1 @@ -50,6 +50,7 @@
2  			struct list_head *a, struct list_head *b)
3  {
4  	struct list_head *tail = head;
5 +	u8 count = 0;
6 
7  	for (;;) {
8  		/* if equal, take 'a' -- important for sort stability */
9 @@ -75,6 +76,15 @@
10  	/* Finish linking remainder of list b on to tail */
11  	tail->next = b;
12  	do {
13 +		/*
14 +		 * If the merge is highly unbalanced (e.g. the input is
15 +		 * already sorted), this loop may run many iterations.
16 +		 * Continue callbacks to the client even though no
17 +		 * element comparison is needed, so the client's cmp()
18 +		 * routine can invoke cond_resched() periodically.
19 +		 */
20 +		if (unlikely(!++count))
21 +			cmp(priv, b, b);
22  		b->prev = tail;
23  		tail = b;
24  		b = b->next;
25