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 f69f86788c2..6ddd6a6556c 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)
 
 /*