perf script python: Allocate memory only if handler exists

Avoid allocating memory if hook handler is not available. This saves
unused memory allocation and simplifies error path.

Let handler in python_process_tracepoint point to either tracepoint
specific or trace_unhandled hook. Use dict to check if handler points to
trace_unhandled.

Remove the exit label in python_process_general_event and return when no
handler is available.

Signed-off-by: Arun Kalyanasundaram <arunkaly@google.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Carrillo-Cisneros <davidcc@google.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Seongjae Park <sj38.park@gmail.com>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/20170721220422.63962-2-arunkaly@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/scripting-engines/trace-event-python.c b/tools/perf/util/scripting-engines/trace-event-python.c
index 57b7a00..8a8f482 100644 (file)
--- a/tools/perf/util/scripting-engines/trace-event-python.c
+++ b/tools/perf/util/scripting-engines/trace-event-python.c
@@ -407,10 +407,7 @@ static void python_process_tracepoint(struct perf_sample *sample,
        void *data = sample->raw_data;
        unsigned long long nsecs = sample->time;
        const char *comm = thread__comm_str(al->thread);
-
-       t = PyTuple_New(MAX_FIELDS);
-       if (!t)
-               Py_FatalError("couldn't create Python tuple");
+       const char *default_handler_name = "trace_unhandled";
 
        if (!event) {
                snprintf(handler_name, sizeof(handler_name),
@@ -427,10 +424,19 @@ static void python_process_tracepoint(struct perf_sample *sample,
 
        handler = get_handler(handler_name);
        if (!handler) {
+               handler = get_handler(default_handler_name);
+               if (!handler)
+                       return;
                dict = PyDict_New();
                if (!dict)
                        Py_FatalError("couldn't create Python dict");
        }
+
+       t = PyTuple_New(MAX_FIELDS);
+       if (!t)
+               Py_FatalError("couldn't create Python tuple");
+
+
        s = nsecs / NSEC_PER_SEC;
        ns = nsecs - s * NSEC_PER_SEC;
 
@@ -445,7 +451,7 @@ static void python_process_tracepoint(struct perf_sample *sample,
        /* ip unwinding */
        callchain = python_process_callchain(sample, evsel, al);
 
-       if (handler) {
+       if (!dict) {
                PyTuple_SetItem(t, n++, PyInt_FromLong(cpu));
                PyTuple_SetItem(t, n++, PyInt_FromLong(s));
                PyTuple_SetItem(t, n++, PyInt_FromLong(ns));
@@ -484,23 +490,23 @@ static void python_process_tracepoint(struct perf_sample *sample,
                } else { /* FIELD_IS_NUMERIC */
                        obj = get_field_numeric_entry(event, field, data);
                }
-               if (handler)
+               if (!dict)
                        PyTuple_SetItem(t, n++, obj);
                else
                        pydict_set_item_string_decref(dict, field->name, obj);
 
        }
 
-       if (!handler)
+       if (dict)
                PyTuple_SetItem(t, n++, dict);
 
        if (_PyTuple_Resize(&t, n) == -1)
                Py_FatalError("error resizing Python tuple");
 
-       if (handler) {
+       if (!dict) {
                call_object(handler, t, handler_name);
        } else {
-               try_call_object("trace_unhandled", t);
+               call_object(handler, t, default_handler_name);
                Py_DECREF(dict);
        }
 
@@ -799,6 +805,12 @@ static void python_process_general_event(struct perf_sample *sample,
        static char handler_name[64];
        unsigned n = 0;
 
+       snprintf(handler_name, sizeof(handler_name), "%s", "process_event");
+
+       handler = get_handler(handler_name);
+       if (!handler)
+               return;
+
        /*
         * Use the MAX_FIELDS to make the function expandable, though
         * currently there is only one item for the tuple.
@@ -815,12 +827,6 @@ static void python_process_general_event(struct perf_sample *sample,
        if (!dict_sample)
                Py_FatalError("couldn't create Python dictionary");
 
-       snprintf(handler_name, sizeof(handler_name), "%s", "process_event");
-
-       handler = get_handler(handler_name);
-       if (!handler)
-               goto exit;
-
        pydict_set_item_string_decref(dict, "ev_name", PyString_FromString(perf_evsel__name(evsel)));
        pydict_set_item_string_decref(dict, "attr", PyString_FromStringAndSize(
                        (const char *)&evsel->attr, sizeof(evsel->attr)));
@@ -861,7 +867,7 @@ static void python_process_general_event(struct perf_sample *sample,
                Py_FatalError("error resizing Python tuple");
 
        call_object(handler, t, handler_name);
-exit:
+
        Py_DECREF(dict);
        Py_DECREF(t);
 }