tracing/ftrace: change the type of the print_line callback

We need a kind of disambiguation when a print_line callback
returns 0.

_There is not enough space to print all the entry.
 Please flush the seq and retry.
_I can't handle this type of entry

This patch changes the type of this callback for better information.

Also some changes have been made in this V2.

_ Only relay to default functions after the print_line callback fails.
_ This patch doesn't fix the issue with the broken pipe (see patch 2/4 for that)

Some things are still in discussion:

_ Find better names for the enum print_line_t values
_ Change the type of print_trace_line into boolean.

Patches to change that can be sent later.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Pekka Paalanen <pq@iki.fi>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 9 insertions, 1 deletions

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index e541a6b7e312..a921ba5d292d 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -177,6 +177,14 @@ struct trace_array {
         struct trace_array_cpu  *data[NR_CPUS];
 };
 
+
+/* Return values for print_line callback */
+enum print_line_t {
+        TRACE_TYPE_PARTIAL_LINE = 0,    /* Retry after flushing the seq */
+        TRACE_TYPE_HANDLED      = 1,
+        TRACE_TYPE_UNHANDLED    = 2     /* Relay to other output functions */
+};
+
 /*
  * A specific tracer, represented by methods that operate on a trace array:
  */
@@ -197,7 +205,7 @@ struct tracer {
         int                     (*selftest)(struct tracer *trace,
                                             struct trace_array *tr);
 #endif
-        int                     (*print_line)(struct trace_iterator *iter);
+        enum print_line_t       (*print_line)(struct trace_iterator *iter);
         struct tracer           *next;
         int                     print_max;
 };