       BT_LOGV("Calling upstream notification iterator's \"next\" method: "
+               "muxer-upstream-notif-iter-wrap-addr=%p, notif-iter-addr=%p",
+               muxer_upstream_notif_iter,
+               muxer_upstream_notif_iter->notif_iter);
+       status = bt_notification_iterator_next(
                muxer_upstream_notif_iter->notif_iter);
+       BT_LOGV("Upstream notification iterator's \"next\" method returned: "
+               "status=%s", bt_notification_iterator_status_string(status));
 
-       switch (next_status) {
+       switch (status) {
        case BT_NOTIFICATION_ITERATOR_STATUS_OK:
-               /* Everything okay */
+               /*
+                * Notification iterator's current notification is valid:
+                * it must be considered for muxing operations.
+                */
+               BT_LOGV_STR("Validated upstream notification iterator wrapper.");
+               muxer_upstream_notif_iter->is_valid = true;
                break;
        case BT_NOTIFICATION_ITERATOR_STATUS_AGAIN:
-               muxer_notif_iter_add_upstream_notif_iter_to_retry(
-                       muxer_notif_iter, muxer_upstream_notif_iter);
+               /*
+                * Notification iterator's current notification is not
+                * valid anymore. Return
+                * BT_NOTIFICATION_ITERATOR_STATUS_AGAIN
+                * immediately.
+                */
+               BT_LOGV_STR("Invalidated upstream notification iterator wrapper because of BT_NOTIFICATION_ITERATOR_STATUS_AGAIN.");
+               muxer_upstream_notif_iter->is_valid = false;
                break;
-       case BT_NOTIFICATION_ITERATOR_STATUS_END:
+       case BT_NOTIFICATION_ITERATOR_STATUS_END:       /* Fall-through. */
+       case BT_NOTIFICATION_ITERATOR_STATUS_CANCELED:
                /*
                 * Notification iterator reached the end: release it. It
                 * won't be considered again to find the youngest
                 * notification.
                 */
+               BT_LOGV_STR("Invalidated upstream notification iterator wrapper because of BT_NOTIFICATION_ITERATOR_STATUS_END or BT_NOTIFICATION_ITERATOR_STATUS_CANCELED.");
                BT_PUT(muxer_upstream_notif_iter->notif_iter);
-               goto end;
+               muxer_upstream_notif_iter->is_valid = false;
+               status = BT_NOTIFICATION_ITERATOR_STATUS_OK;
+               break;
        default:
                /* Error or unsupported status code */
-               ret = next_status;
+               BT_LOGE("Error or unsupported status code: "
+                       "status-code=%d", status);
+               status = BT_NOTIFICATION_ITERATOR_STATUS_ERROR;
+               break;
        }
 
-end:
-       return ret;
+       return status;
 }
 
 static
-int muxer_notif_iter_handle_newly_connected_ports(struct muxer_comp *muxer_comp,
+int muxer_notif_iter_handle_newly_connected_ports(
                struct muxer_notif_iter *muxer_notif_iter)
 {
-       struct bt_component *comp = NULL;
        int ret = 0;
 
-       comp = bt_component_from_private_component(muxer_comp->priv_comp);
-       assert(comp);
+       BT_LOGV("Handling newly connected ports: "
+               "muxer-notif-iter-addr=%p", muxer_notif_iter);
 
        /*
         * Here we create one upstream notification iterator for each
-        * newly connected port. The list of newly connected ports to
-        * handle here is updated by muxer_port_connected().
-        *
-        * An initial "next" operation is performed on each new upstream
-        * notification iterator. The possible return values of this
-        * initial "next" operation are:
-        *
-        * * BT_NOTIFICATION_ITERATOR_STATUS_OK: Perfect, we have a
-        *   current notification.
-        *
-        * * BT_NOTIFICATION_ITERATOR_STATUS_AGAIN: No notification so
-        *   far, but the muxer upstream notification iterator is added
-        *   to the list of upstream notification iterators to retry
-        *   before finding the next youngest notification.
-        *
-        * * BT_NOTIFICATION_ITERATOR_STATUS_END: No notification, and
-        *   we immediately release the upstream notification iterator
-        *   because it's useless.
-        *
-        * A possible side effect of this initial "next" operation, on
-        * each notification iterator, is the connection of a new port.
-        * In this case the list of newly connected ports is updated and
-        * this loop continues.
-        *
-        * Once this loop finishes successfully, the set of upstream
-        * notification iterators is considered _stable_, that is, it is
-        * safe, if no notification iterators must be retried, to select
-        * the youngest notification amongst them to be returned by the
-        * next "next" method call.
+        * newly connected port. We do not perform an initial "next" on
+        * those new upstream notification iterators: they are
+        * invalidated, to be validated later. The list of newly
+        * connected ports to handle here is updated by
+        * muxer_port_connected().
         */
        while (true) {
                GList *node = muxer_notif_iter->newly_connected_priv_ports;
@@ -439,8 +549,8 @@ int muxer_notif_iter_handle_newly_connected_ports(struct muxer_comp *muxer_comp,
                        /*
                         * Looks like this port is not connected
                         * anymore: we can't create an upstream
-                        * notification iterator on its connection in
-                        * this case.
+                        * notification iterator on its (non-existing)
+                        * connection in this case.
                         */
                        goto remove_node;
                }
@@ -449,8 +559,8 @@ int muxer_notif_iter_handle_newly_connected_ports(struct muxer_comp *muxer_comp,
                upstream_notif_iter = create_notif_iter_on_input_port(priv_port,
                        &ret);
                if (ret) {
+                       /* create_notif_iter_on_input_port() logs errors */
                        assert(!upstream_notif_iter);
-                       bt_put(priv_port);
                        goto error;
                }
 
