tracing: Move enabling tracepoints to just after rcu_init()

Enabling tracepoints at boot up can be very useful. The tracepoint
can be initialized right after RCU has been. There's no need to
wait for the early_initcall() to be called. That's too late for some
things that can use tracepoints for debugging. Move the logic to
enable tracepoints out of the initcalls and into init/main.c to
right after rcu_init().

This also allows trace_printk() to be used early too.

Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1412121539300.16494@nanos
Link: http://lkml.kernel.org/r/20141214164104.307127356@goodmis.org

Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

4 files changed, 30 insertions, 8 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 4ceb254..ec3ca69 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6876,6 +6876,13 @@ out:
 	return ret;
 }
 
+void __init trace_init(void)
+{
+	tracer_alloc_buffers();
+	init_ftrace_syscalls();
+	trace_event_init();	
+}
+
 __init static int clear_boot_tracer(void)
 {
 	/*
@@ -6895,6 +6902,5 @@ __init static int clear_boot_tracer(void)
 	return 0;
 }
 
-early_initcall(tracer_alloc_buffers);
 fs_initcall(tracer_init_debugfs);
 late_initcall(clear_boot_tracer);
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 3255dfb..c138c14 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1301,4 +1301,17 @@ int perf_ftrace_event_register(struct ftrace_event_call *call,
 #define perf_ftrace_event_register NULL
 #endif
 
+#ifdef CONFIG_FTRACE_SYSCALLS
+void init_ftrace_syscalls(void);
+#else
+static inline void init_ftrace_syscalls(void) { }
+#endif
+
+#ifdef CONFIG_EVENT_TRACING
+void trace_event_init(void);
+#else
+static inline void __init trace_event_init(void) { }
+#endif
+
+
 #endif /* _LINUX_KERNEL_TRACE_H */
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index f9d0cbe..fd9deb0 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -2477,8 +2477,14 @@ static __init int event_trace_init(void)
 #endif
 	return 0;
 }
-early_initcall(event_trace_memsetup);
-core_initcall(event_trace_enable);
+
+void __init trace_event_init(void)
+{
+	event_trace_memsetup();
+	init_ftrace_syscalls();
+	event_trace_enable();
+}
+
 fs_initcall(event_trace_init);
 
 #ifdef CONFIG_FTRACE_STARTUP_TEST
diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index a72f3d8..ec23977 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -514,7 +514,7 @@ unsigned long __init __weak arch_syscall_addr(int nr)
 	return (unsigned long)sys_call_table[nr];
 }
 
-static int __init init_ftrace_syscalls(void)
+void __init init_ftrace_syscalls(void)
 {
 	struct syscall_metadata *meta;
 	unsigned long addr;
@@ -524,7 +524,7 @@ static int __init init_ftrace_syscalls(void)
 				    GFP_KERNEL);
 	if (!syscalls_metadata) {
 		WARN_ON(1);
-		return -ENOMEM;
+		return;
 	}
 
 	for (i = 0; i < NR_syscalls; i++) {
@@ -536,10 +536,7 @@ static int __init init_ftrace_syscalls(void)
 		meta->syscall_nr = i;
 		syscalls_metadata[i] = meta;
 	}
-
-	return 0;
 }
-early_initcall(init_ftrace_syscalls);
 
 #ifdef CONFIG_PERF_EVENTS