ftrace: new continue entry - separate out from trace_entry

Some tracers will need to work with more than one entry. In order to do this
the trace_entry structure was split into two fields. One for the start of
all entries, and one to continue an existing entry.

The trace_entry structure now has a "field" entry that consists of the previous
content of the trace_entry, and a "cont" entry that is just a string buffer
the size of the "field" entry.

Thanks to Andrew Morton for suggesting this idea.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 14 insertions, 3 deletions

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index f69f86788c2b..6ddd6a6556cf 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -61,13 +61,12 @@ struct stack_entry {
 };
 
 /*
- * The trace entry - the most basic unit of tracing. This is what
+ * The trace field - the most basic unit of tracing. This is what
  * is printed in the end as a single line in the trace output, such as:
  *
  *     bash-15816 [01]   235.197585: idle_cpu <- irq_enter
  */
-struct trace_entry {
-        char                    type;
+struct trace_field {
         char                    cpu;
         char                    flags;
         char                    preempt_count;
@@ -83,6 +82,18 @@ struct trace_entry {
         };
 };
 
+struct trace_field_cont {
+        char                            buf[sizeof(struct trace_field)];
+};
+
+struct trace_entry {
+        char                            type;
+        union {
+                struct trace_field      field;
+                struct trace_field_cont cont;
+        };
+};
+
 #define TRACE_ENTRY_SIZE        sizeof(struct trace_entry)
 
 /*