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// 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/ref_counted.h"
#include "base/stringprintf.h"
#include "base/task.h"
#include "base/threading/platform_thread.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
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