?? pis.c
字號:
/* PISE_Send_To_Front_Of_Pipe Error checking shell */
/* */
/* CALLS */
/* */
/* CSC_Place_On_List Place on suspend 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 */
/* [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 pipe */
/* TCT_Unprotect Release protection */
/* */
/* INPUTS */
/* */
/* pipe_ptr Pipe control block pointer */
/* message Pointer to message to send */
/* size Size of message to send */
/* suspend Suspension option if full */
/* */
/* OUTPUTS */
/* */
/* NU_SUCCESS If service is successful */
/* NU_PIPE_FULL If pipe is currently full */
/* NU_TIMEOUT If timeout on service expires*/
/* NU_PIPE_DELETED If pipe was deleted during */
/* suspension */
/* NU_PIPE_RESET If pipe was reset during */
/* suspension */
/* */
/* HISTORY */
/* */
/* DATE REMARKS */
/* */
/* 03-01-1993 Created initial version 1.0 */
/* 04-19-1993 Verified version 1.0 */
/* 03-01-1994 Changed function interfaces to */
/* match those in prototype, */
/* added register options, changed */
/* protection logic to reduce */
/* overhead, optimized copy loop, */
/* resulting in version 1.1 */
/* */
/* 03-18-1994 Verified version 1.1 */
/* */
/*************************************************************************/
STATUS PIS_Send_To_Front_Of_Pipe(NU_PIPE *pipe_ptr, VOID *message,
UNSIGNED size, UNSIGNED suspend)
{
R1 PI_PCB *pipe; /* Pipe control block ptr */
PI_SUSPEND suspend_block; /* Allocate suspension block */
PI_SUSPEND *suspend_ptr; /* Pointer to suspend block */
R2 BYTE_PTR source; /* Pointer to source */
R3 BYTE_PTR destination; /* Pointer to destination */
UNSIGNED copy_size; /* Partial copy size */
R4 INT i; /* Working counter */
UNSIGNED pad = 0; /* Number of pad bytes */
TC_TCB *task; /* Task pointer */
STATUS preempt; /* Preempt flag */
STATUS status; /* Completion status */
NU_SUPERV_USER_VARIABLES
/* Switch to supervisor mode */
NU_SUPERVISOR_MODE();
/* Move input pipe pointer into internal pointer. */
pipe = (PI_PCB *) pipe_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_FRONT_OF_PIPE_ID, (UNSIGNED) pipe,
(UNSIGNED) message, (UNSIGNED) size);
#endif
/* Initialize the status as successful. */
status = NU_SUCCESS;
/* Protect against simultaneous access to the pipe. */
TCT_System_Protect();
/* Determine if an extra word of overhead needs to be added to the
calculation. */
if (pipe -> pi_fixed_size)
/* No overhead. */
i = 0;
else
{
/* Variable messages have one additional word of overhead. */
i = sizeof(UNSIGNED);
/* Calculate the number of pad bytes necessary to keep the pipe
write pointer on an UNSIGNED data element alignment. */
pad = (((size + sizeof(UNSIGNED) - 1)/sizeof(UNSIGNED)) *
sizeof(UNSIGNED)) - size;
/* Insure that padding is included in the overhead. */
i = i + ((INT) pad);
/* Make special check to see if a suspension needs to be
forced for a variable length message. */
if ((pipe -> pi_suspension_list) && (pipe -> pi_messages))
{
/* Pickup task control block pointer. */
task = (TC_TCB *) TCT_Current_Thread();
/* Now we know that there are other task(s) are suspended trying
to send a variable length message. Determine whether or not
a suspension should be forced. */
if ((pipe -> pi_fifo_suspend) ||
(suspend == NU_NO_SUSPEND) ||
((pipe -> pi_suspension_list) -> pi_suspend_link.cs_priority <=
TCC_Task_Priority(task)))
/* Bump the computed size to avoid placing the new variable
length message ahead of the suspended tasks. */
i = (INT) pipe -> pi_available;
}
}
/* Determine if there is enough room in the pipe for the message. */
if (pipe -> pi_available < (size + i))
{
