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| author | Mychaela Falconia <falcon@freecalypso.org> |
|---|---|
| date | Fri, 15 May 2020 05:59:55 +0000 |
| parents | 92470e5d0b9e |
| children |
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/*************************************************************************/ /* */ /* Copyright Mentor Graphics Corporation 2002 */ /* All Rights Reserved. */ /* */ /* THIS WORK CONTAINS TRADE SECRET AND PROPRIETARY INFORMATION WHICH IS */ /* THE PROPERTY OF MENTOR GRAPHICS CORPORATION OR ITS LICENSORS AND IS */ /* SUBJECT TO LICENSE TERMS. */ /* */ /*************************************************************************/ /*************************************************************************/ /* */ /* FILE NAME VERSION */ /* */ /* tmc.c Nucleus PLUS 1.14 */ /* */ /* COMPONENT */ /* */ /* TM - Timer Management */ /* */ /* DESCRIPTION */ /* */ /* This file contains the core routines for the timer management */ /* component. */ /* */ /* DATA STRUCTURES */ /* */ /* None */ /* */ /* FUNCTIONS */ /* */ /* TMC_Init_Task_Timer Initialize task timer */ /* TMC_Start_Task_Timer Start task timer */ /* TMC_Stop_Task_Timer Stop task timer */ /* TMC_Start_Timer Actually start a timer */ /* TMC_Stop_Timer Actually stop a timer */ /* TMC_Timer_HISR Timer High-Level Interrupt */ /* Service Routine (HISR) */ /* TMC_Timer_Expiration Timer expiration function */ /* */ /* DEPENDENCIES */ /* */ /* cs_extr.h Common Service functions */ /* tc_extr.h Thread Control functions */ /* tm_extr.h Timer functions */ /* hi_extr.h History functions */ /* */ /* HISTORY */ /* */ /* DATE REMARKS */ /* */ /* 03-01-1993 Created initial version 1.0 */ /* 04-19-1993 Verified version 1.0 */ /* 08-09-1993 Corrected the following problems */ /* - Moved sleep, timeout, and */ /* application timer expiration */ /* processing to system timer */ /* HISR. Removed timer task */ /* logic */ /* - Corrected a disable timer */ /* problem that caused a delay */ /* in subsequent timer */ /* expiration */ /* - Corrected the application */ /* timer ID returned by the */ /* timer information service */ /* Corrected the loop to return */ /* all application timer */ /* pointers */ /* - Corrected timer expiration */ /* while accessing from an LISR */ /* - Using the task time slice ptr */ /* instead of the time slice */ /* state flag */ /* Modifications resulted in */ /* version 1.0a */ /* 08-09-1993 Verified version 1.0a */ /* 03-01-1994 Moved non-core functions into */ /* supplemental files, modified */ /* protection logic to use system */ /* protect mechanism, removed the */ /* disable timer logic in start */ /* timer, insured valid time- */ /* slice task pointer, added */ /* register logic, resulting */ /* in version 1.1 */ /* */ /* 3-18-1994 Verified version 1.1 */ /* 08-25-95 Made the following changes */ /* */ /* +INT type = 0; Type of expiration */ /* +VOID *pointer = NU_NULL; Pointer type */ /* +UNSIGNED id = 0; Application timer ID */ /* -INT type; Type of expiration */ /* -VOID *pointer; Pointer type */ /* -UNSIGNED id; Application timer ID */ /* Expiration routine ptr */ /* +VOID (*expiration_routine)(UNSIGNED)= NU_NULL; */ /* -VOID (*expiration_routine)(UNSIGNED); */ /* 04-17-1996 updated to version 1.2 */ /* 03-24-1998 Released version 1.3. */ /* 03-26-1999 Released 1.11m (new release */ /* numbering scheme) */ /* 04-17-2002 Released version 1.13m */ /* 11-07-2002 Released version 1.14 */ /*************************************************************************/ #define NU_SOURCE_FILE #include "cs_extr.h" /* Common service functions */ #include "tc_extr.h" /* Thread control functions */ #include "tm_extr.h" /* Timer functions */ #include "hi_extr.h" /* History functions */ /* Define external inner-component global data references. */ extern TM_TCB *TMD_Active_Timers_List; extern INT TMD_Active_List_Busy; extern UNSIGNED TMD_System_Clock; extern UNSIGNED TMD_Timer_Start; extern UNSIGNED TMD_Timer; extern INT TMD_Timer_State; extern UNSIGNED