@@ -458,22 +568,18 @@ int muxer_notif_iter_handle_newly_connected_ports(struct muxer_comp *muxer_comp,
                        muxer_notif_iter_add_upstream_notif_iter(
                                muxer_notif_iter, upstream_notif_iter,
                                priv_port);
-               BT_PUT(priv_port);
                BT_PUT(upstream_notif_iter);
                if (!muxer_upstream_notif_iter) {
-                       goto error;
-               }
-
-               ret = muxer_upstream_notif_iter_next(muxer_notif_iter,
-                       muxer_upstream_notif_iter);
-               if (ret) {
+                       /*
+                        * muxer_notif_iter_add_upstream_notif_iter()
+                        * logs errors.
+                        */
                        goto error;
                }
 
 remove_node:
                bt_put(upstream_notif_iter);
                bt_put(port);
-               bt_put(priv_port);
                muxer_notif_iter->newly_connected_priv_ports =
                        g_list_delete_link(
                                muxer_notif_iter->newly_connected_priv_ports,
@@ -483,17 +589,17 @@ remove_node:
        goto end;
 
 error:
-       if (ret == 0) {
+       if (ret >= 0) {
                ret = -1;
        }
 
 end:
-       bt_put(comp);
        return ret;
 }
 
 static
 int get_notif_ts_ns(struct muxer_comp *muxer_comp,
+               struct muxer_notif_iter *muxer_notif_iter,
                struct bt_notification *notif, int64_t last_returned_ts_ns,
                int64_t *ts_ns)
 {
@@ -502,10 +608,17 @@ int get_notif_ts_ns(struct muxer_comp *muxer_comp,
        struct bt_ctf_clock_value *clock_value = NULL;
        struct bt_ctf_event *event = NULL;
        int ret = 0;
+       const unsigned char *cc_uuid;
+       const char *cc_name;
 
        assert(notif);
        assert(ts_ns);
 
+       BT_LOGV("Getting notification's timestamp: "
+               "muxer-notif-iter-addr=%p, notif-addr=%p, "
+               "last-returned-ts=%" PRId64,
+               muxer_notif_iter, notif, last_returned_ts_ns);
+
        switch (bt_notification_get_type(notif)) {
        case BT_NOTIFICATION_TYPE_EVENT:
                cc_prio_map =
@@ -519,15 +632,15 @@ int get_notif_ts_ns(struct muxer_comp *muxer_comp,
                                notif);
                break;
        default:
-               /*
-                * All the other notifications have a higher
-                * priority.
-                */
+               /* All the other notifications have a higher priority */
+               BT_LOGV_STR("Notification has no timestamp: using the last returned timestamp.");
                *ts_ns = last_returned_ts_ns;
                goto end;
        }
 
        if (!cc_prio_map) {
+               BT_LOGE("Cannot get notification's clock class priority map: "
+                       "notif-addr=%p", notif);
                goto error;
        }
 
@@ -537,6 +650,8 @@ int get_notif_ts_ns(struct muxer_comp *muxer_comp,
         * the youngest.
         */
        if (bt_clock_class_priority_map_get_clock_class_count(cc_prio_map) == 0) {
+               BT_LOGV_STR("Notification's clock class priorty map contains 0 clock classes: "
+                       "using the last returned timestamp.");
                *ts_ns = last_returned_ts_ns;
                goto end;
        }
@@ -545,12 +660,160 @@ int get_notif_ts_ns(struct muxer_comp *muxer_comp,
                bt_clock_class_priority_map_get_highest_priority_clock_class(
                        cc_prio_map);
        if (!clock_class) {
+               BT_LOGE("Cannot get the clock class with the highest priority from clock class priority map: "
+                       "cc-prio-map-addr=%p", cc_prio_map);
                goto error;
        }
 
