tracing: Remove get_trigger_ops() and add count_func() from trigger ops

The struct event_command has a callback function called get_trigger_ops().
This callback returns the "trigger_ops" to use for the trigger. These ops
define the trigger function, how to init the trigger, how to print the
trigger and how to free it.

The only reason there's a callback function to get these ops is because
some triggers have two types of operations. One is an "always on"
operation, and the other is a "count down" operation. If a user passes in
a parameter to say how many times the trigger should execute. For example:

  echo stacktrace:5 > events/kmem/kmem_cache_alloc/trigger

It will trigger the stacktrace for the first 5 times the kmem_cache_alloc
event is hit.

Instead of having two different trigger_ops since the only difference
between them is the tigger itself (the print, init and free functions are
all the same), just use a single ops that the event_command points to and
add a function field to the trigger_ops to have a count_func.

When a trigger is added to an event, if there's a count attached to it and
the trigger ops has the count_func field, the data allocated to represent
this trigger will have a new flag set called COUNT.

Then when the trigger executes, it will check if the COUNT data flag is
set, and if so, it will call the ops count_func(). If that returns false,
it returns without executing the trigger.

This removes the need for duplicate event_trigger_ops structures.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: https://patch.msgid.link/20251125200932.274566147@kernel.org
Reviewed-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

1 files changed, 92 insertions, 165 deletions

diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index cbfc306c0159..576bad18bcdb 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -28,6 +28,20 @@ void trigger_data_free(struct event_trigger_data *data)
 	kfree(data);
 }
 
+static inline void data_ops_trigger(struct event_trigger_data *data,
+				    struct trace_buffer *buffer,  void *rec,
+				    struct ring_buffer_event *event)
+{
+	const struct event_trigger_ops *ops = data->ops;
+
+	if (data->flags & EVENT_TRIGGER_FL_COUNT) {
+		if (!ops->count_func(data, buffer, rec, event))
+			return;
+	}
+
+	ops->trigger(data, buffer, rec, event);
+}
+
 /**
  * event_triggers_call - Call triggers associated with a trace event
  * @file: The trace_event_file associated with the event
@@ -70,7 +84,7 @@ event_triggers_call(struct trace_event_file *file,
 		if (data->paused)
 			continue;
 		if (!rec) {
-			data->ops->trigger(data, buffer, rec, event);
+			data_ops_trigger(data, buffer, rec, event);
 			continue;
 		}
 		filter = rcu_dereference_sched(data->filter);
@@ -80,7 +94,7 @@ event_triggers_call(struct trace_event_file *file,
 			tt |= data->cmd_ops->trigger_type;
 			continue;
 		}
-		data->ops->trigger(data, buffer, rec, event);
+		data_ops_trigger(data, buffer, rec, event);
 	}
 	return tt;
 }
@@ -122,7 +136,7 @@ event_triggers_post_call(struct trace_event_file *file,
 		if (data->paused)
 			continue;
 		if (data->cmd_ops->trigger_type & tt)
-			data->ops->trigger(data, NULL, NULL, NULL);
+			data_ops_trigger(data, NULL, NULL, NULL);
 	}
 }
 EXPORT_SYMBOL_GPL(event_triggers_post_call);
@@ -378,6 +392,36 @@ __init int unregister_event_command(struct event_command *cmd)
 }
 
