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Commit 7e8b88a3 authored Jan 15, 2018 by Tom Zanussi Committed by Steven Rostedt (VMware) Mar 10, 2018

tracing: Add hist trigger support for variable reference aliases

Add support for alias=$somevar where alias can be used as
onmatch.xxx($alias).

Aliases are a way of creating a new name for an existing variable, for
flexibly in making naming more clear in certain cases.  For example in
the below the user perhaps feels that using $new_lat in the synthetic
event invocation is opaque or doesn't fit well stylistically with
previous triggers, so creates an alias of $new_lat named $latency and
uses that in the call instead:

  # echo 'hist:keys=next_pid:new_lat=common_timestamp.usecs' >
    /sys/kernel/debug/tracing/events/sched/sched_switch/trigger

  # echo 'hist:keys=pid:latency=$new_lat:
    onmatch(sched.sched_switch).wake2($latency,pid)' >
    /sys/kernel/debug/tracing/events/synthetic/wake1/trigger

Link: http://lkml.kernel.org/r/ef20a65d921af3a873a6f1e8c71407c926d5586f.1516069914.git.tom.zanussi@linux.intel.com



Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

parent 8b7622bf

kernel/trace/trace_events_hist.c

+67 −7

Original line number	Original line	Diff line number	Diff line
	@@ -228,6 +228,7 @@ enum hist_field_flags {
	HIST_FIELD_FL_EXPR = 1 << 13,		HIST_FIELD_FL_EXPR = 1 << 13,
	HIST_FIELD_FL_VAR_REF = 1 << 14,		HIST_FIELD_FL_VAR_REF = 1 << 14,
	HIST_FIELD_FL_CPU = 1 << 15,		HIST_FIELD_FL_CPU = 1 << 15,
			HIST_FIELD_FL_ALIAS = 1 << 16,
	};		};

	struct var_defs {		struct var_defs {
	@@ -1609,7 +1610,8 @@ static const char hist_field_name(struct hist_field field,

	if (field->field)		if (field->field)
	field_name = field->field->name;		field_name = field->field->name;
	else if (field->flags & HIST_FIELD_FL_LOG2)		else if (field->flags & HIST_FIELD_FL_LOG2 \|\|
			field->flags & HIST_FIELD_FL_ALIAS)
	field_name = hist_field_name(field->operands[0], ++level);		field_name = hist_field_name(field->operands[0], ++level);
	else if (field->flags & HIST_FIELD_FL_TIMESTAMP)		else if (field->flags & HIST_FIELD_FL_TIMESTAMP)
	field_name = "common_timestamp";		field_name = "common_timestamp";
	@@ -2080,7 +2082,7 @@ static struct hist_field create_hist_field(struct hist_trigger_data hist_data,

	hist_field->hist_data = hist_data;		hist_field->hist_data = hist_data;

	if (flags & HIST_FIELD_FL_EXPR)		if (flags & HIST_FIELD_FL_EXPR \|\| flags & HIST_FIELD_FL_ALIAS)
	goto out; /* caller will populate */		goto out; /* caller will populate */

	if (flags & HIST_FIELD_FL_VAR_REF) {		if (flags & HIST_FIELD_FL_VAR_REF) {
	@@ -2217,11 +2219,19 @@ static int init_var_ref(struct hist_field *ref_field,
	}		}
	}		}

			if (var_field->var.name) {
	ref_field->name = kstrdup(var_field->var.name, GFP_KERNEL);		ref_field->name = kstrdup(var_field->var.name, GFP_KERNEL);
	if (!ref_field->name) {		if (!ref_field->name) {
	err = -ENOMEM;		err = -ENOMEM;
	goto free;		goto free;
	}		}
			} else if (var_field->name) {
			ref_field->name = kstrdup(var_field->name, GFP_KERNEL);
			if (!ref_field->name) {
			err = -ENOMEM;
			goto free;
			}
			}

	ref_field->type = kstrdup(var_field->type, GFP_KERNEL);		ref_field->type = kstrdup(var_field->type, GFP_KERNEL);
	if (!ref_field->type) {		if (!ref_field->type) {
	@@ -2382,6 +2392,28 @@ parse_field(struct hist_trigger_data hist_data, struct trace_event_file file,
	return field;		return field;
	}		}

			static struct hist_field create_alias(struct hist_trigger_data hist_data,
			struct hist_field *var_ref,
			char *var_name)
			{
			struct hist_field *alias = NULL;
			unsigned long flags = HIST_FIELD_FL_ALIAS \| HIST_FIELD_FL_VAR;

			alias = create_hist_field(hist_data, NULL, flags, var_name);
			if (!alias)
			return NULL;

			alias->fn = var_ref->fn;
			alias->operands[0] = var_ref;

			if (init_var_ref(alias, var_ref, var_ref->system, var_ref->event_name)) {
			destroy_hist_field(alias, 0);
			return NULL;
			}

			return alias;
			}

	static struct hist_field parse_atom(struct hist_trigger_data hist_data,		static struct hist_field parse_atom(struct hist_trigger_data hist_data,
	struct trace_event_file file, char str,		struct trace_event_file file, char str,
	unsigned long flags, char var_name)		unsigned long flags, char var_name)
	@@ -2415,6 +2447,13 @@ static struct hist_field parse_atom(struct hist_trigger_data hist_data,
	if (hist_field) {		if (hist_field) {
	hist_data->var_refs[hist_data->n_var_refs] = hist_field;		hist_data->var_refs[hist_data->n_var_refs] = hist_field;
	hist_field->var_ref_idx = hist_data->n_var_refs++;		hist_field->var_ref_idx = hist_data->n_var_refs++;
			if (var_name) {
			hist_field = create_alias(hist_data, hist_field, var_name);
			if (!hist_field) {
			ret = -ENOMEM;
			goto out;
			}
			}
	return hist_field;		return hist_field;
	}		}
	} else		} else
	@@ -2515,6 +2554,26 @@ static int check_expr_operands(struct hist_field *operand1,
	unsigned long operand1_flags = operand1->flags;		unsigned long operand1_flags = operand1->flags;
	unsigned long operand2_flags = operand2->flags;		unsigned long operand2_flags = operand2->flags;

			if ((operand1_flags & HIST_FIELD_FL_VAR_REF) \|\|
			(operand1_flags & HIST_FIELD_FL_ALIAS)) {
			struct hist_field *var;

			var = find_var_field(operand1->var.hist_data, operand1->name);
			if (!var)
			return -EINVAL;
			operand1_flags = var->flags;
			}

			if ((operand2_flags & HIST_FIELD_FL_VAR_REF) \|\|
			(operand2_flags & HIST_FIELD_FL_ALIAS)) {
			struct hist_field *var;

			var = find_var_field(operand2->var.hist_data, operand2->name);
			if (!var)
			return -EINVAL;
			operand2_flags = var->flags;
			}

	if ((operand1_flags & HIST_FIELD_FL_TIMESTAMP_USECS) !=		if ((operand1_flags & HIST_FIELD_FL_TIMESTAMP_USECS) !=
	(operand2_flags & HIST_FIELD_FL_TIMESTAMP_USECS))		(operand2_flags & HIST_FIELD_FL_TIMESTAMP_USECS))
	return -EINVAL;		return -EINVAL;
	@@ -4646,7 +4705,8 @@ static void hist_field_print(struct seq_file m, struct hist_field hist_field)
	else if (hist_field->flags & HIST_FIELD_FL_CPU)		else if (hist_field->flags & HIST_FIELD_FL_CPU)
	seq_puts(m, "cpu");		seq_puts(m, "cpu");
	else if (field_name) {		else if (field_name) {
	if (hist_field->flags & HIST_FIELD_FL_VAR_REF)		if (hist_field->flags & HIST_FIELD_FL_VAR_REF \|\|
			hist_field->flags & HIST_FIELD_FL_ALIAS)
	seq_putc(m, '$');		seq_putc(m, '$');
	seq_printf(m, "%s", field_name);		seq_printf(m, "%s", field_name);
	}		}