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 <[email protected]> --- 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
