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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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38
kernel/trace/trace_dynevent.c
View File

@ -13,11 +13,49 @@
#include <linux/tracefs.h>
#include "trace.h"
#include "trace_output.h" /* for trace_event_sem */
#include "trace_dynevent.h"
static DEFINE_MUTEX(dyn_event_ops_mutex);
static LIST_HEAD(dyn_event_ops_list);
bool trace_event_dyn_try_get_ref(struct trace_event_call *dyn_call)
{
struct trace_event_call *call;
bool ret = false;
if (WARN_ON_ONCE(!(dyn_call->flags & TRACE_EVENT_FL_DYNAMIC)))
return false;
down_read(&trace_event_sem);
list_for_each_entry(call, &ftrace_events, list) {
if (call == dyn_call) {
atomic_inc(&dyn_call->refcnt);
ret = true;
}
}
up_read(&trace_event_sem);
return ret;
}
void trace_event_dyn_put_ref(struct trace_event_call *call)
{
if (WARN_ON_ONCE(!(call->flags & TRACE_EVENT_FL_DYNAMIC)))
return;
if (WARN_ON_ONCE(atomic_read(&call->refcnt) <= 0)) {
atomic_set(&call->refcnt, 0);
return;
}
atomic_dec(&call->refcnt);
}
bool trace_event_dyn_busy(struct trace_event_call *call)
{
return atomic_read(&call->refcnt) != 0;
}
int dyn_event_register(struct dyn_event_operations *ops)
{
if (!ops || !ops->create || !ops->show || !ops->is_busy ||