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).

2 files changed, 31 insertions, 18 deletions

diff --git a/include/litmus/trace.h b/include/litmus/trace.h
index b7f705dca20b..059cee4c7ffd 100644
--- a/include/litmus/trace.h
+++ b/include/litmus/trace.h
@@ -47,6 +47,8 @@ feather_callback void save_timestamp_time(unsigned long event, unsigned long tim
 #define TIMESTAMP_TIME(id, time_ptr) \
         ft_event1(id, save_timestamp_time, (unsigned long) time_ptr)
 
+#define TIMESTAMP_PID(id) ft_event0(id, save_timestamp_pid)
+
 #else /* !CONFIG_SCHED_OVERHEAD_TRACE */
 
 #define TIMESTAMP(id)        /* no tracing */
@@ -61,6 +63,8 @@ feather_callback void save_timestamp_time(unsigned long event, unsigned long tim
 
 #define TIMESTAMP_TIME(id, time_ptr) /* no tracing */
 
+#define TIMESTAMP_PID(id) /* no tracing */
+
 #endif
 
 
@@ -73,10 +77,18 @@ feather_callback void save_timestamp_time(unsigned long event, unsigned long tim
  */
 
 #define TS_SYSCALL_IN_START(p)          TIMESTAMP_TIME(10, p)
-#define TS_SYSCALL_IN_END               TIMESTAMP(11)
+#define TS_SYSCALL_IN_END               TIMESTAMP_PID(11)
+
+#define TS_SYSCALL_OUT_START            TIMESTAMP_PID(20)
+#define TS_SYSCALL_OUT_END              TIMESTAMP_PID(21)
 
-#define TS_SYSCALL_OUT_START            TIMESTAMP(20)
-#define TS_SYSCALL_OUT_END              TIMESTAMP(21)
+#define TS_LOCK_START                   TIMESTAMP_PID(30)
+#define TS_LOCK_SUSPEND                 TIMESTAMP_PID(31)
+#define TS_LOCK_RESUME                  TIMESTAMP_PID(32)
+#define TS_LOCK_END                     TIMESTAMP_PID(33)
+
+#define TS_UNLOCK_START                 TIMESTAMP_PID(40)
+#define TS_UNLOCK_END                   TIMESTAMP_PID(41)
 
 #define TS_SCHED_START                  DTIMESTAMP(100, TSK_UNKNOWN) /* we only
                                                                       * care
@@ -108,11 +120,6 @@ feather_callback void save_timestamp_time(unsigned long event, unsigned long tim
 #define TS_EXIT_NP_START                TIMESTAMP(150)
 #define TS_EXIT_NP_END                  TIMESTAMP(151)
 
-#define TS_LOCK_START                   TIMESTAMP(170)
-#define TS_LOCK_END                     TIMESTAMP(171)
-#define TS_UNLOCK_START                 TIMESTAMP(172)
-#define TS_UNLOCK_END                   TIMESTAMP(173)
-
 #define TS_SEND_RESCHED_START(c)        CTIMESTAMP(190, c)
 #define TS_SEND_RESCHED_END             DTIMESTAMP(191, TSK_UNKNOWN)
 
diff --git a/litmus/trace.c b/litmus/trace.c
index 23763c19fa6b..49f8246cda50 100644
--- a/litmus/trace.c
+++ b/litmus/trace.c
@@ -37,14 +37,7 @@ 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;
@@ -55,12 +48,25 @@ 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);