Add support for alias=$somevar where alias can be used as
onmatch($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
Signed-off-by: Tom Zanussi <[email protected]>
---
kernel/trace/trace_events_hist.c | 61 ++++++++++++++++++++++++++++++++++++++--
1 file changed, 58 insertions(+), 3 deletions(-)
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 5b3d66f..fad93ee 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -227,6 +227,7 @@ enum hist_field_flags {
HIST_FIELD_FL_EXPR = 1 << 14,
HIST_FIELD_FL_VAR_REF = 1 << 15,
HIST_FIELD_FL_CPU = 1 << 16,
+ HIST_FIELD_FL_ALIAS = 1 << 17,
};
struct var_defs {
@@ -1527,7 +1528,8 @@ static const char *hist_field_name(struct hist_field
*field,
if (field->field)
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);
else if (field->flags & HIST_FIELD_FL_TIMESTAMP)
field_name = "$common_timestamp";
@@ -1983,7 +1985,7 @@ static struct hist_field *create_hist_field(struct
hist_trigger_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 */
if (flags & HIST_FIELD_FL_VAR_REF) {
@@ -2241,6 +2243,29 @@ static struct hist_field *parse_var_ref(struct
trace_array *tr,
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 |
+ HIST_FIELD_FL_VAR_ONLY;
+
+ 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)) {
+ destroy_hist_field(alias, 0);
+ return NULL;
+ }
+
+ return alias;
+}
+
struct hist_field *parse_atom(struct hist_trigger_data *hist_data,
struct trace_event_file *file, char *str,
unsigned long *flags, char *var_name)
@@ -2275,6 +2300,13 @@ struct hist_field *parse_atom(struct hist_trigger_data
*hist_data,
if (hist_field) {
hist_data->var_refs[hist_data->n_var_refs] = hist_field;
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;
}
} else
@@ -2378,6 +2410,26 @@ static int check_expr_operands(struct hist_field
*operand1,
unsigned long operand1_flags = operand1->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) !=
(operand2_flags & HIST_FIELD_FL_TIMESTAMP_USECS))
return -EINVAL;
@@ -4379,8 +4431,11 @@ static void hist_field_print(struct seq_file *m, struct
hist_field *hist_field)
seq_puts(m, "$common_timestamp");
else if (hist_field->flags & HIST_FIELD_FL_CPU)
seq_puts(m, "cpu");
- else if (field_name)
+ else if (field_name) {
+ if (hist_field->flags & HIST_FIELD_FL_ALIAS)
+ seq_putc(m, '$');
seq_printf(m, "%s", field_name);
+ }
if (hist_field->flags) {
const char *flags_str = get_hist_field_flags(hist_field);
--
1.9.3
