erts: Implement tracer modules

Add the possibility to use modules as trace data receivers. The functions
in the module have to be nifs as otherwise complex trace probes will be
very hard to handle (complex means trace probes for ports for example).

This commit changes the way that the ptab->tracer field works from always
being an immediate, to now be NIL if no tracer is present or else be
the tuple {TracerModule, TracerState} where TracerModule is an atom that
is later used to lookup the appropriate tracer callbacks to call and
TracerState is just passed to the tracer callback. The default process and
port tracers have been rewritten to use the new API.

This commit also changes the order which trace messages are delivered to the
potential tracer process. Any enif_send done in a tracer module may be delayed
indefinitely because of lock order issues. If a message is delayed any other
trace message send from that process is also delayed so that order is preserved
for each traced entity. This means that for some trace events (i.e. send/receive)
the events may come in an unintuitive order (receive before send) to the
trace receiver. Timestamps are taken when the trace message is generated so
trace messages from differented processes may arrive with the timestamp
out of order.

Both the erlang:trace and seq_trace:set_system_tracer accept the new tracer
module tracers and also the backwards compatible arguments.

OTP-10267

1 files changed, 29 insertions, 0 deletions

diff --git a/erts/emulator/beam/erlang_dtrace.d b/erts/emulator/beam/erlang_dtrace.d
index 73ef5a108a..237889e0f5 100644
--- a/erts/emulator/beam/erlang_dtrace.d
+++ b/erts/emulator/beam/erlang_dtrace.d
@@ -700,6 +700,35 @@ provider erlang {
      */
     probe efile_drv__return(int, int, char *, int, int, int);
 
+
+/*
+ * The set of probes called by the erlang tracer nif backend. In order
+ * to receive events on these you both have to enable tracing in erlang
+ * using the trace bifs and also from dtrace/systemtap.
+ */
+
+
+    /**
+     * A trace message of type `event` was triggered by process `p`.
+     *
+     *
+     * @param p the PID (string form) of the process
+     * @param event the event that was triggered (i.e. call or spawn)
+     * @param state the state of the tracer nif as a string
+     * @param arg1 first argument to the trace event
+     * @param arg2 second argument to the trace event
+     */
+    probe trace(char *p, char *event, char *state, char *arg1, char *arg2);
+
+    /**
+     * A sequence trace message of type `label` was triggered.
+     *
+     * @param state the state of the tracer nif as a string
+     * @param label the seq trace label
+     * @param seq_info the seq trace info tuple as a string
+     */
+    probe trace_seq(char *state, char *label, char *seq_info);
+
 /*
  * NOTE:
  * For formatting int64_t arguments within a D script, see: