ftrace: make ftrace_printk usable with the other tracers

Currently ftrace_printk only works with the ftrace tracer, switch it to an
iter_ctrl setting so we can make us of them with other tracers too.

[rostedt@redhat.com: tweak to the disable condition]

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/trace/trace.c

@@ -235,6 +235,7 @@ static const char *trace_options[] = {
 	"block",
 	"stacktrace",
 	"sched-tree",
+	"ftrace_printk",
 	NULL
 };
 
@@ -3091,25 +3092,26 @@ static __init void tracer_init_debugfs(void)
 
 int __ftrace_printk(unsigned long ip, const char *fmt, ...)
 {
-	struct trace_array *tr = &global_trace;
 	static DEFINE_SPINLOCK(trace_buf_lock);
 	static char trace_buf[TRACE_BUF_SIZE];
+
+	struct trace_array *tr = &global_trace;
 	struct trace_array_cpu *data;
 	struct trace_entry *entry;
 	unsigned long flags;
 	long disabled;
 	va_list ap;
 	int cpu, len = 0, write, written = 0;
 
-	if (likely(!ftrace_function_enabled))
+	if (!(trace_flags & TRACE_ITER_PRINTK) || !tr->ctrl || tracing_disabled)
 		return 0;
 
 	local_irq_save(flags);
 	cpu = raw_smp_processor_id();
 	data = tr->data[cpu];
 	disabled = atomic_inc_return(&data->disabled);
 
-	if (unlikely(disabled != 1 || !ftrace_function_enabled))
+	if (unlikely(disabled != 1))
 		goto out;
 
 	spin_lock(&trace_buf_lock);

kernel/trace/trace.h

@@ -356,6 +356,7 @@ enum trace_iterator_flags {
 	TRACE_ITER_BLOCK		= 0x80,
 	TRACE_ITER_STACKTRACE		= 0x100,
 	TRACE_ITER_SCHED_TREE		= 0x200,
+	TRACE_ITER_PRINTK		= 0x400,
 };
 
 #endif /* _LINUX_KERNEL_TRACE_H */