| /* |
| * |
| * Copyright 2016 gRPC authors. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| * |
| */ |
| |
| #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); |
| } |
| |
| void 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); |
| } |
| |
| 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; |
| } |