-       if (!bt_ctf_clock_class_get_is_absolute(clock_class)) {
-               // TODO: Allow this with an explicit parameter
-               goto error;
+       cc_uuid = bt_ctf_clock_class_get_uuid(clock_class);
+       cc_name = bt_ctf_clock_class_get_name(clock_class);
+
+       if (muxer_notif_iter->clock_class_expectation ==
+                       MUXER_NOTIF_ITER_CLOCK_CLASS_EXPECTATION_ANY) {
+               /*
+                * This is the first clock class that this muxer
+                * notification iterator encounters. Its properties
+                * determine what to expect for the whole lifetime of
+                * the iterator without a true
+                * `assume-absolute-clock-classes` parameter.
+                */
+               if (bt_ctf_clock_class_is_absolute(clock_class)) {
+                       /* Expect absolute clock classes */
+                       muxer_notif_iter->clock_class_expectation =
+                               MUXER_NOTIF_ITER_CLOCK_CLASS_EXPECTATION_ABSOLUTE;
+               } else {
+                       if (cc_uuid) {
+                               /*
+                                * Expect non-absolute clock classes
+                                * with a specific UUID.
+                                */
+                               muxer_notif_iter->clock_class_expectation =
+                                       MUXER_NOTIF_ITER_CLOCK_CLASS_EXPECTATION_NOT_ABS_SPEC_UUID;
+                               memcpy(muxer_notif_iter->expected_clock_class_uuid,
+                                       cc_uuid, BABELTRACE_UUID_LEN);
+                       } else {
+                               /*
+                                * Expect non-absolute clock classes
+                                * with no UUID.
+                                */
+                               muxer_notif_iter->clock_class_expectation =
+                                       MUXER_NOTIF_ITER_CLOCK_CLASS_EXPECTATION_NOT_ABS_NO_UUID;
+                       }
+               }
+       }
+
+       if (!muxer_comp->assume_absolute_clock_classes) {
+               switch (muxer_notif_iter->clock_class_expectation) {
+               case MUXER_NOTIF_ITER_CLOCK_CLASS_EXPECTATION_ABSOLUTE:
+                       if (!bt_ctf_clock_class_is_absolute(clock_class)) {
+                               BT_LOGE("Expecting an absolute clock class, "
+                                       "but got a non-absolute one: "
+                                       "clock-class-addr=%p, clock-class-name=\"%s\"",
+                                       clock_class, cc_name);
+                               goto error;
+                       }
+                       break;
+               case MUXER_NOTIF_ITER_CLOCK_CLASS_EXPECTATION_NOT_ABS_NO_UUID:
+                       if (bt_ctf_clock_class_is_absolute(clock_class)) {
+                               BT_LOGE("Expecting a non-absolute clock class with no UUID, "
+                                       "but got an absolute one: "
+                                       "clock-class-addr=%p, clock-class-name=\"%s\"",
+                                       clock_class, cc_name);
+                               goto error;
+                       }
+
+                       if (cc_uuid) {
+                               BT_LOGE("Expecting a non-absolute clock class with no UUID, "
+                                       "but got one with a UUID: "
+                                       "clock-class-addr=%p, clock-class-name=\"%s\", "
+                                       "uuid=\"%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x\"",
+                                       clock_class, cc_name,
+                                       (unsigned int) cc_uuid[0],
+                                       (unsigned int) cc_uuid[1],
+                                       (unsigned int) cc_uuid[2],
+                                       (unsigned int) cc_uuid[3],
+                                       (unsigned int) cc_uuid[4],
+                                       (unsigned int) cc_uuid[5],
+                                       (unsigned int) cc_uuid[6],
+                                       (unsigned int) cc_uuid[7],
+                                       (unsigned int) cc_uuid[8],
+                                       (unsigned int) cc_uuid[9],
+                                       (unsigned int) cc_uuid[10],
+                                       (unsigned int) cc_uuid[11],
+                                       (unsigned int) cc_uuid[12],
+                                       (unsigned int) cc_uuid[13],
+                                       (unsigned int) cc_uuid[14],
+                                       (unsigned int) cc_uuid[15]);
+                               goto error;
+                       }
+                       break;
+               case MUXER_NOTIF_ITER_CLOCK_CLASS_EXPECTATION_NOT_ABS_SPEC_UUID:
+                       if (bt_ctf_clock_class_is_absolute(clock_class)) {
+                               BT_LOGE("Expecting a non-absolute clock class with a specific UUID, "
+                                       "but got an absolute one: "
+                                       "clock-class-addr=%p, clock-class-name=\"%s\"",
+                                       clock_class, cc_name);
+                               goto error;
+                       }
+
+                       if (!cc_uuid) {
+                               BT_LOGE("Expecting a non-absolute clock class with a specific UUID, "
+                                       "but got one with no UUID: "
+                                       "clock-class-addr=%p, clock-class-name=\"%s\"",
+                                       clock_class, cc_name);
+                               goto error;
+                       }
+
+                       if (memcmp(muxer_notif_iter->expected_clock_class_uuid,
+                                       cc_uuid, BABELTRACE_UUID_LEN) != 0) {
+                               BT_LOGE("Expecting a non-absolute clock class with a specific UUID, "
+                                       "but got one with different UUID: "
+                                       "clock-class-addr=%p, clock-class-name=\"%s\", "
+                                       "expected-uuid=\"%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x\", "
+                                       "uuid=\"%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x\"",
+                                       clock_class, cc_name,
+                                       (unsigned int) muxer_notif_iter->expected_clock_class_uuid[0],
+                                       (unsigned int) muxer_notif_iter->expected_clock_class_uuid[1],
+                                       (unsigned int) muxer_notif_iter->expected_clock_class_uuid[2],
+                                       (unsigned int) muxer_notif_iter->expected_clock_class_uuid[3],
+                                       (unsigned int) muxer_notif_iter->expected_clock_class_uuid[4],
+                                       (unsigned int) muxer_notif_iter->expected_clock_class_uuid[5],
+                                       (unsigned int) muxer_notif_iter->expected_clock_class_uuid[6],
+                                       (unsigned int) muxer_notif_iter->expected_clock_class_uuid[7],
+                                       (unsigned int) muxer_notif_iter->expected_clock_class_uuid[8],
+                                       (unsigned int) muxer_notif_iter->expected_clock_class_uuid[9],
+                                       (unsigned int) muxer_notif_iter->expected_clock_class_uuid[10],
+                                       (unsigned int) muxer_notif_iter->expected_clock_class_uuid[11],
+                                       (unsigned int) muxer_notif_iter->expected_clock_class_uuid[12],
+                                       (unsigned int) muxer_notif_iter->expected_clock_class_uuid[13],
+                                       (unsigned int) muxer_notif_iter->expected_clock_class_uuid[14],
+                                       (unsigned int) muxer_notif_iter->expected_clock_class_uuid[15],
+                                       (unsigned int) cc_uuid[0],
+                                       (unsigned int) cc_uuid[1],
+                                       (unsigned int) cc_uuid[2],
+                                       (unsigned int) cc_uuid[3],
+                                       (unsigned int) cc_uuid[4],
+                                       (unsigned int) cc_uuid[5],
+                                       (unsigned int) cc_uuid[6],
+                                       (unsigned int) cc_uuid[7],
+                                       (unsigned int) cc_uuid[8],
+                                       (unsigned int) cc_uuid[9],
+                                       (unsigned int) cc_uuid[10],
+                                       (unsigned int) cc_uuid[11],
+                                       (unsigned int) cc_uuid[12],
+                                       (unsigned int) cc_uuid[13],
+                                       (unsigned int) cc_uuid[14],
+                                       (unsigned int) cc_uuid[15]);
+                               goto error;
+                       }
+                       break;
+               default:
+                       /* Unexpected */
+                       BT_LOGF("Unexpected clock class expectation: "
+                               "expectation-code=%d",
+                               muxer_notif_iter->clock_class_expectation);
+                       abort();
+               }
        }
 
        switch (bt_notification_get_type(notif)) {
@@ -565,15 +828,22 @@ int get_notif_ts_ns(struct muxer_comp *muxer_comp,
                        notif, clock_class);
                break;
        default:
-               assert(false);
+               BT_LOGF("Unexpected notification type at this point: "
+                       "type=%d", bt_notification_get_type(notif));
+               abort();
        }
 
        if (!clock_value) {
+               BT_LOGE("Cannot get notification's clock value for clock class: "
+                       "clock-class-addr=%p, clock-class-name=\"%s\"",
+                       clock_class, cc_name);
                goto error;
        }
 
        ret = bt_ctf_clock_value_get_value_ns_from_epoch(clock_value, ts_ns);
        if (ret) {
+               BT_LOGE("Cannot get nanoseconds from Epoch of clock value: "
+                       "clock-value-addr=%p", clock_value);
                goto error;
        }
 
