core/sched: fix pid/tcb & refactor SCHEDSTATISTICS

pid and tcb_t were compared instead of pid and pid

SCHEDSTATISTICS:
- reduce hwtimer_now calls
- dont use thread_last_pid anymore
- increase readability

core/sched.c

@@ -59,6 +59,10 @@ void sched_run(void)
 {
     sched_context_switch_request = 0;
 
+#ifdef SCHEDSTATISTICS
+    unsigned long time = hwtimer_now();
+#endif
+
     tcb_t *my_active_thread = (tcb_t *)sched_active_thread;
 
     if (my_active_thread) {
@@ -72,15 +76,12 @@ void sched_run(void)
         }
 #endif
 
-    }
-
 #ifdef SCHEDSTATISTICS
-    unsigned long time = hwtimer_now();
-
-    if (my_active_thread && (sched_pidlist[my_active_thread->pid].laststart)) {
-        sched_pidlist[my_active_thread->pid].runtime_ticks += time - sched_pidlist[my_active_thread->pid].laststart;
-    }
+        if (sched_pidlist[my_active_thread->pid].laststart) {
+            sched_pidlist[my_active_thread->pid].runtime_ticks += time - sched_pidlist[my_active_thread->pid].laststart;
+        }
 #endif
+    }
 
     DEBUG("\nscheduler: previous task: %s\n", (my_active_thread == NULL) ? "none" : my_active_thread->name);
 
@@ -92,22 +93,23 @@ void sched_run(void)
     DEBUG("scheduler: first in queue: %s\n", ((tcb_t *)next.data)->name);
     clist_advance(&(sched_runqueues[nextrq]));
     my_active_thread = (tcb_t *)next.data;
-    sched_active_pid = (volatile int) my_active_thread->pid;
+
+    int my_next_pid = my_active_thread->pid;
 
 #if SCHEDSTATISTICS
-    sched_pidlist[my_active_thread->pid].laststart = time;
-    sched_pidlist[my_active_thread->pid].schedules++;
-    if ((sched_cb) && (sched_active_thread != thread_last_pid)) {
-        sched_cb(hwtimer_now(), my_active_thread->pid);
-        thread_last_pid = my_active_thread->pid;
+    sched_pidlist[my_next_pid].laststart = time;
+    sched_pidlist[my_next_pid].schedules++;
+    if ((sched_cb) && (my_next_pid != sched_active_pid)) {
+        sched_cb(time, my_next_pid);
     }
 #endif
 
 #ifdef MODULE_NSS
-    if (sched_active_thread && sched_active_thread != thread_last_pid) {
-        thread_last_pid = sched_active_thread;
+    if (sched_active_thread && (my_next_pid != thread_last_pid)) {
+        thread_last_pid = sched_active_pid;
     }
 #endif
+    sched_active_pid = my_next_pid;
 
     DEBUG("scheduler: next task: %s\n", my_active_thread->name);