[for-next][PATCH 24/26] tracing: Enable creating new instance early boot

Steven Rostedt
2020-09-22T01:25:11Z

Enable creating new trace_array instance in early boot stage.
If the instances directory is not created, postpone it until
the tracefs is initialized.

Link: https://lkml.kernel.org/r/159974154763.478751.6289753509587233103.stgit@devnote2

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
kernel/trace/trace.c | 53 +++++++++++++++++++++++++++-------
kernel/trace/trace.h | 7 +++++
kernel/trace/trace_functions.c | 22 +++++++++-----
3 files changed, 63 insertions(+), 19 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c35fcd2f2529..6211a13b3327 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -8636,6 +8636,24 @@ struct trace_array *trace_array_find_get(const char *instance)
return tr;
}

+static int trace_array_create_dir(struct trace_array *tr)
+{
+ int ret;
+
+ tr->dir = tracefs_create_dir(tr->name, trace_instance_dir);
+ if (!tr->dir)
+ return -EINVAL;
+
+ ret = event_trace_add_tracer(tr->dir, tr);
+ if (ret)
+ tracefs_remove(tr->dir);
+
+ init_tracer_tracefs(tr, tr->dir);
+ __update_tracer_options(tr);
+
+ return ret;
+}
+
static struct trace_array *trace_array_create(const char *name)
{
struct trace_array *tr;
@@ -8671,30 +8689,27 @@ static struct trace_array *trace_array_create(const char *name)
if (allocate_trace_buffers(tr, trace_buf_size) < 0)
goto out_free_tr;

- tr->dir = tracefs_create_dir(name, trace_instance_dir);
- if (!tr->dir)
- goto out_free_tr;
-
- ret = event_trace_add_tracer(tr->dir, tr);
- if (ret) {
- tracefs_remove(tr->dir);
+ if (ftrace_allocate_ftrace_ops(tr) < 0)
goto out_free_tr;
- }

ftrace_init_trace_array(tr);

- init_tracer_tracefs(tr, tr->dir);
init_trace_flags_index(tr);
- __update_tracer_options(tr);
+
+ if (trace_instance_dir) {
+ ret = trace_array_create_dir(tr);
+ if (ret)
+ goto out_free_tr;
+ }

list_add(&tr->list, &ftrace_trace_arrays);

tr->ref++;

-
return tr;

out_free_tr:
+ ftrace_free_ftrace_ops(tr);
free_trace_buffers(tr);
free_cpumask_var(tr->tracing_cpumask);
kfree(tr->name);
@@ -8852,11 +8867,27 @@ static int instance_rmdir(const char *name)

static __init void create_trace_instances(struct dentry *d_tracer)
{
+ struct trace_array *tr;
+
trace_instance_dir = tracefs_create_instance_dir("instances", d_tracer,
instance_mkdir,
instance_rmdir);
if (MEM_FAIL(!trace_instance_dir, "Failed to create instances directory\n"))
return;
+
+ mutex_lock(&event_mutex);
+ mutex_lock(&trace_types_lock);
+
+ list_for_each_entry(tr, &ftrace_trace_arrays, list) {
+ if (!tr->name)
+ continue;
+ if (MEM_FAIL(trace_array_create_dir(tr) < 0,
+ "Failed to create instance directory\n"))
+ break;
+ }
+
+ mutex_unlock(&trace_types_lock);
+ mutex_unlock(&event_mutex);
}

static void
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 0d3a405fe446..525434145eea 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1125,6 +1125,8 @@ extern int ftrace_is_dead(void);
int ftrace_create_function_files(struct trace_array *tr,
struct dentry *parent);
void ftrace_destroy_function_files(struct trace_array *tr);
+int ftrace_allocate_ftrace_ops(struct trace_array *tr);
+void ftrace_free_ftrace_ops(struct trace_array *tr);
void ftrace_init_global_array_ops(struct trace_array *tr);
void ftrace_init_array_ops(struct trace_array *tr, ftrace_func_t func);
void ftrace_reset_array_ops(struct trace_array *tr);
@@ -1146,6 +1148,11 @@ ftrace_create_function_files(struct trace_array *tr,
{
return 0;
}
+static inline int ftrace_allocate_ftrace_ops(struct trace_array *tr)
+{
+ return 0;
+}
+static inline void ftrace_free_ftrace_ops(struct trace_array *tr) { }
static inline void ftrace_destroy_function_files(struct trace_array *tr) { }
static inline __init void
ftrace_init_global_array_ops(struct trace_array *tr) { }
diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index dd4dff71d89a..2c2126e1871d 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -34,10 +34,14 @@ enum {
TRACE_FUNC_OPT_STACK = 0x1,
};

-static int allocate_ftrace_ops(struct trace_array *tr)
+int ftrace_allocate_ftrace_ops(struct trace_array *tr)
{
struct ftrace_ops *ops;

+ /* The top level array uses the "global_ops" */
+ if (tr->flags & TRACE_ARRAY_FL_GLOBAL)
+ return 0;
+
ops = kzalloc(sizeof(*ops), GFP_KERNEL);
if (!ops)
return -ENOMEM;
@@ -48,15 +52,19 @@ static int allocate_ftrace_ops(struct trace_array *tr)

tr->ops = ops;
ops->private = tr;
+
return 0;
}

+void ftrace_free_ftrace_ops(struct trace_array *tr)
+{
+ kfree(tr->ops);
+ tr->ops = NULL;
+}

int ftrace_create_function_files(struct trace_array *tr,
struct dentry *parent)
{
- int ret;
-
/*
* The top level array uses the "global_ops", and the files are
* created on boot up.
@@ -64,9 +72,8 @@ int ftrace_create_function_files(struct trace_array *tr,
if (tr->flags & TRACE_ARRAY_FL_GLOBAL)
return 0;

- ret = allocate_ftrace_ops(tr);
- if (ret)
- return ret;
+ if (!tr->ops)
+ return -EINVAL;

ftrace_create_filter_files(tr->ops, parent);

@@ -76,8 +83,7 @@ int ftrace_create_function_files(struct trace_array *tr,
void ftrace_destroy_function_files(struct trace_array *tr)
{
ftrace_destroy_filter_files(tr->ops);
- kfree(tr->ops);
- tr->ops = NULL;
+ ftrace_free_ftrace_ops(tr);
}

static int function_trace_init(struct trace_array *tr)
--
2.28.0