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authorLukas Larsson <[email protected]>2015-12-10 11:10:46 +0100
committerLukas Larsson <[email protected]>2016-04-15 15:06:27 +0200
commit37092dab15448ef6a078800e3ff0cc41880ea765 (patch)
treecb8a30fe427cec5f82d96b3e05258d4fd263e58f /lib/kernel/doc
parent13bd4ca2493d8a76f9d835c27163b56ba86c2aef (diff)
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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
Diffstat (limited to 'lib/kernel/doc')
-rw-r--r--lib/kernel/doc/src/seq_trace.xml11
1 files changed, 6 insertions, 5 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