From: Steven Rostedt <rostedt@goodmis.org>
To: Tom Zanussi <zanussi@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>
Subject: Re: Unresolved reference for histogram variable
Date: Thu, 16 Jan 2020 16:56:58 -0500 [thread overview]
Message-ID: <20200116165658.4e8d15fb@gandalf.local.home> (raw)
In-Reply-To: <20200116154216.58ca08eb@gandalf.local.home>
On Thu, 16 Jan 2020 15:42:16 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:
> in parse_expr():
>
> operand1->read_once = true;
> operand2->read_once = true;
>
> Why is that?
>
> This means that any variable used in an expression can not be use later
> on.
>
> Or should the variable be detected that it is used multiple times in
> the expression, and have the parser detect this, and just reuse the
> same variable multiple times?
This patch seems to fix the problem, and lets us reuse the same
variable multiple times.
-- Steve
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 117a1202a6b9..b7f944735a4a 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -116,6 +116,7 @@ struct hist_field {
struct ftrace_event_field *field;
unsigned long flags;
hist_field_fn_t fn;
+ unsigned int ref;
unsigned int size;
unsigned int offset;
unsigned int is_signed;
@@ -2432,8 +2433,16 @@ static int contains_operator(char *str)
return field_op;
}
+static void get_hist_field(struct hist_field *hist_field)
+{
+ hist_field->ref++;
+}
+
static void __destroy_hist_field(struct hist_field *hist_field)
{
+ if (--hist_field->ref > 1)
+ return;
+
kfree(hist_field->var.name);
kfree(hist_field->name);
kfree(hist_field->type);
@@ -2475,6 +2484,8 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
if (!hist_field)
return NULL;
+ hist_field->ref = 1;
+
hist_field->hist_data = hist_data;
if (flags & HIST_FIELD_FL_EXPR || flags & HIST_FIELD_FL_ALIAS)
@@ -2670,6 +2681,19 @@ static struct hist_field *create_var_ref(struct hist_trigger_data *hist_data,
{
unsigned long flags = HIST_FIELD_FL_VAR_REF;
struct hist_field *ref_field;
+ int i;
+
+ for (i = 0; i < hist_data->n_var_refs; i++) {
+ ref_field = hist_data->var_refs[i];
+ /* Maybe this is overkill? */
+ if (ref_field->var.idx == var_field->var.idx &&
+ ref_field->var.hist_data == var_field->hist_data &&
+ ref_field->size == var_field->size &&
+ ref_field->is_signed == var_field->is_signed) {
+ get_hist_field(ref_field);
+ return ref_field;
+ }
+ }
ref_field = create_hist_field(var_field->hist_data, NULL, flags, NULL);
if (ref_field) {
next prev parent reply other threads:[~2020-01-16 21:57 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-16 20:42 Unresolved reference for histogram variable Steven Rostedt
2020-01-16 21:56 ` Steven Rostedt [this message]
2020-01-17 4:26 ` Tom Zanussi
2020-01-17 22:04 ` Tom Zanussi
2020-01-20 21:13 ` Steven Rostedt
2020-01-16 23:08 ` Tom Zanussi
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