[patch 8/9] x86, ftrace: call trace->open() before stopping tracing; add trace->print_header()

[patch 8/9] x86, ftrace: call trace->open() before stopping tracing; add trace->print_header()

[Markus Metzger]

Add a callback to allow an ftrace plug-in to write its own header.

Move the call to trace->open() up a few lines.

The changes are required by the BTS ftrace plug-in.

Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
---

Index: ftrace/kernel/trace/trace.c
===================================================================
--- ftrace.orig/kernel/trace/trace.c	2008-11-24 13:46:26.000000000 +0100
+++ ftrace/kernel/trace/trace.c	2008-11-25 08:18:05.000000000 +0100
@@ -2298,7 +2298,9 @@
 			seq_printf(m, "# tracer: %s\n", iter->trace->name);
 			seq_puts(m, "#\n");
 		}
-		if (iter->iter_flags & TRACE_FILE_LAT_FMT) {
+		if (iter->trace && iter->trace->print_header)
+			iter->trace->print_header(m);
+		else if (iter->iter_flags & TRACE_FILE_LAT_FMT) {
 			/* print nothing if the buffers are empty */
 			if (trace_empty(iter))
 				return 0;
@@ -2350,6 +2352,10 @@
 	iter->trace = current_trace;
 	iter->pos = -1;
 
+	/* Notify the tracer early; before we stop tracing. */
+	if (iter->trace && iter->trace->open)
+			iter->trace->open(iter);
+
 	/* Annotate start of buffers if we had overruns */
 	if (ring_buffer_overruns(iter->tr->buffer))
 		iter->iter_flags |= TRACE_FILE_ANNOTATE;
@@ -2375,9 +2381,6 @@
 	/* stop the trace while dumping */
 	tracing_stop();
 
-	if (iter->trace && iter->trace->open)
-			iter->trace->open(iter);
-
 	mutex_unlock(&trace_types_lock);
 
  out:
Index: ftrace/kernel/trace/trace.h
===================================================================
--- ftrace.orig/kernel/trace/trace.h	2008-11-24 13:46:26.000000000 +0100
+++ ftrace/kernel/trace/trace.h	2008-11-25 08:18:05.000000000 +0100
@@ -311,6 +311,7 @@
 	int			(*selftest)(struct tracer *trace,
 					    struct trace_array *tr);
 #endif
+	void			(*print_header)(struct seq_file *m);
 	enum print_line_t	(*print_line)(struct trace_iterator *iter);
 	/* If you handled the flag setting, return 0 */
 	int			(*set_flag)(u32 old_flags, u32 bit, int set);
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Re: [patch 8/9] x86, ftrace: call trace->open() before stopping tracing; add trace->print_header()

[Frédéric Weisbecker]

2008/11/25 Markus Metzger <markus.t.metzger@intel.com>:
> Add a callback to allow an ftrace plug-in to write its own header.


That's a good idea IMHO. The trace file has always the same header
which fits the needs of function
tracer for example, but these headers are wrong for other tracers. And
be able to set custom header
for each one will help for new users of a tracer.