henrike@webrtc.org | f7795df | 2014-05-13 18:00:26 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 2004 The WebRTC Project Authors. All rights reserved. |
| 3 | * |
| 4 | * Use of this source code is governed by a BSD-style license |
| 5 | * that can be found in the LICENSE file in the root of the source |
| 6 | * tree. An additional intellectual property rights grant can be found |
| 7 | * in the file PATENTS. All contributing project authors may |
| 8 | * be found in the AUTHORS file in the root of the source tree. |
| 9 | */ |
| 10 | |
| 11 | #include <algorithm> |
| 12 | |
| 13 | #include "webrtc/base/taskrunner.h" |
| 14 | |
| 15 | #include "webrtc/base/common.h" |
| 16 | #include "webrtc/base/scoped_ptr.h" |
| 17 | #include "webrtc/base/task.h" |
| 18 | #include "webrtc/base/logging.h" |
| 19 | |
| 20 | namespace rtc { |
| 21 | |
| 22 | TaskRunner::TaskRunner() |
| 23 | : TaskParent(this), |
| 24 | next_timeout_task_(NULL), |
| 25 | tasks_running_(false) |
| 26 | #ifdef _DEBUG |
| 27 | , abort_count_(0), |
| 28 | deleting_task_(NULL) |
| 29 | #endif |
| 30 | { |
| 31 | } |
| 32 | |
| 33 | TaskRunner::~TaskRunner() { |
| 34 | // this kills and deletes children silently! |
| 35 | AbortAllChildren(); |
| 36 | InternalRunTasks(true); |
| 37 | } |
| 38 | |
| 39 | void TaskRunner::StartTask(Task * task) { |
| 40 | tasks_.push_back(task); |
| 41 | |
| 42 | // the task we just started could be about to timeout -- |
| 43 | // make sure our "next timeout task" is correct |
| 44 | UpdateTaskTimeout(task, 0); |
| 45 | |
| 46 | WakeTasks(); |
| 47 | } |
| 48 | |
| 49 | void TaskRunner::RunTasks() { |
| 50 | InternalRunTasks(false); |
| 51 | } |
| 52 | |
| 53 | void TaskRunner::InternalRunTasks(bool in_destructor) { |
| 54 | // This shouldn't run while an abort is happening. |
| 55 | // If that occurs, then tasks may be deleted in this method, |
| 56 | // but pointers to them will still be in the |
| 57 | // "ChildSet copy" in TaskParent::AbortAllChildren. |
| 58 | // Subsequent use of those task may cause data corruption or crashes. |
| 59 | ASSERT(!abort_count_); |
| 60 | // Running continues until all tasks are Blocked (ok for a small # of tasks) |
| 61 | if (tasks_running_) { |
| 62 | return; // don't reenter |
| 63 | } |
| 64 | |
| 65 | tasks_running_ = true; |
| 66 | |
| 67 | int64 previous_timeout_time = next_task_timeout(); |
| 68 | |
| 69 | int did_run = true; |
| 70 | while (did_run) { |
| 71 | did_run = false; |
| 72 | // use indexing instead of iterators because tasks_ may grow |
| 73 | for (size_t i = 0; i < tasks_.size(); ++i) { |
| 74 | while (!tasks_[i]->Blocked()) { |
| 75 | tasks_[i]->Step(); |
| 76 | did_run = true; |
| 77 | } |
| 78 | } |
| 79 | } |
| 80 | // Tasks are deleted when running has paused |
| 81 | bool need_timeout_recalc = false; |
| 82 | for (size_t i = 0; i < tasks_.size(); ++i) { |
| 83 | if (tasks_[i]->IsDone()) { |
| 84 | Task* task = tasks_[i]; |
| 85 | if (next_timeout_task_ && |
| 86 | task->unique_id() == next_timeout_task_->unique_id()) { |
| 87 | next_timeout_task_ = NULL; |
| 88 | need_timeout_recalc = true; |
| 89 | } |
| 90 | |
| 91 | #ifdef _DEBUG |
| 92 | deleting_task_ = task; |
| 93 | #endif |
| 94 | delete task; |
| 95 | #ifdef _DEBUG |
| 96 | deleting_task_ = NULL; |
| 97 | #endif |
| 98 | tasks_[i] = NULL; |
| 99 | } |
| 100 | } |
| 101 | // Finally, remove nulls |
| 102 | std::vector<Task *>::iterator it; |
| 103 | it = std::remove(tasks_.begin(), |
| 104 | tasks_.end(), |
| 105 | reinterpret_cast<Task *>(NULL)); |
| 106 | |
| 107 | tasks_.erase(it, tasks_.end()); |
| 108 | |
| 109 | if (need_timeout_recalc) |
| 110 | RecalcNextTimeout(NULL); |
| 111 | |
| 112 | // Make sure that adjustments are done to account |
| 113 | // for any timeout changes (but don't call this |
| 114 | // while being destroyed since it calls a pure virtual function). |
| 115 | if (!in_destructor) |
| 116 | CheckForTimeoutChange(previous_timeout_time); |
| 117 | |
| 118 | tasks_running_ = false; |
| 119 | } |
| 120 | |
| 121 | void TaskRunner::PollTasks() { |
| 122 | // see if our "next potentially timed-out task" has indeed timed out. |
| 123 | // If it has, wake it up, then queue up the next task in line |
