mbc.c
来自「nucleus 2006 source code」· C语言 代码 · 共 938 行 · 第 1/3 页
C
938 行
/* 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 */
/* */
/*************************************************************************/
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 */
R2 MB_SUSPEND *suspend_ptr; /* Pointer to suspend block */
R3 UNSIGNED *source_ptr; /* Pointer to source */
R4 UNSIGNED *destination_ptr; /* Pointer to destination */
TC_TCB *task; /* Task pointer */
STATUS preempt; /* Preemption flag */
STATUS status; /* Completion status */
NU_SUPERV_USER_VARIABLES
/* Switch to supervisor mode */
NU_SUPERVISOR_MODE();
/* 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_RECEIVE_FROM_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)
{
/* Copy message from mailbox into the caller's area. */
/* Setup the source and destination pointers. */
source_ptr = &(mailbox -> mb_message_area[0]);
destination_ptr = (UNSIGNED *) message;
/* 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);
/* Determine if another task is waiting to place something into the
mailbox. */
if (mailbox -> mb_suspension_list)
{
/* Yes, another task is waiting to send something to the
mailbox. */
/* Decrement the number of tasks waiting counter. */
mailbox -> mb_tasks_waiting--;
#ifdef NU_PROFILE_PLUS
PRF_PLUS_MBC_RECEIVE_FROM_MAILBOX_0
#endif /* NU_PROFILE_PLUS */
/* 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 = suspend_ptr -> mb_message_area;
destination_ptr = &(mailbox -> mb_message_area[0]);
/* 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;
/* Resume the suspended task. */
preempt =
TCC_Resume_Task((NU_TASK *) suspend_ptr -> mb_suspended_task,
NU_MAILBOX_SUSPEND);
/* Determine if a preempt condition is present. */
if (preempt)
/* Transfer control to the system if the resumed task function
detects a preemption condition. */
TCT_Control_To_System();
}
else
{
/* Clear the message present flag. */
mailbox -> mb_message_present = NU_FALSE;
#ifdef NU_PROFILE_PLUS
PRF_PLUS_MBC_RECEIVE_FROM_MAILBOX_1
#endif /* NU_PROFILE_PLUS */
}
}
else
{
/* Mailbox is empty. Determine if suspension is required. */
if (suspend)
{
/* Suspension is required. */
/* Increment the number of tasks waiting on the mailbox counter. */
mailbox -> mb_tasks_waiting++;
#ifdef NU_PROFILE_PLUS
PRF_PLUS_MBC_RECEIVE_FROM_MAILBOX_2
#endif /* NU_PROFILE_PLUS */
/* 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_block.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_block, suspend);
/* Pickup the return status. */
status = suspend_ptr -> mb_return_status;
#ifdef NU_PROFILE_PLUS
PRF_PLUS_MBC_RECEIVE_FROM_MAILBOX_3
#endif /* NU_PROFILE_PLUS */
}
else
{
/* Return a status of NU_MAILBOX_EMPTY because there is
nothing in the mailbox. */
status = NU_MAILBOX_EMPTY;
#ifdef NU_PROFILE_PLUS
PRF_PLUS_MBC_RECEIVE_FROM_MAILBOX_4
#endif /* NU_PROFILE_PLUS */
}
}
/* Release protection. */
TCT_Unprotect();
/* Return to user mode */
NU_USER_MODE();
/* Return the completion status. */
return(status);
}
/*************************************************************************/
/* */
/* FUNCTION */
/* */
/* MBC_Cleanup */
/* */
/* DESCRIPTION */
/* */
/* This function is responsible for removing a suspension block */
/* from a mailbox. It is not called unless a timeout or a task */
/* terminate is in progress. Note that protection is already in */
/* effect - the same protection at suspension time. */
/* */
/* CALLED BY */
/* */
/* TCC_Timeout Task timeout */
/* TCC_Terminate Task terminate */
/* */
/* CALLS */
/* */
/* CSC_Remove_From_List Remove suspend block from */
/* the suspension list */
/* */
/* INPUTS */
/* */
/* information Pointer to suspend block */
/* */
/* OUTPUTS */
/* */
/* None */
/* */
/*************************************************************************/
VOID MBC_Cleanup(VOID *information)
{
MB_SUSPEND *suspend_ptr; /* Suspension block pointer */
NU_SUPERV_USER_VARIABLES
/* Switch to supervisor mode */
NU_SUPERVISOR_MODE();
/* Use the information pointer as a suspend pointer. */
suspend_ptr = (MB_SUSPEND *) information;
/* By default, indicate that the service timed-out. It really does not
matter if this function is called from a terminate request since
the task does not resume. */
suspend_ptr -> mb_return_status = NU_TIMEOUT;
/* Decrement the number of tasks waiting counter. */
(suspend_ptr -> mb_mailbox) -> mb_tasks_waiting--;
/* Unlink the suspend block from the suspension list. */
CSC_Remove_From_List((CS_NODE **)
&((suspend_ptr -> mb_mailbox) -> mb_suspension_list),
&(suspend_ptr -> mb_suspend_link));
/* Return to user mode */
NU_USER_MODE();
}
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