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Commit e91eefd7 authored by Tom Zanussi's avatar Tom Zanussi Committed by Steven Rostedt (VMware)
Browse files

tracing: Add alternative synthetic event trace action syntax 

Add a 'trace(synthetic_event_name, params)' alternative to
synthetic_event_name(params).

Currently, the syntax used for generating synthetic events is to
invoke synthetic_event_name(params) i.e. use the synthetic event name
as a function call.

Users requested a new form that more explicitly shows that the
synthetic event is in effect being traced.  In this version, a new
'trace()' keyword is used, and the synthetic event name is passed in
as the first argument.

In addition, for the sake of consistency with other actions, change
the documention to emphasize the trace() form over the function-call
form, which remains documented as equivalent.

Link: http://lkml.kernel.org/r/d082773e50232a001480cf837679a1e01c1a2eb7.1550100284.git.tom.zanussi@linux.intel.com



Signed-off-by: default avatarTom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent ff0d35e2

Documentation/trace/histogram.rst

+37 −17
Original line number Diff line number Diff line
@@ -1873,31 +1873,45 @@ The available handlers are: 


The available actions are:



  - <synthetic_event_name>(param list)         - generate synthetic event

  - trace(<synthetic_event_name>,param list)   - generate synthetic event

  - save(field,...)                            - save current event fields

  - snapshot()                                 - snapshot the trace buffer



The following commonly-used handler.action pairs are available:



  - onmatch(matching.event).<synthetic_event_name>(param list)

  - onmatch(matching.event).trace(<synthetic_event_name>,param list)



    The 'onmatch(matching.event).<synthetic_event_name>(params)' hist

    trigger action is invoked whenever an event matches and the

    histogram entry would be added or updated.  It causes the named

    synthetic event to be generated with the values given in the

    The 'onmatch(matching.event).trace(<synthetic_event_name>,param

    list)' hist trigger action is invoked whenever an event matches

    and the histogram entry would be added or updated.  It causes the

    named synthetic event to be generated with the values given in the

    'param list'.  The result is the generation of a synthetic event

    that consists of the values contained in those variables at the

    time the invoking event was hit.



    The 'param list' consists of one or more parameters which may be

    either variables or fields defined on either the 'matching.event'

    or the target event.  The variables or fields specified in the

    param list may be either fully-qualified or unqualified.  If a

    variable is specified as unqualified, it must be unique between

    the two events.  A field name used as a param can be unqualified

    if it refers to the target event, but must be fully qualified if

    it refers to the matching event.  A fully-qualified name is of the

    form 'system.event_name.$var_name' or 'system.event_name.field'.

    time the invoking event was hit.  For example, if the synthetic

    event name is 'wakeup_latency', a wakeup_latency event is

    generated using onmatch(event).trace(wakeup_latency,arg1,arg2).



    There is also an equivalent alternative form available for

    generating synthetic events.  In this form, the synthetic event

    name is used as if it were a function name.  For example, using

    the 'wakeup_latency' synthetic event name again, the

    wakeup_latency event would be generated by invoking it as if it

    were a function call, with the event field values passed in as

    arguments: onmatch(event).wakeup_latency(arg1,arg2).  The syntax

    for this form is:



      onmatch(matching.event).<synthetic_event_name>(param list)



    In either case, the 'param list' consists of one or more

    parameters which may be either variables or fields defined on

    either the 'matching.event' or the target event.  The variables or

    fields specified in the param list may be either fully-qualified

    or unqualified.  If a variable is specified as unqualified, it

    must be unique between the two events.  A field name used as a

    param can be unqualified if it refers to the target event, but

    must be fully qualified if it refers to the matching event.  A

    fully-qualified name is of the form 'system.event_name.$var_name'

    or 'system.event_name.field'.



    The 'matching.event' specification is simply the fully qualified

    event name of the event that matches the target event for the
@@ -1928,6 +1942,12 @@ The following commonly-used handler.action pairs are available: 
              wakeup_new_test($testpid) if comm=="cyclictest"' >> \

              /sys/kernel/debug/tracing/events/sched/sched_wakeup_new/trigger



    Or, equivalently, using the 'trace' keyword syntax:



