tracing: Use class->reg() for all registering of events

Because kprobes and syscalls need special processing to register
events, the class->reg() method was created to handle the differences.

But instead of creating a default ->reg for perf and ftrace events,
the code was scattered with:

	if (class->reg)
		class->reg();
	else
		default_reg();

This is messy and can also lead to bugs.

This patch cleans up this code and creates a default reg() entry for
the events allowing for the code to directly call the class->reg()
without the condition.

Reported-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

include/linux/ftrace_event.h

@@ -146,6 +146,9 @@ struct ftrace_event_class {
 	int			(*raw_init)(struct ftrace_event_call *);
 };
 
+extern int ftrace_event_reg(struct ftrace_event_call *event,
+			    enum trace_reg type);
+
 enum {
 	TRACE_EVENT_FL_ENABLED_BIT,
 	TRACE_EVENT_FL_FILTERED_BIT,

include/trace/ftrace.h

@@ -439,6 +439,7 @@ static inline notrace int ftrace_get_offsets_##call(			\
  *	.fields			= LIST_HEAD_INIT(event_class_##call.fields),
  *	.raw_init		= trace_event_raw_init,
  *	.probe			= ftrace_raw_event_##call,
+ *	.reg			= ftrace_event_reg,
  * };
  *
  * static struct ftrace_event_call __used
@@ -567,6 +568,7 @@ static struct ftrace_event_class __used event_class_##call = {		\
 	.fields			= LIST_HEAD_INIT(event_class_##call.fields),\
 	.raw_init		= trace_event_raw_init,			\
 	.probe			= ftrace_raw_event_##call,		\
+	.reg			= ftrace_event_reg,			\
 	_TRACE_PERF_INIT(call)						\
 };
 

kernel/trace/trace_event_perf.c

@@ -54,13 +54,7 @@ static int perf_trace_event_init(struct ftrace_event_call *tp_event,
 		}
 	}
 
-	if (tp_event->class->reg)
 	ret = tp_event->class->reg(tp_event, TRACE_REG_PERF_REGISTER);
-	else
-		ret = tracepoint_probe_register(tp_event->name,
-						tp_event->class->perf_probe,
-						tp_event);
-
 	if (ret)
 		goto fail;
 
@@ -94,9 +88,7 @@ int perf_trace_init(struct perf_event *p_event)
 	mutex_lock(&event_mutex);
 	list_for_each_entry(tp_event, &ftrace_events, list) {
 		if (tp_event->event.type == event_id &&
-		    tp_event->class &&
+		    tp_event->class && tp_event->class->reg &&
-		    (tp_event->class->perf_probe ||
-		     tp_event->class->reg) &&
 		    try_module_get(tp_event->mod)) {
 			ret = perf_trace_event_init(tp_event, p_event);
 			break;
@@ -136,12 +128,7 @@ void perf_trace_destroy(struct perf_event *p_event)
 	if (--tp_event->perf_refcount > 0)
 		goto out;
 
-	if (tp_event->class->reg)
 	tp_event->class->reg(tp_event, TRACE_REG_PERF_UNREGISTER);
-	else
-		tracepoint_probe_unregister(tp_event->name,
-					    tp_event->class->perf_probe,
-					    tp_event);
 
 	/*
 	 * Ensure our callback won't be called anymore. See

kernel/trace/trace_events.c

@@ -141,6 +141,35 @@ int trace_event_raw_init(struct ftrace_event_call *call)
 }
 EXPORT_SYMBOL_GPL(trace_event_raw_init);
 
+int ftrace_event_reg(struct ftrace_event_call *call, enum trace_reg type)
+{
+	switch (type) {
+	case TRACE_REG_REGISTER:
+		return tracepoint_probe_register(call->name,
+						 call->class->probe,
+						 call);
+	case TRACE_REG_UNREGISTER:
+		tracepoint_probe_unregister(call->name,
+					    call->class->probe,
+					    call);
+		return 0;
+
+#ifdef CONFIG_PERF_EVENTS
+	case TRACE_REG_PERF_REGISTER:
+		return tracepoint_probe_register(call->name,
+						 call->class->perf_probe,
+						 call);
+	case TRACE_REG_PERF_UNREGISTER:
+		tracepoint_probe_unregister(call->name,
+					    call->class->perf_probe,
+					    call);
+		return 0;
+#endif
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(ftrace_event_reg);
+
 static int ftrace_event_enable_disable(struct ftrace_event_call *call,
 					int enable)
 {
@@ -151,23 +180,13 @@ static int ftrace_event_enable_disable(struct ftrace_event_call *call,
 		if (call->flags & TRACE_EVENT_FL_ENABLED) {
 			call->flags &= ~TRACE_EVENT_FL_ENABLED;
 			tracing_stop_cmdline_record();
-			if (call->class->reg)
 			call->class->reg(call, TRACE_REG_UNREGISTER);
-			else
-				tracepoint_probe_unregister(call->name,
-							    call->class->probe,
-							    call);
 		}
 		break;
 	case 1:
 		if (!(call->flags & TRACE_EVENT_FL_ENABLED)) {
 			tracing_start_cmdline_record();
-			if (call->class->reg)
 			ret = call->class->reg(call, TRACE_REG_REGISTER);
-			else
-				ret = tracepoint_probe_register(call->name,
-								call->class->probe,
-								call);
 			if (ret) {
 				tracing_stop_cmdline_record();
 				pr_info("event trace: Could not enable event "
@@ -205,8 +224,7 @@ static int __ftrace_set_clr_event(const char *match, const char *sub,
 	mutex_lock(&event_mutex);
 	list_for_each_entry(call, &ftrace_events, list) {
 
-		if (!call->name || !call->class ||
+		if (!call->name || !call->class || !call->class->reg)
-		    (!call->class->probe && !call->class->reg))
 			continue;
 
 		if (match &&
@@ -332,7 +350,7 @@ t_next(struct seq_file *m, void *v, loff_t *pos)
 		 * The ftrace subsystem is for showing formats only.
 		 * They can not be enabled or disabled via the event files.
 		 */
-		if (call->class && (call->class->probe || call->class->reg))
+		if (call->class && call->class->reg)
 			return call;
 	}
 
@@ -485,8 +503,7 @@ system_enable_read(struct file *filp, char __user *ubuf, size_t cnt,
 
 	mutex_lock(&event_mutex);
 	list_for_each_entry(call, &ftrace_events, list) {
-		if (!call->name || !call->class ||
+		if (!call->name || !call->class || !call->class->reg)
-		    (!call->class->probe && !call->class->reg))
 			continue;
 
 		if (system && strcmp(call->class->system, system) != 0)
@@ -977,12 +994,12 @@ event_create_dir(struct ftrace_event_call *call, struct dentry *d_events,
 		return -1;
 	}
 
-	if (call->class->probe || call->class->reg)
+	if (call->class->reg)
 		trace_create_file("enable", 0644, call->dir, call,
 				  enable);
 
 #ifdef CONFIG_PERF_EVENTS
-	if (call->event.type && (call->class->perf_probe || call->class->reg))
+	if (call->event.type && call->class->reg)
 		trace_create_file("id", 0444, call->dir, call,
 		 		  id);
 #endif