CCS/LAUNCHXL-CC26X2R1: printf() not work in Flash mode (But"debug mode" work fine)

Part Number: LAUNCHXL-CC26X2R1

Tool/software: Code Composer Studio

Hi,

We have a customer with below concern:

I try to using "printf()" show in "console:CIO window" , when i using "CCS debug mode", it work fine !
"printf()" and "led flashes" regularly and follow my code.

but when i using CCS flash mode (Click flash icon), "printf()" only show once, but led also flashes regularly,
any mistakes? i using Code Composer Studio 10.1.1.00004 and Below is my code,
Thank you!

#include <ti/display/Display.h>
#include <stdio.h>
#include <xdc/runtime/System.h>
#include <unistd.h>
#include <stdint.h>
#include <stddef.h>
#include <ti/drivers/GPIO.h>
#include "ti_drivers_config.h"

/*
* ======== mainThread ========
*/
void *mainThread(void *arg0)
{
uint32_t time = 1;
GPIO_init();
GPIO_setConfig(CONFIG_GPIO_LED_0, GPIO_CFG_OUT_STD | GPIO_CFG_OUT_LOW);
GPIO_write(CONFIG_GPIO_LED_0, CONFIG_GPIO_LED_ON);

while (1) {
printf("Hello world via printf\n");
GPIO_toggle(CONFIG_GPIO_LED_0);
sleep(time);
}
}