/*@brief: switch out old pcb (p_pcb_old), run the new pcb (gp_current_process)
*@param: p_pcb_old, the old pcb that was in RUN
*@return: RTX_OK upon success
* RTX_ERR upon failure
*PRE: p_pcb_old and gp_current_process are pointing to valid PCBs.
*POST: if gp_current_process was NULL, then it gets set to pcbs[0].
* No other effect on other global variables.
*/
int process_switch(PCB *p_pcb_old)
{
PROC_STATE_E state;
state = gp_current_process->m_state;
if (state == NEW) {
if (gp_current_process != p_pcb_old && p_pcb_old->m_state != NEW) {
p_pcb_old->m_state = RDY;
p_pcb_old->mp_sp = (U32 *) __get_MSP();
}
gp_current_process->m_state = RUN;
__set_MSP((U32) gp_current_process->mp_sp);
__rte(); // pop exception stack frame from the stack for a new processes
}
/* The following will only execute if the if block above is FALSE */
if (gp_current_process != p_pcb_old) {
if (state == RDY){
p_pcb_old->m_state = RDY;
p_pcb_old->mp_sp = (U32 *) __get_MSP(); // save the old process's sp
gp_current_process->m_state = RUN;
__set_MSP((U32) gp_current_process->mp_sp); //switch to the new proc's stack
} else {
gp_current_process = p_pcb_old; // revert back to the old proc on error
return RTX_ERR;
}
}
return RTX_OK;
}
int context_switch(PCB* p_pcb_old) {
PROC_STATE_E state;
state = gp_current_process->m_state;
if (state == NEW) {
if (gp_current_process != p_pcb_old && p_pcb_old->m_state != NEW) {
if (p_pcb_old->m_state != BLOCKED_ON_RECEIVE &&
p_pcb_old->m_state != BLOCKED_ON_MEMORY) {
p_pcb_old->m_state = READY;
}
p_pcb_old->mp_sp = (U32*) __get_MSP();
}
gp_current_process->m_state = RUN;
__set_MSP((U32) gp_current_process->mp_sp);
__rte(); // pop exception stack frame from the stack for a new processes
}
if (gp_current_process != p_pcb_old) {
if (state == READY){
if (p_pcb_old->m_state != BLOCKED_ON_MEMORY && p_pcb_old->m_state != BLOCKED_ON_RECEIVE) {
p_pcb_old->m_state = READY;
}
p_pcb_old->mp_sp = (U32*) __get_MSP(); // save the old process's sp
gp_current_process->m_state = RUN;
__set_MSP((U32) gp_current_process->mp_sp); //switch to the new proc's stack
} else {
gp_current_process = p_pcb_old; // revert back to the old proc on error
return RTX_ERR;
}
}
return RTX_OK;
}
/**
* @brief release_processor().
* @return -1 on error and zero on success
* POST: gp_current_process gets updated
*/
int k_release_processor(void)
{
volatile int pid;
volatile proc_state_t state;
pcb_t * p_pcb_old = NULL;
pid = scheduler();
if (gp_current_process == NULL) {
return -1;
}
p_pcb_old = gp_current_process;
if (pid == 1) {
gp_current_process = &pcb1;
} else if (pid ==2){
gp_current_process = &pcb2;
} else {
return -1;
}
state = gp_current_process->m_state;
if (state == NEW) {
if (p_pcb_old->m_state != NEW) {
p_pcb_old->m_state = RDY;
p_pcb_old->mp_sp = (uint32_t *) __get_MSP();
}
gp_current_process->m_state = RUN;
__set_MSP((uint32_t) gp_current_process->mp_sp);
__rte(); // pop exception stack frame from the stack for new processes
} else if (state == RDY){
p_pcb_old->m_state = RDY;
p_pcb_old->mp_sp = (uint32_t *) __get_MSP(); // save the old process's sp
gp_current_process->m_state = RUN;
__set_MSP((uint32_t) gp_current_process->mp_sp); //switch to the new proc's stack
} else {
gp_current_process = p_pcb_old; // revert back to the old proc on error
return -1;
}
return 0;
}
/*@brief: switch out old pcb (p_pcb_old), run the new pcb (gp_current_process)
*@param: p_pcb_old, the old pcb that was in RUN
*@return: RTX_OK upon success
* RTX_ERR upon failure
*PRE: p_pcb_old and gp_current_process are pointing to valid PCBs.
*POST: if gp_current_process was NULL, then it gets set to pcbs[0].
* No other effect on other global variables.
*/
int process_switch(PCB *p_pcb_old)
{
PROC_STATE_E state;
#ifdef DEBUG_0
//printf("switching from process %d to process %d\n\r", p_pcb_old->m_pid, gp_current_process->m_pid);
#endif /* ! DEBUG_0 */
state = gp_current_process->m_state;
if (state == NEW) {
if (gp_current_process != p_pcb_old && p_pcb_old->m_state != NEW) {
p_pcb_old->mp_sp = (U32 *) __get_MSP();
if (p_pcb_old->m_state != BLK && p_pcb_old->m_state != BLK_RCV) {
p_pcb_old->m_state = RDY;
pq_push(ready_queue, p_pcb_old);
}
}
gp_current_process->m_state = RUN;
__set_MSP((U32) gp_current_process->mp_sp);
__rte(); // pop exception stack frame from the stack for a new processes
}
/* The following will only execute if the if block above is FALSE */
if (gp_current_process != p_pcb_old) {
if (state == RDY){
p_pcb_old->mp_sp = (U32 *) __get_MSP(); // save the old process's sp
if (p_pcb_old->m_state != BLK && p_pcb_old->m_state != BLK_RCV) {
p_pcb_old->m_state = RDY;
pq_push(ready_queue, p_pcb_old);
}
gp_current_process->m_state = RUN;
__set_MSP((U32) gp_current_process->mp_sp); //switch to the new proc's stack
} else {
gp_current_process = p_pcb_old; // revert back to the old proc on error
return RTX_ERR;
}
}
return RTX_OK;
}
