[PATCH] tracing/events: Expand ring buffer for in-kernel event enables

[Manjunath Patil]

Ftrace keeps trace arrays at a boot-minimum ring-buffer size until
tracing is used. Tracefs event-enable paths already call
tracing_update_buffers() before enabling events, but the exported
in-kernel helpers trace_set_clr_event() and trace_array_set_clr_event()
directly enable events through __ftrace_set_clr_event().

This can leave events enabled by in-kernel users recording into the tiny
boot-minimum buffer instead of the configured default-sized buffer. Any
caller that enables events through these exported helpers observes
different buffer-expansion behavior than a userspace tracefs event enable.

Expand the relevant trace array before enabling events through the
exported in-kernel helpers, matching the tracefs event-enable behavior.
Disabling events remains unchanged.

Assisted-by: Codex:gpt-5
Signed-off-by: Manjunath Patil <manjunath.b.patil@xxxxxxxxxx>
---
 kernel/trace/trace_events.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index c46e623e7e0d..3ce5b0121c5c 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1479,10 +1479,22 @@ int ftrace_set_clr_event(struct trace_array *tr, char *buf, int set)
 int trace_set_clr_event(const char *system, const char *event, int set)
 {
 	struct trace_array *tr = top_trace_array();
+	int ret;
 
 	if (!tr)
 		return -ENODEV;
 
+	/*
+	 * Keep in-kernel event enabling consistent with tracefs event
+	 * enabling: once an event is being enabled, expand the boot-minimum
+	 * ring buffer to the configured default size before records arrive.
+	 */
+	if (set) {
+		ret = tracing_update_buffers(tr);
+		if (ret < 0)
+			return ret;
+	}
+
 	return __ftrace_set_clr_event(tr, NULL, system, event, set, NULL);
 }
 EXPORT_SYMBOL_GPL(trace_set_clr_event);
@@ -1504,11 +1516,24 @@ int trace_array_set_clr_event(struct trace_array *tr, const char *system,
 		const char *event, bool enable)
 {
 	int set;
+	int ret;
 
 	if (!tr)
 		return -ENOENT;
 
 	set = (enable == true) ? 1 : 0;
+
+	/*
+	 * Keep in-kernel event enabling consistent with tracefs event
+	 * enabling: once an event is being enabled, expand the boot-minimum
+	 * ring buffer to the configured default size before records arrive.
+	 */
+	if (set) {
+		ret = tracing_update_buffers(tr);
+		if (ret < 0)
+			return ret;
+	}
+
 	return __ftrace_set_clr_event(tr, NULL, system, event, set, NULL);
 }
 EXPORT_SYMBOL_GPL(trace_array_set_clr_event);

base-commit: e43ffb69e0438cddd72aaa30898b4dc446f664f8
-- 
2.47.3