 /**
+ * event_trigger_count - Optional count function for event triggers
+ * @data: Trigger-specific data
+ * @buffer: The ring buffer that the event is being written to
+ * @rec: The trace entry for the event, NULL for unconditional invocation
+ * @event: The event meta data in the ring buffer
+ *
+ * For triggers that can take a count parameter that doesn't do anything
+ * special, they can use this function to assign to their .count_func
+ * field.
+ *
+ * This simply does a count down of the @data->count field.
+ *
+ * If the @data->count is greater than zero, it will decrement it.
+ *
+ * Returns false if @data->count is zero, otherwise true.
+ */
+bool event_trigger_count(struct event_trigger_data *data,
+			 struct trace_buffer *buffer,  void *rec,
+			 struct ring_buffer_event *event)
+{
+	if (!data->count)
+		return false;
+
+	if (data->count != -1)
+		(data->count)--;
+
+	return true;
+}
+
+/**
  * event_trigger_print - Generic event_trigger_ops @print implementation
  * @name: The name of the event trigger
  * @m: The seq_file being printed to
@@ -807,9 +851,13 @@ int event_trigger_separate_filter(char *param_and_filter, char **param,
  * @private_data: User data to associate with the event trigger
  *
  * Allocate an event_trigger_data instance and initialize it.  The
- * @cmd_ops are used along with the @cmd and @param to get the
- * trigger_ops to assign to the event_trigger_data.  @private_data can
- * also be passed in and associated with the event_trigger_data.
+ * @cmd_ops defines how the trigger will operate. If @param is set,
+ * and @cmd_ops->trigger_ops->count_func is non NULL, then the
+ * data->count is set to @param and before the trigger is executed, the
+ * @cmd_ops->trigger_ops->count_func() is called. If that function returns
+ * false, the @cmd_ops->trigger_ops->trigger() function will not be called.
+ * @private_data can also be passed in and associated with the
+ * event_trigger_data.
  *
  * Use trigger_data_free() to free an event_trigger_data object.
  *
@@ -821,18 +869,17 @@ struct event_trigger_data *trigger_data_alloc(struct event_command *cmd_ops,
 					      void *private_data)
 {
 	struct event_trigger_data *trigger_data;
-	const struct event_trigger_ops *trigger_ops;
-
-	trigger_ops = cmd_ops->get_trigger_ops(cmd, param);
 
 	trigger_data = kzalloc(sizeof(*trigger_data), GFP_KERNEL);
 	if (!trigger_data)
 		return NULL;
 
 	trigger_data->count = -1;
-	trigger_data->ops = trigger_ops;
+	trigger_data->ops = cmd_ops->trigger_ops;
 	trigger_data->cmd_ops = cmd_ops;
 	trigger_data->private_data = private_data;
+	if (param && cmd_ops->trigger_ops->count_func)
+		trigger_data->flags |= EVENT_TRIGGER_FL_COUNT;
 
 	INIT_LIST_HEAD(&trigger_data->list);
 	INIT_LIST_HEAD(&trigger_data->named_list);
@@ -1271,31 +1318,28 @@ traceon_trigger(struct event_trigger_data *data,
 	tracing_on();
 }
 
-static void
-traceon_count_trigger(struct event_trigger_data *data,
-		      struct trace_buffer *buffer, void *rec,
-		      struct ring_buffer_event *event)
+static bool
+traceon_count_func(struct event_trigger_data *data,
+		   struct trace_buffer *buffer, void *rec,
+		   struct ring_buffer_event *event)
 {
 	struct trace_event_file *file = data->private_data;
 
 	if (file) {
 		if (tracer_tracing_is_on(file->tr))
-			return;
+			return false;
 	} else {
 		if (tracing_is_on())
-			return;
+			return false;
 	}
 
 	if (!data->count)
-		return;
+		return false;
 
 	if (data->count != -1)
 		(data->count)--;
 
-	if (file)
-		tracer_tracing_on(file->tr);
-	else
-		tracing_on();
+	return true;
 }
 
 static void
@@ -1319,31 +1363,28 @@ traceoff_trigger(struct event_trigger_data *data,
 	tracing_off();
 }
 
-static void
-traceoff_count_trigger(struct event_trigger_data *data,
-		       struct trace_buffer *buffer, void *rec,
-		       struct ring_buffer_event *event)
+static bool
+traceoff_count_func(struct event_trigger_data *data,
+		    struct trace_buffer *buffer, void *rec,
+		    struct ring_buffer_event *event)
 {
 	struct trace_event_file *file = data->private_data;
 
 	if (file) {
 		if (!tracer_tracing_is_on(file->tr))
-			return;
+			return false;
 	} else {
 		if (!tracing_is_on())
-			return;
+			return false;
 	}
 
 	if (!data->count)
-		return;
+		return false;
 
 	if (data->count != -1)
 		(data->count)--;
 
