prvTaskExitError异常退出，FreeRTOS启动失败分析

FreeRTOS报错信息如下：

Error:…\src\freertos\portable\RVDS\ARM_CM4F\port.c,233

根据断言信息，报错位置为port.c文件第233行，查看源代码：

staticvoidprvTaskExitError(void){/* A function that implements a task must not exit or attempt to return to * its caller as there is nothing to return to. If a task wants to exit it * should instead call vTaskDelete( NULL ). * * Artificially force an assert() to be triggered if configASSERT() is * defined, then stop here so application writers can catch the error. */configASSERT(uxCriticalNesting==~0UL);portDISABLE_INTERRUPTS();for(;;){}}

发现是执行了prvTaskExitError函数，再根据官方文件注释，FreeRTOS中规定，任务不能退出，如果要退出只能调用vTaskDelete( NULL )，否则就会异常报错，根据这个提示，检查各个任务，是不是有异常退出。

如果有多个任务，可以对在prvTaskExitError函数中增加调试代码，打印任务名称，如下：

staticvoidprvTaskExitError(void){/* A function that implements a task must not exit or attempt to return to * its caller as there is nothing to return to. If a task wants to exit it * should instead call vTaskDelete( NULL ). * * Artificially force an assert() to be triggered if configASSERT() is * defined, then stop here so application writers can catch the error. */TaskHandle_t xTask=xTaskGetCurrentTaskHandle();constchar*pcTaskName=pcTaskGetName(xTask);printf("Error:Task %s exited unexpectedly!\r\n",pcTaskName);configASSERT(uxCriticalNesting==~0UL);portDISABLE_INTERRUPTS();for(;;){}}

再次运行，即可打印出任务名称，从而具体分析某个任务：

Error:Task ftp_server exited unexpectedly!
Error:…\src\freertos\portable\RVDS\ARM_CM4F\port.c,237

可以看出，导致异常退出的任务是ftp_server，分析ftp_server任务，发现是有return返回的地方，导致任务异常退出了。