int API_FUNC qthread_disable_worker(const qthread_worker_id_t w)
{ /*{{{*/
assert(qthread_library_initialized);
unsigned int shep = w % qlib->nshepherds;
unsigned int worker = w / qlib->nshepherds;
qassert_ret((shep < qlib->nshepherds), QTHREAD_BADARGS);
qassert_ret((worker < qlib->nworkerspershep), QTHREAD_BADARGS);
if ((worker == 0) & (shep == 0)) {
/* currently, the "real mccoy" original thread cannot be migrated
* (because I don't know what issues that could cause on all
* architectures). For similar reasons, therefore, the original
* shepherd cannot be disabled. One of the nice aspects of this is that
* therefore it is impossible to disable ALL shepherds.
*
* ... it's entirely possible that I'm being overly cautious. This is a
* policy based on gut feeling rather than specific issues. */
return QTHREAD_NOT_ALLOWED;
}
qthread_debug(SHEPHERD_CALLS, "began on worker(%i-%i)\n", shep, worker);
(void)QT_CAS(qlib->shepherds[shep].workers[worker].active, 1, 0);
qlib->nworkers_active--; // decrement active count
if (worker == 0) { qthread_disable_shepherd(shep); }
return QTHREAD_SUCCESS;
} /*}}}*/
qlfqueue_t *qlfqueue_create(void)
{ /*{{{ */
qlfqueue_t *q;
if (qlfqueue_node_pool == NULL) {
switch ((uintptr_t)qthread_cas_ptr(&qlfqueue_node_pool, NULL, (void *)1)) {
case 0: /* I won, I will allocate */
qlfqueue_node_pool = qpool_create_aligned(sizeof(qlfqueue_node_t), 0);
break;
case 1:
while (qlfqueue_node_pool == (void *)1) {
SPINLOCK_BODY();
}
break;
}
}
qassert_ret((qlfqueue_node_pool != NULL), NULL);
q = MALLOC(sizeof(struct qlfqueue_s));
if (q != NULL) {
q->head = (qlfqueue_node_t *)qpool_alloc(qlfqueue_node_pool);
assert(q->head != NULL);
if (q->head == NULL) { /* if we're not using asserts, fail nicely */
FREE(q, sizeof(struct qlfqueue_s));
return NULL;
}
q->tail = q->head;
q->tail->next = NULL;
}
return q;
} /*}}} */
int qlfqueue_empty(qlfqueue_t *q)
{ /*{{{ */
qlfqueue_node_t *head;
qlfqueue_node_t *tail;
qlfqueue_node_t *next;
qassert_ret((q != NULL), QTHREAD_BADARGS);
while (1) {
head = q->head;
tail = q->tail;
next = head->next;
MACHINE_FENCE;
if (head == q->head) { /* are head, tail, and next consistent? */
if (head == tail) { /* is queue empty or tail falling behind? */
if (next == NULL) { /* queue is empty! */
return 1;
} else { /* tail falling behind (queue NOT empty) */
return 0;
}
} else { /* queue is NOT empty and tail is NOT falling behind */
return 0;
}
}
}
} /*}}} */
void *qlfqueue_dequeue(qlfqueue_t *q)
{ /*{{{ */
void *p = NULL;
qlfqueue_node_t *head;
qlfqueue_node_t *tail;
qlfqueue_node_t *next_ptr;
qassert_ret((q != NULL), NULL);
while (1) {
head = q->head;
hazardous_ptr(0, head);
if (head != q->head) { continue; }
tail = q->tail;
next_ptr = head->next;
hazardous_ptr(1, next_ptr);
if (next_ptr == NULL) { return NULL; } /* queue is empty */
if (head == tail) { /* tail is falling behind! */
/* advance tail ptr... */
(void)qthread_cas_ptr((void **)&(q->tail), (void *)tail, next_ptr);
continue;
}
/* read value before CAS, otherwise another dequeue might free the next node */
p = next_ptr->value;
if (qthread_cas_ptr((void **)&(q->head), (void *)head, next_ptr) == head) {
break; /* success! */
}
}
hazardous_release_node(qlfqueue_pool_free_wrapper, head);
return p;
} /*}}} */
int qlfqueue_destroy(qlfqueue_t *q)
{ /*{{{ */
qassert_ret((q != NULL), QTHREAD_BADARGS);
while (q->head != q->tail) {
qlfqueue_dequeue(q);
COMPILER_FENCE;
}
COMPILER_FENCE;
qpool_free(qlfqueue_node_pool, (void *)(q->head));
FREE(q, sizeof(struct qlfqueue_s));
return QTHREAD_SUCCESS;
} /*}}} */
int qlfqueue_enqueue(qlfqueue_t *q,
void *elem)
{ /*{{{ */
qlfqueue_node_t *tail;
qlfqueue_node_t *next;
qlfqueue_node_t *node;
qassert_ret((elem != NULL), QTHREAD_BADARGS);
qassert_ret((q != NULL), QTHREAD_BADARGS);
node = (qlfqueue_node_t *)qpool_alloc(qlfqueue_node_pool);
/* these asserts should be redundant */
qassert_ret((node != NULL), QTHREAD_MALLOC_ERROR);
memset((void *)node, 0, sizeof(qlfqueue_node_t));
node->value = elem;
while (1) {
tail = q->tail;
hazardous_ptr(0, tail);
if (tail != q->tail) { continue; }
next = tail->next;
if (next != NULL) { /* tail not pointing to last node */
(void)qthread_cas_ptr((void **)&(q->tail), (void *)tail, next);
continue;
}
/* tail must be pointing to the last node */
if (qthread_cas_ptr((void **)&(tail->next), (void *)next, node) == next) {
break; /* success! */
}
}
(void)qthread_cas_ptr((void **)&(q->tail), (void *)tail, node);
hazardous_ptr(0, NULL); // release the ptr (avoid hazardptr resource exhaustion)
return QTHREAD_SUCCESS;
} /*}}} */
qt_threadqueue_t INTERNAL *qt_threadqueue_new(void)
{ /*{{{ */
qt_threadqueue_t *q = ALLOC_THREADQUEUE();
qassert_ret(q != NULL, NULL);
q->q.shadow_head = q->q.head = q->q.tail = NULL;
q->advisory_queuelen = 0;
q->q.nemesis_advisory_queuelen = 0; // redundant
#ifdef QTHREAD_CONDWAIT_BLOCKING_QUEUE
q->frustration = 0;
QTHREAD_COND_INIT(q->trigger);
#endif /* ifdef QTHREAD_CONDWAIT_BLOCKING_QUEUE */
return q;
} /*}}} */