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/**************************************************************************/
/* */
/* Copyright (c) Microsoft Corporation. All rights reserved. */
/* */
/* This software is licensed under the Microsoft Software License */
/* Terms for Microsoft Azure RTOS. Full text of the license can be */
/* found in the LICENSE file at https://aka.ms/AzureRTOS_EULA */
/* and in the root directory of this software. */
/* */
/**************************************************************************/
/**************************************************************************/
/**************************************************************************/
/** */
/** ThreadX Component */
/** */
/** Semaphore */
/** */
/**************************************************************************/
/**************************************************************************/
#define TX_SOURCE_CODE
/* Include necessary system files. */
#include "tx_api.h"
#include "tx_trace.h"
#include "tx_thread.h"
#include "tx_semaphore.h"
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _tx_semaphore_prioritize PORTABLE C */
/* 6.1 */
/* AUTHOR */
/* */
/* William E. Lamie, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function places the highest priority suspended thread at the */
/* front of the suspension list. All other threads remain in the same */
/* FIFO suspension order. */
/* */
/* INPUT */
/* */
/* semaphore_ptr Pointer to semaphore control block*/
/* */
/* OUTPUT */
/* */
/* status Completion status */
/* */
/* CALLS */
/* */
/* _tx_thread_system_preempt_check Check for preemption */
/* */
/* CALLED BY */
/* */
/* Application Code */
/* */
/* RELEASE HISTORY */
/* */
/* DATE NAME DESCRIPTION */
/* */
/* 05-19-2020 William E. Lamie Initial Version 6.0 */
/* 09-30-2020 Yuxin Zhou Modified comment(s), */
/* resulting in version 6.1 */
/* */
/**************************************************************************/
UINT _tx_semaphore_prioritize(TX_SEMAPHORE *semaphore_ptr)
{
TX_INTERRUPT_SAVE_AREA
TX_THREAD *thread_ptr;
TX_THREAD *priority_thread_ptr;
TX_THREAD *head_ptr;
UINT suspended_count;
TX_THREAD *next_thread;
TX_THREAD *previous_thread;
UINT list_changed;
/* Disable interrupts. */
TX_DISABLE
/* If trace is enabled, insert this event into the trace buffer. */
TX_TRACE_IN_LINE_INSERT(TX_TRACE_SEMAPHORE_PRIORITIZE, semaphore_ptr, semaphore_ptr -> tx_semaphore_suspended_count, TX_POINTER_TO_ULONG_CONVERT(&suspended_count), 0, TX_TRACE_SEMAPHORE_EVENTS)
/* Log this kernel call. */
TX_EL_SEMAPHORE_PRIORITIZE_INSERT
/* Pickup the suspended count. */
suspended_count = semaphore_ptr -> tx_semaphore_suspended_count;
/* Determine if there are fewer than 2 suspended threads. */
if (suspended_count < ((UINT) 2))
{
/* Restore interrupts. */
TX_RESTORE
}
/* Determine if there how many threads are suspended on this semaphore. */
else if (suspended_count == ((UINT) 2))
{
/* Pickup the head pointer and the next pointer. */
head_ptr = semaphore_ptr -> tx_semaphore_suspension_list;
next_thread = head_ptr -> tx_thread_suspended_next;
/* Determine if the next suspended thread has a higher priority. */
if ((next_thread -> tx_thread_priority) < (head_ptr -> tx_thread_priority))
{
/* Yes, move the list head to the next thread. */
semaphore_ptr -> tx_semaphore_suspension_list = next_thread;
}
/* Restore interrupts. */
TX_RESTORE
}
else
{
/* Remember the suspension count and head pointer. */
head_ptr = semaphore_ptr -> tx_semaphore_suspension_list;
/* Default the highest priority thread to the thread at the front of the list. */
priority_thread_ptr = head_ptr;
/* Setup search pointer. */
thread_ptr = priority_thread_ptr -> tx_thread_suspended_next;
/* Disable preemption. */
_tx_thread_preempt_disable++;
/* Set the list changed flag to false. */
list_changed = TX_FALSE;
/* Search through the list to find the highest priority thread. */
do
{
/* Is the current thread higher priority? */
if (thread_ptr -> tx_thread_priority < priority_thread_ptr -> tx_thread_priority)
{
/* Yes, remember that this thread is the highest priority. */
priority_thread_ptr = thread_ptr;
}
/* Restore interrupts temporarily. */
TX_RESTORE
/* Disable interrupts again. */
TX_DISABLE
/* Determine if any changes to the list have occurred while
interrupts were enabled. */
/* Is the list head the same? */
if (head_ptr != semaphore_ptr -> tx_semaphore_suspension_list)
{
/* The list head has changed, set the list changed flag. */
list_changed = TX_TRUE;
}
else
{
/* Is the suspended count the same? */
if (suspended_count != semaphore_ptr -> tx_semaphore_suspended_count)
{
/* The list head has changed, set the list changed flag. */
list_changed = TX_TRUE;
}
}
/* Determine if the list has changed. */
if (list_changed == TX_FALSE)
{
/* Yes, everything is the same... move the thread pointer to the next thread. */
thread_ptr = thread_ptr -> tx_thread_suspended_next;
}
else
{
/* No, the list is been modified so we need to start the search over. */
/* Save the suspension count and head pointer. */
head_ptr = semaphore_ptr -> tx_semaphore_suspension_list;
suspended_count = semaphore_ptr -> tx_semaphore_suspended_count;
/* Default the highest priority thread to the thread at the front of the list. */
priority_thread_ptr = head_ptr;
/* Setup search pointer. */
thread_ptr = priority_thread_ptr -> tx_thread_suspended_next;
/* Reset the list changed flag. */
list_changed = TX_FALSE;
}
} while (thread_ptr != head_ptr);
/* Release preemption. */
_tx_thread_preempt_disable--;
/* Now determine if the highest priority thread is at the front
of the list. */
if (priority_thread_ptr != head_ptr)
{
/* No, we need to move the highest priority suspended thread to the
front of the list. */
/* First, remove the highest priority thread by updating the
adjacent suspended threads. */
next_thread = priority_thread_ptr -> tx_thread_suspended_next;
previous_thread = priority_thread_ptr -> tx_thread_suspended_previous;
next_thread -> tx_thread_suspended_previous = previous_thread;
previous_thread -> tx_thread_suspended_next = next_thread;
/* Now, link the highest priority thread at the front of the list. */
previous_thread = head_ptr -> tx_thread_suspended_previous;
priority_thread_ptr -> tx_thread_suspended_next = head_ptr;
priority_thread_ptr -> tx_thread_suspended_previous = previous_thread;
previous_thread -> tx_thread_suspended_next = priority_thread_ptr;
head_ptr -> tx_thread_suspended_previous = priority_thread_ptr;
/* Move the list head pointer to the highest priority suspended thread. */
semaphore_ptr -> tx_semaphore_suspension_list = priority_thread_ptr;
}
/* Restore interrupts. */
TX_RESTORE
/* Check for preemption. */
_tx_thread_system_preempt_check();
}
/* Return completion status. */
return(TX_SUCCESS);
}