feature: add ISR profiling support

- add logic to stop measuring task cycles when ISR is entered
- add logic to resume measuring task cycles when ISR is exited
- add logic to avoid getting negative value for cycles in corner case
  of 32b timestamp overflow

Author: kedar-chitnis

Ports/ARM-Cortex-M/ARMv7-M/os_cpu_c.c

@@ -513,8 +513,10 @@ void  OSTaskSwHook (void)
 #if OS_CFG_TASK_PROFILE_EN > 0u
     ts = OS_TS_GET();
     if (OSTCBCurPtr != OSTCBHighRdyPtr) {
-        OSTCBCurPtr->CyclesDelta  = ts - OSTCBCurPtr->CyclesStart;
-        OSTCBCurPtr->CyclesTotal += (OS_CYCLES)OSTCBCurPtr->CyclesDelta;
+        if (ts > OSTCBCurPtr->CyclesStart) {
+            OSTCBCurPtr->CyclesDelta  = ts - OSTCBCurPtr->CyclesStart;
+            OSTCBCurPtr->CyclesTotal += (OS_CYCLES)OSTCBCurPtr->CyclesDelta;
+        }
     }
 
     OSTCBHighRdyPtr->CyclesStart = ts;

Source/os_core.c

@@ -272,6 +272,18 @@ void  OSIntEnter (void)
         return;                                                 /* Yes                                                  */
     }
 
+#if OS_CFG_TASK_PROFILE_EN > 0u
+    if(OSIntNestingCtr==0) {
+        CPU_TS  ts;
+
+        ts = OS_TS_GET();
+        if(ts > OSTCBCurPtr->CyclesStart) {
+            OSTCBCurPtr->CyclesDelta  = ts - OSTCBCurPtr->CyclesStart;
+            OSTCBCurPtr->CyclesTotal += (OS_CYCLES)OSTCBCurPtr->CyclesDelta;
+        }
+    }
+#endif
+
     OSIntNestingCtr++;                                          /* Increment ISR nesting level                          */
 }
 
@@ -339,6 +351,10 @@ void  OSIntExit (void)
 #endif
 #endif
 
+#if OS_CFG_TASK_PROFILE_EN > 0u
+    OSTCBCurPtr->CyclesStart = OS_TS_GET();
+#endif
+
     OSPrioHighRdy   = OS_PrioGetHighest();                      /* Find highest priority                                */
 #if (OS_CFG_TASK_IDLE_EN > 0u)
     OSTCBHighRdyPtr = OSRdyList[OSPrioHighRdy].HeadPtr;         /* Get highest priority task ready-to-run               */