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tracing: Have dynamic events have a ref counter

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As dynamic events are not created by modules, if something is attached to
one, calling "try_module_get()" on its "mod" field, is not going to keep
the dynamic event from going away.

Since dynamic events do not need the "mod" pointer of the event structure,
make a union out of it in order to save memory (there's one structure for
each of the thousand+ events in the kernel), and have any event with the
DYNAMIC flag set to use a ref counter instead.

Link: https://lore.kernel.org/linux-trace-devel/20210813004448.51c7de69ce432d338f4d226b@kernel.org/
Link: https://lkml.kernel.org/r/20210817035027.174869074@goodmis.org

Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2021-08-16 23:42:57 -04:00
parent 8b0e6c744f
commit 1d18538e6a
9 changed files with 124 additions and 24 deletions
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6
kernel/trace/trace_event_perf.c
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@ -177,7 +177,7 @@ static void perf_trace_event_unreg(struct perf_event *p_event)
}
}
out:
module_put(tp_event->mod);
trace_event_put_ref(tp_event);
}
static int perf_trace_event_open(struct perf_event *p_event)
@ -224,10 +224,10 @@ int perf_trace_init(struct perf_event *p_event)
list_for_each_entry(tp_event, &ftrace_events, list) {
if (tp_event->event.type == event_id &&
tp_event->class && tp_event->class->reg &&
try_module_get(tp_event->mod)) {
trace_event_try_get_ref(tp_event)) {
ret = perf_trace_event_init(tp_event, p_event);
if (ret)
module_put(tp_event->mod);
trace_event_put_ref(tp_event);
break;
}
}