X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=urcu%2Fworkqueue-fifo.h;h=ea6312f8548b28d8c0cf6cef79fb0bec54c1cfd0;hb=8313fa62c9045e03a3a6a38a10311e6105b69f53;hp=bc19967a6a062eebc5d9c2d33598caab3f2a8f64;hpb=e10c65b3279d1868a7ef83588bb91dd46cfe428a;p=userspace-rcu.git diff --git a/urcu/workqueue-fifo.h b/urcu/workqueue-fifo.h index bc19967..ea6312f 100644 --- a/urcu/workqueue-fifo.h +++ b/urcu/workqueue-fifo.h @@ -24,13 +24,18 @@ */ #include -#include +#include #include #include #include #include #include +enum urcu_accept_ret { + URCU_ACCEPT_WORK = 0, + URCU_ACCEPT_SHUTDOWN = 1, +}; + /* * We use RCU to steal work from siblings. Therefore, one of RCU flavors * need to be included before this header. All worker that participate @@ -53,12 +58,18 @@ struct urcu_workqueue { /* RCU linked list head of siblings for work stealing. */ struct cds_list_head sibling_head; pthread_mutex_t sibling_lock; /* Protect sibling list updates */ + + bool shutdown; /* Shutdown performed */ }; struct urcu_worker { + /* Workqueue which can be either used by worker, or stolen. */ struct cds_wfcq_head head; struct cds_wfcq_tail tail; + /* Work belonging to worker. Cannot be stolen. */ + struct urcu_work *own; + struct urcu_wait_node wait_node; /* RCU linked list node of siblings for work stealing. */ struct cds_list_head sibling_node; @@ -75,6 +86,8 @@ void urcu_workqueue_init(struct urcu_workqueue *queue) __cds_wfcq_init(&queue->head, &queue->tail); urcu_wait_queue_init(&queue->waitqueue); CDS_INIT_LIST_HEAD(&queue->sibling_head); + pthread_mutex_init(&queue->sibling_lock, NULL); + queue->shutdown = false; } static inline @@ -100,16 +113,22 @@ void urcu_queue_work(struct urcu_workqueue *queue, struct urcu_work *work) * worker threads when threads are busy enough to still be * running when work is enqueued. */ - if (was_empty) + if (was_empty) { + rcu_read_lock(); /* Protect stack dequeue */ (void) urcu_dequeue_wake_single(&queue->waitqueue); + rcu_read_unlock(); /* Protect stack dequeue */ + } } static inline -void urcu_workqueue_wakeup_all(struct urcu_workqueue *queue) +void __urcu_workqueue_wakeup_all(struct urcu_workqueue *queue) { struct urcu_waiters waiters; + rcu_read_lock(); /* Protect stack dequeue */ urcu_move_waiters(&waiters, &queue->waitqueue); + rcu_read_unlock(); /* Protect stack dequeue */ + (void) urcu_wake_all_waiters(&waiters); } @@ -119,6 +138,7 @@ void urcu_worker_init(struct urcu_worker *worker, int flags) cds_wfcq_init(&worker->head, &worker->tail); worker->flags = flags; urcu_wait_node_init(&worker->wait_node, URCU_WAIT_RUNNING); + worker->own = NULL; } static inline @@ -142,14 +162,14 @@ void urcu_worker_unregister(struct urcu_workqueue *queue, pthread_mutex_lock(&queue->sibling_lock); cds_list_del_rcu(&worker->sibling_node); pthread_mutex_unlock(&queue->sibling_lock); - - /* - * Wait for grace period before freeing or reusing - * "worker" because used by RCU linked list. - */ - synchronize_rcu(); } + /* + * Make sure we are removed from waitqueue. + */ + if (CMM_LOAD_SHARED(worker->wait_node.node.next)) + __urcu_workqueue_wakeup_all(queue); + /* * Put any local work we still have back into the workqueue. */ @@ -163,33 +183,95 @@ void urcu_worker_unregister(struct urcu_workqueue *queue, * Wakeup worker thread if we have put work back into * workqueue that was previously empty. */ + rcu_read_lock(); /* Protect stack dequeue */ (void) urcu_dequeue_wake_single(&queue->waitqueue); + rcu_read_unlock(); /* Protect stack dequeue */ } + + /* + * Wait for grace period before freeing or reusing + * "worker" because used by RCU linked list. + * Also prevents ABA for waitqueue stack dequeue: matches RCU + * read-side critical sections around dequeue and move all + * operations on waitqueue). + */ + synchronize_rcu(); } -/* - * Try stealing work from siblings when we have nothing to do. - */ static inline -bool ___urcu_steal_work(struct urcu_worker *worker, - struct urcu_worker *sibling) +bool ___urcu_grab_work(struct urcu_worker *worker, + cds_wfcq_head_ptr_t src_head, + struct cds_wfcq_tail *src_tail, + bool steal) { enum cds_wfcq_ret splice_ret; + struct __cds_wfcq_head tmp_head; + struct cds_wfcq_tail tmp_tail; + struct cds_wfcq_node *node; /* - * Don't bother grabbing the sibling queue lock if it is empty. + * Don't bother grabbing the src queue lock if it is empty. */ - if (cds_wfcq_empty(&sibling->head, &sibling->tail)) + if (cds_wfcq_empty(src_head, src_tail)) + return false; + __cds_wfcq_init(&tmp_head, &tmp_tail); + + /* Ensure