tracing: Have the reg function allow to fail

Some tracepoints have a registration function that gets enabled when the
tracepoint is enabled. There may be cases that the registraction function
must fail (for example, can't allocate enough memory). In this case, the
tracepoint should also fail to register, otherwise the user would not know
why the tracepoint is not working.

Cc: David Howells <dhowells@redhat.com>
Cc: Seiji Aguchi <seiji.aguchi@hds.com>
Cc: Anton Blanchard <anton@samba.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

2 files changed, 3 insertions, 2 deletions

diff --git a/samples/trace_events/trace-events-sample.c b/samples/trace_events/trace-events-sample.c
index 880a7d1d27d2..30e282d33d4d 100644
--- a/samples/trace_events/trace-events-sample.c
+++ b/samples/trace_events/trace-events-sample.c
@@ -79,7 +79,7 @@ static int simple_thread_fn(void *arg)
 
 static DEFINE_MUTEX(thread_mutex);
 
-void foo_bar_reg(void)
+int foo_bar_reg(void)
 {
         pr_info("Starting thread for foo_bar_fn\n");
         /*
@@ -90,6 +90,7 @@ void foo_bar_reg(void)
         mutex_lock(&thread_mutex);
         simple_tsk_fn = kthread_run(simple_thread_fn, NULL, "event-sample-fn");
         mutex_unlock(&thread_mutex);
+        return 0;
 }
 
 void foo_bar_unreg(void)
diff --git a/samples/trace_events/trace-events-sample.h b/samples/trace_events/trace-events-sample.h
index d6b75bb495b3..76a75ab7a608 100644
--- a/samples/trace_events/trace-events-sample.h
+++ b/samples/trace_events/trace-events-sample.h
@@ -354,7 +354,7 @@ TRACE_EVENT_CONDITION(foo_bar_with_cond,
         TP_printk("foo %s %d", __get_str(foo), __entry->bar)
 );
 
-void foo_bar_reg(void);
+int foo_bar_reg(void);
 void foo_bar_unreg(void);
 
 /*