Is there a RTX context switch time constraint?

Hi.

Is there a RTX context switch time constraint?

I'm testing RTX on TM4C129KCPDT.

My setting is shown below.

Sysclock = 60MHz(,using internal PLL)

When I set tick value 5us,which can't context switch,only running main thread.

If tick value is 10us,which can running context switch.

[question]

1.Since it is described as <300 cycles on RTX specifications, is it possible to context switch with 5us when sysclock is 60MHz?

2.Is there an upper limit sysclock fequency?

[tick value 5us is running only main thread]

[tick value 10us]

code is below.

void led_thread3(void const *argument) {
   for(;;){
     unsigned int tick,delayPeriod;


    tick = osKernelSysTick();
    led3 = 1;
    do {
    } while ((osKernelSysTick() - tick) < osKernelSysTickMicroSec(100));

    tick = osKernelSysTick();
    led3 = 0;

    do {
    } while ((osKernelSysTick() - tick) < osKernelSysTickMicroSec(100))

  }
}

void led_thread2 (void const *argument) {
  for (;;) {
     led2 = 1;
     tick = osKernelSysTick();
     do {
     } while ((osKernelSysTick() - tick) < osKernelSysTickMicroSec(1000));

      led2 = 0;
      tick = osKernelSysTick();

     do {
     } while ((osKernelSysTick() - tick) < osKernelSysTickMicroSec(1000));
  }
}

osThreadDef(led_thread3, osPriorityNormal, 1, 0);
osThreadDef(led_thread2, osPriorityNormal, 1, 0);

uint32_t clock=0;
/*----------------------------------------------------------------------------
* Main: Initialize and start RTX Kernel
*---------------------------------------------------------------------------*/
int main (void) {

SystemCoreClockUpdate();

clock = SysCtlClockFreqSet(
SYSCTL_XTAL_16MHZ |
SYSCTL_OSC_MAIN |
SYSCTL_USE_PLL |
SYSCTL_CFG_VCO_480, 60000000);

osKernelInitialize();

led_ID3 = osThreadCreate(osThread(led_thread3), NULL);
led_ID2 = osThreadCreate(osThread(led_thread2), NULL);

osKernelStart();
}

I would appreciate it if you could teach me.