TMD_Time_Slice; extern TC_TCB *TMD_Time_Slice_Task; extern INT TMD_Time_Slice_State; /* Define internal function prototypes. */ VOID TMC_Start_Timer(TM_TCB *timer, UNSIGNED time); VOID TMC_Stop_Timer(TM_TCB *timer); VOID TMC_Timer_Expiration(VOID); UNSIGNED TMT_Read_Timer(VOID); VOID TMT_Enable_Timer(UNSIGNED time); VOID TMT_Disable_Timer(VOID); /*************************************************************************/ /* */ /* FUNCTION */ /* */ /* TMC_Init_Task_Timer */ /* */ /* DESCRIPTION */ /* */ /* This function is responsible for initializing the supplied task */ /* timer. This routine must be called from Supervisor mode in a */ /* Supervisor/User mode switching kernel. */ /* */ /* CALLED BY */ /* */ /* TCC_Create_Task Task create function */ /* */ /* CALLS */ /* */ /* None */ /* */ /* INPUTS */ /* */ /* timer Timer control block pointer */ /* information Information pointer - always */ /* the task pointer */ /* */ /* OUTPUTS */ /* */ /* None */ /* */ /* HISTORY */ /* */ /* DATE REMARKS */ /* */ /* 03-01-1993 Created initial version 1.0 */ /* 04-19-1993 Verified version 1.0 */ /* */ /*************************************************************************/ VOID TMC_Init_Task_Timer(TM_TCB *timer, VOID *information) { /* Initialize the task timer. */ timer -> tm_timer_type = TM_TASK_TIMER; timer -> tm_information = information; timer -> tm_next_timer = NU_NULL; timer -> tm_previous_timer = NU_NULL; } /*************************************************************************/ /* */ /* FUNCTION */ /* */ /* TMC_Start_Task_Timer */ /* */ /* DESCRIPTION */ /* */ /* This function is responsible for starting a task timer. Note */ /* that there are some special protection considerations since */ /* this function is called from the task control component. This */ /* routine must be called from Supervisor mode in a Supervisor/User */ /* mode switching kernel. */ /* */ /* CALLED BY */ /* */ /* TCC_Suspend_Task Suspend task with a timeout */ /* */ /* CALLS */ /* */ /* TMC_Start_Timer Start the timer */ /* */ /* INPUTS */ /* */ /* timer Timer control block pointer */ /* time Time associated with timer */ /* */ /* OUTPUTS */ /* */ /* None */ /* */ /* HISTORY */ /* */ /* DATE REMARKS */ /* */ /* 03-01-1993 Created initial version 1.0 */ /* 04-19-1993 Verified version 1.0 */ /* 03-01-1994 Removed protection logic since */ /* system protect is in force at */ /* the time this function is */ /* called, resulting in */ /* version 1.1 */ /* */ /* 03-18-1994 Verified version 1.1 */ /* */ /*************************************************************************/ VOID TMC_Start_Task_Timer(TM_TCB *timer, UNSIGNED time) { /* Start the specified timer. */ TMC_Start_Timer(timer, time); } /*************************************************************************/ /* */ /* FUNCTION */ /* */ /* TMC_Stop_Task_Timer */ /* */ /* DESCRIPTION */ /* */ /* This function is responsible for stopping a task timer. Note */ /* that there are some special protection considerations since */ /* this function is called from the task control component. This */ /* routine must be called from Supervisor mode in a Supervisor/User */ /* mode switching kernel. */ /* */ /* CALLED BY */ /* */ /* TCC_Resume_Task Resume task function */ /* TCC_Terminate_Task Terminate task function */ /* */ /* CALLS */ /* */ /* TMC_Stop_Timer Stop the timer */ /* */ /* INPUTS */ /* */ /* timer Timer control block pointer */ /* */ /* OUTPUTS */ /* */ /* None */ /* */ /* HISTORY */ /* */ /* DATE REMARKS */ /* */ /* 03-01-1993 Created initial version 1.0 */ /* 04-19-1993 Verified version 1.0 */ /* 03-01-1994 Removed protection logic since */ /* system protect is in force at */ /* the time this function is */ /* called, resulting in */ /* version 1.1 */ /* */ /* 03-18-1994 Verified version 1.1 */ /* */ /*************************************************************************/ VOID TMC_Stop_Task_Timer(TM_TCB *timer) { /* Stop the specified timer - if it is still active. */ if (timer -> tm_next_timer) TMC_Stop_Timer(timer); } /*************************************************************************/ /* */ /* FUNCTION */ /* */ /* TMC_Start_Timer */ /* */ /* DESCRIPTION */ /* */ /* This function is responsible for starting both application and */ /* task timers. This routine must be called from Supervisor mode */ /* in a Supervisor/User mode switching kernel. */ /* */ /* CALLED BY */ /* */ /* TMC_Control_Timer Control application timer */ /* TMC_Start_Task_Timer Start task timer */ /* */ /* CALLS */ /* */ /* TMT_Read_Timer Read current timer counter */ /* TMT_Adjust_Timer Adjust the count-down timer */ /* TMT_Enable_Timer Enable count-down timer */ /* */ /* INPUTS */ /* */ /* timer Timer control block pointer */ /* time Time associated with timer */ /* */ /* OUTPUTS */ /* */ /* None */ /* */ /* HISTORY */ /* */ /* DATE REMARKS */ /* */ /* 03-01-1993 Created initial version 1.0 */ /* 04-19-1993 Verified version 1.0 */ /* 08-09-1993 Added logic to check for timer */ /* expiration before or during */ /* another LISR's access, */ /* resulting in version 1.0a */ /* 08-09-1993 Verified version 1.0a */ /* 03-01-1994 Removed disable timer logic to */ /* insure there is no timer loss, */ /* added register logic, */ /* resulting in version 1.1 */ /* */ /* 03-18-1994 Verified version 1.1 */ /* */ /*************************************************************************/ VOID TMC_Start_Timer(TM_TCB *timer, UNSIGNED time) { R1 TM_TCB *list_ptr; /* Working pointer timer ptr */ UNSIGNED elapsed; /* Elapsed time variable */ INT done; /* Search finished flag */ /* Note that protection over the active timer list is in force when this function is called. */ /* Determine if the active list is empty. */ if (TMD_Active_Timers_List == NU_NULL) { /* Place the timer on an empty list. */ timer -> tm_next_timer = timer; timer -> tm_previous_timer = timer; /* Link the timer to the list head. */ TMD_Active_Timers_List = timer; /* Setup the actual count-down timer structures. */ TMD_Timer_Start = time; timer -> tm_remaining_time = time; /* BUG FIX FOR NU_RESET WITH INITIAL TIME OF 0 */ /* Determine if there is any time remaining on the timer. If so, enable the timer. Otherwise, the Timer HISR is already pending, so skip starting the timer again. */ if (time != 0) /* Start the actual count-down timer. */ TMT_Enable_Timer(TMD_Timer_Start); else TMD_Timer_State = TM_EXPIRED; } else { /* Place the new timer into the list. */ /* Pickup the head of the list. */ list_ptr = TMD_Active_Timers_List; /* Determine if the timer is being added while the timer expiration task is running. If so, don't attempt to adjust the expiration list. If not, adjust the list. */ if (!TMD_Active_List_Busy) { /* Calculate the elapsed amount of time from the last timer request. */ elapsed = TMD_Timer_Start - TMT_Read_Timer(); /* Adjust the first entry in the timer list and the timer start value accordingly. */ TMD_Timer_Start = TMD_Timer_Start - elapsed; /* Make sure the remaining time is never below zero. */ if (list_ptr -> tm_remaining_time > elapsed) { list_ptr -> tm_remaining_time = list_ptr -> tm_remaining_time - elapsed; } else { list_ptr -> tm_remaining_time = 0; } } /* At this point the timer list is accurate again. Find the appropriate place on the timer list for the new timer. */ /* Determine where to place the timer in the list. */ done = NU_FALSE; do { /* Determine if the timer belongs before the current timer pointed to by list_ptr. */ if (time < list_ptr -> tm_remaining_time) { /* Update the time of the next timer. */ list_ptr -> tm_remaining_time = list_ptr -> tm_remaining_time - time; /* Determine if an insertion at the head of the list is present. */ if (list_ptr == TMD_Active_Timers_List) /* Move the list head to the new timer. */ TMD_Active_Timers_List = timer; /* Set the done flag to end the search. */ done = NU_TRUE; } else { /* Decrement the time by the remaining value of each timer in the list. In this way, the list never has to be searched again. */ time = time - list_ptr -> tm_remaining_time; /* Move the list pointer to the next