always waiting for "heapsem"

Hi,

In my uC/OS project, I have the following task. In this task , I try to allocate a heap by using memalign function.

void ButtonLed1(void)

{

OS_STK * task5_stk = (OS_STK *)memalign(TASK_STACKSIZE*sizeof(OS_STK));

while(1)

{

if(led_button_status & 0x01)

{

led_button_status &= 0xFE;

bLedStatus = 0;

IOWR_ALTERA_AVALON_PIO_DATA(LED_PIO_BASE,bLedStatus);

}

OSTimeDlyHMSM(0, 0, 1, 0);

}

}

But I failed. It stopped at the following position.

/* wait on the other task to yield the heap, then claim ownership of it */

OSSemPend( alt_heapsem, 0, &err );

I'm sure that I didn't call any function to allocate heap in other tasks. So why it always be waiting heapsem?

Could anyone help?

Thanks in advance,

David