@@ -583,6 +853,14 @@ error:
        ret = -1;
 
 end:
+       if (ret == 0) {
+               BT_LOGV("Found notification's timestamp: "
+                       "muxer-notif-iter-addr=%p, notif-addr=%p, "
+                       "last-returned-ts=%" PRId64 ", ts=%" PRId64,
+                       muxer_notif_iter, notif, last_returned_ts_ns,
+                       *ts_ns);
+       }
+
        bt_put(cc_prio_map);
        bt_put(event);
        bt_put(clock_class);
@@ -634,16 +912,21 @@ muxer_notif_iter_youngest_upstream_notif_iter(
 
                if (!cur_muxer_upstream_notif_iter->notif_iter) {
                        /* This upstream notification iterator is ended */
+                       BT_LOGV("Skipping ended upstream notification iterator: "
+                               "muxer-upstream-notif-iter-wrap-addr=%p",
+                               cur_muxer_upstream_notif_iter);
                        continue;
                }
 
+               assert(cur_muxer_upstream_notif_iter->is_valid);
                notif = bt_notification_iterator_get_notification(
                        cur_muxer_upstream_notif_iter->notif_iter);
                assert(notif);
-               ret = get_notif_ts_ns(muxer_comp, notif,
+               ret = get_notif_ts_ns(muxer_comp, muxer_notif_iter, notif,
                        muxer_notif_iter->last_returned_ts_ns, &notif_ts_ns);
                bt_put(notif);
                if (ret) {
+                       /* get_notif_ts_ns() logs errors */
                        *muxer_upstream_notif_iter = NULL;
                        status = BT_NOTIFICATION_ITERATOR_STATUS_ERROR;
                        goto end;
@@ -667,132 +950,214 @@ end:
 }
 
 static
-int muxer_notif_iter_set_next_next_return(struct muxer_comp *muxer_comp,
-               struct muxer_notif_iter *muxer_notif_iter)
+enum bt_notification_iterator_status validate_muxer_upstream_notif_iter(
+       struct muxer_upstream_notif_iter *muxer_upstream_notif_iter)
 {
-       struct muxer_upstream_notif_iter *muxer_upstream_notif_iter;
-       enum bt_notification_iterator_status notif_iter_status;
-       int ret = 0;
+       enum bt_notification_iterator_status status =
+               BT_NOTIFICATION_ITERATOR_STATUS_OK;
 
-       /*
-        * Previous operations might have connected ports. They must be
-        * considered when finding the youngest notification because
-        * their upstream notification iterator does not exist yet.
-        */
-       ret = muxer_notif_iter_handle_newly_connected_ports(muxer_comp,
-               muxer_notif_iter);
-       if (ret) {
-               muxer_notif_iter->next_next_return.status =
-                       BT_NOTIFICATION_ITERATOR_STATUS_ERROR;
-               BT_PUT(muxer_notif_iter->next_next_return.notification);
+       BT_LOGV("Validating muxer's upstream notification iterator wrapper: "
+               "muxer-upstream-notif-iter-wrap-addr=%p",
+               muxer_upstream_notif_iter);
+
+       if (muxer_upstream_notif_iter->is_valid ||
+                       !muxer_upstream_notif_iter->notif_iter) {
                goto end;
        }
 
-       assert(!muxer_notif_iter->newly_connected_priv_ports);
+       /* muxer_upstream_notif_iter_next() logs details/errors */
+       status = muxer_upstream_notif_iter_next(muxer_upstream_notif_iter);
+
+end:
+       return status;
+}
+
+static
+enum bt_notification_iterator_status validate_muxer_upstream_notif_iters(
+       struct muxer_notif_iter *muxer_notif_iter)
+{
+       enum bt_notification_iterator_status status =
+               BT_NOTIFICATION_ITERATOR_STATUS_OK;
+       size_t i;
+
+       BT_LOGV("Validating muxer's upstream notification iterator wrappers: "
+               "muxer-notif-iter-addr=%p", muxer_notif_iter);
+
+       for (i = 0; i < muxer_notif_iter->muxer_upstream_notif_iters->len; i++) {
+               struct muxer_upstream_notif_iter *muxer_upstream_notif_iter =
+                       g_ptr_array_index(
+                               muxer_notif_iter->muxer_upstream_notif_iters,
+                               i);
+
+               status = validate_muxer_upstream_notif_iter(
+                       muxer_upstream_notif_iter);
+               if (status != BT_NOTIFICATION_ITERATOR_STATUS_OK) {
+                       if (status < 0) {
+                               BT_LOGE("Cannot validate muxer's upstream notification iterator wrapper: "
+                                       "muxer-notif-iter-addr=%p, "
+                                       "muxer-upstream-notif-iter-wrap-addr=%p",
+                                       muxer_notif_iter,
+                                       muxer_upstream_notif_iter);
+                       } else {
+                               BT_LOGV("Cannot validate muxer's upstream notification iterator wrapper: "
+                                       "muxer-notif-iter-addr=%p, "
+                                       "muxer-upstream-notif-iter-wrap-addr=%p",
+                                       muxer_notif_iter,
+                                       muxer_upstream_notif_iter);
+                       }
+
+                       goto end;
+               }
 
-       if (muxer_notif_iter_has_upstream_notif_iter_to_retry(
-                       muxer_notif_iter)) {
                /*
-                * At least one upstream notification iterator to retry:
-                * try again later, because we cannot find the youngest
-                * notification if we don't have the current
-                * notification of each upstream notification iterator.
+                * Remove this muxer upstream notification iterator
+                * if it's ended or canceled.
                 */
-               muxer_notif_iter->next_next_return.status =
-                       BT_NOTIFICATION_ITERATOR_STATUS_AGAIN;
-               BT_PUT(muxer_notif_iter->next_next_return.notification);
-               goto end;
+               if (!muxer_upstream_notif_iter->notif_iter) {
+                       /*
+                        * Use g_ptr_array_remove_fast() because the
+                        * order of those elements is not important.
+                        */
+                       BT_LOGV("Removing muxer's upstream notification iterator wrapper: ended or canceled: "
+                               "muxer-notif-iter-addr=%p, "
+                               "muxer-upstream-notif-iter-wrap-addr=%p",
+                               muxer_notif_iter, muxer_upstream_notif_iter);
+                       g_ptr_array_remove_index_fast(
+                               muxer_notif_iter->muxer_upstream_notif_iters,
+                               i);
+                       i--;
+               }
        }
 
