From dbf48157fb9841ec6ccfcfab01f70eefe8f498ce Mon Sep 17 00:00:00 2001
From: gdisirio <gdisirio@35acf78f-673a-0410-8e92-d51de3d6d3f4>
Date: Sat, 14 Mar 2009 13:11:10 +0000
Subject: Made the scheduler code more readable.

git-svn-id: svn://svn.code.sf.net/p/chibios/svn/trunk@849 35acf78f-673a-0410-8e92-d51de3d6d3f4
---
 ports/ARMCM3/chcore.c |  2 --
 src/chschd.c          | 24 ++++++++++--------------
 src/include/debug.h   |  6 ++++++
 3 files changed, 16 insertions(+), 16 deletions(-)

diff --git a/ports/ARMCM3/chcore.c b/ports/ARMCM3/chcore.c
index 0159ee71f..80bd13490 100644
--- a/ports/ARMCM3/chcore.c
+++ b/ports/ARMCM3/chcore.c
@@ -168,9 +168,7 @@ void PendSVVector(void) {
   /* set the round-robin time quantum */
   rlist.r_preempt = CH_TIME_QUANTUM;
 #endif
-#if CH_DBG_ENABLE_TRACE
   chDbgTrace(otp, currp);
-#endif
   sp_thd = currp->p_ctx.r13;
 
   POP_CONTEXT(sp_thd);
diff --git a/src/chschd.c b/src/chschd.c
index 82718342f..441070dcb 100644
--- a/src/chschd.c
+++ b/src/chschd.c
@@ -86,9 +86,7 @@ void chSchGoSleepS(tstate_t newstate) {
 #if CH_USE_ROUNDROBIN
   rlist.r_preempt = CH_TIME_QUANTUM;
 #endif
-#if CH_DBG_ENABLE_TRACE
   chDbgTrace(otp, currp);
-#endif
   chSysSwitchI(otp, currp);
 }
 
@@ -163,25 +161,22 @@ msg_t chSchGoSleepTimeoutS(tstate_t newstate, systime_t time) {
  *       @p chSchRescheduleS() but much more efficient.
  */
 void chSchWakeupS(Thread *ntp, msg_t msg) {
+
   ntp->p_rdymsg = msg;
+  /* If the waken thread has a not-greater priority than the current
+   * one then it is just inserted in the ready list else it made
+   * running immediately and the invoking thread goes in the ready
+   * list instead.*/
   if (ntp->p_prio <= currp->p_prio)
-    /* the woken thread has equal or lower priority than the running thread */
     chSchReadyI(ntp);
   else {
-    /* the woken thread has higher priority than the running thread and thus
-     * preempts the currently running thread. */
     Thread *otp = currp;
     chSchReadyI(otp);
-    /* change the to-be-run thread to running state */
     (currp = ntp)->p_state = PRCURR;
 #if CH_USE_ROUNDROBIN
     rlist.r_preempt = CH_TIME_QUANTUM;
 #endif
-#if CH_DBG_ENABLE_TRACE
-    /* trace the context switch */
     chDbgTrace(otp, ntp);
-#endif
-    /* switch the thread context */
     chSysSwitchI(otp, ntp);
   }
 }
@@ -201,9 +196,7 @@ void chSchDoRescheduleI(void) {
 #if CH_USE_ROUNDROBIN
   rlist.r_preempt = CH_TIME_QUANTUM;
 #endif
-#if CH_DBG_ENABLE_TRACE
   chDbgTrace(otp, currp);
-#endif
   chSysSwitchI(otp, currp);
 }
 
@@ -221,6 +214,8 @@ void chSchRescheduleS(void) {
 
 /**
  * @brief Evaluates if a reschedulation is required.
+ * @details The decision is taken by comparing the relative priorities and
+ *          depending on the state of the round robin timeout counter.
  *
  * @retval TRUE if there is a thread that should go in running state.
  * @retval FALSE if a reschedulation is not required.
@@ -232,10 +227,11 @@ bool_t chSchRescRequiredI(void) {
   /* If the running thread has not reached its time quantum, reschedule only
    * if the first thread on the ready queue has a higher priority.
    * Otherwise, if the running thread has used up its time quantum, reschedule
-   * if the first thread on the ready queue has equal or higher priority.
-   */
+   * if the first thread on the ready queue has equal or higher priority.*/
   return rlist.r_preempt ? p1 > p2 : p1 >= p2;
 #else
+  /* If the round robin feature is not enabled then performs a simpler
+   * comparison.*/
   return p1 > p2;
 #endif
 }
diff --git a/src/include/debug.h b/src/include/debug.h
index 82e784040..3c51f0837 100644
--- a/src/include/debug.h
+++ b/src/include/debug.h
@@ -118,6 +118,12 @@ typedef struct {
 #define chDbgPanic(msg) {}
 #endif
 
+#if !CH_DBG_ENABLE_TRACE
+/* When the trace feature is disabled this function is replaced by an empty
+ * macro.*/
+#define chDbgTrace(otp, ntp) {}
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif
-- 
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