Re: [PATCH v6 7/7] tracing: Add a probe that attaches to trace events

Steven Rostedt
2021-08-19T04:10:10Z

On Thu, 19 Aug 2021 00:03:42 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> Probably. I noticed that it was updated under the dyn_event_ops_mutex,
> and thought that was enough protection. But I now see the lockdep
> assert on the event_mutex in the other functions.

Anyway, here's the new version:

static bool find_event_probe(const char *group, const char *event)
{
struct trace_eprobe *ep;
struct dyn_event *ev;
bool ret = false;

/*
* Must grab the event_mutex to prevent the list from being modified
* by other probes. But the event_probe being only created via the
* dynamic_events file, is only added under the dyn_event_ops_mutex,
* which is currently held. There is no race between this check and
* adding the new probe.
*/
mutex_lock(&event_mutex);
for_each_dyn_event(ev) {
if (ev->ops != &eprobe_dyn_event_ops)
continue;
ep = to_trace_eprobe(ev);
if (strcmp(ep->tp.event->class.system, group) == 0 &&
strcmp(ep->tp.event->call.name, event) == 0) {
ret = true;
break;
}
}
mutex_lock(&event_mutex);

return ret;
}

-- Steve