+end:
+       return status;
+}
+
+static
+struct bt_notification_iterator_next_return muxer_notif_iter_do_next(
+               struct muxer_comp *muxer_comp,
+               struct muxer_notif_iter *muxer_notif_iter)
+{
+       struct muxer_upstream_notif_iter *muxer_upstream_notif_iter = NULL;
+       struct bt_notification_iterator_next_return next_return = {
+               .notification = NULL,
+               .status = BT_NOTIFICATION_ITERATOR_STATUS_OK,
+       };
+       int64_t next_return_ts;
+
+       while (true) {
+               int ret = muxer_notif_iter_handle_newly_connected_ports(
+                       muxer_notif_iter);
+
+               if (ret) {
+                       BT_LOGE("Cannot handle newly connected input ports for muxer's notification iterator: "
+                               "muxer-comp-addr=%p, muxer-notif-iter-addr=%p, "
+                               "ret=%d",
+                               muxer_comp, muxer_notif_iter, ret);
+                       next_return.status =
+                               BT_NOTIFICATION_ITERATOR_STATUS_ERROR;
+                       goto end;
+               }
+
+               next_return.status =
+                       validate_muxer_upstream_notif_iters(muxer_notif_iter);
+               if (next_return.status != BT_NOTIFICATION_ITERATOR_STATUS_OK) {
+                       /* validate_muxer_upstream_notif_iters() logs details */
+                       goto end;
+               }
+
+               /*
+                * At this point, we know that all the existing upstream
+                * notification iterators are valid. However the
+                * operations to validate them (during
+                * validate_muxer_upstream_notif_iters()) may have
+                * connected new ports. If no ports were connected
+                * during this operation, exit the loop.
+                */
+               if (!muxer_notif_iter->newly_connected_priv_ports) {
+                       BT_LOGV("Not breaking this loop: muxer's notification iterator still has newly connected input ports to handle: "
+                               "muxer-comp-addr=%p", muxer_comp);
+                       break;
+               }
+       }
+
+       assert(!muxer_notif_iter->newly_connected_priv_ports);
+
        /*
-        * At this point we know that all our connected ports have an
-        * upstream notification iterator, and that all those iterators
-        * have a current notification (stable state). It is safe to
-        * find the youngest notification. It is possible that calling
-        * "next" on its iterator will connect new ports. This will be
-        * handled by the next call to
-        * muxer_notif_iter_set_next_next_return().
+        * At this point we know that all the existing upstream
+        * notification iterators are valid. We can find the one,
+        * amongst those, of which the current notification is the
+        * youngest.
         */
-       notif_iter_status =
+       next_return.status =
                muxer_notif_iter_youngest_upstream_notif_iter(muxer_comp,
                        muxer_notif_iter, &muxer_upstream_notif_iter,
-                       &muxer_notif_iter->next_next_return_ts_ns);
-       if (notif_iter_status == BT_NOTIFICATION_ITERATOR_STATUS_END) {
-               /* No more active upstream notification iterator */
-               muxer_notif_iter->next_next_return.status =
-                       BT_NOTIFICATION_ITERATOR_STATUS_END;
-               BT_PUT(muxer_notif_iter->next_next_return.notification);
-               goto end;
-       }
+                       &next_return_ts);
+       if (next_return.status < 0 ||
+                       next_return.status == BT_NOTIFICATION_ITERATOR_STATUS_END ||
+                       next_return.status == BT_NOTIFICATION_ITERATOR_STATUS_CANCELED) {
+               if (next_return.status < 0) {
+                       BT_LOGE("Cannot find the youngest upstream notification iterator wrapper: "
+                               "status=%s",
+                               bt_notification_iterator_status_string(next_return.status));
+               } else {
+                       BT_LOGV("Cannot find the youngest upstream notification iterator wrapper: "
+                               "status=%s",
+                               bt_notification_iterator_status_string(next_return.status));
+               }
 
-       if (notif_iter_status < 0) {
-               ret = -1;
                goto end;
        }
 
-       assert(notif_iter_status == BT_NOTIFICATION_ITERATOR_STATUS_OK);
-       BT_PUT(muxer_notif_iter->next_next_return.notification);
-       muxer_notif_iter->next_next_return.notification =
-               bt_notification_iterator_get_notification(
-                       muxer_upstream_notif_iter->notif_iter);
-       assert(muxer_notif_iter->next_next_return.notification);
-       muxer_notif_iter->next_next_return.status =
-               BT_NOTIFICATION_ITERATOR_STATUS_OK;
-       ret = muxer_upstream_notif_iter_next(muxer_notif_iter,
-               muxer_upstream_notif_iter);
-       if (ret) {
+       if (next_return_ts < muxer_notif_iter->last_returned_ts_ns) {
+               BT_LOGE("Youngest upstream notification iterator wrapper's timestamp is less than muxer's notification iterator's last returned timestamp: "
+                       "muxer-notif-iter-addr=%p, ts=%" PRId64 ", "
+                       "last-returned-ts=%" PRId64,
+                       muxer_notif_iter, next_return_ts,
+                       muxer_notif_iter->last_returned_ts_ns);
+               next_return.status = BT_NOTIFICATION_ITERATOR_STATUS_ERROR;
                goto end;
        }
 
-       /*
-        * Here we have the next "next" return value. It won't change
-        * until it is returned by the next call to our "next" method.
-        * If its time is less than the time of the last notification
-        * that our "next" method returned, then fail because the
-        * muxer's output wouldn't be monotonic.
-        */
-       if (muxer_notif_iter->next_next_return_ts_ns <
-                       muxer_notif_iter->last_returned_ts_ns) {
-               ret = -1;
-               goto end;
-       }
+       BT_LOGV("Found youngest upstream notification iterator wrapper: "
+               "muxer-notif-iter-addr=%p, "
+               "muxer-upstream-notif-iter-wrap-addr=%p, "
+               "ts=%" PRId64,
+               muxer_notif_iter, muxer_upstream_notif_iter, next_return_ts);
+       assert(next_return.status == BT_NOTIFICATION_ITERATOR_STATUS_OK);
+       assert(muxer_upstream_notif_iter);
+       next_return.notification = bt_notification_iterator_get_notification(
+               muxer_upstream_notif_iter->notif_iter);
+       assert(next_return.notification);
 
