Feather-Trace: record PID fragments for locking overheads

We need to be able to figure out overlapping suspensions, etc.
So to reuse the existing format, just encode the lower 16bits of
the PID in the cpu and task-type fields (which we don't care about
when collecting locking overheads).

1 files changed, 16 insertions, 11 deletions

diff --git a/litmus/trace.c b/litmus/trace.c
index 6e123e6e0170..39200c8ff74e 100644
--- a/litmus/trace.c
+++ b/litmus/trace.c
@@ -41,7 +41,6 @@ static void __add_timestamp_user(struct timestamp *pre_recorded)
         if (ft_buffer_start_write(trace_ts_buf, (void**)  &ts)) {
                 *ts = *pre_recorded;
                 ts->seq_no = seq_no;
-                ts->cpu = raw_smp_processor_id();
                 ft_buffer_finish_write(trace_ts_buf, ts);
         }
 }
@@ -52,14 +51,7 @@ static inline void __save_timestamp(unsigned long event,
         __save_timestamp_cpu(event, type, raw_smp_processor_id());
 }
 
-static inline uint8_t task_type(struct task_struct* t)
-{
-        if (!t)
-                return TSK_UNKNOWN;
-        else
-                return is_realtime(t) ? TSK_RT : TSK_BE;
-}
-
+/* hack: fake timestamp to user-reported time, and record parts of the PID */
 feather_callback void save_timestamp_time(unsigned long event, unsigned long ptr)
 {
         uint64_t* time = (uint64_t*) ptr;
@@ -70,12 +62,25 @@ feather_callback void save_timestamp_time(unsigned long event, unsigned long ptr
                 ts->event     = event;
                 ts->timestamp = *time;
                 ts->seq_no    = seq_no;
-                ts->cpu       = raw_smp_processor_id();
-                ts->task_type = task_type(current);
+                /* type takes lowest byte of PID */
+                ts->task_type = (uint8_t) current->pid;
+                /* cpu takes second-lowest byte of PID*/
+                ts->cpu       = (uint8_t) (current->pid >> 8);
+
                 ft_buffer_finish_write(trace_ts_buf, ts);
         }
 }
 
+feather_callback void save_timestamp_pid(unsigned long event)
+{
+        /* Abuse existing fields to partially export PID. */
+        __save_timestamp_cpu(event,
+                             /* type takes lowest byte of PID */
+                             (uint8_t) current->pid,
+                             /* cpu takes second-lowest byte of PID*/
+                             (uint8_t) (current->pid >> 8));
+}
+
 feather_callback void save_timestamp(unsigned long event)
 {
         __save_timestamp(event, TSK_UNKNOWN);