ck_hp_fifo: Add try{enqueue,dequeue} variants.

Regression test has been updated and passes.

include/ck_hp_fifo.h

@@ -97,6 +97,35 @@ ck_hp_fifo_enqueue_mpmc(ck_hp_record_t *record,
 	return;
 }
 
+CK_CC_INLINE static bool
+ck_hp_fifo_tryenqueue_mpmc(ck_hp_record_t *record,
+			   struct ck_hp_fifo *fifo,
+			   struct ck_hp_fifo_entry *entry,
+			   void *value)
+{
+	struct ck_hp_fifo_entry *tail, *next;
+
+	entry->value = value;
+	entry->next = NULL;
+	ck_pr_fence_store();
+
+	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))
+		return false;
+
+	next = ck_pr_load_ptr(&tail->next);
+	if (next != NULL) {
+		ck_pr_cas_ptr(&fifo->tail, tail, next);
+		return false;
+	} else if (ck_pr_cas_ptr(&fifo->tail->next, next, entry) == false)
+		return false;
+
+	ck_pr_cas_ptr(&fifo->tail, tail, entry);
+	return true;
+}
+
 CK_CC_INLINE static struct ck_hp_fifo_entry *
 ck_hp_fifo_dequeue_mpmc(ck_hp_record_t *record,
 			struct ck_hp_fifo *fifo,
@@ -133,6 +162,39 @@ ck_hp_fifo_dequeue_mpmc(ck_hp_record_t *record,
 	return (head);
 }
 
+CK_CC_INLINE static struct ck_hp_fifo_entry *
+ck_hp_fifo_trydequeue_mpmc(ck_hp_record_t *record,
+			   struct ck_hp_fifo *fifo,
+			   void *value)
+{
+	struct ck_hp_fifo_entry *head, *tail, *next;
+
+	tail = ck_pr_load_ptr(&fifo->tail);
+	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))
+		return NULL;
+
+	next = ck_pr_load_ptr(&head->next);
+	ck_hp_set(record, 1, next);
+	ck_pr_fence_memory();
+	if (head != ck_pr_load_ptr(&fifo->head))
+		return NULL;
+
+	if (head == tail) {
+		if (next == NULL)
+			return NULL;
+
+		ck_pr_cas_ptr(&fifo->tail, tail, next);
+		return NULL;
+	} else if (ck_pr_cas_ptr(&fifo->head, head, next) == false)
+		return NULL;
+
+	ck_pr_store_ptr(value, next->value);
+	return head;
+}
+
 #define CK_HP_FIFO_ISEMPTY(f) ((f)->head->next == NULL)
 #define CK_HP_FIFO_FIRST(f)   ((f)->head->next)
 #define CK_HP_FIFO_NEXT(m)    ((m)->next)

regressions/ck_hp/validate/ck_hp_fifo.c

@@ -96,6 +96,27 @@ test(void *c)
 		}
 	}
 
+	for (i = 0; i < ITERATIONS; i++) {
+		for (j = 0; j < size; j++) {
+			fifo_entry = malloc(sizeof(ck_hp_fifo_entry_t));
+			entry = malloc(sizeof(struct entry));
+			entry->tid = context->tid;
+
+			while (ck_hp_fifo_tryenqueue_mpmc(&record, &fifo, fifo_entry, entry) == false)
+				ck_pr_stall();
+
+			while (fifo_entry = ck_hp_fifo_trydequeue_mpmc(&record, &fifo, &entry), fifo_entry == NULL)
+				ck_pr_stall();
+
+			if (entry->tid < 0 || entry->tid >= nthr) {
+				fprintf(stderr, "ERROR [%u] Incorrect value in entry.\n", entry->tid);
+				exit(EXIT_FAILURE);
+			}
+
+			ck_hp_free(&record, &fifo_entry->hazard, fifo_entry, fifo_entry);
+		}
+	}
+
 	ck_pr_inc_uint(&e_barrier);
 	while (ck_pr_load_uint(&e_barrier) < (unsigned int)nthr);