        /*
-        * We are now sure that the next "next" return value will not
-        * change until it is returned by this muxer notification
-        * iterator (unless there's a fatal error). It is now safe to
-        * set the last returned time to this one.
+        * We invalidate the upstream notification iterator so that, the
+        * next time this function is called,
+        * validate_muxer_upstream_notif_iters() will make it valid.
         */
-       muxer_notif_iter->last_returned_ts_ns =
-               muxer_notif_iter->next_next_return_ts_ns;
+       muxer_upstream_notif_iter->is_valid = false;
+       muxer_notif_iter->last_returned_ts_ns = next_return_ts;
 
 end:
-       return ret;
+       return next_return;
 }
 
 static
 void destroy_muxer_notif_iter(struct muxer_notif_iter *muxer_notif_iter)
 {
-       GList *node;
-
        if (!muxer_notif_iter) {
                return;
        }
 
+       BT_LOGD("Destroying muxer component's notification iterator: "
+               "muxer-notif-iter-addr=%p", muxer_notif_iter);
+
        if (muxer_notif_iter->muxer_upstream_notif_iters) {
+               BT_LOGD_STR("Destroying muxer's upstream notification iterator wrappers.");
                g_ptr_array_free(
                        muxer_notif_iter->muxer_upstream_notif_iters, TRUE);
        }
 
-       if (muxer_notif_iter->muxer_upstream_notif_iters_to_retry) {
-               g_list_free(muxer_notif_iter->muxer_upstream_notif_iters_to_retry);
-       }
-
-       for (node = muxer_notif_iter->newly_connected_priv_ports;
-                       node; node = g_list_next(node)) {
-               bt_put(node->data);
-       }
-
        g_list_free(muxer_notif_iter->newly_connected_priv_ports);
        g_free(muxer_notif_iter);
 }
@@ -802,8 +1167,8 @@ int muxer_notif_iter_init_newly_connected_ports(struct muxer_comp *muxer_comp,
                struct muxer_notif_iter *muxer_notif_iter)
 {
        struct bt_component *comp;
-       uint64_t count;
-       uint64_t i;
+       int64_t count;
+       int64_t i;
        int ret = 0;
 
        /*
@@ -813,14 +1178,17 @@ int muxer_notif_iter_init_newly_connected_ports(struct muxer_comp *muxer_comp,
         */
        comp = bt_component_from_private_component(muxer_comp->priv_comp);
        assert(comp);
-       ret = bt_component_filter_get_input_port_count(comp, &count);
-       if (ret) {
+       count = bt_component_filter_get_input_port_count(comp);
+       if (count < 0) {
+               BT_LOGD("No input port to initialize for muxer component's notification iterator: "
+                       "muxer-comp-addr=%p, muxer-notif-iter-addr=%p",
+                       muxer_comp, muxer_notif_iter);
                goto end;
        }
 
        for (i = 0; i < count; i++) {
                struct bt_private_port *priv_port =
-                       bt_private_component_filter_get_input_private_port_at_index(
+                       bt_private_component_filter_get_input_private_port_by_index(
                                muxer_comp->priv_comp, i);
                struct bt_port *port;
 
@@ -829,21 +1197,33 @@ int muxer_notif_iter_init_newly_connected_ports(struct muxer_comp *muxer_comp,
                assert(port);
 
                if (!bt_port_is_connected(port)) {
+                       BT_LOGD("Skipping input port: not connected: "
+                               "muxer-comp-addr=%p, port-addr=%p, port-name\"%s\"",
+                               muxer_comp, port, bt_port_get_name(port));
                        bt_put(priv_port);
                        bt_put(port);
                        continue;
                }
 
                bt_put(port);
+               bt_put(priv_port);
                muxer_notif_iter->newly_connected_priv_ports =
                        g_list_append(
                                muxer_notif_iter->newly_connected_priv_ports,
                                priv_port);
                if (!muxer_notif_iter->newly_connected_priv_ports) {
-                       bt_put(priv_port);
+                       BT_LOGE("Cannot append port to muxer's notification iterator list of newly connected input ports: "
+                               "port-addr=%p, port-name=\"%s\", "
+                               "muxer-notif-iter-addr=%p", port,
+                               bt_port_get_name(port), muxer_notif_iter);
                        ret = -1;
                        goto end;
                }
+
+               BT_LOGD("Appended port to muxer's notification iterator list of newly connected input ports: "
+                       "port-addr=%p, port-name=\"%s\", "
+                       "muxer-notif-iter-addr=%p", port,
+                       bt_port_get_name(port), muxer_notif_iter);
        }
 
 end:
@@ -868,19 +1248,26 @@ enum bt_notification_iterator_status muxer_notif_iter_init(
        assert(priv_comp);
        muxer_comp = bt_private_component_get_user_data(priv_comp);
        assert(muxer_comp);
+       BT_LOGD("Initializing muxer component's notification iterator: "
+               "comp-addr=%p, muxer-comp-addr=%p, notif-iter-addr=%p",
+               priv_comp, muxer_comp, priv_notif_iter);
 
        if (muxer_comp->initializing_muxer_notif_iter) {
                /*
-                * Weird, unhandled situation: downstream creates a
-                * muxer notification iterator while creating another
-                * muxer notification iterator (same component).
+                * Weird, unhandled situation detected: downstream
+                * creates a muxer notification iterator while creating
+                * another muxer notification iterator (same component).
                 */
+               BT_LOGE("Recursive initialization of muxer component's notification iterator: "
+                       "comp-addr=%p, muxer-comp-addr=%p, notif-iter-addr=%p",
+                       priv_comp, muxer_comp, priv_notif_iter);
                goto error;
        }
 
        muxer_comp->initializing_muxer_notif_iter = true;
        muxer_notif_iter = g_new0(struct muxer_notif_iter, 1);
        if (!muxer_notif_iter) {
+               BT_LOGE_STR("Failed to allocate one muxer component's notification iterator.");
                goto error;
        }
 
