[for-next][PATCH 15/24] tracing: Remove open-coding of hist trigger var_ref management

Steven Rostedt
2018-12-21T17:57:46Z

From: Tom Zanussi <tom.zanussi@linux.intel.com>

Have create_var_ref() manage the hist trigger's var_ref list, rather
than having similar code doing it in multiple places. This cleans up
the code and makes sure var_refs are always accounted properly.

Also, document the var_ref-related functions to make what their
purpose clearer.

Link: http://lkml.kernel.org/r/05ddae93ff514e66fc03897d6665231892939913.1545161087.git.tom.zanussi@linux.intel.com

Acked-by: Namhyung Kim <namhyung@kernel.org>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
kernel/trace/trace_events_hist.c | 93 +++++++++++++++++++++++++-------
1 file changed, 75 insertions(+), 18 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index f3caf6e484f4..6309f4dbfb9c 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -1292,6 +1292,17 @@ static u64 hist_field_cpu(struct hist_field *hist_field,
return cpu;
}

+/**
+ * check_field_for_var_ref - Check if a VAR_REF field references a variable
+ * @hist_field: The VAR_REF field to check
+ * @var_data: The hist trigger that owns the variable
+ * @var_idx: The trigger variable identifier
+ *
+ * Check the given VAR_REF field to see whether or not it references
+ * the given variable associated with the given trigger.
+ *
+ * Return: The VAR_REF field if it does reference the variable, NULL if not
+ */
static struct hist_field *
check_field_for_var_ref(struct hist_field *hist_field,
struct hist_trigger_data *var_data,
@@ -1306,6 +1317,18 @@ check_field_for_var_ref(struct hist_field *hist_field,
return NULL;
}

+/**
+ * find_var_ref - Check if a trigger has a reference to a trigger variable
+ * @hist_data: The hist trigger that might have a reference to the variable
+ * @var_data: The hist trigger that owns the variable
+ * @var_idx: The trigger variable identifier
+ *
+ * Check the list of var_refs[] on the first hist trigger to see
+ * whether any of them are references to the variable on the second
+ * trigger.
+ *
+ * Return: The VAR_REF field referencing the variable if so, NULL if not
+ */
static struct hist_field *find_var_ref(struct hist_trigger_data *hist_data,
struct hist_trigger_data *var_data,
unsigned int var_idx)
@@ -1322,6 +1345,20 @@ static struct hist_field *find_var_ref(struct hist_trigger_data *hist_data,
return NULL;
}

+/**
+ * find_any_var_ref - Check if there is a reference to a given trigger variable
+ * @hist_data: The hist trigger
+ * @var_idx: The trigger variable identifier
+ *
+ * Check to see whether the given variable is currently referenced by
+ * any other trigger.
+ *
+ * The trigger the variable is defined on is explicitly excluded - the
+ * assumption being that a self-reference doesn't prevent a trigger
+ * from being removed.
+ *
+ * Return: The VAR_REF field referencing the variable if so, NULL if not
+ */
static struct hist_field *find_any_var_ref(struct hist_trigger_data *hist_data,
unsigned int var_idx)
{
@@ -1340,6 +1377,19 @@ static struct hist_field *find_any_var_ref(struct hist_trigger_data *hist_data,
return found;
}

+/**
+ * check_var_refs - Check if there is a reference to any of trigger's variables
+ * @hist_data: The hist trigger
+ *
+ * A trigger can define one or more variables. If any one of them is
+ * currently referenced by any other trigger, this function will
+ * determine that.
+
+ * Typically used to determine whether or not a trigger can be removed
+ * - if there are any references to a trigger's variables, it cannot.
+ *
+ * Return: True if there is a reference to any of trigger's variables
+ */
static bool check_var_refs(struct hist_trigger_data *hist_data)
{
struct hist_field *field;
@@ -2343,7 +2393,23 @@ static int init_var_ref(struct hist_field *ref_field,
goto out;
}

-static struct hist_field *create_var_ref(struct hist_field *var_field,
+/**
+ * create_var_ref - Create a variable reference and attach it to trigger
+ * @hist_data: The trigger that will be referencing the variable
+ * @var_field: The VAR field to create a reference to
+ * @system: The optional system string
+ * @event_name: The optional event_name string
+ *
+ * Given a variable hist_field, create a VAR_REF hist_field that
+ * represents a reference to it.
+ *
+ * This function also adds the reference to the trigger that
+ * now references the variable.
+ *
+ * Return: The VAR_REF field if successful, NULL if not
+ */
+static struct hist_field *create_var_ref(struct hist_trigger_data *hist_data,
+ struct hist_field *var_field,
char *system, char *event_name)
{
unsigned long flags = HIST_FIELD_FL_VAR_REF;
@@ -2355,6 +2421,9 @@ static struct hist_field *create_var_ref(struct hist_field *var_field,
destroy_hist_field(ref_field, 0);
return NULL;
}
+
+ hist_data->var_refs[hist_data->n_var_refs] = ref_field;
+ ref_field->var_ref_idx = hist_data->n_var_refs++;
}

return ref_field;
@@ -2428,7 +2497,8 @@ static struct hist_field *parse_var_ref(struct hist_trigger_data *hist_data,

var_field = find_event_var(hist_data, system, event_name, var_name);
if (var_field)
- ref_field = create_var_ref(var_field, system, event_name);
+ ref_field = create_var_ref(hist_data, var_field,
+ system, event_name);

if (!ref_field)
hist_err_event("Couldn't find variable: $",
@@ -2546,8 +2616,6 @@ static struct hist_field *parse_atom(struct hist_trigger_data *hist_data,
if (!s) {
hist_field = parse_var_ref(hist_data, ref_system, ref_event, ref_var);
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) {
@@ -3321,7 +3389,6 @@ static int onmax_create(struct hist_trigger_data *hist_data,
unsigned int var_ref_idx = hist_data->n_var_refs;
struct field_var *field_var;
char *onmax_var_str, *param;
- unsigned long flags;
unsigned int i;
int ret = 0;

@@ -3338,18 +3405,10 @@ static int onmax_create(struct hist_trigger_data *hist_data,
return -EINVAL;
}

- flags = HIST_FIELD_FL_VAR_REF;
- ref_field = create_hist_field(hist_data, NULL, flags, NULL);
+ ref_field = create_var_ref(hist_data, var_field, NULL, NULL);
if (!ref_field)
return -ENOMEM;

- if (init_var_ref(ref_field, var_field, NULL, NULL)) {
- destroy_hist_field(ref_field, 0);
- ret = -ENOMEM;
- goto out;
- }
- hist_data->var_refs[hist_data->n_var_refs] = ref_field;
- ref_field->var_ref_idx = hist_data->n_var_refs++;
data->onmax.var = ref_field;

data->fn = onmax_save;
@@ -3538,9 +3597,6 @@ static void save_synth_var_ref(struct hist_trigger_data *hist_data,
struct hist_field *var_ref)
{
hist_data->synth_var_refs[hist_data->n_synth_var_refs++] = var_ref;
-
- hist_data->var_refs[hist_data->n_var_refs] = var_ref;
- var_ref->var_ref_idx = hist_data->n_var_refs++;
}

static int check_synth_field(struct synth_event *event,
@@ -3694,7 +3750,8 @@ static int onmatch_create(struct hist_trigger_data *hist_data,
}

if (check_synth_field(event, hist_field, field_pos) == 0) {
- var_ref = create_var_ref(hist_field, system, event_name);
+ var_ref = create_var_ref(hist_data, hist_field,
+ system, event_name);
if (!var_ref) {
kfree(p);
ret = -ENOMEM;
--
2.19.2