Merge branch 'lukas/erts/tracer-module-and-more/PR-1009/OTP-10268'

* lukas/erts/tracer-module-and-more/PR-1009/OTP-10268: (26 commits)
  erts: Don't trace on link events when port is dead
  erts: more logging in trace_bif_SUITE trace_bif_return
  erts: Make trace_delivered go via sys msg dispatcher again
  erts: Add comment about future trace optimizations
  erts: Optimize tracer reload test
  erts: Document erlang:match_spec_test/3
  runtime_tools: Make dbg work with erl_tracer modules
  runtime_rools: Allow new timestamp trace flags
  runtime_tools: Lots of dbg docs updates
  erts: Deallocate heap fragments from trace nif calls
  eprof: Fix tests after tracer module incompatabilities
  fprof: update to work with new spawned trace event
  erts: Add 'spawned' trace event to 'procs' trace flag
  erts: send and receive no longer need status lock
  erts: Do 'unregister' as "self-tracing"
  erts: Silence harmless valgrind warning in dec_term
  erts: Fix end_per_testcase crash in local_trace_SUITE
  observer: Update ttb to work with tracing on ports
  runtime_tools: Update dbg to work with tracing on ports
  erts: Add tracing examples in match spec docs
  ...

3 files changed, 20 insertions, 10 deletions

diff --git a/lib/kernel/doc/src/seq_trace.xml b/lib/kernel/doc/src/seq_trace.xml
index 1feb3fcb07..5ac199b6a7 100644
--- a/lib/kernel/doc/src/seq_trace.xml
+++ b/lib/kernel/doc/src/seq_trace.xml
@@ -213,9 +213,10 @@ seq_trace:set_token(OldToken), % activate the trace token again
       <type name="tracer"/>
       <desc>
         <p>Sets the system tracer. The system tracer can be either a
-          process or port denoted by <c><anno>Tracer</anno></c>. Returns the previous
-          value (which can be <c>false</c> if no system tracer is
-          active).</p>
+          process, port or <seealso marker="erts:erl_tracer">tracer module</seealso>
+          denoted by <c><anno>Tracer</anno></c>.
+          Returns the previous value (which can be <c>false</c> if no system
+          tracer is active).</p>
         <p>Failure: <c>{badarg, Info}}</c> if <c><anno>Pid</anno></c> is not an
           existing local pid.</p>
       </desc>
@@ -225,7 +226,7 @@ seq_trace:set_token(OldToken), % activate the trace token again
       <fsummary>Return the pid() or port() of the current system tracer.</fsummary>
       <type name="tracer"/>
       <desc>
-        <p>Returns the pid or port identifier of the current system
+        <p>Returns the pid, port identifier or tracer module of the current system
           tracer or <c>false</c> if no system tracer is activated.</p>
       </desc>
     </func>
@@ -298,7 +299,7 @@ TimeStamp = {Seconds, Milliseconds, Microseconds}
       matches a message in a receive statement, according to the trace
       token carried by the received message, empty or not.</p>
     <p>On each Erlang node, a process can be set as the <em>system tracer</em>.
-      This process receives trace messages each time
+      This process will receive trace messages each time
       a message with a trace token is sent or received (if the trace
       token flag <c>send</c> or <c>'receive'</c> is set). The system
       tracer can then print each trace event, write it to a file, or
diff --git a/lib/kernel/src/seq_trace.erl b/lib/kernel/src/seq_trace.erl
index 01ac024c88..cc0c10909b 100644
--- a/lib/kernel/src/seq_trace.erl
+++ b/lib/kernel/src/seq_trace.erl
@@ -106,14 +106,24 @@ reset_trace() ->
 
 %% reset_trace(Pid) -> % this might be a useful function too
 
--type tracer() :: (Pid :: pid()) | port() | 'false'.
+-type tracer() :: (Pid :: pid()) | port() |
+                  (TracerModule :: {module(), term()}) |
+                  'false'.
 
 -spec set_system_tracer(Tracer) -> OldTracer when
       Tracer :: tracer(),
       OldTracer :: tracer().
 
-set_system_tracer(Pid) ->
-    erlang:system_flag(sequential_tracer, Pid).
+set_system_tracer({Module, State} = Tracer) ->
+    case erlang:module_loaded(Module) of
+        false ->
+            Module:enabled(trace_status, erlang:self(), State);
+        true ->
+            ok
+    end,
+    erlang:system_flag(sequential_tracer, Tracer);
+set_system_tracer(Tracer) ->
+    erlang:system_flag(sequential_tracer, Tracer).
 
 -spec get_system_tracer() -> Tracer when
       Tracer :: tracer().
diff --git a/lib/kernel/test/seq_trace_SUITE.erl b/lib/kernel/test/seq_trace_SUITE.erl
index 0a03503163..000994751f 100644
--- a/lib/kernel/test/seq_trace_SUITE.erl
+++ b/lib/kernel/test/seq_trace_SUITE.erl
@@ -787,7 +787,6 @@ start_tracer() ->
     seq_trace:set_system_tracer(Pid),
     Pid.
 
-
 set_token_flags([]) ->
     ok;
 set_token_flags([no_timestamp|Flags]) ->
@@ -836,7 +835,7 @@ check_ts(strict_monotonic_timestamp, Ts) ->
 	    ct:fail({unexpected_timestamp, Ts})
     end,
     ok.
-	
+
 start_node(Name, Param) ->
     test_server:start_node(Name, slave, [{args, Param}]).