freeRTOS-任务管理

任务创建与删除
任务的创建有两个函数，一个是xTaskCreate，另一个是xTaskCreateStatic
二者的区别：

• xTaskCreate是使用动态分配内存，系统自动释放内存，适用于资源充足的系统
• xTaskCreateStatic是静态分配内容，要求用户在编译时分配内存，任务释放需要用户手动管理，适用于内存受限系统

任务详细列表

void vTaskList( char *pcWriteBuffer );
功能:
显示任务详细信息 

参数:
@pcWriteBuffer 保存任务状态信息表的存储区<span class="bd-box"><h-char class="bd bd-beg"><h-inner>，</h-inner></h-char></span>须足够大

pcWriteBuffe表中信息:
Name     <span class="bd-box"><h-char class="bd bd-beg"><h-inner>：</h-inner></h-char></span>创建任务的时候给任务分配的名字
State    <span class="bd-box"><h-char class="bd bd-beg"><h-inner>：</h-inner></h-char></span>任务的状态信息<span class="bd-box"><h-char class="bd bd-beg"><h-inner>，</h-inner></h-char></span>X<span class="bd-box"><h-char class="bd bd-beg"><h-inner>：</h-inner></h-char></span>运行态<span class="bd-box"><h-char class="bd bd-beg"><h-inner>，</h-inner></h-char></span>B<span class="bd-box"><h-char class="bd bd-beg"><h-inner>：</h-inner></h-char></span>阻塞态<span class="bd-box"><h-char class="bd bd-beg"><h-inner>，</h-inner></h-char></span>R<span class="bd-box"><h-char class="bd bd-beg"><h-inner>：</h-inner></h-char></span>就绪态<span class="bd-box"><h-char class="bd bd-beg"><h-inner>，</h-inner></h-char></span>S<span class="bd-box"><h-char class="bd bd-beg"><h-inner>：</h-inner></h-char></span>挂起态<span class="bd-box"><h-char class="bd bd-beg"><h-inner>，</h-inner></h-char></span>D<span class="bd-box"><h-char class="bd bd-beg"><h-inner>：</h-inner></h-char></span>删除态
Priority <span class="bd-box"><h-char class="bd bd-beg"><h-inner>：</h-inner></h-char></span>任务优先级
Stack    <span class="bd-box"><h-char class="bd bd-beg"><h-inner>：</h-inner></h-char></span>任务堆栈的<span class="bd-box"><h-char class="bd bd-end"><h-inner>“</h-inner></h-char></span>高水位线<span class="bd-box"><h-char class="bd bd-beg"><h-inner>”</h-inner></h-char><h-char class="bd bd-beg"><h-inner>，</h-inner></h-char></span>就是堆栈历史最小剩余值
Num      <span class="bd-box"><h-char class="bd bd-beg"><h-inner>：</h-inner></h-char></span>任务编号<span class="bd-box"><h-char class="bd bd-beg"><h-inner>，</h-inner></h-char></span>这个编号是唯一的<span class="bd-box"><h-char class="bd bd-beg"><h-inner>；</h-inner></h-char></span>当多个任务使用同一个任务名的时候<span class="bd-box"><h-char class="bd bd-beg"><h-inner>；</h-inner></h-char></span>可以通过编号来区分

注意:
在使用vTaskList前需要在FreeRTOSConfig.h文件中打开如下宏
#define configUSE_TRACE_FACILITY                 1 
#define configGENERATE_RUN_TIME_STATS            1
#define configUSE_STATS_FORMATTING_FUNCTIONS     1

任务的删除

void vTaskDelete( TaskHandle_t xTaskToDelete );
功能:
删除任务

参数:
@xTaskToDelete 任务句柄

任务退出<span class="bd-box"><h-char class="bd bd-beg"><h-inner>：</h-inner></h-char></span>vTaskDelete(NULL)       在任务函数中调用<span class="bd-box"><h-char class="bd bd-beg"><h-inner>，</h-inner></h-char></span>表示退出当前任务
删除任务<span class="bd-box"><h-char class="bd bd-beg"><h-inner>：</h-inner></h-char></span>vTaskDelete(xHandle)

任务的挂起与恢复

void vTaskSuspend( TaskHandle_t xTaskToSuspend );
参数<span class="bd-box"><h-char class="bd bd-beg"><h-inner>：</h-inner></h-char></span>
xTaskToSuspend 被挂起的任务句柄<span class="bd-box"><h-char class="bd bd-beg"><h-inner>。</h-inner></h-char></span>传递空句柄将导致调用任务被暂停<span class="bd-box"><h-char class="bd bd-beg"><h-inner>。</h-inner></h-char></span>

void vTaskResume( TaskHandle_t xTaskToResume );
参数<span class="bd-box"><h-char class="bd bd-beg"><h-inner>：</h-inner></h-char></span>
xTaskToResume 要恢复的任务句柄<span class="bd-box"><h-char class="bd bd-beg"><h-inner>。</h-inner></h-char></span>

任务调度分析
freeRTOS的调度模式有两种，一种是抢占式调度，一种是时间片调度
抢占式调度，就是高优先级资源会抢占低优先级资源
时间片调度由滴答定时器决定，每一个时间片，滴答定时器会产生中断，然后判断当前任务的状态，决定是否进入pendSV中断来完成任务的切换。