/* ********************************************************************************************************* * uC/OS-II * The Real-Time Kernel * SEMAPHORE MANAGEMENT * * (c) Copyright 1992-2006, Jean J. Labrosse, Weston, FL * All Rights Reserved * * File : OS_SEM.C * By : Jean J. Labrosse * Version : V2.83 ********************************************************************************************************* */ #ifndef OS_MASTER_FILE #include #endif #if OS_SEM_EN > 0 /* ********************************************************************************************************* * ACCEPT SEMAPHORE * * Description: This function checks the semaphore to see if a resource is available or, if an event * occurred. Unlike OSSemPend(), OSSemAccept() does not suspend the calling task if the * resource is not available or the event did not occur. * * Arguments : pevent is a pointer to the event control block * * Returns : > 0 if the resource is available or the event did not occur the semaphore is * decremented to obtain the resource. * == 0 if the resource is not available or the event did not occur or, * if 'pevent' is a NULL pointer or, * if you didn't pass a pointer to a semaphore ********************************************************************************************************* */ #if OS_SEM_ACCEPT_EN > 0 INT16U OSSemAccept (OS_EVENT *pevent) { INT16U cnt; #if OS_CRITICAL_METHOD == 3 /* Allocate storage for CPU status register */ OS_CPU_SR cpu_sr = 0; #endif #if OS_ARG_CHK_EN > 0 if (pevent == (OS_EVENT *)0) { /* Validate 'pevent' */ return (0); } #endif if (pevent->OSEventType != OS_EVENT_TYPE_SEM) { /* Validate event block type */ return (0); } OS_ENTER_CRITICAL(); cnt = pevent->OSEventCnt; if (cnt > 0) { /* See if resource is available */ pevent->OSEventCnt--; /* Yes, decrement semaphore and notify caller */ } OS_EXIT_CRITICAL(); return (cnt); /* Return semaphore count */ } #endif /*$PAGE*/ /* ********************************************************************************************************* * CREATE A SEMAPHORE * * Description: This function creates a semaphore. * * Arguments : cnt is the initial value for the semaphore. If the value is 0, no resource is * available (or no event has occurred). You initialize the semaphore to a * non-zero value to specify how many resources are available (e.g. if you have * 10 resources, you would initialize the semaphore to 10). * * Returns : != (void *)0 is a pointer to the event control clock (OS_EVENT) associated with the * created semaphore * == (void *)0 if no event control blocks were available ********************************************************************************************************* */ OS_EVENT *OSSemCreate (INT16U cnt) { OS_EVENT *pevent; #if OS_CRITICAL_METHOD == 3 /* Allocate storage for CPU status register */ OS_CPU_SR cpu_sr = 0; #endif if (OSIntNesting > 0) { /* See if called from ISR ... */ return ((OS_EVENT *)0); /* ... can't CREATE from an ISR */ } OS_ENTER_CRITICAL(); pevent = OSEventFreeList; /* Get next free event control block */ if (OSEventFreeList != (OS_EVENT *)0) { /* See if pool of free ECB pool was empty */ OSEventFreeList = (OS_EVENT *)OSEventFreeList->OSEventPtr; } OS_EXIT_CRITICAL(); if (pevent != (OS_EVENT *)0) { /* Get an event control block */ pevent->OSEventType = OS_EVENT_TYPE_SEM; pevent->OSEventCnt = cnt; /* Set semaphore value */ pevent->OSEventPtr = (void *)0; /* Unlink from ECB free list */ #if OS_EVENT_NAME_SIZE > 1 pevent->OSEventName[0] = '?'; /* Unknown name */ pevent->OSEventName[1] = OS_ASCII_NUL; #endif OS_EventWaitListInit(pevent); /* Initialize to 'nobody waiting' on sem. */ } return (pevent); } /*$PAGE*/ /* ********************************************************************************************************* * DELETE A SEMAPHORE * * Description: This function deletes a semaphore and readies all tasks pending on the semaphore. * * Arguments : pevent is a pointer to the event control block associated with the desired * semaphore. * * opt determines delete options as follows: * opt == OS_DEL_NO_PEND Delete semaphore ONLY if no task pending * opt == OS_DEL_ALWAYS Deletes the semaphore even if tasks are waiting. * In this case, all the tasks pending will be readied. * * err is a pointer to an error code that can contain one of the following values: * OS_NO_ERR The call was successful and the semaphore was deleted * OS_ERR_DEL_ISR If you attempted to delete the semaphore from an ISR * OS_ERR_INVALID_OPT An invalid option was specified * OS_ERR_TASK_WAITING One or more tasks were waiting on the semaphore * OS_ERR_EVENT_TYPE If you didn't pass a pointer to a semaphore * OS_ERR_PEVENT_NULL If 'pevent' is a NULL pointer. * * Returns : pevent upon error * (OS_EVENT *)0 if the semaphore was successfully deleted. * * Note(s) : 1) This function must be used with care. Tasks that would normally expect the presence of * the semaphore MUST check the return code of OSSemPend(). * 2) OSSemAccept() callers will not know that the intended semaphore has been deleted unless * they check 'pevent' to see that it's a NULL pointer. * 3) This call can potentially disable interrupts for a long time. The interrupt disable * time is directly proportional to the number of tasks waiting on the semaphore. * 4) Because ALL tasks pending on the semaphore will be readied, you MUST be careful in * applications where the semaphore is used for mutual exclusion because the resource(s) * will no longer be guarded by the semaphore. ********************************************************************************************************* */ #if OS_SEM_DEL_EN > 0 OS_EVENT *OSSemDel (OS_EVENT *pevent, INT8U opt, INT8U *err) { BOOLEAN tasks_waiting; OS_EVENT *pevent_return; #if OS_CRITICAL_METHOD == 3 /* Allocate storage for CPU status register */ OS_CPU_SR cpu_sr = 0; #endif #if OS_ARG_CHK_EN > 0 if (err == (INT8U *)0) { /* Validate 'err' */ return (pevent); } if (pevent == (OS_EVENT *)0) { /* Validate 'pevent' */ *err = OS_ERR_PEVENT_NULL; return (pevent); } #endif if (pevent->OSEventType != OS_EVENT_TYPE_SEM) { /* Validate event block type */ *err = OS_ERR_EVENT_TYPE; return (pevent); } if (OSIntNesting > 0) { /* See if called from ISR ... */ *err = OS_ERR_DEL_ISR; /* ... can't DELETE from an ISR */ return (pevent); } OS_ENTER_CRITICAL(); if (pevent->OSEventGrp != 0) { /* See if any tasks waiting on semaphore */ tasks_waiting = OS_TRUE; /* Yes */ } else { tasks_waiting = OS_FALSE; /* No */ } switch (opt) { case OS_DEL_NO_PEND: /* Delete semaphore only if no task waiting */ if (tasks_waiting == OS_FALSE) { #if OS_EVENT_NAME_SIZE > 1 pevent->OSEventName[0] = '?'; /* Unknown name */ pevent->OSEventName[1] = OS_ASCII_NUL; #endif pevent->OSEventType = OS_EVENT_TYPE_UNUSED; pevent->OSEventPtr = OSEventFreeList; /* Return Event Control Block to free list */ pevent->OSEventCnt = 0; OSEventFreeList = pevent; /* Get next free event control block */ OS_EXIT_CRITICAL(); *err = OS_NO_ERR; pevent_return = (OS_EVENT *)0; /* Semaphore has been deleted */ } else { OS_EXIT_CRITICAL(); *err = OS_ERR_TASK_WAITING; pevent_return = pevent; } break; case OS_DEL_ALWAYS: /* Always delete the semaphore */ while (pevent->OSEventGrp != 0) { /* Ready ALL tasks waiting for semaphore */ (void)OS_EventTaskRdy(pevent, (void *)0, OS_STAT_SEM); } #if OS_EVENT_NAME_SIZE > 1 pevent->OSEventName[0] = '?'; /* Unknown name */ pevent->OSEventName[1] = OS_ASCII_NUL; #endif pevent->OSEventType = OS_EVENT_TYPE_UNUSED; pevent->OSEventPtr = OSEventFreeList; /* Return Event Control Block to free list */ pevent->OSEventCnt = 0; OSEventFreeList = pevent; /* Get next free event control block */ OS_EXIT_CRITICAL(); if (tasks_waiting == OS_TRUE) { /* Reschedule only if task(s) were waiting */ OS_Sched(); /* Find highest priority task ready to run */ } *err = OS_NO_ERR; pevent_return = (OS_EVENT *)0; /* Semaphore has been deleted */ break; default: OS_EXIT_CRITICAL(); *err = OS_ERR_INVALID_OPT; pevent_return = pevent; break; } return (pevent_return); } #endif /*$PAGE*/ /* ********************************************************************************************************* * PEND