ftrace: change buffers to producer consumer

This patch changes the way the CPU trace buffers are handled.
Instead of always starting from the trace page head, the logic
is changed to a producer consumer logic. This allows for the
buffers to be drained while they are alive.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 4 insertions, 2 deletions

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 5df8ff2b84a7..0ce127455b4b 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -53,13 +53,15 @@ struct trace_entry {
  * the trace, etc.)
  */
 struct trace_array_cpu {
-        void                    *trace_current;
         struct list_head        trace_pages;
         atomic_t                disabled;
         cycle_t                 time_offset;
 
         /* these fields get copied into max-trace: */
-        unsigned                trace_current_idx;
+        unsigned                trace_head_idx;
+        unsigned                trace_tail_idx;
+        void                    *trace_head; /* producer */
+        void                    *trace_tail; /* consumer */
         unsigned long           trace_idx;
         unsigned long           saved_latency;
         unsigned long           critical_start;