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/*
*********************************************************************************************************
* uC/OS-II
* The Real-Time Kernel
* MUTUAL EXCLUSION SEMAPHORE MANAGEMENT
*
* (c) Copyright 1992-2010, Micrium, Weston, FL
* All Rights Reserved
*
* File : OS_MUTEX.C
* By : Jean J. Labrosse
* Version : V2.92
*
* LICENSING TERMS:
* ---------------
* uC/OS-II is provided in source form for FREE evaluation, for educational use or for peaceful research.
* If you plan on using uC/OS-II in a commercial product you need to contact Micri祄 to properly license
* its use in your product. We provide ALL the source code for your convenience and to help you experience
* uC/OS-II. The fact that the source is provided does NOT mean that you can use it without paying a
* licensing fee.
*********************************************************************************************************
*/
#ifndef OS_MASTER_FILE
#include <ucos_ii.h>
#endif
#if OS_MUTEX_EN > 0u
/*
*********************************************************************************************************
* LOCAL CONSTANTS
*********************************************************************************************************
*/
#define OS_MUTEX_KEEP_LOWER_8 ((INT16U)0x00FFu)
#define OS_MUTEX_KEEP_UPPER_8 ((INT16U)0xFF00u)
#define OS_MUTEX_AVAILABLE ((INT16U)0x00FFu)
/*
*********************************************************************************************************
* LOCAL CONSTANTS
*********************************************************************************************************
*/
static void OSMutex_RdyAtPrio(OS_TCB *ptcb, INT8U prio);
/*$PAGE*/
/*
*********************************************************************************************************
* ACCEPT MUTUAL EXCLUSION SEMAPHORE
*
* Description: This function checks the mutual exclusion semaphore to see if a resource is available.
* Unlike OSMutexPend(), OSMutexAccept() 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
*
* perr is a pointer to an error code which will be returned to your application:
* OS_ERR_NONE if the call was successful.
* OS_ERR_EVENT_TYPE if 'pevent' is not a pointer to a mutex
* OS_ERR_PEVENT_NULL 'pevent' is a NULL pointer
* OS_ERR_PEND_ISR if you called this function from an ISR
* OS_ERR_PCP_LOWER If the priority of the task that owns the Mutex is
* HIGHER (i.e. a lower number) than the PCP. This error
* indicates that you did not set the PCP higher (lower
* number) than ALL the tasks that compete for the Mutex.
* Unfortunately, this is something that could not be
* detected when the Mutex is created because we don't know
* what tasks will be using the Mutex.
*
* Returns : == OS_TRUE if the resource is available, the mutual exclusion semaphore is acquired
* == OS_FALSE a) if the resource is not available
* b) you didn't pass a pointer to a mutual exclusion semaphore
* c) you called this function from an ISR
*
* Warning(s) : This function CANNOT be called from an ISR because mutual exclusion semaphores are
* intended to be used by tasks only.
*********************************************************************************************************
*/
#if OS_MUTEX_ACCEPT_EN > 0u
BOOLEAN OSMutexAccept (OS_EVENT *pevent,
INT8U *perr)
{
INT8U pcp; /* Priority Ceiling Priority (PCP) */
#if OS_CRITICAL_METHOD == 3u /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr = 0u;
#endif
#ifdef OS_SAFETY_CRITICAL
if (perr == (INT8U *)0)
{
OS_SAFETY_CRITICAL_EXCEPTION();
return (OS_FALSE);
}
#endif
#if OS_ARG_CHK_EN > 0u
if (pevent == (OS_EVENT *)0) /* Validate 'pevent' */
{
*perr = OS_ERR_PEVENT_NULL;
return (OS_FALSE);
}
#endif
if (pevent->OSEventType != OS_EVENT_TYPE_MUTEX) /* Validate event block type */
{
*perr = OS_ERR_EVENT_TYPE;
return (OS_FALSE);
}
if (OSIntNesting > 0u) /* Make sure it's not called from an ISR */
{
*perr = OS_ERR_PEND_ISR;
return (OS_FALSE);
}
OS_ENTER_CRITICAL(); /* Get value (0 or 1) of Mutex */
pcp = (INT8U)(pevent->OSEventCnt >> 8u); /* Get PCP from mutex */
if ((pevent->OSEventCnt & OS_MUTEX_KEEP_LOWER_8) == OS_MUTEX_AVAILABLE)
{
pevent->OSEventCnt &= OS_MUTEX_KEEP_UPPER_8; /* Mask off LSByte (Acquire Mutex) */
pevent->OSEventCnt |= OSTCBCur->OSTCBPrio; /* Save current task priority in LSByte */
pevent->OSEventPtr = (void *)OSTCBCur; /* Link TCB of task owning Mutex */
if ((pcp != OS_PRIO_MUTEX_CEIL_DIS) &&
(OSTCBCur->OSTCBPrio <= pcp)) /* PCP 'must' have a SMALLER prio ... */
{
OS_EXIT_CRITICAL(); /* ... than current task! */
*perr = OS_ERR_PCP_LOWER;
}
else
{
OS_EXIT_CRITICAL();
*perr = OS_ERR_NONE;
}
return (OS_TRUE);
}
OS_EXIT_CRITICAL();
*perr = OS_ERR_NONE;
return (OS_FALSE);
}
#endif
/*$PAGE*/
/*
*********************************************************************************************************
* CREATE A MUTUAL EXCLUSION SEMAPHORE
*
* Description: This function creates a mutual exclusion semaphore.
