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authorLukas Larsson <[email protected]>2016-05-11 11:16:16 +0200
committerRickard Green <[email protected]>2016-05-11 16:48:37 +0200
commit3471d44a6a5ed5ab038c4cdc76b350119fe745e2 (patch)
tree629de2dea305b83ee00d685cffe6b8e9533eb7d7 /erts/doc/src
parent4aea719054a594a06aceb34afca0ea3df65ead77 (diff)
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erts: Only allow remove from trace_status callback
Make it so that it is only possible to remove a tracer via returning remove from an erl_tracer. This limition is put in place in order to avoid a lot of lock checking and taking in various places, especially in regards to trace events happening on dirty schedulers.
Diffstat (limited to 'erts/doc/src')
-rw-r--r--erts/doc/src/erl_tracer.xml20
1 files changed, 11 insertions, 9 deletions
diff --git a/erts/doc/src/erl_tracer.xml b/erts/doc/src/erl_tracer.xml
index 2075b962d8..7fd5512b33 100644
--- a/erts/doc/src/erl_tracer.xml
+++ b/erts/doc/src/erl_tracer.xml
@@ -90,7 +90,7 @@
<item>If not set to <c>true</c>, the tracer has been requested to
include the output of a match specification that was run.</item>
<tag><c>scheduler_id</c></tag>
- <item>Set to a number of the scheduler id is to be included by the tracer.
+ <item>Set to a number if the scheduler id is to be included by the tracer.
Otherwise it is set to <c>undefined</c>.</item>
</taglist>
</p>
@@ -155,14 +155,13 @@
overhead associated with tracing. If <c>trace</c> is returned the
necessary trace data will be created and the trace call-back of the tracer
will be called. If <c>discard</c> is returned, this trace call
- will be discarded and no call to trace will be done. If
- <c>remove</c> is returned, the VM will attempt to remove this tracer
- from the tracee, together with any trace flags set on the tracee.
+ will be discarded and no call to trace will be done.
</p>
<p><c>trace_status</c> is a special type of <c>TraceTag</c> which is used
to check if the tracer should still be active. It is called in multiple
scenarios, but most significantly it is used when tracing is started
- using this tracer.</p>
+ using this tracer. If <c>remove</c> is returned when the <c>trace_status</c>
+ is checked, the tracer will be removed from the tracee.</p>
<p>This function may be called multiple times per tracepoint, so it
is important that it is both fast and side effect free.</p>
</desc>
@@ -617,7 +616,7 @@ static int upgrade(ErlNifEnv* env, void** priv_data, void** old_priv_data,
}
/*
- * argv[0]: Trace Tag
+ * argv[0]: TraceTag
* argv[1]: TracerState
* argv[2]: Tracee
*/
@@ -626,8 +625,11 @@ static ERL_NIF_TERM enabled(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
ErlNifPid to_pid;
if (enif_get_local_pid(env, argv[1], &amp;to_pid))
if (!enif_is_process_alive(env, &amp;to_pid))
- /* tracer is dead so we should remove this tracepoint */
- return enif_make_atom(env, "remove");
+ if (enif_is_identical(enif_make_atom(env, "trace_status"), argv[0]))
+ /* tracer is dead so we should remove this tracepoint */
+ return enif_make_atom(env, "remove");
+ else
+ return enif_make_atom(env, "discard");
/* Only generate trace for when tracer != tracee */
if (enif_is_identical(argv[1], argv[2]))
@@ -645,7 +647,7 @@ static ERL_NIF_TERM enabled(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
}
/*
- * argv[0]: Trace Tag, should only be 'send'
+ * argv[0]: TraceTag, should only be 'send'
* argv[1]: TracerState, process to send {argv[2], argv[4]} to
* argv[2]: Tracee
* argv[3]: Message, ignored