i use below code for waiting interrupt and read data, this code work fine but it use 100% of cpu.
How use semaphore to avoid cpu 100% usage?

static irqreturn_t tsc_irq_handler(int irq,void *dev_id) 
{
    write_pointer=  *TSF_CBWPR;
    read_pointer =  *TSF_CBRPR;
    flag = 1;
    return IRQ_HANDLED;
}

int thread_fn(void *unused) 
{
    while (!kthread_should_stop()) 
    {
        while(!flag){};
        flag=0;
        //do some code, like write to file.
    }
    return 0;
}