*
* Arguments : prio is the priority to use when accessing the mutual exclusion semaphore. In
* other words, when the semaphore is acquired and a higher priority task
* attempts to obtain the semaphore then the priority of the task owning the
* semaphore is raised to this priority. It is assumed that you will specify
* a priority that is LOWER in value than ANY of the tasks competing for the
* mutex. If the priority is specified as OS_PRIO_MUTEX_CEIL_DIS, then the
* priority ceiling promotion is disabled. This way, the tasks accessing the
* semaphore do not have their priority promoted.
*
* perr is a pointer to an error code which will be returned to your application:
* OS_ERR_NONE if the call was successful.
* OS_ERR_CREATE_ISR if you attempted to create a MUTEX from an ISR
* OS_ERR_PRIO_EXIST if a task at the priority ceiling priority
* already exist.
* OS_ERR_PEVENT_NULL No more event control blocks available.
* OS_ERR_PRIO_INVALID if the priority you specify is higher that the
* maximum allowed (i.e. > OS_LOWEST_PRIO)
*
* Returns : != (void *)0 is a pointer to the event control clock (OS_EVENT) associated with the
* created mutex.
* == (void *)0 if an error is detected.
*
* Note(s) : 1) The LEAST significant 8 bits of '.OSEventCnt' hold the priority number of the task
* owning the mutex or 0xFF if no task owns the mutex.
*
* 2) The MOST significant 8 bits of '.OSEventCnt' hold the priority number used to
* reduce priority inversion or 0xFF (OS_PRIO_MUTEX_CEIL_DIS) if priority ceiling
* promotion is disabled.
*********************************************************************************************************
*/
OS_EVENT *OSMutexCreate (INT8U prio,
INT8U *perr)
{
OS_EVENT *pevent;
#if OS_CRITICAL_METHOD == 3u /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr = 0u;
#endif
#ifdef OS_SAFETY_CRITICAL
if (perr == (INT8U *)0)
{
OS_SAFETY_CRITICAL_EXCEPTION();
return ((OS_EVENT *)0);
}
#endif
#ifdef OS_SAFETY_CRITICAL_IEC61508
if (OSSafetyCriticalStartFlag == OS_TRUE)
{
OS_SAFETY_CRITICAL_EXCEPTION();
return ((OS_EVENT *)0);
}
#endif
#if OS_ARG_CHK_EN > 0u
if (prio != OS_PRIO_MUTEX_CEIL_DIS)
{
if (prio >= OS_LOWEST_PRIO) /* Validate PCP */
{
*perr = OS_ERR_PRIO_INVALID;
return ((OS_EVENT *)0);
}
}
#endif
if (OSIntNesting > 0u) /* See if called from ISR ... */
{
*perr = OS_ERR_CREATE_ISR; /* ... can't CREATE mutex from an ISR */
return ((OS_EVENT *)0);
}
OS_ENTER_CRITICAL();
if (prio != OS_PRIO_MUTEX_CEIL_DIS)
{
if (OSTCBPrioTbl[prio] != (OS_TCB *)0) /* Mutex priority must not already exist */
{
OS_EXIT_CRITICAL(); /* Task already exist at priority ... */
*perr = OS_ERR_PRIO_EXIST; /* ... ceiling priority */
return ((OS_EVENT *)0);
}
OSTCBPrioTbl[prio] = OS_TCB_RESERVED; /* Reserve the table entry */
}
pevent = OSEventFreeList; /* Get next free event control block */
if (pevent == (OS_EVENT *)0) /* See if an ECB was available */
{
if (prio != OS_PRIO_MUTEX_CEIL_DIS)
{
OSTCBPrioTbl[prio] = (OS_TCB *)0; /* No, Release the table entry */
}
OS_EXIT_CRITICAL();
*perr = OS_ERR_PEVENT_NULL; /* No more event control blocks */
return (pevent);
}
OSEventFreeList = (OS_EVENT *)OSEventFreeList->OSEventPtr; /* Adjust the free list */
OS_EXIT_CRITICAL();
pevent->OSEventType = OS_EVENT_TYPE_MUTEX;
pevent->OSEventCnt = (INT16U)((INT16U)prio << 8u) | OS_MUTEX_AVAILABLE; /* Resource is avail. */
pevent->OSEventPtr = (void *)0; /* No task owning the mutex */
#if OS_EVENT_NAME_EN > 0u
pevent->OSEventName = (INT8U *)(void *)"?";
#endif
OS_EventWaitListInit(pevent);
*perr = OS_ERR_NONE;
return (pevent);
}
/*$PAGE*/
/*
*********************************************************************************************************
* DELETE A MUTEX
*
* Description: This function deletes a mutual exclusion semaphore and readies all tasks pending on the it.
*
* Arguments : pevent is a pointer to the event control block associated with the desired mutex.
*
* opt determines delete options as follows:
* opt == OS_DEL_NO_PEND Delete mutex ONLY if no task pending
* opt == OS_DEL_ALWAYS Deletes the mutex even if tasks are waiting.
* In this case, all the tasks pending will be readied.
*
* perr is a pointer to an error code that can contain one of the following values:
* OS_ERR_NONE The call was successful and the mutex was deleted
* OS_ERR_DEL_ISR If you attempted to delete the MUTEX from an ISR
* OS_ERR_INVALID_OPT An invalid option was specified
* OS_ERR_TASK_WAITING One or more tasks were waiting on the mutex
* OS_ERR_EVENT_TYPE If you didn't pass a pointer to a mutex
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