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/*
*
* Copyright 2017 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/iomgr/call_combiner.h"
#include <inttypes.h>
#include <grpc/support/log.h>
grpc_tracer_flag grpc_call_combiner_trace =
GRPC_TRACER_INITIALIZER(false, "call_combiner");
static grpc_error* decode_cancel_state_error(gpr_atm cancel_state) {
if (cancel_state & 1) {
return (grpc_error*)(cancel_state & ~(gpr_atm)1);
}
return GRPC_ERROR_NONE;
}
static gpr_atm encode_cancel_state_error(grpc_error* error) {
return (gpr_atm)1 | (gpr_atm)error;
}
void grpc_call_combiner_init(grpc_call_combiner* call_combiner) {
gpr_mpscq_init(&call_combiner->queue);
}
void grpc_call_combiner_destroy(grpc_call_combiner* call_combiner) {
gpr_mpscq_destroy(&call_combiner->queue);
GRPC_ERROR_UNREF(decode_cancel_state_error(call_combiner->cancel_state));
}
#ifndef NDEBUG
#define DEBUG_ARGS , const char *file, int line
#define DEBUG_FMT_STR "%s:%d: "
#define DEBUG_FMT_ARGS , file, line
#else
#define DEBUG_ARGS
#define DEBUG_FMT_STR
#define DEBUG_FMT_ARGS
#endif
void grpc_call_combiner_start(grpc_exec_ctx* exec_ctx,
grpc_call_combiner* call_combiner,
grpc_closure* closure,
grpc_error* error DEBUG_ARGS,
const char* reason) {
if (GRPC_TRACER_ON(grpc_call_combiner_trace)) {
gpr_log(GPR_DEBUG,
"==> grpc_call_combiner_start() [%p] closure=%p [" DEBUG_FMT_STR
"%s] error=%s",
call_combiner, closure DEBUG_FMT_ARGS, reason,
grpc_error_string(error));
}
size_t prev_size =
(size_t)gpr_atm_full_fetch_add(&call_combiner->size, (gpr_atm)1);
if (GRPC_TRACER_ON(grpc_call_combiner_trace)) {
gpr_log(GPR_DEBUG, " size: %" PRIdPTR " -> %" PRIdPTR, prev_size,
prev_size + 1);
}
if (prev_size == 0) {
if (GRPC_TRACER_ON(grpc_call_combiner_trace)) {
gpr_log(GPR_DEBUG, " EXECUTING IMMEDIATELY");
}
// Queue was empty, so execute this closure immediately.
GRPC_CLOSURE_SCHED(exec_ctx, closure, error);
} else {
if (GRPC_TRACER_ON(grpc_call_combiner_trace)) {
gpr_log(GPR_INFO, " QUEUING");
}
// Queue was not empty, so add closure to queue.
closure->error_data.error = error;
gpr_mpscq_push(&call_combiner->queue, (gpr_mpscq_node*)closure);
}
}
void grpc_call_combiner_stop(grpc_exec_ctx* exec_ctx,
grpc_call_combiner* call_combiner DEBUG_ARGS,
const char* reason) {
if (GRPC_TRACER_ON(grpc_call_combiner_trace)) {
gpr_log(GPR_DEBUG,
"==> grpc_call_combiner_stop() [%p] [" DEBUG_FMT_STR "%s]",
call_combiner DEBUG_FMT_ARGS, reason);
}
size_t prev_size =
(size_t)gpr_atm_full_fetch_add(&call_combiner->size, (gpr_atm)-1);
if (GRPC_TRACER_ON(grpc_call_combiner_trace)) {
gpr_log(GPR_DEBUG, " size: %" PRIdPTR " -> %" PRIdPTR, prev_size,
prev_size - 1);
}
GPR_ASSERT(prev_size >= 1);
if (prev_size > 1) {
while (true) {
if (GRPC_TRACER_ON(grpc_call_combiner_trace)) {
gpr_log(GPR_DEBUG, " checking queue");
}
bool empty;
grpc_closure* closure = (grpc_closure*)gpr_mpscq_pop_and_check_end(
&call_combiner->queue, &empty);
if (closure == NULL) {
// This can happen either due to a race condition within the mpscq
// code or because of a race with grpc_call_combiner_start().
