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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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45
include/linux/trace_events.h
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@@ -350,7 +350,14 @@ struct trace_event_call {
struct trace_event event;
char *print_fmt;
struct event_filter *filter;
void *mod;
/*
* Static events can disappear with modules,
* where as dynamic ones need their own ref count.
*/
union {
void *module;
atomic_t refcnt;
};
void *data;
/* See the TRACE_EVENT_FL_* flags above */
@@ -366,6 +373,42 @@ struct trace_event_call {
#endif
};
#ifdef CONFIG_DYNAMIC_EVENTS
bool trace_event_dyn_try_get_ref(struct trace_event_call *call);
void trace_event_dyn_put_ref(struct trace_event_call *call);
bool trace_event_dyn_busy(struct trace_event_call *call);
#else
static inline bool trace_event_dyn_try_get_ref(struct trace_event_call *call)
{
/* Without DYNAMIC_EVENTS configured, nothing should be calling this */
return false;
}
static inline void trace_event_dyn_put_ref(struct trace_event_call *call)
{
}
static inline bool trace_event_dyn_busy(struct trace_event_call *call)
{
/* Nothing should call this without DYNAIMIC_EVENTS configured. */
return true;
}
#endif
static inline bool trace_event_try_get_ref(struct trace_event_call *call)
{
if (call->flags & TRACE_EVENT_FL_DYNAMIC)
return trace_event_dyn_try_get_ref(call);
else
return try_module_get(call->module);
}
static inline void trace_event_put_ref(struct trace_event_call *call)
{
if (call->flags & TRACE_EVENT_FL_DYNAMIC)
trace_event_dyn_put_ref(call);
else
module_put(call->module);
}
#ifdef CONFIG_PERF_EVENTS
static inline bool bpf_prog_array_valid(struct trace_event_call *call)
{