本帖最后由 hgjinwei 于 2017-3-6 08:28 编辑
理论上不可以。
INT8U OSMboxPost (OS_EVENT *pevent, void *pmsg)
{
#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);
}
<font color="Red"><u> if (pmsg == (void *)0) { /* Make sure we are not posting a NULL pointer */
return (OS_ERR_POST_NULL_PTR);
}</u></font>
#endif
if (pevent->OSEventType != OS_EVENT_TYPE_MBOX) { /* Validate event block type */
return (OS_ERR_EVENT_TYPE);
}
OS_ENTER_CRITICAL();
if (pevent->OSEventGrp != 0) { /* See if any task pending on mailbox */
/* Ready HPT waiting on event */
(void)OS_EventTaskRdy(pevent, pmsg, OS_STAT_MBOX, OS_STAT_PEND_OK);
OS_EXIT_CRITICAL();
OS_Sched(); /* Find highest priority task ready to run */
return (OS_ERR_NONE);
}
if (pevent->OSEventPtr != (void *)0) { /* Make sure mailbox doesn't already have a msg */
OS_EXIT_CRITICAL();
return (OS_ERR_MBOX_FULL);
}
pevent->OSEventPtr = pmsg; /* Place message in mailbox */
OS_EXIT_CRITICAL();
return (OS_ERR_NONE);
}
如果“OS_ARG_CHK_EN”开启，直接就返回“OS_ERR_POST_NULL_PTR”错误（见13-15行）。
如果“OS_ARG_CHK_EN”不开启，此时是可以将消息发往邮箱的，但是，
void *OSMboxPend (OS_EVENT *pevent, INT16U timeout, INT8U *perr)
{
void *pmsg;
INT8U pend_stat;
#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 (perr == (INT8U *)0) { /* Validate 'perr' */
return ((void *)0);
}
if (pevent == (OS_EVENT *)0) { /* Validate 'pevent' */
*perr = OS_ERR_PEVENT_NULL;
return ((void *)0);
}
#endif
if (pevent->OSEventType != OS_EVENT_TYPE_MBOX) { /* Validate event block type */
*perr = OS_ERR_EVENT_TYPE;
return ((void *)0);
}
if (OSIntNesting > 0) { /* See if called from ISR ... */
*perr = OS_ERR_PEND_ISR; /* ... can't PEND from an ISR */
return ((void *)0);
}
if (OSLockNesting > 0) { /* See if called with scheduler locked ... */
*perr = OS_ERR_PEND_LOCKED; /* ... can't PEND when locked */
return ((void *)0);
}
OS_ENTER_CRITICAL();
pmsg = pevent->OSEventPtr;
<font color="Red"><u> if (pmsg != (void *)0) { /* See if there is already a message */
pevent->OSEventPtr = (void *)0; /* Clear the mailbox */
OS_EXIT_CRITICAL();
*perr = OS_ERR_NONE;
return (pmsg); /* Return the message received (or NULL) */
}</u></font>
OSTCBCur->OSTCBStat |= OS_STAT_MBOX; /* Message not available, task will pend */
OSTCBCur->OSTCBStatPend = OS_STAT_PEND_OK;
OSTCBCur->OSTCBDly = timeout; /* Load timeout in TCB */
OS_EventTaskWait(pevent); /* Suspend task until event or timeout occurs */
OS_EXIT_CRITICAL();
OS_Sched(); /* Find next highest priority task ready to run */
OS_ENTER_CRITICAL();
if (OSTCBCur->OSTCBStatPend != OS_STAT_PEND_OK) { /* See if we weren't given the message */
pend_stat = OSTCBCur->OSTCBStatPend;
OS_EventTOAbort(pevent); /* Timed out, Make task ready */
OS_EXIT_CRITICAL();
switch (pend_stat) {
case OS_STAT_PEND_TO:
default:
*perr = OS_ERR_TIMEOUT; /* Indicate that a timeout occured */
break;
case OS_STAT_PEND_ABORT:
*perr = OS_ERR_PEND_ABORT; /* Indicate that we aborted */
break;
}
return ((void *)0); /* Return a NULL message */
}
pmsg = OSTCBCur->OSTCBMsg;
OSTCBCur->OSTCBMsg = (void *)0; /* Yes, clear message received */
OSTCBCur->OSTCBStat = OS_STAT_RDY;
OSTCBCur->OSTCBEventPtr = (OS_EVENT *)0; /* No longer waiting for event */
OS_EXIT_CRITICAL();
*perr = OS_ERR_NONE;
return (pmsg); /* Return the message received */
}
此消息只能发给当前正在等待消息的任务，如果此时没有任务等待消息，此消息将被忽略（见34-39行）。 | 
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