From fad3891f3158a4285984bb60415c1e4ebc2b767b Mon Sep 17 00:00:00 2001 From: Brian Demsky Date: Thu, 7 Mar 2013 23:54:06 -0800 Subject: [PATCH 1/1] my changes --- ms-queue/my_queue.c | 27 +++++++++++++-------------- 1 file changed, 13 insertions(+), 14 deletions(-) diff --git a/ms-queue/my_queue.c b/ms-queue/my_queue.c index d658407..c63f254 100644 --- a/ms-queue/my_queue.c +++ b/ms-queue/my_queue.c @@ -61,6 +61,7 @@ void enqueue(queue_t *q, unsigned int val) pointer next; pointer tmp; + /* Get a fresh node, set its value field, then set it's next reference to null */ node = new_node(); store_32(&q->nodes[node].value, val); tmp = atomic_load_explicit(&q->nodes[node].next, relaxed); @@ -68,29 +69,30 @@ void enqueue(queue_t *q, unsigned int val) atomic_store_explicit(&q->nodes[node].next, tmp, relaxed); while (!success) { - tail = atomic_load_explicit(&q->tail, acquire); - next = atomic_load_explicit(&q->nodes[get_ptr(tail)].next, acquire); + //tail isn't actually synchronization point + tail = atomic_load_explicit(&q->tail, relaxed); + //acquire reference + next = atomic_load_explicit(&q->nodes[get_ptr(tail)].next, relaxed); if (tail == atomic_load_explicit(&q->tail, relaxed)) { if (get_ptr(next) == 0) { // == NULL pointer value = MAKE_POINTER(node, get_count(next) + 1); success = atomic_compare_exchange_strong_explicit(&q->nodes[get_ptr(tail)].next, - &next, value, memory_order_acq_rel, memory_order_acq_rel); + &next, value, memory_order_release, memory_order_release); } if (!success) { - unsigned int ptr = get_ptr(atomic_load_explicit(&q->nodes[get_ptr(tail)].next, memory_order_seq_cst)); + unsigned int ptr = get_ptr(atomic_load_explicit(&q->nodes[get_ptr(tail)].next, memory_order_relaxed)); pointer value = MAKE_POINTER(ptr, get_count(tail) + 1); atomic_compare_exchange_strong_explicit(&q->tail, &tail, value, - memory_order_acq_rel, memory_order_acq_rel); - thrd_yield(); + memory_order_relaxed, memory_order_relaxed); } } } atomic_compare_exchange_strong_explicit(&q->tail, &tail, MAKE_POINTER(node, get_count(tail) + 1), - memory_order_acq_rel, memory_order_acq_rel); + memory_order_relaxed, memory_order_relaxed); } unsigned int dequeue(queue_t *q) @@ -102,8 +104,8 @@ unsigned int dequeue(queue_t *q) pointer next; while (!success) { - head = atomic_load_explicit(&q->head, acquire); - tail = atomic_load_explicit(&q->tail, acquire); + head = atomic_load_explicit(&q->head, relaxed); + tail = atomic_load_explicit(&q->tail, relaxed); next = atomic_load_explicit(&q->nodes[get_ptr(head)].next, acquire); if (atomic_load_explicit(&q->head, relaxed) == head) { if (get_ptr(head) == get_ptr(tail)) { @@ -113,16 +115,13 @@ unsigned int dequeue(queue_t *q) atomic_compare_exchange_strong_explicit(&q->tail, &tail, MAKE_POINTER(get_ptr(next), get_count(tail) + 1), - memory_order_acq_rel, memory_order_acq_rel); - thrd_yield(); + memory_order_relaxed, memory_order_relaxed); } else { value = load_32(&q->nodes[get_ptr(next)].value); success = atomic_compare_exchange_strong_explicit(&q->head, &head, MAKE_POINTER(get_ptr(next), get_count(head) + 1), - memory_order_acq_rel, memory_order_acq_rel); - if (!success) - thrd_yield(); + memory_order_relaxed, memory_order_relaxed); } } } -- 2.34.1