timer in the list. */ list_ptr = list_ptr -> tm_next_timer; /* Check to see if the list has wrapped around. */ if (list_ptr == TMD_Active_Timers_List) /* Searching is done. */ done = NU_TRUE; } } while (!done); /* Link the new timer into the list. */ timer -> tm_next_timer = list_ptr; timer -> tm_previous_timer = list_ptr -> tm_previous_timer; (list_ptr -> tm_previous_timer) -> tm_next_timer = timer; list_ptr -> tm_previous_timer = timer; /* Update the remaining time parameter. */ timer -> tm_remaining_time = time; /* Determine if a new timer should be started. */ if (!TMD_Active_List_Busy) { /* Calculate the new timer expiration. */ time = TMD_Active_Timers_List -> tm_remaining_time; /* Determine if the new expiration is less than the current time, if any. If not, let already started time expire. */ if (time <= TMD_Timer_Start) { /* Setup for a smaller timer expiration. */ TMD_Timer_Start = time; /* Determine if there is any time remaining on the timer in the front of the list. If so, adjust the timer. Otherwise, the Timer HISR is already pending, so skip starting the timer again. */ if (TMD_Timer_Start) /* Still some remaining time, adjust the timer. */ TMT_Adjust_Timer(TMD_Timer_Start); else /* Indicate that the task and application timer has expired. */ TMD_Timer_State = TM_EXPIRED; } } } } /*************************************************************************/ /* */ /* FUNCTION */ /* */ /* TMC_Stop_Timer */ /* */ /* DESCRIPTION */ /* */ /* This function is responsible for stopping both application and */ /* task timers. This routine must be called from Supervisor mode */ /* in a Supervisor/User mode switching kernel. */ /* */ /* CALLED BY */ /* */ /* TMC_Control_Timer Control application timer */ /* TMC_Stop_Task_Timer Start task timer */ /* */ /* CALLS */ /* */ /* TMT_Disable_Timer Disable the count-down timer */ /* */ /* INPUTS */ /* */ /* timer Timer control block pointer */ /* */ /* OUTPUTS */ /* */ /* None */ /* */ /* HISTORY */ /* */ /* DATE REMARKS */ /* */ /* 03-01-1993 Created initial version 1.0 */ /* 04-19-1993 Verified version 1.0 */ /* 08-09-1993 Corrected a problem associated */ /* with stopping the last timer */ /* on the active list, resulting */ /* in version 1.0a */ /* 08-09-1993 Verified version 1.0a */ /* */ /*************************************************************************/ VOID TMC_Stop_Timer(TM_TCB *timer) { /* Note that the active timer list is already under protection. */ /* If the next neighbor of the timer that needs to be stopped is not the head of the timer list, add the remaining time field to the remaining time of the next neighbor. */ if ((timer -> tm_next_timer) != TMD_Active_Timers_List) /* Adjust the next neighbor's remaining time field. */ (timer -> tm_next_timer) -> tm_remaining_time = (timer -> tm_next_timer) -> tm_remaining_time + timer -> tm_remaining_time; /* Unlink the timer from the active list. */ if (timer -> tm_next_timer == timer) { /* Only timer on the list. */ TMD_Active_Timers_List = NU_NULL; /* Disable the timer. */ TMT_Disable_Timer(); } else { /* More than one timer on the list. */ (timer -> tm_previous_timer) -> tm_next_timer = timer -> tm_next_timer; (timer -> tm_next_timer) -> tm_previous_timer = timer -> tm_previous_timer; /* Determine if the timer is at the head of the list. */ if (TMD_Active_Timers_List == timer) /* Yes, move the head pointer to the next timer. */ TMD_Active_Timers_List = timer -> tm_next_timer; } /* Clear the timer's next and previous pointers. */ timer -> tm_next_timer = NU_NULL; timer -> tm_previous_timer = NU_NULL; } /*************************************************************************/ /* */ /* FUNCTION */ /* */ /* TMC_Timer_HISR */ /* */ /* DESCRIPTION */ /* */ /* This function is responsible for High-Level interrupt processing */ /* of a timer expiration. If an application timer has expired, */ /* the timer expiration function is called. Otherwise, if the */ /* time-slice timer has expired, time-slice processing is invoked. */ /* */ /* CALLED BY */ /* */ /* None */ /* */ /* CALLS */ /* */ /* TCC_Time_Slice Task time-slice processing */ /* TMC_Timer_Expiration Timer expiration processing */ /* TMT_Retrieve_TS_Task Retrieve time-sliced task ptr*/ /* */ /* INPUTS */ /* */ /* None */ /* */ /* OUTPUTS */ /* */ /* None */ /* */ /* HISTORY */ /* */ /* DATE REMARKS */ /* */ /* 03-01-1993 Created initial version 1.0 */ /* 04-19-1993 Verified version 1.0 */ /* 08-09-1993 Added sleep, timeout, and */ /* application timer expiration */ /* processing to the timer HISR, */ /* using time slice task pointer */ /* instead of state flag, */ /* resulting in version 1.0a */ /* 08-09-1993 Verified version 1.0a */ /* 03-01-1994 Modified function interface to */ /* TCC_Time_Slice, added logic to */ /* insure valid pointer for some */ /* ports, resulting in version 1.1 */ /* */ /* 03-18-1994 Verified version 1.1 */ /* */ /*************************************************************************/ VOID TMC_Timer_HISR(VOID) { NU_TASK *task; /* Time slice task. */ /* Determine if the task timer has expired. */ if (TMD_Timer_State == TM_EXPIRED) /* Resume the timer task. */ TMC_Timer_Expiration(); /* Determine if the time-slice timer has expired. */ task = TMT_Retrieve_TS_Task(); if (task) { NU_SUPERV_USER_VARIABLES /* Switch to supervisor mode Note that this HISR function can make the switch to supervisor mode this is only possible because the code lives within the kernel */ NU_SUPERVISOR_MODE(); /* Reset the time-slice state. */ TMD_Time_Slice_State = TM_NOT_ACTIVE; /* Process the time-slice. */ TCC_Time_Slice(task); /* Clear the time slice task pointer. */ TMD_Time_Slice_Task = NU_NULL; /* Return to user mode */ NU_USER_MODE(); } } /*************************************************************************/ /* */ /* FUNCTION */ /* */ /* TMC_Timer_Expiration */ /* */ /* DESCRIPTION */ /* */ /* This function is responsible for processing all task timer */ /* expirations. This includes application timers and basic task */ /* timers that are used for task sleeping and timeouts. */ /* */ /* CALLED BY */ /* */ /* None */ /* */ /* CALLS */ /* */ /* expiration_function Application specified timer */ /* expiration function */ /* TCC_Task_Timeout Task timeout function */ /* TCT_System_Protect Protect active timer list */ /* TCT_Unprotect Release protection of list */ /* TMC_Stop_Timer Stop timer */ /* TMC_Start_Timer Start timer */ /* TMT_Disable_Timer Disable timer */ /* TMT_Enable_Timer Enable timer */ /* */ /* INPUTS */ /* */ /* None */ /* */ /* OUTPUTS */ /* */ /* None */ /* */ /* HISTORY */ /* */ /* DATE REMARKS */ /* */ /* 03-01-1993 Created initial version 1.0 */ /* 04-19-1993 Verified version 1.0 */ /* 08-09-1993 Changed from TMC_Timer_Task to */ /* TMC_Timer_Expiration, */ /* resulting in version 1.0a */ /* 08-09-1993 Verified version 1.0a */ /* 03-01-1994 Modified function interface to */ /* TCC_Task_Timeout, changed */ /* protection logic to use system */ /* protetion, added register */ /* logic, resulting in version 1.1 */ /* */ /* 03-18-1994 Verified version 1.1 */ /* 08-25-95 Made the following changes */ /* */ /* +INT type = 0; Type of expiration */ /* +VOID *pointer = NU_NULL; Pointer type */ /* +UNSIGNED id = 0; Application timer ID */ /* -INT type; Type of expiration */ /* -VOID *pointer; Pointer type */ /* -UNSIGNED id; Application timer ID */ /* Expiration routine ptr */ /* +VOID (*expiration_routine)(UNSIGNED)= NU_NULL; */ /* -VOID (*expiration_routine)(UNSIGNED); */ /* */ /*************************************************************************/ VOID TMC_Timer_Expiration(VOID) { R1 TM_TCB *timer; /* Pointer to timer */ R2 TM_APP_TCB *app_timer; /* Pointer to app timer */ INT done; /* Expiration completion */ INT type = 0; /* Type of expiration */ VOID *pointer = NU_NULL; /* Pointer type */ UNSIGNED id = 0; /* Application timer ID */ /* Expiration routine ptr */ VOID (*expiration_routine)(UNSIGNED)= NU_NULL; NU_SUPERV_USER_VARIABLES /* Switch to supervisor mode */ NU_SUPERVISOR_MODE(); /* Use system protect to protect the