📄 tcs.c
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same priority. */
}
else
{
/* Add the TCB to an empty list. */
task -> tc_ready_previous = task;
task -> tc_ready_next = task;
*(task -> tc_priority_head)= task;
/* Update the priority group bit map to indicate that this
priority now has a task ready. */
TCD_Priority_Groups =
TCD_Priority_Groups | (task -> tc_priority_group);
/* Update the sub-priority bit map to show that this priority
is ready. */
*(task -> tc_sub_priority_ptr) =
(*(task -> tc_sub_priority_ptr)) | task -> tc_sub_priority;
}
/* Determine the highest priority task in the system. */
if (TCD_Priority_Groups & TC_HIGHEST_MASK)
/* Base of sub-group is 0. */
index = 0;
else if (TCD_Priority_Groups & TC_NEXT_HIGHEST_MASK)
/* Base of sub-group is 8. */
index = 8;
else if (TCD_Priority_Groups & TC_NEXT_LOWEST_MASK)
/* Base of sub-group is 16. */
index = 16;
else
/* Base of sub-group is 24. */
index = 24;
/* Calculate the highest available priority. */
index = index + TCD_Lowest_Set_Bit[(INT)
((TCD_Priority_Groups >> index) & TC_HIGHEST_MASK)];
/* Get the mask of the priority within the group of 8 priorities. */
temp = TCD_Sub_Priority_Groups[index];
/* Calculate the actual priority. */
TCD_Highest_Priority = (index << 3) + TCD_Lowest_Set_Bit[temp];
/* Check for preemption. */
if ((TCD_Highest_Priority <= ((INT) TCD_Execute_Task -> tc_priority))
&& (TCD_Execute_Task -> tc_preemption))
{
/* Update the current task pointer. */
TCT_Set_Execute_Task(TCD_Priority_List[TCD_Highest_Priority]);
/* Now, check and see if the current thread is a task.
If so, return a status that indicates a context
switch is needed. */
if ((TCD_Current_Thread) &&
(((TC_TCB *) TCD_Current_Thread) -> tc_id == TC_TASK_ID))
/* Transfer control to the system. */
TCT_Control_To_System();
}
}
else
{
/* Just modify the priority. */
task -> tc_priority = new_priority;
/* Build the other priority information. */
task -> tc_priority = new_priority;
task -> tc_priority_head = &(TCD_Priority_List[new_priority]);
task -> tc_sub_priority = (DATA_ELEMENT) (1 << (new_priority & 7));
task -> tc_priority_group = ((UNSIGNED) 1) << (new_priority >> 3);
task -> tc_sub_priority_ptr =
&(TCD_Sub_Priority_Groups[(new_priority >> 3)]);
}
/* Release the protection of the scheduling list. */
TCT_Unprotect();
/* Return the old priority. */
return(old_priority);
}
/*************************************************************************/
/* */
/* FUNCTION */
/* */
/* TCS_Change_Preemption */
/* */
/* DESCRIPTION */
/* */
/* This function changes the preemption posture of the calling */
/* task. Preemption for a task may be enabled or disabled. If */
/* it is disabled, the task runs until it suspends or relinquishes. */
/* If a preemption is pending, a call to this function to enable */
/* preemption causes a context switch. */
/* */
/* AUTHOR */
/* */
/* William E. Lamie, Accelerated Technology, Inc. */
/* */
/* CALLED BY */
/* */
/* Application */
/* TCSE_Change_Preemption Error checking function */
/* */
/* CALLS */
/* */
/* [HIC_Make_History_Entry] Make entry in history log */
/* [TCT_Check_Stack] Stack checking function */
/* TCT_Control_To_System Transfer control to system */
/* TCT_Protect Protect scheduling info */
/* TCT_Set_Execute_Task Set TCD_Execute_Task pointer */
/* TCT_Unprotect Release protection of info */
/* */
/* INPUTS */
/* */
/* preempt Preempt selection parameter */
