Warn on event registration/unregistration failure

Warn whenever event registration/unregistration fails, including when
synchonizing the event list.

Silently ignoring errors makes identification of those failures tricky.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I764455c8535ddb906325942e70aa689ca21c04bb

diff --git a/src/lttng-events.c b/src/lttng-events.c
index 1bfa49433aaeae36d38bdcad278cd583f2e9971b..2b4b1039803222cf0e383ad943c6dc991cc1dcb1 100644 (file)
--- a/src/lttng-events.c
+++ b/src/lttng-events.c
@@ -71,7 +71,7 @@ static void lttng_event_enabler_sync(struct lttng_event_enabler_common *event_en
 
 static void _lttng_event_destroy(struct lttng_kernel_event_common *event);
 static void _lttng_channel_destroy(struct lttng_kernel_channel_buffer *chan);
-static int _lttng_event_unregister(struct lttng_kernel_event_common *event);
+static void _lttng_event_unregister(struct lttng_kernel_event_common *event);
 static
 int _lttng_event_recorder_metadata_statedump(struct lttng_kernel_event_common *event);
 static
@@ -360,10 +360,8 @@ void lttng_session_destroy(struct lttng_kernel_session *session)
                ret = lttng_syscalls_unregister_syscall_table(&chan_priv->parent.syscall_table);
                WARN_ON(ret);
        }
-       list_for_each_entry(event_recorder_priv, &session->priv->events, parent.node) {
-               ret = _lttng_event_unregister(&event_recorder_priv->pub->parent);
-               WARN_ON(ret);
-       }
+       list_for_each_entry(event_recorder_priv, &session->priv->events, parent.node)
+               _lttng_event_unregister(&event_recorder_priv->pub->parent);
        synchronize_trace();    /* Wait for in-flight events to complete */
        list_for_each_entry(chan_priv, &session->priv->chan, node) {
                ret = lttng_syscalls_destroy_syscall_table(&chan_priv->parent.syscall_table);
@@ -410,10 +408,8 @@ void lttng_event_notifier_group_destroy(
        WARN_ON(ret);
 
        list_for_each_entry_safe(event_notifier_priv, tmpevent_notifier_priv,
-                       &event_notifier_group->event_notifiers_head, parent.node) {
-               ret = _lttng_event_unregister(&event_notifier_priv->pub->parent);
-               WARN_ON(ret);
-       }
+                       &event_notifier_group->event_notifiers_head, parent.node)
+               _lttng_event_unregister(&event_notifier_priv->pub->parent);
 
        /* Wait for in-flight event notifier to complete */
        synchronize_trace();
@@ -1337,15 +1333,14 @@ int lttng_kernel_counter_clear(struct lttng_counter *counter,
        return counter->ops->counter_clear(counter->counter, dim_indexes);
 }
 
-/* Only used for tracepoints for now. */
+/* Only used for tracepoints and system calls for now. */
 static
 void register_event(struct lttng_kernel_event_common *event)
 {
        const struct lttng_kernel_event_desc *desc;
        int ret = -EINVAL;
 
-       if (event->priv->registered)
-               return;
+       WARN_ON_ONCE(event->priv->registered);
 
        desc = event->priv->desc;
        switch (event->priv->instrumentation) {
@@ -1383,18 +1378,19 @@ void register_event(struct lttng_kernel_event_common *event)
        default:
                WARN_ON_ONCE(1);
        }
+       WARN_ON_ONCE(ret);
        if (!ret)
                event->priv->registered = 1;
 }
 
-int _lttng_event_unregister(struct lttng_kernel_event_common *event)
+static
+void unregister_event(struct lttng_kernel_event_common *event)
 {
        struct lttng_kernel_event_common_private *event_priv = event->priv;
        const struct lttng_kernel_event_desc *desc;
        int ret = -EINVAL;
 
-       if (!event_priv->registered)
-               return 0;
+       WARN_ON_ONCE(!event->priv->registered);
 
        desc = event_priv->desc;
        switch (event_priv->instrumentation) {
@@ -1446,9 +1442,16 @@ int _lttng_event_unregister(struct lttng_kernel_event_common *event)
        default:
                WARN_ON_ONCE(1);
        }
+       WARN_ON_ONCE(ret);
        if (!ret)
                event_priv->registered = 0;
-       return ret;
+}
+
+static
+void _lttng_event_unregister(struct lttng_kernel_event_common *event)
+{
+       if (event->priv->registered)
+               unregister_event(event);
 }
 
 /*
@@ -2652,9 +2655,11 @@ void lttng_sync_event_list(struct list_head *event_enabler_list,
                 * Sync tracepoint registration with event enabled state.
                 */
                if (enabled) {
-                       register_event(event);
+                       if (!event_priv->registered)
+                               register_event(event);
                } else {
-                       _lttng_event_unregister(event);
+                       if (event_priv->registered)
+                               unregister_event(event);
                }
 
                lttng_event_sync_filter_state(event);