-	if (file)
-		tracer_tracing_off(file->tr);
-	else
-		tracing_off();
+	return true;
 }
 
 static int
@@ -1362,13 +1403,7 @@ traceoff_trigger_print(struct seq_file *m, struct event_trigger_data *data)
 
 static const struct event_trigger_ops traceon_trigger_ops = {
 	.trigger		= traceon_trigger,
-	.print			= traceon_trigger_print,
-	.init			= event_trigger_init,
-	.free			= event_trigger_free,
-};
-
-static const struct event_trigger_ops traceon_count_trigger_ops = {
-	.trigger		= traceon_count_trigger,
+	.count_func		= traceon_count_func,
 	.print			= traceon_trigger_print,
 	.init			= event_trigger_init,
 	.free			= event_trigger_free,
@@ -1376,41 +1411,19 @@ static const struct event_trigger_ops traceon_count_trigger_ops = {
 
 static const struct event_trigger_ops traceoff_trigger_ops = {
 	.trigger		= traceoff_trigger,
+	.count_func		= traceoff_count_func,
 	.print			= traceoff_trigger_print,
 	.init			= event_trigger_init,
 	.free			= event_trigger_free,
 };
 
-static const struct event_trigger_ops traceoff_count_trigger_ops = {
-	.trigger		= traceoff_count_trigger,
-	.print			= traceoff_trigger_print,
-	.init			= event_trigger_init,
-	.free			= event_trigger_free,
-};
-
-static const struct event_trigger_ops *
-onoff_get_trigger_ops(char *cmd, char *param)
-{
-	const struct event_trigger_ops *ops;
-
-	/* we register both traceon and traceoff to this callback */
-	if (strcmp(cmd, "traceon") == 0)
-		ops = param ? &traceon_count_trigger_ops :
-			&traceon_trigger_ops;
-	else
-		ops = param ? &traceoff_count_trigger_ops :
-			&traceoff_trigger_ops;
-
-	return ops;
-}
-
 static struct event_command trigger_traceon_cmd = {
 	.name			= "traceon",
 	.trigger_type		= ETT_TRACE_ONOFF,
+	.trigger_ops		= &traceon_trigger_ops,
 	.parse			= event_trigger_parse,
 	.reg			= register_trigger,
 	.unreg			= unregister_trigger,
-	.get_trigger_ops	= onoff_get_trigger_ops,
 	.set_filter		= set_trigger_filter,
 };
 
@@ -1418,10 +1431,10 @@ static struct event_command trigger_traceoff_cmd = {
 	.name			= "traceoff",
 	.trigger_type		= ETT_TRACE_ONOFF,
 	.flags			= EVENT_CMD_FL_POST_TRIGGER,
+	.trigger_ops		= &traceoff_trigger_ops,
 	.parse			= event_trigger_parse,
 	.reg			= register_trigger,
 	.unreg			= unregister_trigger,
-	.get_trigger_ops	= onoff_get_trigger_ops,
 	.set_filter		= set_trigger_filter,
 };
 
@@ -1439,20 +1452,6 @@ snapshot_trigger(struct event_trigger_data *data,
 		tracing_snapshot();
 }
 
-static void
-snapshot_count_trigger(struct event_trigger_data *data,
-		       struct trace_buffer *buffer, void *rec,
-		       struct ring_buffer_event *event)
-{
-	if (!data->count)
-		return;
-
-	if (data->count != -1)
-		(data->count)--;
-
-	snapshot_trigger(data, buffer, rec, event);
-}
-
 static int
 register_snapshot_trigger(char *glob,
 			  struct event_trigger_data *data,
@@ -1486,31 +1485,19 @@ snapshot_trigger_print(struct seq_file *m, struct event_trigger_data *data)
 
 static const struct event_trigger_ops snapshot_trigger_ops = {
 	.trigger		= snapshot_trigger,
+	.count_func		= event_trigger_count,
 	.print			= snapshot_trigger_print,
 	.init			= event_trigger_init,
 	.free			= event_trigger_free,
 };
 
