X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu-wait.h;h=94f3e3559ba8c32492234f911911db7faa1337a9;hp=13f26cca99fde2ba59acb01397969d2930fd7ce2;hb=7dea28e7c3827cfcfaea71caa81648ea8a19cfe5;hpb=cba82d7bd73c2d3d9772190d51314c59bd2ef309 diff --git a/urcu-wait.h b/urcu-wait.h index 13f26cc..94f3e35 100644 --- a/urcu-wait.h +++ b/urcu-wait.h @@ -24,6 +24,8 @@ */ #include +#include +#include "urcu-die.h" /* * Number of busy-loop attempts before waiting on futex for grace period @@ -36,72 +38,164 @@ enum urcu_wait_state { URCU_WAIT_WAITING = 0, /* non-zero are used as masks. */ URCU_WAIT_WAKEUP = (1 << 0), - URCU_WAIT_AWAKENED = (1 << 1), + URCU_WAIT_RUNNING = (1 << 1), URCU_WAIT_TEARDOWN = (1 << 2), }; -struct urcu_wait { - int32_t futex; +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 -void urcu_wait_init(struct urcu_wait *wait) +bool urcu_wait_add(struct urcu_wait_queue *queue, + struct urcu_wait_node *node) { - wait->futex = URCU_WAIT_WAITING; + 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 futex + * 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 *wait) +void urcu_adaptative_wake_up(struct urcu_wait_node *wait) { cmm_smp_mb(); - assert(uatomic_read(&wait->futex) == URCU_WAIT_WAITING); - uatomic_set(&wait->futex, URCU_WAIT_WAKEUP); - if (!(uatomic_read(&wait->futex) & URCU_WAIT_AWAKENED)) - futex_noasync(&wait->futex, FUTEX_WAKE, 1, NULL, NULL, 0); + 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->futex, URCU_WAIT_TEARDOWN); + uatomic_or(&wait->state, URCU_WAIT_TEARDOWN); } /* * Caller must initialize "value" to URCU_WAIT_WAITING before passing its * memory to waker thread. */ -static void urcu_adaptative_busy_wait(struct urcu_wait *wait) +static inline +void urcu_adaptative_busy_wait(struct urcu_wait_node *wait) { unsigned int i; - /* Load and test condition before read futex */ + /* Load and test condition before read state */ cmm_smp_rmb(); for (i = 0; i < URCU_WAIT_ATTEMPTS; i++) { - if (uatomic_read(&wait->futex) != URCU_WAIT_WAITING) + if (uatomic_read(&wait->state) != URCU_WAIT_WAITING) goto skip_futex_wait; caa_cpu_relax(); } - futex_noasync(&wait->futex, FUTEX_WAIT, - URCU_WAIT_WAITING, NULL, NULL, 0); + 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 awakened. */ - uatomic_or(&wait->futex, URCU_WAIT_AWAKENED); + /* 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->futex) & URCU_WAIT_TEARDOWN) + if (uatomic_read(&wait->state) & URCU_WAIT_TEARDOWN) break; caa_cpu_relax(); } - while (!(uatomic_read(&wait->futex) & URCU_WAIT_TEARDOWN)) + while (!(uatomic_read(&wait->state) & URCU_WAIT_TEARDOWN)) poll(NULL, 0, 10); - assert(uatomic_read(&wait->futex) & URCU_WAIT_TEARDOWN); + 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 */