On Tue, 18 Mar 2025 18:09:05 +0000
Douglas RAILLARD <douglas.raill...@arm.com> wrote:
> From: Douglas Raillard <douglas.raill...@arm.com>
>
> Currently, using synth_event_delete() will fail if the event is being
> used (tracing in progress), but that is normally done in the module exit
> function. At that stage, failing is problematic as returning a non-zero
> status means the module will become locked (impossible to unload or
> reload again).
>
> Instead, ensure the module exit function does not get called in the
> first place by increasing the module refcnt when the event is enabled.
>
OK, I think this is correct way to fix that scenario.
Acked-by: Masami Hiramatsu (Google) <mhira...@kernel.org>
Thank you,
> Signed-off-by: Douglas Raillard <douglas.raill...@arm.com>
> ---
> kernel/trace/trace_events_synth.c | 30 +++++++++++++++++++++++++++++-
> 1 file changed, 29 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/trace/trace_events_synth.c
> b/kernel/trace/trace_events_synth.c
> index e3f7d09e5512..bb7ef6e76991 100644
> --- a/kernel/trace/trace_events_synth.c
> +++ b/kernel/trace/trace_events_synth.c
> @@ -852,6 +852,34 @@ static struct trace_event_fields
> synth_event_fields_array[] = {
> {}
> };
>
> +static int synth_event_reg(struct trace_event_call *call,
> + enum trace_reg type, void *data)
> +{
> + struct synth_event *event = container_of(call, struct synth_event,
> call);
> +
> + switch (type) {
> + case TRACE_REG_REGISTER:
> + case TRACE_REG_PERF_REGISTER:
> + if (!try_module_get(event->mod))
> + return -EBUSY;
> + break;
> + default:
> + break;
> + }
> +
> + int ret = trace_event_reg(call, type, data);
> +
> + switch (type) {
> + case TRACE_REG_UNREGISTER:
> + case TRACE_REG_PERF_UNREGISTER:
> + module_put(event->mod);
> + break;
> + default:
> + break;
> + }
> + return ret;
> +}
> +
> static int register_synth_event(struct synth_event *event)
> {
> struct trace_event_call *call = &event->call;
> @@ -881,7 +909,7 @@ static int register_synth_event(struct synth_event *event)
> goto out;
> }
> call->flags = TRACE_EVENT_FL_TRACEPOINT;
> - call->class->reg = trace_event_reg;
> + call->class->reg = synth_event_reg;
> call->class->probe = trace_event_raw_event_synth;
> call->data = event;
> call->tp = event->tp;
> --
> 2.43.0
>
--
Masami Hiramatsu (Google) <mhira...@kernel.org>
