Merge tag 'trace-3.19-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing updates from Steven Rostedt:
 "As the merge window is still open, and this code was not as complex as
  I thought it might be.  I'm pushing this in now.

  This will allow Thomas to debug his irq work for 3.20.

  This adds two new features:

  1) Allow traceopoints to be enabled right after mm_init().

     By passing in the trace_event= kernel command line parameter,
     tracepoints can be enabled at boot up.  For debugging things like
     the initialization of interrupts, it is needed to have tracepoints
     enabled very early.  People have asked about this before and this
     has been on my todo list.  As it can be helpful for Thomas to debug
     his upcoming 3.20 IRQ work, I'm pushing this now.  This way he can
     add tracepoints into the IRQ set up and have users enable them when
     things go wrong.

  2) Have the tracepoints printed via printk() (the console) when they
     are triggered.

     If the irq code locks up or reboots the box, having the tracepoint
     output go into the kernel ring buffer is useless for debugging.
     But being able to add the tp_printk kernel command line option
     along with the trace_event= option will have these tracepoints
     printed as they occur, and that can be really useful for debugging
     early lock up or reboot problems.

  This code is not that intrusive and it passed all my tests.  Thomas
  tried them out too and it works for his needs.

   Link: http://lkml.kernel.org/r/20141214201609.126831471@goodmis.org"

* tag 'trace-3.19-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  tracing: Add tp_printk cmdline to have tracepoints go to printk()
  tracing: Move enabling tracepoints to just after rcu_init()

1 files changed, 40 insertions, 2 deletions

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index d0e4f92b5eb6..366a78a3e61e 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -212,8 +212,40 @@ void *ftrace_event_buffer_reserve(struct ftrace_event_buffer *fbuffer,
 }
 EXPORT_SYMBOL_GPL(ftrace_event_buffer_reserve);
 
+static DEFINE_SPINLOCK(tracepoint_iter_lock);
+
+static void output_printk(struct ftrace_event_buffer *fbuffer)
+{
+	struct ftrace_event_call *event_call;
+	struct trace_event *event;
+	unsigned long flags;
+	struct trace_iterator *iter = tracepoint_print_iter;
+
+	if (!iter)
+		return;
+
+	event_call = fbuffer->ftrace_file->event_call;
+	if (!event_call || !event_call->event.funcs ||
+	    !event_call->event.funcs->trace)
+		return;
+
+	event = &fbuffer->ftrace_file->event_call->event;
+
+	spin_lock_irqsave(&tracepoint_iter_lock, flags);
+	trace_seq_init(&iter->seq);
+	iter->ent = fbuffer->entry;
+	event_call->event.funcs->trace(iter, 0, event);
+	trace_seq_putc(&iter->seq, 0);
+	printk("%s", iter->seq.buffer);
+
+	spin_unlock_irqrestore(&tracepoint_iter_lock, flags);
+}
+
 void ftrace_event_buffer_commit(struct ftrace_event_buffer *fbuffer)
 {
+	if (tracepoint_printk)
+		output_printk(fbuffer);
+
 	event_trigger_unlock_commit(fbuffer->ftrace_file, fbuffer->buffer,
 				    fbuffer->event, fbuffer->entry,
 				    fbuffer->flags, fbuffer->pc);
@@ -2480,8 +2512,14 @@ 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