tracing: Update modules to persistent instances when loaded

When a module is loaded and a persistent buffer is actively tracing, add
it to the list of modules in the persistent memory.

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://lore.kernel.org/20250305164609.469844721@goodmis.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

1 files changed, 28 insertions, 12 deletions

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 513de9ceb80e..7b3ef1d26167 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1818,28 +1818,28 @@ event_enable_write(struct file *filp, const char __user *ubuf, size_t cnt,
 	return cnt;
 }
 
-static ssize_t
-system_enable_read(struct file *filp, char __user *ubuf, size_t cnt,
-		   loff_t *ppos)
+/*
+ * Returns:
+ *   0 : no events exist?
+ *   1 : all events are disabled
+ *   2 : all events are enabled
+ *   3 : some events are enabled and some are enabled
+ */
+int trace_events_enabled(struct trace_array *tr, const char *system)
 {
-	const char set_to_char[4] = { '?', '0', '1', 'X' };
-	struct trace_subsystem_dir *dir = filp->private_data;
-	struct event_subsystem *system = dir->subsystem;
 	struct trace_event_call *call;
 	struct trace_event_file *file;
-	struct trace_array *tr = dir->tr;
-	char buf[2];
 	int set = 0;
-	int ret;
 
-	mutex_lock(&event_mutex);
+	guard(mutex)(&event_mutex);
+
 	list_for_each_entry(file, &tr->events, list) {
 		call = file->event_call;
 		if ((call->flags & TRACE_EVENT_FL_IGNORE_ENABLE) ||
 		    !trace_event_name(call) || !call->class || !call->class->reg)
 			continue;
 
-		if (system && strcmp(call->class->system, system->name) != 0)
+		if (system && strcmp(call->class->system, system) != 0)
 			continue;
 
 		/*
@@ -1855,7 +1855,23 @@ system_enable_read(struct file *filp, char __user *ubuf, size_t cnt,
 		if (set == 3)
 			break;
 	}
-	mutex_unlock(&event_mutex);
+
+	return set;
+}
+
+static ssize_t
+system_enable_read(struct file *filp, char __user *ubuf, size_t cnt,
+		   loff_t *ppos)
+{
+	const char set_to_char[4] = { '?', '0', '1', 'X' };
+	struct trace_subsystem_dir *dir = filp->private_data;
+	struct event_subsystem *system = dir->subsystem;
+	struct trace_array *tr = dir->tr;
+	char buf[2];
+	int set;
+	int ret;
+
+	set = trace_events_enabled(tr, system ? system->name : NULL);
 
 	buf[0] = set_to_char[set];
 	buf[1] = '\n';