-static const struct event_trigger_ops snapshot_count_trigger_ops = {
-	.trigger		= snapshot_count_trigger,
-	.print			= snapshot_trigger_print,
-	.init			= event_trigger_init,
-	.free			= event_trigger_free,
-};
-
-static const struct event_trigger_ops *
-snapshot_get_trigger_ops(char *cmd, char *param)
-{
-	return param ? &snapshot_count_trigger_ops : &snapshot_trigger_ops;
-}
-
 static struct event_command trigger_snapshot_cmd = {
 	.name			= "snapshot",
 	.trigger_type		= ETT_SNAPSHOT,
+	.trigger_ops		= &snapshot_trigger_ops,
 	.parse			= event_trigger_parse,
 	.reg			= register_snapshot_trigger,
 	.unreg			= unregister_snapshot_trigger,
-	.get_trigger_ops	= snapshot_get_trigger_ops,
 	.set_filter		= set_trigger_filter,
 };
 
@@ -1558,20 +1545,6 @@ stacktrace_trigger(struct event_trigger_data *data,
 		trace_dump_stack(STACK_SKIP);
 }
 
-static void
-stacktrace_count_trigger(struct event_trigger_data *data,
-			 struct trace_buffer *buffer, void *rec,
-			 struct ring_buffer_event *event)
-{
-	if (!data->count)
-		return;
-
-	if (data->count != -1)
-		(data->count)--;
-
-	stacktrace_trigger(data, buffer, rec, event);
-}
-
 static int
 stacktrace_trigger_print(struct seq_file *m, struct event_trigger_data *data)
 {
@@ -1581,32 +1554,20 @@ stacktrace_trigger_print(struct seq_file *m, struct event_trigger_data *data)
 
 static const struct event_trigger_ops stacktrace_trigger_ops = {
 	.trigger		= stacktrace_trigger,
+	.count_func		= event_trigger_count,
 	.print			= stacktrace_trigger_print,
 	.init			= event_trigger_init,
 	.free			= event_trigger_free,
 };
 
-static const struct event_trigger_ops stacktrace_count_trigger_ops = {
-	.trigger		= stacktrace_count_trigger,
-	.print			= stacktrace_trigger_print,
-	.init			= event_trigger_init,
-	.free			= event_trigger_free,
-};
-
-static const struct event_trigger_ops *
-stacktrace_get_trigger_ops(char *cmd, char *param)
-{
-	return param ? &stacktrace_count_trigger_ops : &stacktrace_trigger_ops;
-}
-
 static struct event_command trigger_stacktrace_cmd = {
 	.name			= "stacktrace",
 	.trigger_type		= ETT_STACKTRACE,
+	.trigger_ops		= &stacktrace_trigger_ops,
 	.flags			= EVENT_CMD_FL_POST_TRIGGER,
 	.parse			= event_trigger_parse,
 	.reg			= register_trigger,
 	.unreg			= unregister_trigger,
-	.get_trigger_ops	= stacktrace_get_trigger_ops,
 	.set_filter		= set_trigger_filter,
 };
 
@@ -1642,24 +1603,24 @@ event_enable_trigger(struct event_trigger_data *data,
 		set_bit(EVENT_FILE_FL_SOFT_DISABLED_BIT, &enable_data->file->flags);
 }
 
-static void
-event_enable_count_trigger(struct event_trigger_data *data,
-			   struct trace_buffer *buffer,  void *rec,
-			   struct ring_buffer_event *event)
+static bool
+event_enable_count_func(struct event_trigger_data *data,
+			struct trace_buffer *buffer,  void *rec,
+			struct ring_buffer_event *event)
 {
 	struct enable_trigger_data *enable_data = data->private_data;
 
 	if (!data->count)
-		return;
+		return false;
 