/* */
/* OUTPUTS */
/* */
/* old_preempt Original preempt value */
/* */
/* HISTORY */
/* */
/* NAME DATE REMARKS */
/* */
/* W. Lamie 03-01-1993 Created initial version 1.0 */
/* D. Lamie 04-19-1993 Verified version 1.0 */
/* W. Lamie 03-01-1994 Modified protection logic, */
/* resulting in version 1.1 */
/* R. Pfaff - */
/* D. Lamie 03-18-1994 Verified version 1.1 */
/* */
/*************************************************************************/
OPTION TCS_Change_Preemption(OPTION preempt)
{
TC_TCB *task; /* Pointer to task */
OPTION old_preempt;
#ifdef NU_ENABLE_STACK_CHECK
/* Call stack checking function to check for an overflow condition. */
TCT_Check_Stack();
#endif
#ifdef NU_ENABLE_HISTORY
/* Make an entry that corresponds to this function in the system history
log. */
HIC_Make_History_Entry(NU_CHANGE_PREEMPTION_ID, (UNSIGNED) preempt,
(UNSIGNED) 0, (UNSIGNED) 0);
#endif
/* Protect the scheduling information. */
TCT_Protect(&TCD_System_Protect);
/* Pickup the current thread and place it in the task pointer. */
task = (TC_TCB *) TCD_Current_Thread;
/* Save the old preempt value. */
if (task -> tc_preemption)
/* Previously enabled. */
old_preempt = NU_PREEMPT;
else
/* Previously disabled. */
old_preempt = NU_NO_PREEMPT;
/* Process the new value. */
if (preempt == NU_NO_PREEMPT)
/* Disable preemption. */
TCD_Execute_Task -> tc_preemption = NU_FALSE;
else
{
/* Enable preemption. */
task -> tc_preemption = NU_TRUE;
/* Check for a preemption condition. */
if ((task == TCD_Execute_Task) &&
(TCD_Highest_Priority < ((INT) TCD_Execute_Task -> tc_priority)))
{
/* Preempt the current task. */
TCT_Set_Execute_Task(TCD_Priority_List[TCD_Highest_Priority]);
/* Transfer control to the system. */
TCT_Control_To_System();
}
}
/* Release protection of information. */
TCT_Unprotect();
/* Return the previous preemption posture. */
return(old_preempt);
}
/*************************************************************************/
/* */
/* FUNCTION */
/* */
/* TCS_Change_Time_Slice */
/* */
/* DESCRIPTION */
/* */
/* This function changes the time slice of the specified task. A */
/* time slice value of 0 disables time slicing. */
/* */
/* AUTHOR */
/* */
/* William E. Lamie, Accelerated Technology, Inc. */
/* */
/* CALLED BY */
/* */
/* Application */
/* TCES_Change_Preemption Error checking function */
/* */
/* CALLS */
/* */
/* [HIC_Make_History_Entry] Make entry in history log */
/* [TCT_Check_Stack] Stack checking function */
/* TCT_Protect Protect scheduling info */
/* TCT_Unprotect Release protection of info */
/* */
/* INPUTS */
/* */
/* task_ptr Task control block pointer */
/* time_slice New time slice value */
/* */
/* OUTPUTS */
/* */
/* old_time_slice Original time slice value */
/* */
/* HISTORY */
/* */
/* NAME DATE REMARKS */
/* */
/* W. Lamie 03-01-1993 Created initial version 1.0 */
/* D. Lamie 04-19-1993 Verified version 1.0 */
/* W. Lamie 03-01-1994 Modified function interface, */
/* added register optimizations, */
/* modified protection logic, */
/* resulting in version 1.1 */
/* R. Pfaff - */
/* D. Lamie 03-18-1994 Verified version 1.1 */
/* */
/*************************************************************************/
UNSIGNED TCS_Change_Time_Slice(NU_TASK *task_ptr, UNSIGNED time_slice)
{
TC_TCB *task; /* Task control block ptr */
UNSIGNED old_time_slice; /* Old time slice value */
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