@@ -889,6 +1276,7 @@ enum bt_notification_iterator_status muxer_notif_iter_init(
                g_ptr_array_new_with_free_func(
                        (GDestroyNotify) destroy_muxer_upstream_notif_iter);
        if (!muxer_notif_iter->muxer_upstream_notif_iters) {
+               BT_LOGE_STR("Failed to allocate a GPtrArray.");
                goto error;
        }
 
@@ -904,19 +1292,21 @@ enum bt_notification_iterator_status muxer_notif_iter_init(
        ret = muxer_notif_iter_init_newly_connected_ports(muxer_comp,
                muxer_notif_iter);
        if (ret) {
-               goto error;
-       }
-
-       /* Set the initial "next" return value */
-       ret = muxer_notif_iter_set_next_next_return(muxer_comp,
-               muxer_notif_iter);
-       if (ret) {
+               BT_LOGE("Cannot initialize newly connected input ports for muxer component's notification iterator: "
+                       "comp-addr=%p, muxer-comp-addr=%p, "
+                       "muxer-notif-iter-addr=%p, notif-iter-addr=%p, ret=%d",
+                       priv_comp, muxer_comp, muxer_notif_iter,
+                       priv_notif_iter, ret);
                goto error;
        }
 
        ret = bt_private_notification_iterator_set_user_data(priv_notif_iter,
                muxer_notif_iter);
        assert(ret == 0);
+       BT_LOGD("Initialized muxer component's notification iterator: "
+               "comp-addr=%p, muxer-comp-addr=%p, muxer-notif-iter-addr=%p, "
+               "notif-iter-addr=%p",
+               priv_comp, muxer_comp, muxer_notif_iter, priv_notif_iter);
        goto end;
 
 error:
@@ -951,6 +1341,10 @@ void muxer_notif_iter_finalize(
                priv_notif_iter);
        assert(priv_comp);
        muxer_comp = bt_private_component_get_user_data(priv_comp);
+       BT_LOGD("Finalizing muxer component's notification iterator: "
+               "comp-addr=%p, muxer-comp-addr=%p, muxer-notif-iter-addr=%p, "
+               "notif-iter-addr=%p",
+               priv_comp, muxer_comp, muxer_notif_iter, priv_notif_iter);
 
        if (muxer_comp) {
                (void) g_ptr_array_remove_fast(muxer_comp->muxer_notif_iters,
@@ -965,15 +1359,11 @@ BT_HIDDEN
 struct bt_notification_iterator_next_return muxer_notif_iter_next(
                struct bt_private_notification_iterator *priv_notif_iter)
 {
-       struct bt_notification_iterator_next_return next_ret = {
-               .notification = NULL,
-       };
+       struct bt_notification_iterator_next_return next_ret;
        struct muxer_notif_iter *muxer_notif_iter =
                bt_private_notification_iterator_get_user_data(priv_notif_iter);
        struct bt_private_component *priv_comp = NULL;
        struct muxer_comp *muxer_comp = NULL;
-       GList *retry_node;
-       int ret;
 
        assert(muxer_notif_iter);
        priv_comp = bt_private_notification_iterator_get_private_component(
@@ -982,86 +1372,36 @@ struct bt_notification_iterator_next_return muxer_notif_iter_next(
        muxer_comp = bt_private_component_get_user_data(priv_comp);
        assert(muxer_comp);
 
+       BT_LOGV("Muxer component's notification iterator's \"next\" method called: "
+               "comp-addr=%p, muxer-comp-addr=%p, muxer-notif-iter-addr=%p, "
+               "notif-iter-addr=%p",
+               priv_comp, muxer_comp, muxer_notif_iter, priv_notif_iter);
+
        /* Are we in an error state set elsewhere? */
        if (unlikely(muxer_comp->error)) {
-               goto error;
-       }
-
-       /*
-        * If we have upstream notification iterators to retry, retry
-        * them now. Each one we find which now has a notification or
-        * is in "end" state, we set it to NULL in this array. Then
-        * we remove all the NULL values from this array.
-        */
-       retry_node = muxer_notif_iter->muxer_upstream_notif_iters_to_retry;
-       while (retry_node) {
-               struct muxer_upstream_notif_iter *muxer_upstream_notif_iter =
-                       retry_node->data;
-               enum bt_notification_iterator_status status;
-               GList *next_retry_node = g_list_next(retry_node);
-
-               assert(muxer_upstream_notif_iter->notif_iter);
-               status = bt_notification_iterator_next(
-                       muxer_upstream_notif_iter->notif_iter);
-               if (status < 0) {
-                       goto error;
-               }
-
-               if (status == BT_NOTIFICATION_ITERATOR_STATUS_END) {
-                       /*
-                        * This upstream notification iterator is done.
-                        * Put the iterator and remove node from list.
-                        */
-                       BT_PUT(muxer_upstream_notif_iter->notif_iter);
-                       muxer_notif_iter->muxer_upstream_notif_iters_to_retry =
-                               g_list_delete_link(
-                                       muxer_notif_iter->muxer_upstream_notif_iters_to_retry,
-                                       retry_node);
-                       retry_node = next_retry_node;
-                       continue;
-               }
-
-               assert(status == BT_NOTIFICATION_ITERATOR_STATUS_OK ||
-                       status == BT_NOTIFICATION_ITERATOR_STATUS_AGAIN);
-
-               if (status == BT_NOTIFICATION_ITERATOR_STATUS_OK) {
-                       /*
-                        * This upstream notification iterator now has.
-                        * a notification. Remove it from this list.
-                        */
-                       muxer_notif_iter->muxer_upstream_notif_iters_to_retry =
-                               g_list_delete_link(
-                                       muxer_notif_iter->muxer_upstream_notif_iters_to_retry,
-                                       retry_node);
-               }
-
-               retry_node = next_retry_node;
+               BT_LOGE("Muxer component is already in an error state: returning BT_NOTIFICATION_ITERATOR_STATUS_ERROR: "
+                       "comp-addr=%p, muxer-comp-addr=%p, muxer-notif-iter-addr=%p, "
+                       "notif-iter-addr=%p",
+                       priv_comp, muxer_comp, muxer_notif_iter, priv_notif_iter);
+               next_ret.notification = NULL;
+               next_ret.status = BT_NOTIFICATION_ITERATOR_STATUS_ERROR;
+               goto end;
        }
 
