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@ -1,6 +1,6 @@ |
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/*
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* |
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* Copyright 2015, Google Inc. |
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* Copyright 2016, Google Inc. |
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* All rights reserved. |
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* |
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* Redistribution and use in source and binary forms, with or without |
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@ -40,105 +40,44 @@ |
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#define NO_CONSUMER ((gpr_atm)1) |
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static void bad_action(grpc_exec_ctx *exec_ctx, void *arg) { |
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GPR_UNREACHABLE_CODE(return ); |
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} |
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void grpc_aelock_init(grpc_aelock *lock, grpc_workqueue *optional_workqueue) { |
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lock->optional_workqueue = optional_workqueue; |
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gpr_atm_no_barrier_store(&lock->head, NO_CONSUMER); |
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gpr_atm_no_barrier_store(&lock->tombstone.next, 0); |
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lock->tombstone.action = bad_action; |
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lock->tail = &lock->tombstone; |
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gpr_atm_no_barrier_store(&lock->locked, 0); |
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gpr_mpscq_init(&lock->queue); |
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} |
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void grpc_aelock_destroy(grpc_aelock *lock) { |
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GPR_ASSERT(gpr_atm_no_barrier_load(&lock->head) == NO_CONSUMER); |
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GPR_ASSERT(gpr_atm_no_barrier_load(&lock->locked) == 0); |
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gpr_mpscq_destroy(&lock->queue); |
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} |
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static void finish(grpc_exec_ctx *exec_ctx, grpc_aelock *lock) { |
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for (;;) { |
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grpc_aelock_qnode *tail = lock->tail; |
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grpc_aelock_qnode *next = |
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(grpc_aelock_qnode *)gpr_atm_acq_load(&tail->next); |
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if (tail == &lock->tombstone) { |
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if (next == NULL) { |
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if (gpr_atm_rel_cas(&lock->head, (gpr_atm)&lock->tombstone, |
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NO_CONSUMER)) { |
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return; |
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} |
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// TODO(ctiller): consider sleeping
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continue; |
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} else { |
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// skip the tombstone: we'll re-add it later
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lock->tail = next; |
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tail = next; |
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next = (grpc_aelock_qnode *)gpr_atm_acq_load(&tail->next); |
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} |
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} |
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if (next != NULL) { |
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// found a node
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lock->tail = next; |
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tail->action(exec_ctx, tail->arg); |
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gpr_free(tail); |
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} else { |
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// nothing there: might be in an incosistant state
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grpc_aelock_qnode *head = |
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(grpc_aelock_qnode *)gpr_atm_acq_load(&lock->head); |
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if (head != tail) { |
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// non-empty list: spin for a bit
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// TODO(ctiller): consider sleeping?
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continue; |
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} |
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// must have swallowed tombstone above: re-add it
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gpr_atm_no_barrier_store(&lock->tombstone.next, 0); |
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while (!gpr_atm_rel_cas(&lock->head, (gpr_atm)head, |
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(gpr_atm)&lock->tombstone)) { |
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head = (grpc_aelock_qnode *)gpr_atm_acq_load(&lock->head); |
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} |
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gpr_atm_rel_store(&head->next, (gpr_atm)&lock->tombstone); |
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while (gpr_atm_full_fetch_add(&lock->locked, -1) != 1) { |
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gpr_mpscq_node *n; |
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while ((n = gpr_mpscq_pop(&lock->queue)) == NULL) { |
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// TODO(ctiller): find something to fill in the time
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} |
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grpc_aelock_qnode *ln = (grpc_aelock_qnode*)n; |
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ln->action(exec_ctx, ln->arg); |
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gpr_free(ln); |
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} |
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} |
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void grpc_aelock_execute(grpc_exec_ctx *exec_ctx, grpc_aelock *lock, |
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grpc_aelock_action action, void *arg, |
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size_t sizeof_arg) { |
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gpr_atm head; |
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retry_top: |
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head = gpr_atm_acq_load(&lock->head); |
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if (head == NO_CONSUMER) { |
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if (!gpr_atm_rel_cas(&lock->head, NO_CONSUMER, (gpr_atm)&lock->tombstone)) { |
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goto retry_top; |
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} |
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if (gpr_atm_full_fetch_add(&lock->locked, 1) == 0) { |
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action(exec_ctx, arg); |
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finish(exec_ctx, lock); |
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return; // early out
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} |
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grpc_aelock_qnode *n = gpr_malloc(sizeof(*n) + sizeof_arg); |
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n->action = action; |
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if (sizeof_arg > 0) { |
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memcpy(n + 1, arg, sizeof_arg); |
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n->arg = n + 1; |
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} else { |
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n->arg = arg; |
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} |
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gpr_atm_rel_store(&n->next, 0); |
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while (!gpr_atm_rel_cas(&lock->head, head, (gpr_atm)n)) { |
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retry_queue_load: |
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head = gpr_atm_acq_load(&lock->head); |
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if (head == NO_CONSUMER) { |
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if (!gpr_atm_rel_cas(&lock->head, NO_CONSUMER, |
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(gpr_atm)&lock->tombstone)) { |
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goto retry_queue_load; |
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} |
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gpr_free(n); |
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action(exec_ctx, arg); |
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finish(exec_ctx, lock); |
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return; // early out
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grpc_aelock_qnode *n = gpr_malloc(sizeof(*n) + sizeof_arg); |
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n->action = action; |
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if (sizeof_arg > 0) { |
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memcpy(n + 1, arg, sizeof_arg); |
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n->arg = n + 1; |
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} else { |
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n->arg = arg; |
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} |
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gpr_mpscq_push(&lock->queue, &n->mpscq_node); |
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} |
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GPR_ASSERT(gpr_atm_rel_cas(&((grpc_aelock_qnode *)head)->next, 0, (gpr_atm)n)); |
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// gpr_atm_rel_store(&((grpc_aelock_qnode *)head)->next, (gpr_atm)n);
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} |
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Craig Tiller
9 years ago