📄 mbc.c
字号:
/* Move input mailbox pointer into internal pointer. */
mailbox = (MB_MCB *) mailbox_ptr;
#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_SEND_TO_MAILBOX_ID, (UNSIGNED) mailbox,
(UNSIGNED) message, (UNSIGNED) suspend);
#endif
/* Initialize the status as successful. */
status = NU_SUCCESS;
/* Protect against simultaneous access to the mailbox. */
TCT_System_Protect();
/* Determine if the mailbox is empty or full. */
if (mailbox -> mb_message_present)
{
/* Mailbox already has a message. Determine if suspension is
required. */
if (suspend)
{
/* Suspension is requested. */
/* Increment the number of tasks waiting. */
mailbox -> mb_tasks_waiting++;
/* Setup the suspend block and suspend the calling task. */
suspend_ptr = &suspend_block;
suspend_ptr -> mb_mailbox = mailbox;
suspend_ptr -> mb_suspend_link.cs_next = NU_NULL;
suspend_ptr -> mb_suspend_link.cs_previous = NU_NULL;
suspend_ptr -> mb_message_area = (UNSIGNED *) message;
task = (TC_TCB *) TCT_Current_Thread();
suspend_ptr -> mb_suspended_task = task;
/* Determine if priority or FIFO suspension is associated with the
mailbox. */
if (mailbox -> mb_fifo_suspend)
{
/* FIFO suspension is required. Link the suspend block into
the list of suspended tasks on this mailbox. */
CSC_Place_On_List((CS_NODE **) &(mailbox ->mb_suspension_list),
&(suspend_ptr -> mb_suspend_link));
}
else
{
/* Get the priority of the current thread so the suspend block
can be placed in the appropriate place. */
suspend_ptr -> mb_suspend_link.cs_priority =
TCC_Task_Priority(task);
CSC_Priority_Place_On_List((CS_NODE **)
&(mailbox -> mb_suspension_list),
&(suspend_ptr -> mb_suspend_link));
}
/* Finally, suspend the calling task. Note that the suspension call
automatically clears the protection on the mailbox. */
TCC_Suspend_Task((NU_TASK *) task, NU_MAILBOX_SUSPEND,
MBC_Cleanup, suspend_ptr, suspend);
/* Pickup the return status. */
status = suspend_ptr -> mb_return_status;
}
else
/* Return a status of NU_MAILBOX_FULL because there is no
room in the mailbox for the message. */
status = NU_MAILBOX_FULL;
}
else
{
/* Determine if a task is waiting on the mailbox. */
if (mailbox -> mb_suspension_list)
{
/* Task is waiting on mailbox for a message. */
/* Decrement the number of tasks waiting on mailbox. */
mailbox -> mb_tasks_waiting--;
/* Remove the first suspended block from the list. */
suspend_ptr = mailbox -> mb_suspension_list;
CSC_Remove_From_List((CS_NODE **)
&(mailbox -> mb_suspension_list),
&(suspend_ptr -> mb_suspend_link));
/* Setup the source and destination pointers. */
source_ptr = (UNSIGNED *) message;
destination_ptr = suspend_ptr -> mb_message_area;
/* Copy the message directly into the waiting task's
destination. */
*destination_ptr = *source_ptr;
*(destination_ptr + 1) = *(source_ptr + 1);
*(destination_ptr + 2) = *(source_ptr + 2);
*(destination_ptr + 3) = *(source_ptr + 3);
/* Setup the appropriate return value. */
suspend_ptr -> mb_return_status = NU_SUCCESS;
/* Wakeup the waiting task and check for preemption. */
preempt =
TCC_Resume_Task((NU_TASK *) suspend_ptr -> mb_suspended_task,
NU_MAILBOX_SUSPEND);
/* Determine if preemption needs to take place. */
if (preempt)
/* Transfer control to the system if the resumed task function
detects a preemption condition. */
TCT_Control_To_System();
}
else
{
/* Mailbox is empty and no task is waiting. */
/* Setup the source and destination pointers. */
source_ptr = (UNSIGNED *) message;
destination_ptr = &(mailbox -> mb_message_area[0]);
/* Place the message in the mailbox. */
*destination_ptr = *source_ptr;
*(destination_ptr + 1) = *(source_ptr + 1);
*(destination_ptr + 2) = *(source_ptr + 2);
*(destination_ptr + 3) = *(source_ptr + 3);
/* Indicate that the mailbox has a message. */
mailbox -> mb_message_present = NU_TRUE;
}
}
/* Release protection. */
TCT_Unprotect();
/* Return the completion status. */
return(status);
}
/*************************************************************************/
/* */
/* FUNCTION */
/* */
/* MBC_Receive_From_Mailbox */
/* */
/* DESCRIPTION */
/* */
/* This function receives a message from the specified mailbox. */
/* If there is a message currently in the mailbox, the message is */
/* removed from the mailbox and placed in the caller's area. */
/* Otherwise, if no message is present in the mailbox, suspension */
/* of the calling task is possible. */
/* */
/* AUTHOR */
/* */
/* William E. Lamie, Accelerated Technology, Inc. */
/* */
/* CALLED BY */
/* */
/* Application */
/* MBCE_Receive_From_Mailbox Error checking shell */
/* */
/* CALLS */
/* */
/* CSC_Place_On_List Place on suspend list */
/* CSC_Priority_Place_On_List Place on priority list */
/* CSC_Remove_From_List Remove from suspend list */
/* [HIC_Make_History_Entry] Make entry in history log */
/* TCC_Resume_Task Resume a suspended task */
/* TCC_Suspend_Task Suspend calling task */
/* TCC_Task_Priority Pickup task priority */
/* [TCT_Check_Stack] Stack checking function */
/* TCT_Control_To_System Transfer control to system */
/* TCT_Current_Thread Pickup current thread pointer*/
/* TCT_System_Protect Protect mailbox */
/* TCT_Unprotect Release protection */
/* */
/* INPUTS */
/* */
/* mailbox_ptr Mailbox control block pointer*/
/* message Pointer to message to send */
/* suspend Suspension option if empty */
/* */
/* OUTPUTS */
/* */
/* NU_SUCCESS If service is successful */
/* NU_MAILBOX_EMPTY If mailbox is currently empty*/
/* NU_TIMEOUT If timeout on service expires*/
/* NU_MAILBOX_DELETED If mailbox is deleted during */
/* suspension */
/* NU_MAILBOX_RESET If mailbox is deleted during */
/* suspension */
/* */
/* 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 Changed function interface to */
/* match the prototype, added */
/* register variable logic, */
/* optimized protection logic, */
/* resulting in version 1.1 */
/* R. Pfaff - */
/* D. Lamie 03-18-1994 Verified version 1.1 */
/* */
/*************************************************************************/
STATUS MBC_Receive_From_Mailbox(NU_MAILBOX *mailbox_ptr, VOID *message,
UNSIGNED suspend)
{
R1 MB_MCB *mailbox; /* Mailbox control block ptr */
MB_SUSPEND suspend_block; /* Allocate suspension block */
⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -