tracing: Remove unneeded synth_event_mutex

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>

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 414aabd67d1f14d3beb7c4b6b61002dd4bcec0b2..21e4954375a119660f78dbb9c9f22326308bcbcd 100644 (file)
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -444,8 +444,6 @@ static bool have_hist_err(void)
        return false;
 }
 
-static DEFINE_MUTEX(synth_event_mutex);
-
 struct synth_trace_event {
        struct trace_entry      ent;
        u64                     fields[];
@@ -1077,7 +1075,6 @@ 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) {
@@ -1119,7 +1116,6 @@ 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;
@@ -1139,7 +1135,6 @@ 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)
@@ -1153,7 +1148,6 @@ 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;
        }
@@ -3535,7 +3529,7 @@ 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);
@@ -3548,8 +3542,6 @@ 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)
@@ -3700,15 +3692,14 @@ 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;
 
@@ -3782,9 +3773,7 @@ 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;
 }
@@ -5492,6 +5481,8 @@ 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;
 
@@ -5501,12 +5492,10 @@ 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)
@@ -5532,6 +5521,8 @@ 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();
@@ -5622,14 +5613,10 @@ 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;
        }
@@ -5665,13 +5652,10 @@ 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: