Move some misc thread-related stuff from base to base/thread and into the bas...

base/threading/worker_pool_posix.cc

+// Copyright (c) 2010 The Chromium 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 "base/threading/worker_pool_posix.h"
+
+#include "base/lazy_instance.h"
+#include "base/logging.h"
+#include "base/platform_thread.h"
+#include "base/ref_counted.h"
+#include "base/stringprintf.h"
+#include "base/task.h"
+#include "base/threading/worker_pool.h"
+
+namespace base {
+
+namespace {
+
+const int kIdleSecondsBeforeExit = 10 * 60;
+// A stack size of 64 KB is too small for the CERT_PKIXVerifyCert
+// function of NSS because of NSS bug 439169.
+const int kWorkerThreadStackSize = 128 * 1024;
+
+class WorkerPoolImpl {
+ public:
+  WorkerPoolImpl();
+  ~WorkerPoolImpl();
+
+  void PostTask(const tracked_objects::Location& from_here, Task* task,
+                bool task_is_slow);
+
+ private:
+  scoped_refptr<base::PosixDynamicThreadPool> pool_;
+};
+
+WorkerPoolImpl::WorkerPoolImpl()
+    : pool_(new base::PosixDynamicThreadPool("WorkerPool",
+                                             kIdleSecondsBeforeExit)) {
+}
+
+WorkerPoolImpl::~WorkerPoolImpl() {
+  pool_->Terminate();
+}
+
+void WorkerPoolImpl::PostTask(const tracked_objects::Location& from_here,
+                              Task* task, bool task_is_slow) {
+  task->SetBirthPlace(from_here);
+  pool_->PostTask(task);
+}
+
+base::LazyInstance<WorkerPoolImpl> g_lazy_worker_pool(base::LINKER_INITIALIZED);
+
+class WorkerThread : public PlatformThread::Delegate {
+ public:
+  WorkerThread(const std::string& name_prefix, int idle_seconds_before_exit,
+               base::PosixDynamicThreadPool* pool)
+      : name_prefix_(name_prefix),
+        idle_seconds_before_exit_(idle_seconds_before_exit),
+        pool_(pool) {}
+
+  virtual void ThreadMain();
+
+ private:
+  const std::string name_prefix_;
+  const int idle_seconds_before_exit_;
+  scoped_refptr<base::PosixDynamicThreadPool> pool_;
+
+  DISALLOW_COPY_AND_ASSIGN(WorkerThread);
+};
+
+void WorkerThread::ThreadMain() {
+  const std::string name = base::StringPrintf(
+      "%s/%d", name_prefix_.c_str(), PlatformThread::CurrentId());
+  PlatformThread::SetName(name.c_str());
+
+  for (;;) {
+    Task* task = pool_->WaitForTask();
+    if (!task)
+      break;
+    task->Run();
+    delete task;
+  }
+
+  // The WorkerThread is non-joinable, so it deletes itself.
+  delete this;
+}
+
+}  // namespace
+
+bool WorkerPool::PostTask(const tracked_objects::Location& from_here,
+                          Task* task, bool task_is_slow) {
+  g_lazy_worker_pool.Pointer()->PostTask(from_here, task, task_is_slow);
+  return true;
+}
+
+PosixDynamicThreadPool::PosixDynamicThreadPool(
+    const std::string& name_prefix,
+    int idle_seconds_before_exit)
+    : name_prefix_(name_prefix),
+      idle_seconds_before_exit_(idle_seconds_before_exit),
+      tasks_available_cv_(&lock_),
+      num_idle_threads_(0),
+      terminated_(false),
+      num_idle_threads_cv_(NULL) {}
+
+PosixDynamicThreadPool::~PosixDynamicThreadPool() {
+  while (!tasks_.empty()) {
+    Task* task = tasks_.front();
+    tasks_.pop();
+    delete task;
+  }
+}
+
+void PosixDynamicThreadPool::Terminate() {
+  {
+    AutoLock locked(lock_);
+    DCHECK(!terminated_) << "Thread pool is already terminated.";
+    terminated_ = true;
+  }
+  tasks_available_cv_.Broadcast();
+}
+
+void PosixDynamicThreadPool::PostTask(Task* task) {
+  AutoLock locked(lock_);
+  DCHECK(!terminated_) <<
+      "This thread pool is already terminated.  Do not post new tasks.";
+
+  tasks_.push(task);
+
+  // We have enough worker threads.
+  if (static_cast<size_t>(num_idle_threads_) >= tasks_.size()) {
+    tasks_available_cv_.Signal();
+  } else {
+    // The new PlatformThread will take ownership of the WorkerThread object,
+    // which will delete itself on exit.
+    WorkerThread* worker =
+        new WorkerThread(name_prefix_, idle_seconds_before_exit_, this);
+    PlatformThread::CreateNonJoinable(kWorkerThreadStackSize, worker);
+  }
+}
+
+Task* PosixDynamicThreadPool::WaitForTask() {
+  AutoLock locked(lock_);
+
+  if (terminated_)
+    return NULL;
+
+  if (tasks_.empty()) {  // No work available, wait for work.
+    num_idle_threads_++;
+    if (num_idle_threads_cv_.get())
+      num_idle_threads_cv_->Signal();
+    tasks_available_cv_.TimedWait(
+        TimeDelta::FromSeconds(kIdleSecondsBeforeExit));
+    num_idle_threads_--;
+    if (num_idle_threads_cv_.get())
+      num_idle_threads_cv_->Signal();
+    if (tasks_.empty()) {
+      // We waited for work, but there's still no work.  Return NULL to signal
+      // the thread to terminate.
+      return NULL;
+    }
+  }
+
+  Task* task = tasks_.front();
+  tasks_.pop();
+  return task;
+}
+
+}  // namespace base