that we preserve FIFO work order. */ + assert(!steal || worker->own == NULL); + + /* Splice to temporary queue. */ + if (steal) + cds_wfcq_dequeue_lock(src_head.h, src_tail); + splice_ret = __cds_wfcq_splice_blocking(&tmp_head, + &tmp_tail, + src_head, + src_tail); + if (steal) + cds_wfcq_dequeue_unlock(src_head.h, src_tail); + if (splice_ret == CDS_WFCQ_RET_SRC_EMPTY) return false; - cds_wfcq_dequeue_lock(&sibling->head, &sibling->tail); + + /* + * Keep one work entry for ourself. This ensures forward + * progress amongst stealing co-workers. This also ensures that + * when a worker grab some work from the global workqueue, it + * will have at least one work item to deal with. + */ + if (worker->own == NULL) { + if (!steal) { + /* + * Try to grab own work from worker workqueue to + * preserve FIFO order. + */ + node = cds_wfcq_dequeue_blocking(&worker->head, + &worker->tail); + if (node) + goto got_node; + } + node = __cds_wfcq_dequeue_blocking(&tmp_head, &tmp_tail); + assert(node != NULL); +got_node: + worker->own = caa_container_of(node, struct urcu_work, node); + } + + /* Splice into worker workqueue. */ splice_ret = __cds_wfcq_splice_blocking(&worker->head, &worker->tail, - &sibling->head, - &sibling->tail); - cds_wfcq_dequeue_unlock(&sibling->head, &sibling->tail); + &tmp_head, + &tmp_tail); /* Ensure that we preserve FIFO work order. */ - assert(splice_ret != CDS_WFCQ_RET_DEST_NON_EMPTY); - return splice_ret != CDS_WFCQ_RET_SRC_EMPTY; + assert(!steal || splice_ret != CDS_WFCQ_RET_DEST_NON_EMPTY); + return true; +} + +/* + * Try stealing work from siblings when we have nothing to do. + */ +static inline +bool ___urcu_steal_work(struct urcu_worker *worker, + struct urcu_worker *sibling) +{ + return ___urcu_grab_work(worker, &sibling->head, &sibling->tail, 1); } static inline @@ -275,26 +357,22 @@ end: } static inline -void urcu_accept_work(struct urcu_workqueue *queue, - struct urcu_worker *worker, - int blocking) +enum urcu_accept_ret urcu_accept_work(struct urcu_workqueue *queue, + struct urcu_worker *worker) { enum cds_wfcq_ret wfcq_ret; + bool has_work; - wfcq_ret = __cds_wfcq_splice_blocking(&worker->head, - &worker->tail, - &queue->head, - &queue->tail); + has_work = ___urcu_grab_work(worker, &queue->head, &queue->tail, 0); /* Don't wait if we have work to do. */ - if (wfcq_ret != CDS_WFCQ_RET_SRC_EMPTY - || !cds_wfcq_empty(&worker->head, - &worker->tail)) + if (has_work || !cds_wfcq_empty(&worker->head, &worker->tail)) goto do_work; /* Try to steal work from sibling instead of blocking */ if (__urcu_steal_work(queue, worker)) goto do_work; - if (!blocking) - return; + /* No more work to do, check shutdown state */ + if (CMM_LOAD_SHARED(queue->shutdown)) + return URCU_ACCEPT_SHUTDOWN; urcu_wait_set_state(&worker->wait_node, URCU_WAIT_WAITING); if (!CMM_LOAD_SHARED(worker->wait_node.node.next)) { @@ -304,7 +382,9 @@ void urcu_accept_work(struct urcu_workqueue *queue, * NULL next pointer. We are therefore not in * the queue. */ - cds_wfs_node_init(&worker->wait_node.node); + cds_lfs_node_init(&worker->wait_node.node); + /* Protect stack dequeue against ABA */ + synchronize_rcu(); was_empty = !urcu_wait_add(&queue->waitqueue, &worker->wait_node); /* @@ -317,8 +397,11 @@ void urcu_accept_work(struct urcu_workqueue *queue, * a wake up. */ if (was_empty && !cds_wfcq_empty(&queue->head, - &queue->tail)) + &queue->tail)) { + rcu_read_lock(); /* Protect stack dequeue */ (void) urcu_dequeue_wake_single(&queue->waitqueue); + rcu_read_unlock(); /* Protect stack dequeue */ + } } else { /* * Non-NULL next pointer. We are therefore in @@ -339,6 +422,7 @@ do_work: * they can steal from us. */ (void) __urcu_wakeup_siblings(queue, worker); + return URCU_ACCEPT_WORK; } static inline @@ -346,6 +430,14 @@ struct urcu_work *urcu_dequeue_work(struct urcu_worker *worker) { struct cds_wfcq_node *node; + if (worker->own) { + struct urcu_work *work; + + /* Process our own work entry. */ + work = worker->own; + worker->own = NULL; + return work; + } /* * If we are registered for work stealing, we need to dequeue * safely against siblings. @@ -368,4 +460,13 @@ struct urcu_work *urcu_dequeue_work(struct urcu_worker *worker) return caa_container_of(node, struct urcu_work, node); } +static inline +void urcu_workqueue_shutdown(struct urcu_workqueue *queue) +{ + /* Set shutdown */ + CMM_STORE_SHARED(queue->shutdown, true); + /* Wakeup all workers */ + __urcu_workqueue_wakeup_all(queue); +} + #endif /* _URCU_WORKQUEUE_FIFO_H */