 	/* Skip if the event is in a state we want to switch to */
 	if (enable_data->enable == !(enable_data->file->flags & EVENT_FILE_FL_SOFT_DISABLED))
-		return;
+		return false;
 
 	if (data->count != -1)
 		(data->count)--;
 
-	event_enable_trigger(data, buffer, rec, event);
+	return true;
 }
 
 int event_enable_trigger_print(struct seq_file *m,
@@ -1706,13 +1667,7 @@ void event_enable_trigger_free(struct event_trigger_data *data)
 
 static const struct event_trigger_ops event_enable_trigger_ops = {
 	.trigger		= event_enable_trigger,
-	.print			= event_enable_trigger_print,
-	.init			= event_trigger_init,
-	.free			= event_enable_trigger_free,
-};
-
-static const struct event_trigger_ops event_enable_count_trigger_ops = {
-	.trigger		= event_enable_count_trigger,
+	.count_func		= event_enable_count_func,
 	.print			= event_enable_trigger_print,
 	.init			= event_trigger_init,
 	.free			= event_enable_trigger_free,
@@ -1720,13 +1675,7 @@ static const struct event_trigger_ops event_enable_count_trigger_ops = {
 
 static const struct event_trigger_ops event_disable_trigger_ops = {
 	.trigger		= event_enable_trigger,
-	.print			= event_enable_trigger_print,
-	.init			= event_trigger_init,
-	.free			= event_enable_trigger_free,
-};
-
-static const struct event_trigger_ops event_disable_count_trigger_ops = {
-	.trigger		= event_enable_count_trigger,
+	.count_func		= event_enable_count_func,
 	.print			= event_enable_trigger_print,
 	.init			= event_trigger_init,
 	.free			= event_enable_trigger_free,
@@ -1906,45 +1855,23 @@ void event_enable_unregister_trigger(char *glob,
 		data->ops->free(data);
 }
 
-static const struct event_trigger_ops *
-event_enable_get_trigger_ops(char *cmd, char *param)
-{
-	const struct event_trigger_ops *ops;
-	bool enable;
-
-#ifdef CONFIG_HIST_TRIGGERS
-	enable = ((strcmp(cmd, ENABLE_EVENT_STR) == 0) ||
-		  (strcmp(cmd, ENABLE_HIST_STR) == 0));
-#else
-	enable = strcmp(cmd, ENABLE_EVENT_STR) == 0;
-#endif
-	if (enable)
-		ops = param ? &event_enable_count_trigger_ops :
-			&event_enable_trigger_ops;
-	else
-		ops = param ? &event_disable_count_trigger_ops :
-			&event_disable_trigger_ops;
-
-	return ops;
-}
-
 static struct event_command trigger_enable_cmd = {
 	.name			= ENABLE_EVENT_STR,
 	.trigger_type		= ETT_EVENT_ENABLE,
+	.trigger_ops		= &event_enable_trigger_ops,
 	.parse			= event_enable_trigger_parse,
 	.reg			= event_enable_register_trigger,
 	.unreg			= event_enable_unregister_trigger,
-	.get_trigger_ops	= event_enable_get_trigger_ops,
 	.set_filter		= set_trigger_filter,
 };
 
 static struct event_command trigger_disable_cmd = {
 	.name			= DISABLE_EVENT_STR,
 	.trigger_type		= ETT_EVENT_ENABLE,
+	.trigger_ops		= &event_disable_trigger_ops,
 	.parse			= event_enable_trigger_parse,
 	.reg			= event_enable_register_trigger,
 	.unreg			= event_enable_unregister_trigger,
-	.get_trigger_ops	= event_enable_get_trigger_ops,
 	.set_filter		= set_trigger_filter,
 };