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/*
* Copyright 2004 The WebRTC 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 in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include <algorithm>
#include "webrtc/base/taskrunner.h"
#include "webrtc/base/common.h"
#include "webrtc/base/scoped_ptr.h"
#include "webrtc/base/task.h"
#include "webrtc/base/logging.h"
namespace rtc {
TaskRunner::TaskRunner()
: TaskParent(this),
next_timeout_task_(NULL),
tasks_running_(false)
#ifdef _DEBUG
, abort_count_(0),
deleting_task_(NULL)
#endif
{
}
TaskRunner::~TaskRunner() {
// this kills and deletes children silently!
AbortAllChildren();
InternalRunTasks(true);
}
void TaskRunner::StartTask(Task * task) {
tasks_.push_back(task);
// the task we just started could be about to timeout --
// make sure our "next timeout task" is correct
UpdateTaskTimeout(task, 0);
WakeTasks();
}
void TaskRunner::RunTasks() {
InternalRunTasks(false);
}
void TaskRunner::InternalRunTasks(bool in_destructor) {
// This shouldn't run while an abort is happening.
// If that occurs, then tasks may be deleted in this method,
// but pointers to them will still be in the
// "ChildSet copy" in TaskParent::AbortAllChildren.
// Subsequent use of those task may cause data corruption or crashes.
ASSERT(!abort_count_);
// Running continues until all tasks are Blocked (ok for a small # of tasks)
if (tasks_running_) {
return; // don't reenter
}
tasks_running_ = true;
int64_t previous_timeout_time = next_task_timeout();
int did_run = true;
while (did_run) {
did_run = false;
// use indexing instead of iterators because tasks_ may grow
for (size_t i = 0; i < tasks_.size(); ++i) {
while (!tasks_[i]->Blocked()) {
tasks_[i]->Step();
did_run = true;
}
}
}
// Tasks are deleted when running has paused
bool need_timeout_recalc = false;
for (size_t i = 0; i < tasks_.size(); ++i) {
if (tasks_[i]->IsDone()) {
Task* task = tasks_[i];
if (next_timeout_task_ &&
task->unique_id() == next_timeout_task_->unique_id()) {
next_timeout_task_ = NULL;
need_timeout_recalc = true;
}
#ifdef _DEBUG
deleting_task_ = task;
#endif
delete task;
#ifdef _DEBUG
deleting_task_ = NULL;
#endif
tasks_[i] = NULL;
}
}
// Finally, remove nulls
std::vector<Task *>::iterator it;
it = std::remove(tasks_.begin(),
tasks_.end(),
reinterpret_cast<Task *>(NULL));
tasks_.erase(it, tasks_.end());
if (need_timeout_recalc)
RecalcNextTimeout(NULL);
// Make sure that adjustments are done to account
// for any timeout changes (but don't call this
// while being destroyed since it calls a pure virtual function).
if (!in_destructor)
CheckForTimeoutChange(previous_timeout_time);
tasks_running_ = false;
}
void TaskRunner::PollTasks() {
// see if our "next potentially timed-out task" has indeed timed out.
// If it has, wake it up, then queue up the next task in line
// Repeat while we have new timed-out tasks.
// TODO: We need to guard against WakeTasks not updating
// next_timeout_task_. Maybe also add documentation in the header file once
// we understand this code better.
Task* old_timeout_task = NULL;
while (next_timeout_task_ &&
old_timeout_task != next_timeout_task_ &&
next_timeout_task_->TimedOut()) {
old_timeout_task = next_timeout_task_;
next_timeout_task_->Wake();
WakeTasks();
}
}
int64_t TaskRunner::next_task_timeout() const {
if (next_timeout_task_) {
return next_timeout_task_->timeout_time();
}
return 0;
}
// this function gets called frequently -- when each task changes
// state to something other than DONE, ERROR or BLOCKED, it calls
// ResetTimeout(), which will call this function to make sure that
// the next timeout-able task hasn't changed. The logic in this function
// prevents RecalcNextTimeout() from getting called in most cases,
// effectively making the task scheduler O-1 instead of O-N
void TaskRunner::UpdateTaskTimeout(Task* task,
int64_t previous_task_timeout_time) {
ASSERT(task != NULL);
int64_t previous_timeout_time = next_task_timeout();
bool task_is_timeout_task = next_timeout_task_ != NULL &&
task->unique_id() == next_timeout_task_->unique_id();
if (task_is_timeout_task) {
previous_timeout_time = previous_task_timeout_time;
}
// if the relevant task has a timeout, then
// check to see if it's closer than the current
// "about to timeout" task
if (task->timeout_time()) {
if (next_timeout_task_ == NULL ||
(task->timeout_time() <= next_timeout_task_->timeout_time())) {
next_timeout_task_ = task;
}
} else if (task_is_timeout_task) {
// otherwise, if the task doesn't have a timeout,
// and it used to be our "about to timeout" task,
// walk through all the tasks looking for the real
// "about to timeout" task
RecalcNextTimeout(task);
}
// Note when task_running_, then the running routine
// (TaskRunner::InternalRunTasks) is responsible for calling
// CheckForTimeoutChange.
if (!tasks_running_) {
CheckForTimeoutChange(previous_timeout_time);
}
}
void TaskRunner::RecalcNextTimeout(Task *exclude_task) {
// walk through all the tasks looking for the one
// which satisfies the following:
// it's not finished already
// we're not excluding it
// it has the closest timeout time
int64_t next_timeout_time = 0;
next_timeout_task_ = NULL;
for (size_t i = 0; i < tasks_.size(); ++i) {
Task *task = tasks_[i];
// if the task isn't complete, and it actually has a timeout time
if (!task->IsDone() && (task->timeout_time() > 0))
// if it doesn't match our "exclude" task
if (exclude_task == NULL ||
exclude_task->unique_id() != task->unique_id())
// if its timeout time is sooner than our current timeout time
if (next_timeout_time == 0 ||
task->timeout_time() <= next_timeout_time) {
// set this task as our next-to-timeout
next_timeout_time = task->timeout_time();
next_timeout_task_ = task;
}
}
}
void TaskRunner::CheckForTimeoutChange(int64_t previous_timeout_time) {
int64_t next_timeout = next_task_timeout();
bool timeout_change = (previous_timeout_time == 0 && next_timeout != 0) ||
next_timeout < previous_timeout_time ||
(previous_timeout_time <= CurrentTime() &&
previous_timeout_time != next_timeout);
if (timeout_change) {
OnTimeoutChange();
}
}
} // namespace rtc
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