    # echo 'hist:keys=$testpid:testpid=pid:onmatch(sched.sched_wakeup_new).\

            trace(wakeup_new_test,$testpid) if comm=="cyclictest"' >> \

            /sys/kernel/debug/tracing/events/sched/sched_wakeup_new/trigger



    Creating and displaying a histogram based on those events is now

    just a matter of using the fields and new synthetic event in the

    tracing/events/synthetic directory, as usual::

kernel/trace/trace.c

+1 −1
Original line number Diff line number Diff line
@@ -4918,7 +4918,7 @@ static const char readme_msg[] = 
	"\t        onmax(var)               - invoke if var exceeds current max\n"

	"\t        onchange(var)            - invoke action if var changes\n\n"

	"\t    The available actions are:\n\n"

	"\t        <synthetic_event>(param list)        - generate synthetic event\n"

	"\t        trace(<synthetic_event>,param list)  - generate synthetic event\n"

	"\t        save(field,...)                      - save current event fields\n"

#ifdef CONFIG_TRACER_SNAPSHOT

	"\t        snapshot()                           - snapshot the trace buffer\n"

kernel/trace/trace_events_hist.c

+38 −4
Original line number Diff line number Diff line
@@ -419,6 +419,8 @@ struct action_data { 
	 */

	unsigned int		var_ref_idx;

	struct synth_event	*synth_event;

	bool			use_trace_keyword;

	char			*synth_event_name;



	union {

		struct {
@@ -3700,6 +3702,8 @@ static void action_data_destroy(struct action_data *data) 
	if (data->synth_event)

		data->synth_event->ref--;



	kfree(data->synth_event_name);



	kfree(data);

}
@@ -3781,6 +3785,7 @@ static int track_data_create(struct hist_trigger_data *hist_data, 
static int parse_action_params(char *params, struct action_data *data)

{

	char *param, *saved_param;

	bool first_param = true;

	int ret = 0;



	while (params) {
@@ -3809,6 +3814,13 @@ static int parse_action_params(char *params, struct action_data *data) 
			goto out;

		}



		if (first_param && data->use_trace_keyword) {

			data->synth_event_name = saved_param;

			first_param = false;

			continue;

		}

		first_param = false;



		data->params[data->n_params++] = saved_param;

	}

 out:
@@ -3886,6 +3898,9 @@ static int action_parse(char *str, struct action_data *data, 
	} else {

		char *params = strsep(&str, ")");



		if (str_has_prefix(action_name, "trace"))

			data->use_trace_keyword = true;



		if (params) {

			ret = parse_action_params(params, data);

			if (ret)
@@ -4088,13 +4103,19 @@ static int trace_action_create(struct hist_trigger_data *hist_data, 
	unsigned int i, var_ref_idx;

	unsigned int field_pos = 0;

	struct synth_event *event;

	char *synth_event_name;

	int ret = 0;



	lockdep_assert_held(&event_mutex);



	event = find_synth_event(data->action_name);

	if (data->use_trace_keyword)

		synth_event_name = data->synth_event_name;

	else

		synth_event_name = data->action_name;



	event = find_synth_event(synth_event_name);

	if (!event) {

		hist_err("trace action: Couldn't find synthetic event: ", data->action_name);

		hist_err("trace action: Couldn't find synthetic event: ", synth_event_name);

		return -EINVAL;

	}
@@ -4841,8 +4862,10 @@ static void print_action_spec(struct seq_file *m, 
				seq_puts(m, ",");

		}

	} else if (data->action == ACTION_TRACE) {

		if (data->use_trace_keyword)

			seq_printf(m, "%s", data->synth_event_name);

		for (i = 0; i < data->n_params; i++) {

			if (i)

			if (i || data->use_trace_keyword)

				seq_puts(m, ",");

			seq_printf(m, "%s", data->params[i]);

		}
@@ -4890,6 +4913,7 @@ static bool actions_match(struct hist_trigger_data *hist_data, 
	for (i = 0; i < hist_data->n_actions; i++) {

		struct action_data *data = hist_data->actions[i];

		struct action_data *data_test = hist_data_test->actions[i];

		char *action_name, *action_name_test;



		if (data->handler != data_test->handler)

			return false;
@@ -4904,7 +4928,17 @@ static bool actions_match(struct hist_trigger_data *hist_data, 
				return false;

		}



		if (strcmp(data->action_name, data_test->action_name) != 0)

		if (data->use_trace_keyword)

			action_name = data->synth_event_name;

		else

			action_name = data->action_name;



		if (data_test->use_trace_keyword)

			action_name_test = data_test->synth_event_name;

		else

			action_name_test = data_test->action_name;



		if (strcmp(action_name, action_name_test) != 0)

			return false;



		if (data->handler == HANDLER_ONMATCH) {