ck_hp: Remove barrier from set and allow user to batch.

A user may want to batch multiple slot updates. Enforcing strong
semantics in set would not allow this.

include/ck_hp.h

@@ -76,7 +76,6 @@ ck_hp_set(struct ck_hp_record *record, unsigned int i, void *pointer)
 {
 
 	ck_pr_store_ptr(&record->pointers[i], pointer);
-	ck_pr_fence_store();
 	return;
 }
 

include/ck_hp_fifo.h

@@ -82,6 +82,7 @@ ck_hp_fifo_enqueue_mpmc(ck_hp_record_t *record,
 	for (;;) {
 		tail = ck_pr_load_ptr(&fifo->tail);
 		ck_hp_set(record, 0, tail);
+		ck_pr_fence_memory();
 		if (tail != ck_pr_load_ptr(&fifo->tail))
 			continue;
 
@@ -108,6 +109,7 @@ ck_hp_fifo_dequeue_mpmc(ck_hp_record_t *record,
 
 		head = ck_pr_load_ptr(&fifo->head);
 		ck_hp_set(record, 0, head);
+		ck_pr_fence_memory();
 		if (head != ck_pr_load_ptr(&fifo->head))
 			continue;
 

include/ck_hp_stack.h

@@ -57,6 +57,7 @@ ck_hp_stack_pop_mpmc(ck_hp_record_t *record, struct ck_stack *target)
 			return (NULL);
 
 		ck_hp_set(record, 0, entry);
+		ck_pr_fence_memory();
 	} while (entry != ck_pr_load_ptr(&target->head));
 
 	while (ck_pr_cas_ptr_value(&target->head, entry, entry->next, &entry) == false) {
@@ -64,9 +65,11 @@ ck_hp_stack_pop_mpmc(ck_hp_record_t *record, struct ck_stack *target)
 			return (NULL);
 
 		ck_hp_set(record, 0, entry);
+		ck_pr_fence_memory();
 		update = ck_pr_load_ptr(&target->head);
 		while (entry != update) {
 			ck_hp_set(record, 0, update);
+			ck_pr_fence_memory();
 			entry = update;
 			update = ck_pr_load_ptr(&target->head);
 			if (update == NULL)