Something

static void *eb_insert(struct eb *eb)
{
	unsigned char *p;
	unsigned long flags;
	int n, c;

	spin_lock_irqsave(&eb->lock, flags);
	p = eb->buf + (eb->in * eb->elem_size);		/* in is where we want to put the frame in the buffer */

/*
 * Update the index to reflect the next frame to remove.
 * If the buffer's full, overwrite the oldest data and update the 'out'
 */
	n = eb->in + 1;
	if(n >= eb->depth)
		n = 0;
	if(n == eb->out) {
		eb->over++;
		eb->out++;			/* update the tail (overwrite oldest data) */
		if(eb->out >= eb->depth)	/* wrap the tail if needed */
			eb->out = 0;
		}
	eb->in = n;

/* update stats */
	c = cycles();
	eb->dt_in = c - eb->lastin;
	if(eb->dt_in < 0)
		eb->dt_in += INT_MAX;

/* update max and maxlife */
	if(eb->dt_in > eb->dt_in_max)
		eb->dt_in_max = eb->dt_in;
	if(eb->dt_in > eb->dt_in_maxlife)
		eb->dt_in_maxlife = eb->dt_in;

	eb->lastin = c;

	if(eb->lastop == EB_OP_INSERT) {
		eb->inin++;
		eb->dt_2in = c - eb->last2in;
		if(eb->dt_2in < 0)
			eb->dt_2in += INT_MAX;
		eb->last2in = c;
		}
	eb->lastop = EB_OP_INSERT;

	spin_unlock_irqrestore(&eb->lock, flags);
	return p;
}

static void *eb_remove(struct eb *eb)
{
	unsigned char *p;
	unsigned long flags;
	int n, c;

	spin_lock_irqsave(&eb->lock, flags);
	p = eb->buf + (eb->out * eb->elem_size);	/* out is the frame we want to pull out of the buffer */

/* update the index to reflect the next frame to remove.  If the buffer's empty, don't update the pointer. */
	n = eb->out + 1;
	if(n >= eb->depth)
		n = 0;
	if(n == eb->in) {
//		p = interpolate(eb);		/* TODO: eventually... */
//printk("underrun...\n");
		n = eb->out;
		eb->under++;
		}
	eb->out = n;

/* update stats */
	c = cycles();
	eb->dt_out = c - eb->lastout;
	if(eb->dt_out < 0)
		eb->out += INT_MAX;

	if(eb->dt_out > eb->dt_out_max)
		eb->dt_out_max = eb->dt_out;

	if(eb->dt_out > eb->dt_out_maxlife)
		eb->dt_out_maxlife = eb->dt_out;
	eb->lastout = c;

	if(eb->lastop == EB_OP_REMOVE) {
		eb->outout++;
		eb->dt_2out = c - eb->last2out;
		if(eb->dt_2out < 0)
			eb->dt_2out += INT_MAX;
		eb->last2out = c;
		}
	eb->lastop = EB_OP_REMOVE;

	spin_unlock_irqrestore(&eb->lock, flags);
	return p;
}