x86, ftrace: call trace->open() before stopping tracing; add trace->print_header()

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>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 8 insertions, 4 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a45b59e53fbc..8df8fdd69c95 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2298,7 +2298,9 @@ static int s_show(struct seq_file *m, void *v)
                         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 @@ __tracing_open(struct inode *inode, struct file *file, int *ret)
         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 @@ __tracing_open(struct inode *inode, struct file *file, int *ret)
         /* stop the trace while dumping */
         tracing_stop();
 
-        if (iter->trace && iter->trace->open)
-                        iter->trace->open(iter);
-
         mutex_unlock(&trace_types_lock);
 
  out:
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 28c15c2ebc22..717f9f045c6f 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -311,6 +311,7 @@ struct tracer {
         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);