if (GRPC_TRACER_ON(grpc_call_combiner_trace)) {
gpr_log(GPR_DEBUG, " queue returned no result; checking again");
}
continue;
}
if (GRPC_TRACER_ON(grpc_call_combiner_trace)) {
gpr_log(GPR_DEBUG, " EXECUTING FROM QUEUE: closure=%p error=%s",
closure, grpc_error_string(closure->error_data.error));
}
GRPC_CLOSURE_SCHED(exec_ctx, closure, closure->error_data.error);
break;
}
} else if (GRPC_TRACER_ON(grpc_call_combiner_trace)) {
gpr_log(GPR_DEBUG, " queue empty");
}
}
void grpc_call_combiner_set_notify_on_cancel(grpc_exec_ctx* exec_ctx,
grpc_call_combiner* call_combiner,
grpc_closure* closure) {
while (true) {
// Decode original state.
gpr_atm original_state = gpr_atm_acq_load(&call_combiner->cancel_state);
grpc_error* original_error = decode_cancel_state_error(original_state);
// If error is set, invoke the cancellation closure immediately.
// Otherwise, store the new closure.
if (original_error != GRPC_ERROR_NONE) {
if (GRPC_TRACER_ON(grpc_call_combiner_trace)) {
gpr_log(GPR_DEBUG,
"call_combiner=%p: scheduling notify_on_cancel callback=%p "
"for pre-existing cancellation",
call_combiner, closure);
}
GRPC_CLOSURE_SCHED(exec_ctx, closure, GRPC_ERROR_REF(original_error));
break;
} else {
if (gpr_atm_full_cas(&call_combiner->cancel_state, original_state,
(gpr_atm)closure)) {
if (GRPC_TRACER_ON(grpc_call_combiner_trace)) {
gpr_log(GPR_DEBUG, "call_combiner=%p: setting notify_on_cancel=%p",
call_combiner, closure);
}
// If we replaced an earlier closure, invoke the original
// closure with GRPC_ERROR_NONE. This allows callers to clean
// up any resources they may be holding for the callback.
if (original_state != 0) {
closure = (grpc_closure*)original_state;
if (GRPC_TRACER_ON(grpc_call_combiner_trace)) {
gpr_log(GPR_DEBUG,
"call_combiner=%p: scheduling old cancel callback=%p",
call_combiner, closure);
}
GRPC_CLOSURE_SCHED(exec_ctx, closure, GRPC_ERROR_NONE);
}
break;
}
}
// cas failed, try again.
}
}
void grpc_call_combiner_cancel(grpc_exec_ctx* exec_ctx,
grpc_call_combiner* call_combiner,
grpc_error* error) {
while (true) {
gpr_atm original_state = gpr_atm_acq_load(&call_combiner->cancel_state);
grpc_error* original_error = decode_cancel_state_error(original_state);
if (original_error != GRPC_ERROR_NONE) {
GRPC_ERROR_UNREF(error);
break;
}
if (gpr_atm_full_cas(&call_combiner->cancel_state, original_state,
encode_cancel_state_error(error))) {
if (original_state != 0) {
grpc_closure* notify_on_cancel = (grpc_closure*)original_state;
if (GRPC_TRACER_ON(grpc_call_combiner_trace)) {
gpr_log(GPR_DEBUG,
"call_combiner=%p: scheduling notify_on_cancel callback=%p",
call_combiner, notify_on_cancel);
}
GRPC_CLOSURE_SCHED(exec_ctx, notify_on_cancel, GRPC_ERROR_REF(error));
}
break;
}
// cas failed, try again.
}
}
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