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/***************************************************************************
* Copyright (c) 2024 Microsoft Corporation
*
* This program and the accompanying materials are made available under the
* terms of the MIT License which is available at
* https://opensource.org/licenses/MIT.
*
* SPDX-License-Identifier: MIT
**************************************************************************/
/**************************************************************************/
/**************************************************************************/
/** */
/** ThreadX Component */
/** */
/** Thread */
/** */
/**************************************************************************/
/**************************************************************************/
#define TX_SOURCE_CODE
/* Include necessary system files. */
#include "tx_api.h"
#include "tx_trace.h"
#include "tx_thread.h"
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _tx_thread_preemption_change PORTABLE C */
/* 6.1 */
/* AUTHOR */
/* */
/* William E. Lamie, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function processes preemption-threshold change requests. The */
/* previous preemption is returned to the caller. If the new request */
/* allows a higher priority thread to execute, preemption takes place */
/* inside of this function. */
/* */
/* INPUT */
/* */
/* thread_ptr Pointer to thread */
/* new_threshold New preemption threshold */
/* old_threshold Old preemption threshold */
/* */
/* OUTPUT */
/* */
/* status Service return 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_thread_preemption_change(TX_THREAD *thread_ptr, UINT new_threshold, UINT *old_threshold)
{
TX_INTERRUPT_SAVE_AREA
#ifndef TX_DISABLE_PREEMPTION_THRESHOLD
ULONG priority_bit;
#if TX_MAX_PRIORITIES > 32
UINT map_index;
#endif
#endif
UINT status;
/* Default status to success. */
status = TX_SUCCESS;
#ifdef TX_DISABLE_PREEMPTION_THRESHOLD
/* Only allow 0 (disable all preemption) and returning preemption-threshold to the
current thread priority if preemption-threshold is disabled. All other threshold
values are converted to 0. */
if (thread_ptr -> tx_thread_user_priority != new_threshold)
{
/* Is the new threshold zero? */
if (new_threshold != ((UINT) 0))
{
/* Convert the new threshold to disable all preemption, since preemption-threshold is
not supported. */
new_threshold = ((UINT) 0);
}
}
#endif
/* Lockout interrupts while the thread is being resumed. */
TX_DISABLE
/* If trace is enabled, insert this event into the trace buffer. */
TX_TRACE_IN_LINE_INSERT(TX_TRACE_THREAD_PREEMPTION_CHANGE, thread_ptr, new_threshold, thread_ptr -> tx_thread_preempt_threshold, thread_ptr -> tx_thread_state, TX_TRACE_THREAD_EVENTS)
/* Log this kernel call. */
TX_EL_THREAD_PREEMPTION_CHANGE_INSERT
/* Determine if the new threshold is greater than the current user priority. */
if (new_threshold > thread_ptr -> tx_thread_user_priority)
{
/* Return error. */
status = TX_THRESH_ERROR;
}
else
{
#ifndef TX_DISABLE_PREEMPTION_THRESHOLD
/* Determine if the new threshold is the same as the priority. */
if (thread_ptr -> tx_thread_user_priority == new_threshold)
{
/* Determine if this thread is at the head of the list. */
if (_tx_thread_priority_list[thread_ptr -> tx_thread_priority] == thread_ptr)
{
#if TX_MAX_PRIORITIES > 32
/* Calculate the index into the bit map array. */
map_index = (thread_ptr -> tx_thread_priority)/((UINT) 32);
#endif
/* Yes, this thread is at the front of the list. Make sure
the preempted bit is cleared for this thread. */
TX_MOD32_BIT_SET(thread_ptr -> tx_thread_priority, priority_bit)
_tx_thread_preempted_maps[MAP_INDEX] = _tx_thread_preempted_maps[MAP_INDEX] & (~(priority_bit));
#if TX_MAX_PRIORITIES > 32
/* Determine if there are any other bits set in this preempt map. */
