trace: add trace_event_get_state_backends()
Code that checks dstate is unaware of SystemTap and LTTng UST dstate, so
the following trace event will not fire when solely enabled by SystemTap
or LTTng UST:
if (trace_event_get_state(TRACE_MY_EVENT)) {
str = g_strdup_printf("Expensive string to generate ...",
...);
trace_my_event(str);
g_free(str);
}
Add trace_event_get_state_backends() to fetch backend dstate. Those
backends that use QEMU dstate fetch it as part of
generate_h_backend_dstate().
Update existing trace_event_get_state() callers to use
trace_event_get_state_backends() instead.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20170731140718.22010-3-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
diff --git a/trace/control.h b/trace/control.h
index b931824..1903e22 100644
--- a/trace/control.h
+++ b/trace/control.h
@@ -96,7 +96,7 @@
* trace_event_get_state:
* @id: Event identifier name.
*
- * Get the tracing state of an event (both static and dynamic).
+ * Get the tracing state of an event, both static and the QEMU dynamic state.
*
* If the event has the disabled property, the check will have no performance
* impact.
@@ -105,6 +105,22 @@
((id ##_ENABLED) && trace_event_get_state_dynamic_by_id(id))
/**
+ * trace_event_get_state_backends:
+ * @id: Event identifier name.
+ *
+ * Get the tracing state of an event, both static and dynamic state from all
+ * compiled-in backends.
+ *
+ * If the event has the disabled property, the check will have no performance
+ * impact.
+ *
+ * Returns: true if at least one backend has the event enabled and the event
+ * does not have the disabled property.
+ */
+#define trace_event_get_state_backends(id) \
+ ((id ##_ENABLED) && id ##_BACKEND_DSTATE())
+
+/**
* trace_event_get_vcpu_state:
* @vcpu: Target vCPU.
* @id: Event identifier name.