+++ /dev/null
-#ifndef _URCU_WAIT_H
-#define _URCU_WAIT_H
-
-/*
- * urcu-wait.h
- *
- * Userspace RCU library wait/wakeup management
- *
- * Copyright (c) 2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation; either
- * version 2.1 of the License, or (at your option) any later version.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
- */
-
-#include <urcu/uatomic.h>
-#include <urcu/wfstack.h>
-#include "urcu-die.h"
-
-/*
- * Number of busy-loop attempts before waiting on futex for grace period
- * batching.
- */
-#define URCU_WAIT_ATTEMPTS 1000
-
-enum urcu_wait_state {
- /* URCU_WAIT_WAITING is compared directly (futex compares it). */
- URCU_WAIT_WAITING = 0,
- /* non-zero are used as masks. */
- URCU_WAIT_WAKEUP = (1 << 0),
- URCU_WAIT_RUNNING = (1 << 1),
- URCU_WAIT_TEARDOWN = (1 << 2),
-};
-
-struct urcu_wait_node {
- struct cds_wfs_node node;
- int32_t state; /* enum urcu_wait_state */
-};
-
-#define URCU_WAIT_NODE_INIT(name, _state) \
- { .state = _state }
-
-#define DEFINE_URCU_WAIT_NODE(name, state) \
- struct urcu_wait_node name = URCU_WAIT_NODE_INIT(name, state)
-
-#define DECLARE_URCU_WAIT_NODE(name) \
- struct urcu_wait_node name
-
-struct urcu_wait_queue {
- struct cds_wfs_stack stack;
-};
-
-#define URCU_WAIT_QUEUE_HEAD_INIT(name) \
- { .stack.head = CDS_WFS_END, .stack.lock = PTHREAD_MUTEX_INITIALIZER }
-
-#define DECLARE_URCU_WAIT_QUEUE(name) \
- struct urcu_wait_queue name
-
-#define DEFINE_URCU_WAIT_QUEUE(name) \
- struct urcu_wait_queue name = URCU_WAIT_QUEUE_HEAD_INIT(name)
-
-struct urcu_waiters {
- struct cds_wfs_head *head;
-};
-
-/*
- * Add ourself atomically to a wait queue. Return 0 if queue was
- * previously empty, else return 1.
- * A full memory barrier is issued before being added to the wait queue.
- */
-static inline
-bool urcu_wait_add(struct urcu_wait_queue *queue,
- struct urcu_wait_node *node)
-{
- return cds_wfs_push(&queue->stack, &node->node);
-}
-
-/*
- * Atomically move all waiters from wait queue into our local struct
- * urcu_waiters.
- */
-static inline
-void urcu_move_waiters(struct urcu_waiters *waiters,
- struct urcu_wait_queue *queue)
-{
- waiters->head = __cds_wfs_pop_all(&queue->stack);
-}
-
-static inline
-void urcu_wait_set_state(struct urcu_wait_node *node,
- enum urcu_wait_state state)
-{
- node->state = state;
-}
-
-static inline
-void urcu_wait_node_init(struct urcu_wait_node *node,
- enum urcu_wait_state state)
-{
- urcu_wait_set_state(node, state);
- cds_wfs_node_init(&node->node);
-}
-
-/*
- * Note: urcu_adaptative_wake_up needs "value" to stay allocated
- * throughout its execution. In this scheme, the waiter owns the node
- * memory, and we only allow it to free this memory when it receives the
- * URCU_WAIT_TEARDOWN flag.
- */
-static inline
-void urcu_adaptative_wake_up(struct urcu_wait_node *wait)
-{
- cmm_smp_mb();
- assert(uatomic_read(&wait->state) == URCU_WAIT_WAITING);
- uatomic_set(&wait->state, URCU_WAIT_WAKEUP);
- if (!(uatomic_read(&wait->state) & URCU_WAIT_RUNNING)) {
- if (futex_noasync(&wait->state, FUTEX_WAKE, 1,
- NULL, NULL, 0) < 0)
- urcu_die(errno);
- }
- /* Allow teardown of struct urcu_wait memory. */
- uatomic_or(&wait->state, URCU_WAIT_TEARDOWN);
-}
-
-/*
- * Caller must initialize "value" to URCU_WAIT_WAITING before passing its
- * memory to waker thread.
- */
-static inline
-void urcu_adaptative_busy_wait(struct urcu_wait_node *wait)
-{
- unsigned int i;
-
- /* Load and test condition before read state */
- cmm_smp_rmb();
- for (i = 0; i < URCU_WAIT_ATTEMPTS; i++) {
- if (uatomic_read(&wait->state) != URCU_WAIT_WAITING)
- goto skip_futex_wait;
- caa_cpu_relax();
- }
- while (futex_noasync(&wait->state, FUTEX_WAIT, URCU_WAIT_WAITING,
- NULL, NULL, 0)) {
- switch (errno) {
- case EWOULDBLOCK:
- /* Value already changed. */
- goto skip_futex_wait;
- case EINTR:
- /* Retry if interrupted by signal. */
- break; /* Get out of switch. */
- default:
- /* Unexpected error. */
- urcu_die(errno);
- }
- }
-skip_futex_wait:
-
- /* Tell waker thread than we are running. */
- uatomic_or(&wait->state, URCU_WAIT_RUNNING);
-
- /*
- * Wait until waker thread lets us know it's ok to tear down
- * memory allocated for struct urcu_wait.
- */
- for (i = 0; i < URCU_WAIT_ATTEMPTS; i++) {
- if (uatomic_read(&wait->state) & URCU_WAIT_TEARDOWN)
- break;
- caa_cpu_relax();
- }
- while (!(uatomic_read(&wait->state) & URCU_WAIT_TEARDOWN))
- poll(NULL, 0, 10);
- assert(uatomic_read(&wait->state) & URCU_WAIT_TEARDOWN);
-}
-
-static inline
-void urcu_wake_all_waiters(struct urcu_waiters *waiters)
-{
- struct cds_wfs_node *iter, *iter_n;
-
- /* Wake all waiters in our stack head */
- cds_wfs_for_each_blocking_safe(waiters->head, iter, iter_n) {
- struct urcu_wait_node *wait_node =
- caa_container_of(iter, struct urcu_wait_node, node);
-
- /* Don't wake already running threads */
- if (wait_node->state & URCU_WAIT_RUNNING)
- continue;
- urcu_adaptative_wake_up(wait_node);
- }
-}
-
-#endif /* _URCU_WAIT_H */
projects / urcu.git / blobdiff