OSTaskSwHook

Description

OSTaskSwHook() is always called by either OSCtxSw() or OSIntCtxSw() (see os_cpu_a.asm), just after saving the CPU registers onto the task being switched out. This hook function allows the port developer to perform additional operations (if needed) when µC/OS-III performs a context switch.

Before calling OSTaskSwHook(), OSTCBCurPtr points at the OS_TCB of the task being switched out, and OSTCBHighRdyPtr points at the OS_TCB of the new task being switched in.

The code shown in the example below should be included in all implementations of OSTaskSwHook(), and is used for performance measurements. This code is written in C for portability.

Files

os.h/os_cpu_c.c and os_app_hooks.c

Prototype

void  OSTaskSwHook (void)

Arguments

None

Returned Values

None

Required Configuration

OS_CFG_APP_HOOKS_EN must be enabled in os_cfg.h. Refer to µC-OS-III Configuration Manual.

Callers

OSCtxSw() and OSIntCtxSw().

Notes/Warnings

None

Example Usage

The code below calls an application specific hook that the application programmer can define. The user can simply set the value of OS_AppTaskSwHookPtr to point to the desired hook function. When µC/OS-III performs a context switch, it calls OSTaskSwHook() which in turn calls App_OS_TaskSwHook() through OS_AppTaskSwHookPtr.

OSTaskSwHook() example usage

          void  App_OS_TaskSwHook (void)                              /* os_app_hooks.c          */
          {
              /* Your code goes here! */
          }
           
           
          void App_OS_SetAllHooks (void)                              /* os_app_hooks.c          */
          {
              CPU_SR_ALLOC();
           
              CPU_CRITICAL_ENTER();
              :
              OS_AppTaskSwHookPtr = App_OS_TaskSwHook;
              :
              CPU_CRITICAL_EXIT();
          }
           
          void  OSTaskSwHook (void)                                   /* os_cpu_c.c              */
          {
          #if OS_CFG_TASK_PROFILE_EN > 0u
              CPU_TS     ts;
          #endif
          #ifdef  CPU_CFG_TIME_MEAS_INT_DIS_EN
              CPU_TS     int_dis_time;        
          #endif
           
 
          #if OS_CFG_APP_HOOKS_EN > 0u
              if (OS_AppTaskSwHookPtr != (OS_APP_HOOK_VOID)0) {
                  (*OS_AppTaskSwHookPtr)();
              }
          #endif
 
          #if OS_CFG_TASK_PROFILE_EN > 0u
              ts = OS_TS_GET();
              if (OSTCBCurPtr != OSTCBHighRdyPtr) {
                  OSTCBCurPtr->CyclesDelta  = ts - OSTCBCurPtr->CyclesStart;
                  OSTCBCurPtr->CyclesTotal += OSTCBCurPtr->CyclesDelta;
              }
              OSTCBHighRdyPtr->CyclesStart = ts;
          #endif
 
          #ifdef  CPU_CFG_INT_DIS_MEAS_EN        
              int_dis_time = CPU_IntDisMeasMaxCurReset();
              if (int_dis_time > OSTCBCurPtr->IntDisTimeMax) {
                  OSTCBCurPtr->IntDisTimeMax = int_dis_time;
              }
          #endif
 
          #if OS_CFG_SCHED_LOCK_TIME_MEAS_EN > 0u
              if (OSTCBCurPtr->SchedLockTimeMax < OSSchedLockTimeMaxCur) {
                  OSTCBCurPtr->SchedLockTimeMax = OSSchedLockTimeMaxCur;
              }
              OSSchedLockTimeMaxCur         = (CPU_TS)0;              
          #endif
 
          #if (OS_CFG_TASK_STK_REDZONE_EN == DEF_ENABLED)
              stk_status = OSTaskStkRedzoneChk(DEF_NULL);
              if (stk_status != DEF_OK) {
                  OSRedzoneHitHook(OSTCBCurPtr);
              }
          #endif
          }