ON SEMAPHORE * * Description: This function waits for a semaphore. * * Arguments : pevent is a pointer to the event control block associated with the desired * semaphore. * * timeout is an optional timeout period (in clock ticks). If non-zero, your task will * wait for the resource up to the amount of time specified by this argument. * If you specify 0, however, your task will wait forever at the specified * semaphore or, until the resource becomes available (or the event occurs). * * err is a pointer to where an error message will be deposited. Possible error * messages are: * * OS_NO_ERR The call was successful and your task owns the resource * or, the event you are waiting for occurred. * OS_TIMEOUT The semaphore was not received within the specified * timeout. * OS_ERR_EVENT_TYPE If you didn't pass a pointer to a semaphore. * OS_ERR_PEND_ISR If you called this function from an ISR and the result * would lead to a suspension. * OS_ERR_PEVENT_NULL If 'pevent' is a NULL pointer. * * Returns : none ********************************************************************************************************* */ void OSSemPend (OS_EVENT *pevent, INT16U timeout, INT8U *err) { #if OS_CRITICAL_METHOD == 3 /* Allocate storage for CPU status register */ OS_CPU_SR cpu_sr = 0; #endif #if OS_ARG_CHK_EN > 0 if (err == (INT8U *)0) { /* Validate 'err' */ return; } if (pevent == (OS_EVENT *)0) { /* Validate 'pevent' */ *err = OS_ERR_PEVENT_NULL; return; } #endif if (pevent->OSEventType != OS_EVENT_TYPE_SEM) { /* Validate event block type */ *err = OS_ERR_EVENT_TYPE; return; } if (OSIntNesting > 0) { /* See if called from ISR ... */ *err = OS_ERR_PEND_ISR; /* ... can't PEND from an ISR */ return; } if (OSLockNesting > 0) { /* See if called with scheduler locked ... */ *err = OS_ERR_PEND_LOCKED; /* ... can't PEND when locked */ return; } OS_ENTER_CRITICAL(); if (pevent->OSEventCnt > 0) { /* If sem. is positive, resource available ... */ pevent->OSEventCnt--; /* ... decrement semaphore only if positive. */ OS_EXIT_CRITICAL(); *err = OS_NO_ERR; return; } /* Otherwise, must wait until event occurs */ OSTCBCur->OSTCBStat |= OS_STAT_SEM; /* Resource not available, pend on semaphore */ OSTCBCur->OSTCBPendTO = OS_FALSE; OSTCBCur->OSTCBDly = timeout; /* Store pend timeout in TCB */ OS_EventTaskWait(pevent); /* Suspend task until event or timeout occurs */ OS_EXIT_CRITICAL(); OS_Sched(); /* Find next highest priority task ready */ OS_ENTER_CRITICAL(); if (OSTCBCur->OSTCBPendTO == OS_TRUE) { /* See if we timedout */ OS_EventTO(pevent); OS_EXIT_CRITICAL(); *err = OS_TIMEOUT; /* Indicate that didn't get event within TO */ return; } OSTCBCur->OSTCBEventPtr = (OS_EVENT *)0; OS_EXIT_CRITICAL(); *err = OS_NO_ERR; } /*$PAGE*/ /* ********************************************************************************************************* * POST TO A SEMAPHORE * * Description: This function signals a semaphore * * Arguments : pevent is a pointer to the event control block associated with the desired * semaphore. * * Returns : OS_NO_ERR The call was successful and the semaphore was signaled. * OS_SEM_OVF If the semaphore count exceeded its limit. In other words, you have * signalled the semaphore more often than you waited on it with either * OSSemAccept() or OSSemPend(). * OS_ERR_EVENT_TYPE If you didn't pass a pointer to a semaphore * OS_ERR_PEVENT_NULL If 'pevent' is a NULL pointer. ********************************************************************************************************* */ INT8U OSSemPost (OS_EVENT *pevent) { #if OS_CRITICAL_METHOD == 3 /* Allocate storage for CPU status register */ OS_CPU_SR cpu_sr = 0; #endif #if OS_ARG_CHK_EN > 0 if (pevent == (OS_EVENT *)0) { /* Validate 'pevent' */ return (OS_ERR_PEVENT_NULL); } #endif if (pevent->OSEventType != OS_EVENT_TYPE_SEM) { /* Validate event block type */ return (OS_ERR_EVENT_TYPE); } OS_ENTER_CRITICAL(); if (pevent->OSEventGrp != 0) { /* See if any task waiting for semaphore*/ (void)OS_EventTaskRdy(pevent, (void *)0, OS_STAT_SEM); /* Ready HPT waiting on event */ OS_EXIT_CRITICAL(); OS_Sched(); /* Find HPT ready to run */ return (OS_NO_ERR); } if (pevent->OSEventCnt < 65535u) { /* Make sure semaphore will not overflow */ pevent->OSEventCnt++; /* Increment semaphore count to register event */ OS_EXIT_CRITICAL(); return (OS_NO_ERR); } OS_EXIT_CRITICAL(); /* Semaphore value has reached its maximum */ return (OS_SEM_OVF); } /*$PAGE*/ /* ********************************************************************************************************* * QUERY A SEMAPHORE * * Description: This function obtains information about a semaphore * * Arguments : pevent is a pointer to the event control block associated with the desired * semaphore * * p_sem_data is a pointer to a structure that will contain information about the * semaphore. * * Returns : OS_NO_ERR The call was successful and the message was sent * OS_ERR_EVENT_TYPE If you are attempting to obtain data from a non semaphore. * OS_ERR_PEVENT_NULL If 'pevent' is a NULL pointer. * OS_ERR_PDATA_NULL If 'p_sem_data' is a NULL pointer ********************************************************************************************************* */ #if OS_SEM_QUERY_EN > 0 INT8U OSSemQuery (OS_EVENT *pevent, OS_SEM_DATA *p_sem_data) { #if OS_LOWEST_PRIO <= 63 INT8U *psrc; INT8U *pdest; #else INT16U *psrc; INT16U *pdest; #endif INT8U i; #if OS_CRITICAL_METHOD == 3 /* Allocate storage for CPU status register */ OS_CPU_SR cpu_sr = 0; #endif #if OS_ARG_CHK_EN > 0 if (pevent == (OS_EVENT *)0) { /* Validate 'pevent' */ return (OS_ERR_PEVENT_NULL); } if (p_sem_data == (OS_SEM_DATA *)0) { /* Validate 'p_sem_data' */ return (OS_ERR_PDATA_NULL); } #endif if (pevent->OSEventType != OS_EVENT_TYPE_SEM) { /* Validate event block type */ return (OS_ERR_EVENT_TYPE); } OS_ENTER_CRITICAL(); p_sem_data->OSEventGrp = pevent->OSEventGrp; /* Copy message mailbox wait list */ psrc = &pevent->OSEventTbl[0]; pdest = &p_sem_data->OSEventTbl[0]; for (i = 0; i < OS_EVENT_TBL_SIZE; i++) { *pdest++ = *psrc++; } p_sem_data->OSCnt = pevent->OSEventCnt; /* Get semaphore count */ OS_EXIT_CRITICAL(); return (OS_NO_ERR); } #endif /* OS_SEM_QUERY_EN */ /*$PAGE*/ /* ********************************************************************************************************* * SET SEMAPHORE * * Description: This function sets the semaphore count to the value specified as an argument. Typically, * this value would be 0. * * You would typically use this function when a semaphore is used as a signaling mechanism * and, you want to reset the count value. * * Arguments : pevent is a pointer to the event control block * * cnt is the new value for the semaphore count. You would pass 0 to reset the * semaphore count. * * err is a pointer to an error code returned by the function as follows: * * OS_NO_ERR The call was successful and the semaphore value was set. * OS_ERR_EVENT_TYPE If you didn't pass a pointer to a semaphore. * OS_ERR_PEVENT_NULL If 'pevent' is a NULL pointer. * OS_ERR_TASK_WAITING If tasks are waiting on the semaphore. ********************************************************************************************************* */ #if OS_SEM_SET_EN > 0 void OSSemSet (OS_EVENT *pevent, INT16U cnt, INT8U *err) { #if OS_CRITICAL_METHOD == 3 /* Allocate storage for CPU status register */ OS_CPU_SR cpu_sr = 0; #endif #if OS_ARG_CHK_EN > 0 if (err == (INT8U *)0) { /* Validate 'err' */ return; } if (pevent == (OS_EVENT *)0) { /* Validate 'pevent' */ *err = OS_ERR_PEVENT_NULL; return; } #endif if (pevent->OSEventType != OS_EVENT_TYPE_SEM) { /* Validate event block type */ *err = OS_ERR_EVENT_TYPE; return; } OS_ENTER_CRITICAL(); *err = OS_NO_ERR; if (pevent->OSEventCnt > 0) { /* See if semaphore already has a count */ pevent->OSEventCnt = cnt; /* Yes, set it to the new value specified. */ } else { /* No */ if (pevent->OSEventGrp == 0) { /* See if task(s) waiting? */ pevent->OSEventCnt = cnt; /* No, OK to set the value */ } else { *err = OS_ERR_TASK_WAITING; } } OS_EXIT_CRITICAL(); } #endif #endif /* OS_SEM_EN */