/* pipe does not have room for the message. Determine if
suspension is required. */
if (suspend)
{
/* Suspension is requested. */
/* Increment the number of tasks waiting. */
pipe -> pi_tasks_waiting++;
#ifdef INCLUDE_PROVIEW
_RTProf_DumpPipe(RT_PROF_SEND_TO_FRONT_OF_PIPE,pipe,RT_PROF_WAIT);
#endif /* INCLUDE_PROVIEW */
/* Setup the suspend block and suspend the calling task. */
suspend_ptr = &suspend_block;
suspend_ptr -> pi_pipe = pipe;
suspend_ptr -> pi_suspend_link.cs_next = NU_NULL;
suspend_ptr -> pi_suspend_link.cs_previous = NU_NULL;
suspend_ptr -> pi_message_area = (BYTE_PTR) message;
suspend_ptr -> pi_message_size = size;
task = (TC_TCB *) TCT_Current_Thread();
suspend_ptr -> pi_suspended_task = task;
/* Place the task on the urgent message suspension list. */
CSC_Place_On_List((CS_NODE **) &(pipe -> pi_urgent_list),
&(suspend_ptr -> pi_suspend_link));
/* Move the head pointer of the list to make this suspension the
first in the list. */
pipe -> pi_urgent_list = (PI_SUSPEND *)
(pipe -> pi_urgent_list) -> pi_suspend_link.cs_previous;
/* Finally, suspend the calling task. Note that the suspension call
automatically clears the protection on the pipe. */
TCC_Suspend_Task((NU_TASK *) task, NU_PIPE_SUSPEND,
PIC_Cleanup, suspend_ptr, suspend);
/* Pickup the return status. */
status = suspend_ptr -> pi_return_status;
}
else
{
/* Return a status of NU_PIPE_FULL because there is no
room in the pipe for the message. */
status = NU_PIPE_FULL;
#ifdef INCLUDE_PROVIEW
_RTProf_DumpPipe(RT_PROF_SEND_TO_FRONT_OF_PIPE,pipe,RT_PROF_FAIL);
#endif /* INCLUDE_PROVIEW */
}
}
else
{
/* Determine if a task is waiting on an empty pipe. */
if ((pipe -> pi_suspension_list) && (pipe -> pi_messages == 0))
{
/* Task is waiting on pipe for a message. */
/* Decrement the number of tasks waiting on pipe. */
pipe -> pi_tasks_waiting--;
#ifdef INCLUDE_PROVIEW
_RTProf_DumpPipe(RT_PROF_SEND_TO_FRONT_OF_PIPE,pipe,RT_PROF_OK);
#endif /* INCLUDE_PROVIEW */
/* Remove the first suspended block from the list. */
suspend_ptr = pipe -> pi_suspension_list;
CSC_Remove_From_List((CS_NODE **) &(pipe -> pi_suspension_list),
&(suspend_ptr -> pi_suspend_link));
/* Setup the source and destination pointers. */
source = (BYTE_PTR) message;
destination = suspend_ptr -> pi_message_area;
/* Initialize the return status. */
suspend_ptr -> pi_return_status = NU_SUCCESS;
/* Loop to actually copy the message. */
i = (INT) size;
do
{
*(destination++) = *(source);
if ((--i) == 0)
break;
source++;
} while (1);
/* Return the size of the message copied. */
suspend_ptr -> pi_actual_size = size;
/* Wakeup the waiting task and check for preemption. */
preempt =
TCC_Resume_Task((NU_TASK *) suspend_ptr -> pi_suspended_task,
NU_PIPE_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
{
/* There is enough room in the pipe and no task is waiting. */
/* Setup the source pointer. */
source = (BYTE_PTR) message;
destination = pipe -> pi_read;
/* Process according to the type of message supported. */
if (pipe -> pi_fixed_size)
{
/* Fixed-size message pipe. */
/* Determine if the read pointer is at the top of the pipe
area. */
if (destination == pipe -> pi_start)
/* Prepare to place the message in the lower part of the
pipe area. */
destination = pipe -> pi_end - size;
else
/* Backup the length of the message from the current
read pointer. */
destination = destination - size;
/* Adjust the actual read pointer before the copy is done. */
pipe -> pi_read = destination;
/* Copy the message into the pipe area. */
i = (INT) size;
do
{
*(destination++) = *(source);
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