yieldthread.c

zilog的实时操作系统RZK,可以移植到多种处理器上

/*
* File			:	YieldThread.c
*
* Description	:	This file contains the YieldThread function which yields
*					to give control to a same priority thread.
* 
* Copyright 2004 ZiLOG Inc.  ALL RIGHTS RESERVED.
*
* This file contains unpublished confidential and proprietary information
* of ZiLOG, Inc.
* NO PART OF THIS WORK MAY BE DUPLICATED, STORED, PUBLISHED OR DISCLOSED 
* IN ANY FORM WITHOUT THE PRIOR WRITTEN CONSENT OF ZiLOG, INC.
* This is not a license and no use of any kind of this work is authorized
* in the absence of a written license granted by ZiLOG, Inc. in ZiLOG's 
* sole discretion 
*/


#include "ZSysgen.h"
#include "ZTypes.h" 
#include "ZThread.h"
#include "ZQueue.h"
#include "ZScheduler.h"
#include "ZInterrupt.h"

#define pCurrentThread  ((RZK_TCB_t *)hCurrentThread)
 
/** extern functions */
//extern void RZKScheduler(); // IAR commented
extern void DispatchQueueNodeAppend(RZK_TCB_t *pObjectToAppend);
extern void DispatchQueueAppend(RZK_TCB_t *pObjectToRemove );
extern void DispatchQueueRemove(RZK_TCB_t *pObjectToRemove );

/** extern variables */ 
extern  RZK_DISPATCHQ_t DispatchQueue[DMAX_PRIORITY_P1];
extern RZK_THREADHANDLE_t hCurrentThread;


/*
* Function		:	YieldThread
*
* Description	:	A thread yields itself by relinquishing the processor and 
*					appending itself at the end of ready to run threads at 
*					it's priority level.
* 
* Inputs		:	None	
*
* Outputs		:	None
*
* Dependencies	:	
*/


RZK_STATUS_t  RZKYieldThread()
{
	UINTRMASK mInterruptMask;
	RZK_STATE_t uState;

	uState = RZKDisablePreemption();

	/* As yieldthread is a manual round robin facility tRRTime should be forcibly 
	initialised which is generally done in RZKSystemTimerIsr.c */
	pCurrentThread->tRRTime = pCurrentThread->tQuantum;

	mInterruptMask = RZKDisableInterrupts();
	/* It is then removed from the dispatch queue */
	DispatchQueueRemove(pCurrentThread);
	/*The same thread is appended at the end in the dispatch queue at its priority level */
	DispatchQueueAppend(pCurrentThread);
	RZKEnableInterrupts(mInterruptMask);

	/*If preemption was enabled before this API was called, then just restore preemption and
	call scheduler else forcibly enable preemption, call scheduler redisable preemption at the end of this API. */
	if(uState)
		RZKRestorePreemption(uState);
	else
	{
		RZKEnablePreemption();
		pCurrentThread->uOperationMode &= ~(RZK_THREAD_PREEMPTION);
	}

	return RZKERR_SUCCESS;
}/* End of RZKYieldThread */