From 0e2b81f7b52a1c1a8c46986f9ca01eb7b3c421f8 Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Mon, 5 Nov 2018 18:04:01 +0900 Subject: [PATCH] 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 Tested-by: Tom Zanussi Signed-off-by: Masami Hiramatsu Signed-off-by: Steven Rostedt (VMware) --- 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 414aabd67d1f..21e4954375a1 100644 --- 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 @@ enable: 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: