Add __string_from_user

[lttng-modules.git] / probes / lttng-ftrace.c

diff --git a/probes/lttng-ftrace.c b/probes/lttng-ftrace.c
index c18a4702c90be4d8df6ef06490b2445385ed7e4d..1aa71831e86fd4bd21780278bb78d385f79ebc8b 100644 (file)
--- a/probes/lttng-ftrace.c
+++ b/probes/lttng-ftrace.c
@@ -11,6 +11,10 @@
  * Ftrace function tracer does not seem to provide synchronization between probe
  * teardown and callback execution. Therefore, we make this module permanently
  * loaded (unloadable).
+ *
+ * TODO: Move to register_ftrace_function() (which is exported for
+ * modules) for Linux >= 3.0. It is faster (only enables the selected
+ * functions), and will stay there.
  */
 
 #include <linux/module.h>
@@ -34,9 +38,14 @@ void lttng_ftrace_handler(unsigned long ip, unsigned long parent_ip, void **data
        } payload;
        int ret;
 
-       if (!ACCESS_ONCE(chan->session->active))
+       if (unlikely(!ACCESS_ONCE(chan->session->active)))
+               return;
+       if (unlikely(!ACCESS_ONCE(chan->enabled)))
                return;
-       lib_ring_buffer_ctx_init(&ctx, chan->chan, NULL,
+       if (unlikely(!ACCESS_ONCE(event->enabled)))
+               return;
+
+       lib_ring_buffer_ctx_init(&ctx, chan->chan, event,
                                 sizeof(payload), ltt_alignof(payload), -1);
        ret = chan->ops->event_reserve(&ctx, event->id);
        if (ret < 0)