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// Copyright 2015 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/cancelable-task.h"
#include "src/base/platform/platform.h"
#include "src/isolate.h"
namespace v8 {
namespace internal {
Cancelable::~Cancelable() {
// The following check is needed to avoid calling an already terminated
// manager object. This happens when the manager cancels all pending tasks
// in {CancelAndWait} only before destroying the manager object.
Status previous;
if (TryRun(&previous) || previous == kRunning) {
parent_->RemoveFinishedTask(id_);
}
}
CancelableTaskManager::CancelableTaskManager()
: task_id_counter_(kInvalidTaskId), canceled_(false) {}
CancelableTaskManager::~CancelableTaskManager() {
// It is required that {CancelAndWait} is called before the manager object is
// destroyed. This guarantees that all tasks managed by this
// {CancelableTaskManager} are either canceled or finished their execution
// when the {CancelableTaskManager} dies.
CHECK(canceled_);
}
CancelableTaskManager::Id CancelableTaskManager::Register(Cancelable* task) {
base::MutexGuard guard(&mutex_);
if (canceled_) {
// The CancelableTaskManager has already been canceled. Therefore we mark
// the new task immediately as canceled so that it does not get executed.
task->Cancel();
return kInvalidTaskId;
}
CancelableTaskManager::Id id = ++task_id_counter_;
// Id overflows are not supported.
CHECK_NE(kInvalidTaskId, id);
CHECK(!canceled_);
cancelable_tasks_[id] = task;
return id;
}
void CancelableTaskManager::RemoveFinishedTask(CancelableTaskManager::Id id) {
CHECK_NE(kInvalidTaskId, id);
base::MutexGuard guard(&mutex_);
size_t removed = cancelable_tasks_.erase(id);
USE(removed);
DCHECK_NE(0u, removed);
cancelable_tasks_barrier_.NotifyOne();
}
TryAbortResult CancelableTaskManager::TryAbort(CancelableTaskManager::Id id) {
CHECK_NE(kInvalidTaskId, id);
base::MutexGuard guard(&mutex_);
auto entry = cancelable_tasks_.find(id);
if (entry != cancelable_tasks_.end()) {
Cancelable* value = entry->second;
if (value->Cancel()) {
// Cannot call RemoveFinishedTask here because of recursive locking.
cancelable_tasks_.erase(entry);
cancelable_tasks_barrier_.NotifyOne();
return TryAbortResult::kTaskAborted;
} else {
return TryAbortResult::kTaskRunning;
}
}
return TryAbortResult::kTaskRemoved;
}
void CancelableTaskManager::CancelAndWait() {
// Clean up all cancelable fore- and background tasks. Tasks are canceled on
// the way if possible, i.e., if they have not started yet. After each round
// of canceling we wait for the background tasks that have already been
// started.
base::MutexGuard guard(&mutex_);
canceled_ = true;
// Cancelable tasks could be running or could potentially register new
// tasks, requiring a loop here.
while (!cancelable_tasks_.empty()) {
for (auto it = cancelable_tasks_.begin(); it != cancelable_tasks_.end();) {
auto current = it;
// We need to get to the next element before erasing the current.
++it;
if (current->second->Cancel()) {
cancelable_tasks_.erase(current);
}
}
// Wait for already running background tasks.
if (!cancelable_tasks_.empty()) {
cancelable_tasks_barrier_.Wait(&mutex_);
}
}
}
TryAbortResult CancelableTaskManager::TryAbortAll() {
// Clean up all cancelable fore- and background tasks. Tasks are canceled on
// the way if possible, i.e., if they have not started yet.
base::MutexGuard guard(&mutex_);
if (cancelable_tasks_.empty()) return TryAbortResult::kTaskRemoved;
for (auto it = cancelable_tasks_.begin(); it != cancelable_tasks_.end();) {
if (it->second->Cancel()) {
it = cancelable_tasks_.erase(it);
} else {
++it;
}
}
return cancelable_tasks_.empty() ? TryAbortResult::kTaskAborted
: TryAbortResult::kTaskRunning;
}
CancelableTask::CancelableTask(Isolate* isolate)
: CancelableTask(isolate->cancelable_task_manager()) {}
CancelableTask::CancelableTask(CancelableTaskManager* manager)
: Cancelable(manager) {}
CancelableIdleTask::CancelableIdleTask(Isolate* isolate)
: CancelableIdleTask(isolate->cancelable_task_manager()) {}
CancelableIdleTask::CancelableIdleTask(CancelableTaskManager* manager)
: Cancelable(manager) {}
} // namespace internal
} // namespace v8
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