| /* |
| * |
| * Copyright 2016, Google Inc. |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions are |
| * met: |
| * |
| * * Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * * Redistributions in binary form must reproduce the above |
| * copyright notice, this list of conditions and the following disclaimer |
| * in the documentation and/or other materials provided with the |
| * distribution. |
| * * Neither the name of Google Inc. nor the names of its |
| * contributors may be used to endorse or promote products derived from |
| * this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| * |
| */ |
| |
| #include "src/core/lib/support/mpscq.h" |
| |
| #include <grpc/support/log.h> |
| |
| void gpr_mpscq_init(gpr_mpscq *q) { |
| gpr_atm_no_barrier_store(&q->head, (gpr_atm)&q->stub); |
| q->tail = &q->stub; |
| gpr_atm_no_barrier_store(&q->stub.next, (gpr_atm)NULL); |
| } |
| |
| void gpr_mpscq_destroy(gpr_mpscq *q) { |
| GPR_ASSERT(gpr_atm_no_barrier_load(&q->head) == (gpr_atm)&q->stub); |
| GPR_ASSERT(q->tail == &q->stub); |
| } |
| |
| bool gpr_mpscq_push(gpr_mpscq *q, gpr_mpscq_node *n) { |
| gpr_atm_no_barrier_store(&n->next, (gpr_atm)NULL); |
| gpr_mpscq_node *prev = |
| (gpr_mpscq_node *)gpr_atm_full_xchg(&q->head, (gpr_atm)n); |
| gpr_atm_rel_store(&prev->next, (gpr_atm)n); |
| return prev == &q->stub; |
| } |
| |
| gpr_mpscq_node *gpr_mpscq_pop(gpr_mpscq *q) { |
| bool empty; |
| return gpr_mpscq_pop_and_check_end(q, &empty); |
| } |
| |
| gpr_mpscq_node *gpr_mpscq_pop_and_check_end(gpr_mpscq *q, bool *empty) { |
| gpr_mpscq_node *tail = q->tail; |
| gpr_mpscq_node *next = (gpr_mpscq_node *)gpr_atm_acq_load(&tail->next); |
| if (tail == &q->stub) { |
| // indicates the list is actually (ephemerally) empty |
| if (next == NULL) { |
| *empty = true; |
| return NULL; |
| } |
| q->tail = next; |
| tail = next; |
| next = (gpr_mpscq_node *)gpr_atm_acq_load(&tail->next); |
| } |
| if (next != NULL) { |
| *empty = false; |
| q->tail = next; |
| return tail; |
| } |
| gpr_mpscq_node *head = (gpr_mpscq_node *)gpr_atm_acq_load(&q->head); |
| if (tail != head) { |
| *empty = false; |
| // indicates a retry is in order: we're still adding |
| return NULL; |
| } |
| gpr_mpscq_push(q, &q->stub); |
| next = (gpr_mpscq_node *)gpr_atm_acq_load(&tail->next); |
| if (next != NULL) { |
| q->tail = next; |
| return tail; |
| } |
| // indicates a retry is in order: we're still adding |
| *empty = false; |
| return NULL; |
| } |
| |
| void gpr_locked_mpscq_init(gpr_locked_mpscq *q) { |
| gpr_mpscq_init(&q->queue); |
| q->read_lock = GPR_SPINLOCK_INITIALIZER; |
| } |
| |
| void gpr_locked_mpscq_destroy(gpr_locked_mpscq *q) { |
| gpr_mpscq_destroy(&q->queue); |
| } |
| |
| bool gpr_locked_mpscq_push(gpr_locked_mpscq *q, gpr_mpscq_node *n) { |
| return gpr_mpscq_push(&q->queue, n); |
| } |
| |
| gpr_mpscq_node *gpr_locked_mpscq_pop(gpr_locked_mpscq *q) { |
| if (gpr_spinlock_trylock(&q->read_lock)) { |
| gpr_mpscq_node *n = gpr_mpscq_pop(&q->queue); |
| gpr_spinlock_unlock(&q->read_lock); |
| return n; |
| } |
| return NULL; |
| } |