| 124 | // Repeat while we have new timed-out tasks. |
| 125 | // TODO: We need to guard against WakeTasks not updating |
| 126 | // next_timeout_task_. Maybe also add documentation in the header file once |
| 127 | // we understand this code better. |
| 128 | Task* old_timeout_task = NULL; |
| 129 | while (next_timeout_task_ && |
| 130 | old_timeout_task != next_timeout_task_ && |
| 131 | next_timeout_task_->TimedOut()) { |
| 132 | old_timeout_task = next_timeout_task_; |
| 133 | next_timeout_task_->Wake(); |
| 134 | WakeTasks(); |
| 135 | } |
| 136 | } |
| 137 | |
| 138 | int64 TaskRunner::next_task_timeout() const { |
| 139 | if (next_timeout_task_) { |
| 140 | return next_timeout_task_->timeout_time(); |
| 141 | } |
| 142 | return 0; |
| 143 | } |
| 144 | |
| 145 | // this function gets called frequently -- when each task changes |
| 146 | // state to something other than DONE, ERROR or BLOCKED, it calls |
| 147 | // ResetTimeout(), which will call this function to make sure that |
| 148 | // the next timeout-able task hasn't changed. The logic in this function |
| 149 | // prevents RecalcNextTimeout() from getting called in most cases, |
| 150 | // effectively making the task scheduler O-1 instead of O-N |
| 151 | |
| 152 | void TaskRunner::UpdateTaskTimeout(Task* task, |
| 153 | int64 previous_task_timeout_time) { |
| 154 | ASSERT(task != NULL); |
| 155 | int64 previous_timeout_time = next_task_timeout(); |
| 156 | bool task_is_timeout_task = next_timeout_task_ != NULL && |
| 157 | task->unique_id() == next_timeout_task_->unique_id(); |
| 158 | if (task_is_timeout_task) { |
| 159 | previous_timeout_time = previous_task_timeout_time; |
| 160 | } |
| 161 | |
| 162 | // if the relevant task has a timeout, then |
| 163 | // check to see if it's closer than the current |
| 164 | // "about to timeout" task |
| 165 | if (task->timeout_time()) { |
| 166 | if (next_timeout_task_ == NULL || |
| 167 | (task->timeout_time() <= next_timeout_task_->timeout_time())) { |
| 168 | next_timeout_task_ = task; |
| 169 | } |
| 170 | } else if (task_is_timeout_task) { |
| 171 | // otherwise, if the task doesn't have a timeout, |
| 172 | // and it used to be our "about to timeout" task, |
| 173 | // walk through all the tasks looking for the real |
| 174 | // "about to timeout" task |
| 175 | RecalcNextTimeout(task); |
| 176 | } |
| 177 | |
| 178 | // Note when task_running_, then the running routine |
| 179 | // (TaskRunner::InternalRunTasks) is responsible for calling |
| 180 | // CheckForTimeoutChange. |
| 181 | if (!tasks_running_) { |
| 182 | CheckForTimeoutChange(previous_timeout_time); |
| 183 | } |
| 184 | } |
| 185 | |
| 186 | void TaskRunner::RecalcNextTimeout(Task *exclude_task) { |
| 187 | // walk through all the tasks looking for the one |
| 188 | // which satisfies the following: |
| 189 | // it's not finished already |
| 190 | // we're not excluding it |
| 191 | // it has the closest timeout time |
| 192 | |
| 193 | int64 next_timeout_time = 0; |
| 194 | next_timeout_task_ = NULL; |
| 195 | |
| 196 | for (size_t i = 0; i < tasks_.size(); ++i) { |
| 197 | Task *task = tasks_[i]; |
| 198 | // if the task isn't complete, and it actually has a timeout time |
| 199 | if (!task->IsDone() && (task->timeout_time() > 0)) |
| 200 | // if it doesn't match our "exclude" task |
| 201 | if (exclude_task == NULL || |
| 202 | exclude_task->unique_id() != task->unique_id()) |
| 203 | // if its timeout time is sooner than our current timeout time |
| 204 | if (next_timeout_time == 0 || |
| 205 | task->timeout_time() <= next_timeout_time) { |
| 206 | // set this task as our next-to-timeout |
| 207 | next_timeout_time = task->timeout_time(); |
| 208 | next_timeout_task_ = task; |
| 209 | } |
| 210 | } |
| 211 | } |
| 212 | |
| 213 | void TaskRunner::CheckForTimeoutChange(int64 previous_timeout_time) { |
| 214 | int64 next_timeout = next_task_timeout(); |
| 215 | bool timeout_change = (previous_timeout_time == 0 && next_timeout != 0) || |
| 216 | next_timeout < previous_timeout_time || |
| 217 | (previous_timeout_time <= CurrentTime() && |
| 218 | previous_timeout_time != next_timeout); |
| 219 | if (timeout_change) { |
| 220 | OnTimeoutChange(); |
| 221 | } |
| 222 | } |
| 223 | |
| 224 | } // namespace rtc |