tracing/ftrace: change the type of the init() callback

Impact: extend the ->init() method with the ability to fail

This bring a way to know if the initialization of a tracer successed.
A tracer must return 0 on success and a traditional error (ie:
-ENOMEM) if it fails.

If a tracer fails to init, it is free to print a detailed warn. The
tracing api will not and switch to a new tracer will just return the
error from the init callback.

Note: this will be used for the return tracer.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 2 insertions, 1 deletions

diff --git a/kernel/trace/trace_branch.c b/kernel/trace/trace_branch.c
index 8526555..44bd395 100644
--- a/kernel/trace/trace_branch.c
+++ b/kernel/trace/trace_branch.c
@@ -125,7 +125,7 @@ static void stop_branch_trace(struct trace_array *tr)
 	disable_branch_tracing();
 }
 
-static void branch_trace_init(struct trace_array *tr)
+static int branch_trace_init(struct trace_array *tr)
 {
 	int cpu;
 
@@ -133,6 +133,7 @@ static void branch_trace_init(struct trace_array *tr)
 		tracing_reset(tr, cpu);
 
 	start_branch_trace(tr);
+	return 0;
 }
 
 static void branch_trace_reset(struct trace_array *tr)