active timer list. */ TCT_System_Protect(); /* Reset the timer state flag. */ TMT_Disable_Timer(); /* Set the busy flag to indicate that the list is being processed. */ TMD_Active_List_Busy = NU_TRUE; /* Update the head of the list with the timer expiration value. */ timer = TMD_Active_Timers_List; if (timer) { /* Adjust the active timer's remaining time value. Note that TMD_Timer_Start is never greater than the value in the first timer location. */ if (timer -> tm_remaining_time > TMD_Timer_Start) /* Timer has not expired. Simply subtract the last timer value. */ timer -> tm_remaining_time = timer -> tm_remaining_time - TMD_Timer_Start; else /* Clear the remaining time field of the timer. */ timer -> tm_remaining_time = 0; } /* Release protection, but keep the busy flag set to prevent activating new timers. */ TCT_Unprotect(); /* Find expired timers. Note that the expired timers have values of 0 in the remaining time field. */ done = NU_FALSE; do { /* Protect against list access. */ TCT_System_Protect(); /* Pickup the head of the active list. */ timer = TMD_Active_Timers_List; /* Determine if the timer now at the head of the list has expired. Processing continues until the list is empty or until a non-expired timer is at the front of the list. */ if ((timer) && (timer -> tm_remaining_time == 0)) { /* Timer has expired. Determine which type of timer has expired. */ if (timer -> tm_timer_type == TM_APPL_TIMER) { /* Application timer has expired. */ type = TM_APPL_TIMER; /* Pickup the pointer to the application timer control block. */ app_timer = (TM_APP_TCB *) timer -> tm_information; /* Increment the number of expirations. */ app_timer -> tm_expirations++; #ifdef INCLUDE_PROVIEW _RTProf_DumpTimer(RT_PROF_APP_TIMER_EXPIRED,app_timer,RT_PROF_OK); #endif /* Move the expiration information into local variables in case they get corrupted before this expiration can be processed. Expirations are processed without the list protection in force. */ id = app_timer -> tm_expiration_id; expiration_routine = app_timer -> tm_expiration_routine; /* Clear the enabled flag and remove the timer from the list. */ app_timer -> tm_enabled = NU_FALSE; TMC_Stop_Timer(timer); /* Determine if this timer should be started again. */ if (app_timer -> tm_reschedule_time) { /* Timer needs to be rescheduled. */ /* Setup the enable flag to show that the timer is enabled. */ app_timer -> tm_enabled = NU_TRUE; /* Call the start timer function to actually enable the timer. This also puts it in the proper place on the list. */ TMC_Start_Timer(timer,app_timer -> tm_reschedule_time); } } else { /* Task timer has expired (sleeps and timeouts). */ type = TM_TASK_TIMER; /* Remove the timer from the list. */ TMC_Stop_Timer(timer); /* Save-off the task control block pointer. */ pointer = timer -> tm_information; } } else /* Processing is now complete- no more expired timers on the list. */ done = NU_TRUE; /* Release protection of active list. */ TCT_Unprotect(); /* Determine if a timer expiration needs to be finished. Note that the actual expiration processing is done with protection disabled. This prevents deadlock situations from arising. */ if (!done) { /* Determine which type of timer has expired. */ if (type == TM_APPL_TIMER) /* Call application timer's expiration function. */ (*(expiration_routine)) (id); else /* Call the task timeout function in the thread control function. */ TCC_Task_Timeout((NU_TASK *) pointer); } } while (!done); /* Protect the active list again. */ TCT_System_Protect(); /* Clear the busy flag to indicate that list processing is complete. */ TMD_Active_List_Busy = NU_FALSE; /* Determine if a new timer should be enabled. */ if (TMD_Active_Timers_List) { /* Yes, a new timer should be activated. */ /* Pickup the new timer expiration value. */ TMD_Timer_Start = TMD_Active_Timers_List -> tm_remaining_time; /* Start the new timer. */ TMT_Enable_Timer(TMD_Timer_Start); } /* Release protection of the active timer list. */ TCT_Unprotect(); /* Return to user mode */ NU_USER_MODE(); }