[PATCH 4.19.y 04/13] tracing: Remove unneeded synth_event_mutex

George Guo
2024-05-09T02:30:14Z

From: Masami Hiramatsu <mhiramat@kernel.org>

commit 0e2b81f7b52a1c1a8c46986f9ca01eb7b3c421f8 upstream.

Rmove unneeded synth_event_mutex. This mutex protects the reference
count in synth_event, however, those operational points are already
protected by event_mutex.

1. In __create_synth_event() and create_or_delete_synth_event(),
those synth_event_mutex clearly obtained right after event_mutex.

2. event_hist_trigger_func() is trigger_hist_cmd.func() which is
called by trigger_process_regex(), which is a part of
event_trigger_regex_write() and this function takes event_mutex.

3. hist_unreg_all() is trigger_hist_cmd.unreg_all() which is called
by event_trigger_regex_open() and it takes event_mutex.

4. onmatch_destroy() and onmatch_create() have long call tree,
but both are finally invoked from event_trigger_regex_write()
and event_trace_del_tracer(), former takes event_mutex, and latter
ensures called under event_mutex locked.

Finally, I ensured there is no resource conflict. For safety,
I added lockdep_assert_held(&event_mutex) for each function.

Link: http://lkml.kernel.org/r/154140864134.17322.4796059721306031894.stgit@devbox

Reviewed-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Tested-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: George Guo <guodongtai@kylinos.cn>
---
kernel/trace/trace_events_hist.c | 30 +++++++-----------------------
1 file changed, 7 insertions(+), 23 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 1996da54f2b2..1a32b64d350b 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -443,8 +443,6 @@ static bool have_hist_err(void)
return false;
}

-static DEFINE_MUTEX(synth_event_mutex);
-
struct synth_trace_event {
struct trace_entry ent;
u64 fields[];
@@ -1097,7 +1095,6 @@ static int __create_synth_event(int argc, const char *name, const char **argv)
return -EINVAL;

mutex_lock(&event_mutex);
- mutex_lock(&synth_event_mutex);

event = find_synth_event(name);
if (event) {
@@ -1139,7 +1136,6 @@ static int __create_synth_event(int argc, const char *name, const char **argv)
else
free_synth_event(event);
out:
- mutex_unlock(&synth_event_mutex);
mutex_unlock(&event_mutex);

return ret;
@@ -1159,7 +1155,6 @@ static int create_or_delete_synth_event(int argc, char **argv)
/* trace_run_command() ensures argc != 0 */
if (name[0] == '!') {
mutex_lock(&event_mutex);
- mutex_lock(&synth_event_mutex);
event = find_synth_event(name + 1);
if (event) {
if (event->ref)
@@ -1173,7 +1168,6 @@ static int create_or_delete_synth_event(int argc, char **argv)
}
} else
ret = -ENOENT;
- mutex_unlock(&synth_event_mutex);
mutex_unlock(&event_mutex);
return ret;
}
@@ -3660,7 +3654,7 @@ static void onmatch_destroy(struct action_data *data)
{
unsigned int i;

- mutex_lock(&synth_event_mutex);
+ lockdep_assert_held(&event_mutex);

kfree(data->onmatch.match_event);
kfree(data->onmatch.match_event_system);
@@ -3673,8 +3667,6 @@ static void onmatch_destroy(struct action_data *data)
data->onmatch.synth_event->ref--;

kfree(data);
-
- mutex_unlock(&synth_event_mutex);
}

static void destroy_field_var(struct field_var *field_var)
@@ -3810,15 +3802,14 @@ static int onmatch_create(struct hist_trigger_data *hist_data,
struct synth_event *event;
int ret = 0;

- mutex_lock(&synth_event_mutex);
+ lockdep_assert_held(&event_mutex);
+
event = find_synth_event(data->onmatch.synth_event_name);
if (!event) {
hist_err("onmatch: Couldn't find synthetic event: ", data->onmatch.synth_event_name);
- mutex_unlock(&synth_event_mutex);
return -EINVAL;
}
event->ref++;
- mutex_unlock(&synth_event_mutex);

var_ref_idx = hist_data->n_var_refs;

@@ -3892,9 +3883,7 @@ static int onmatch_create(struct hist_trigger_data *hist_data,
out:
return ret;
err:
- mutex_lock(&synth_event_mutex);
event->ref--;
- mutex_unlock(&synth_event_mutex);

goto out;
}
@@ -5611,6 +5600,8 @@ static void hist_unreg_all(struct trace_event_file *file)
struct synth_event *se;
const char *se_name;

+ lockdep_assert_held(&event_mutex);
+
if (hist_file_check_refs(file))
return;

@@ -5620,12 +5611,10 @@ static void hist_unreg_all(struct trace_event_file *file)
list_del_rcu(&test->list);
trace_event_trigger_enable_disable(file, 0);

- mutex_lock(&synth_event_mutex);
se_name = trace_event_name(file->event_call);
se = find_synth_event(se_name);
if (se)
se->ref--;
- mutex_unlock(&synth_event_mutex);

update_cond_flag(file);
if (hist_data->enable_timestamps)
@@ -5651,6 +5640,8 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
char *trigger, *p;
int ret = 0;

+ lockdep_assert_held(&event_mutex);
+
if (glob && strlen(glob)) {
last_cmd_set(param);
hist_err_clear();
@@ -5741,14 +5732,10 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
}

cmd_ops->unreg(glob+1, trigger_ops, trigger_data, file);
-
- mutex_lock(&synth_event_mutex);
se_name = trace_event_name(file->event_call);
se = find_synth_event(se_name);
if (se)
se->ref--;
- mutex_unlock(&synth_event_mutex);
-
ret = 0;
goto out_free;
}
@@ -5787,13 +5774,10 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
if (ret)
goto out_unreg;

- mutex_lock(&synth_event_mutex);
se_name = trace_event_name(file->event_call);
se = find_synth_event(se_name);
if (se)
se->ref++;
- mutex_unlock(&synth_event_mutex);
-
/* Just return zero, not the number of registered triggers */
ret = 0;
out:
--
2.34.1