if (_tx_thread_preempted_maps[MAP_INDEX] == ((ULONG) 0))
{
/* No, clear the active bit to signify this preempt map has nothing set. */
TX_DIV32_BIT_SET(thread_ptr -> tx_thread_priority, priority_bit)
_tx_thread_preempted_map_active = _tx_thread_preempted_map_active & (~(priority_bit));
}
#endif
}
}
#endif
/* Return the user's preemption-threshold. */
*old_threshold = thread_ptr -> tx_thread_user_preempt_threshold;
/* Setup the new threshold. */
thread_ptr -> tx_thread_user_preempt_threshold = new_threshold;
/* Determine if the new threshold represents a higher priority than the priority inheritance threshold. */
if (new_threshold < thread_ptr -> tx_thread_inherit_priority)
{
/* Update the actual preemption-threshold with the new threshold. */
thread_ptr -> tx_thread_preempt_threshold = new_threshold;
}
else
{
/* Update the actual preemption-threshold with the priority inheritance. */
thread_ptr -> tx_thread_preempt_threshold = thread_ptr -> tx_thread_inherit_priority;
}
/* Is the thread priority less than the current highest priority? If not, no preemption is required. */
if (_tx_thread_highest_priority < thread_ptr -> tx_thread_priority)
{
/* Is the new thread preemption-threshold less than the current highest priority? If not, no preemption is required. */
if (_tx_thread_highest_priority < new_threshold)
{
/* If the current execute pointer is the same at this thread, preemption needs to take place. */
if (_tx_thread_execute_ptr == thread_ptr)
{
/* Preemption needs to take place. */
#ifndef TX_DISABLE_PREEMPTION_THRESHOLD
/* Determine if this thread has preemption threshold set. */
if (thread_ptr -> tx_thread_preempt_threshold != thread_ptr -> tx_thread_priority)
{
#if TX_MAX_PRIORITIES > 32
/* Calculate the index into the bit map array. */
map_index = (thread_ptr -> tx_thread_priority)/((UINT) 32);
/* Set the active bit to remember that the preempt map has something set. */
TX_DIV32_BIT_SET(thread_ptr -> tx_thread_priority, priority_bit)
_tx_thread_preempted_map_active = _tx_thread_preempted_map_active | priority_bit;
#endif
/* Remember that this thread was preempted by a thread above the thread's threshold. */
TX_MOD32_BIT_SET(thread_ptr -> tx_thread_priority, priority_bit)
_tx_thread_preempted_maps[MAP_INDEX] = _tx_thread_preempted_maps[MAP_INDEX] | priority_bit;
}
#endif
#ifdef TX_THREAD_ENABLE_PERFORMANCE_INFO
/* Determine if the caller is an interrupt or from a thread. */
if (TX_THREAD_GET_SYSTEM_STATE() == ((ULONG) 0))
{
/* Caller is a thread, so this is a solicited preemption. */
_tx_thread_performance_solicited_preemption_count++;
/* Increment the thread's solicited preemption counter. */
thread_ptr -> tx_thread_performance_solicited_preemption_count++;
}
/* Remember the thread that preempted this thread. */
thread_ptr -> tx_thread_performance_last_preempting_thread = _tx_thread_priority_list[_tx_thread_highest_priority];
/* Is the execute pointer different? */
if (_tx_thread_performance_execute_log[_tx_thread_performance__execute_log_index] != _tx_thread_execute_ptr)
{
/* Move to next entry. */
_tx_thread_performance__execute_log_index++;
/* Check for wrap condition. */
if (_tx_thread_performance__execute_log_index >= TX_THREAD_EXECUTE_LOG_SIZE)
{
/* Set the index to the beginning. */
_tx_thread_performance__execute_log_index = ((UINT) 0);
}
/* Log the new execute pointer. */
_tx_thread_performance_execute_log[_tx_thread_performance__execute_log_index] = _tx_thread_execute_ptr;
}
#endif
/* Setup the highest priority thread to execute. */
_tx_thread_execute_ptr = _tx_thread_priority_list[_tx_thread_highest_priority];
/* Restore interrupts. */
TX_RESTORE
/* Check for preemption. */
_tx_thread_system_preempt_check();
/* Disable interrupts. */
TX_DISABLE
}
}
}
}
/* Restore interrupts. */
TX_RESTORE
/* Return completion status. */
return(status);
}
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