-       /* Take our next "next" next return value */
-       next_ret = muxer_notif_iter->next_next_return;
-       muxer_notif_iter->next_next_return.status =
-               BT_NOTIFICATION_ITERATOR_STATUS_ERROR;
-       muxer_notif_iter->next_next_return.notification = NULL;
-
-       /* Set the next "next" return value */
-       ret = muxer_notif_iter_set_next_next_return(muxer_comp,
-               muxer_notif_iter);
-       if (ret) {
-               goto error;
+       next_ret = muxer_notif_iter_do_next(muxer_comp, muxer_notif_iter);
+       if (next_ret.status < 0) {
+               BT_LOGE("Cannot get next notification: "
+                       "comp-addr=%p, muxer-comp-addr=%p, muxer-notif-iter-addr=%p, "
+                       "notif-iter-addr=%p, status=%s",
+                       priv_comp, muxer_comp, muxer_notif_iter, priv_notif_iter,
+                       bt_notification_iterator_status_string(next_ret.status));
+       } else {
+               BT_LOGV("Returning from muxer component's notification iterator's \"next\" method: "
+                       "status=%s, notif-addr=%p",
+                       bt_notification_iterator_status_string(next_ret.status),
+                       next_ret.notification);
        }
 
-       goto end;
-
-error:
-       /*
-        * Technically we already have a next "next" return value which
-        * is ready for this call, but we're failing within this call,
-        * so discard this buffer and return the error ASAP.
-        */
-       BT_PUT(next_ret.notification);
-       next_ret.status = BT_NOTIFICATION_ITERATOR_STATUS_ERROR;
-
 end:
        bt_put(priv_comp);
        return next_ret;
@@ -1078,20 +1418,19 @@ void muxer_port_connected(
        struct muxer_comp *muxer_comp =
                bt_private_component_get_user_data(priv_comp);
        size_t i;
+       int ret;
 
        assert(self_port);
        assert(muxer_comp);
-
-       if (bt_port_get_type(self_port) == BT_PORT_TYPE_INPUT) {
-               int ret;
-
-               /* One less available input port */
-               muxer_comp->available_input_ports--;
-               ret = ensure_available_input_port(priv_comp);
-               if (ret) {
-                       muxer_comp->error = true;
-                       goto end;
-               }
+       BT_LOGD("Port connected: "
+               "comp-addr=%p, muxer-comp-addr=%p, "
+               "port-addr=%p, port-name=\"%s\", "
+               "other-port-addr=%p, other-port-name=\"%s\"",
+               priv_comp, muxer_comp, self_port, bt_port_get_name(self_port),
+               other_port, bt_port_get_name(other_port));
+
+       if (bt_port_get_type(self_port) == BT_PORT_TYPE_OUTPUT) {
+               goto end;
        }
 
        for (i = 0; i < muxer_comp->muxer_notif_iters->len; i++) {
@@ -1104,18 +1443,39 @@ void muxer_port_connected(
                 * the end of this list while
                 * muxer_notif_iter_handle_newly_connected_ports()
                 * removes the nodes from the beginning.
-                *
-                * The list node owns the private port.
                 */
                muxer_notif_iter->newly_connected_priv_ports =
                        g_list_append(
                                muxer_notif_iter->newly_connected_priv_ports,
-                               bt_get(self_private_port));
+                               self_private_port);
                if (!muxer_notif_iter->newly_connected_priv_ports) {
-                       bt_put(self_private_port);
+                       BT_LOGE("Cannot append port to muxer's notification iterator list of newly connected input ports: "
+                               "port-addr=%p, port-name=\"%s\", "
+                               "muxer-notif-iter-addr=%p", self_port,
+                               bt_port_get_name(self_port), muxer_notif_iter);
                        muxer_comp->error = true;
                        goto end;
                }
+
+               BT_LOGD("Appended port to muxer's notification iterator list of newly connected input ports: "
+                       "port-addr=%p, port-name=\"%s\", "
+                       "muxer-notif-iter-addr=%p", self_port,
+                       bt_port_get_name(self_port), muxer_notif_iter);
+       }
+
+       /* One less available input port */
+       muxer_comp->available_input_ports--;
+       ret = ensure_available_input_port(priv_comp);
+       if (ret) {
+               /*
+                * Only way to report an error later since this
+                * method does not return anything.
+                */
+               BT_LOGE("Cannot ensure that at least one muxer component's input port is available: "
+                       "muxer-comp-addr=%p, status=%s",
+                       muxer_comp, bt_component_status_string(ret));
+               muxer_comp->error = true;
+               goto end;
        }
 
 end:
@@ -1132,6 +1492,10 @@ void muxer_port_disconnected(struct bt_private_component *priv_comp,
 
        assert(port);
        assert(muxer_comp);
+       BT_LOGD("Port disconnected: "
+               "comp-addr=%p, muxer-comp-addr=%p, port-addr=%p, "
+               "port-name=\"%s\"", priv_comp, muxer_comp,
+               port, bt_port_get_name(port));
 
        /*
         * There's nothing special to do when a port is disconnected
@@ -1139,13 +1503,19 @@ void muxer_port_disconnected(struct bt_private_component *priv_comp,
         * iterators which were already created thanks to connected
         * ports. The fact that the port is disconnected does not cancel
         * the upstream notification iterators created using its
-        * connection: they still exist. The only way to remove an
-        * upstream notification iterator is for its "next" operation to
-        * return BT_NOTIFICATION_ITERATOR_STATUS_END.
+        * connection: they still exist, even if the connection is dead.
+        * The only way to remove an upstream notification iterator is
+        * for its "next" operation to return
+        * BT_NOTIFICATION_ITERATOR_STATUS_END.
         */
        if (bt_port_get_type(port) == BT_PORT_TYPE_INPUT) {
                /* One more available input port */
                muxer_comp->available_input_ports++;
+               BT_LOGD("Leaving disconnected input port available for future connections: "
+                       "comp-addr=%p, muxer-comp-addr=%p, port-addr=%p, "
+                       "port-name=\"%s\", avail-input-port-count=%zu",
+                       priv_comp, muxer_comp, port, bt_port_get_name(port),
+                       muxer_comp->available_input_ports);
        }
 
        bt_put(port);
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