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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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4
kernel/trace/trace.c
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@@ -3697,11 +3697,11 @@ static bool trace_safe_str(struct trace_iterator *iter, const char *str)
return false;
event = container_of(trace_event, struct trace_event_call, event);
if (!event->mod)
if ((event->flags & TRACE_EVENT_FL_DYNAMIC) || !event->module)
return false;
/* Would rather have rodata, but this will suffice */
if (within_module_core(addr, event->mod))
if (within_module_core(addr, event->module))
return true;
return false;