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/*
* Copyright (C) 2012 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "thread_pool.h"
#include <sys/mman.h>
#include <sys/resource.h>
#include <sys/time.h>
#include <pthread.h>
#include <android-base/logging.h>
#include <android-base/stringprintf.h>
#include "base/bit_utils.h"
#include "base/casts.h"
#include "base/stl_util.h"
#include "base/time_utils.h"
#include "base/utils.h"
#include "runtime.h"
#include "thread-current-inl.h"
namespace art {
using android::base::StringPrintf;
static constexpr bool kMeasureWaitTime = false;
ThreadPoolWorker::ThreadPoolWorker(ThreadPool* thread_pool, const std::string& name,
size_t stack_size)
: thread_pool_(thread_pool),
name_(name) {
// Add an inaccessible page to catch stack overflow.
stack_size += kPageSize;
std::string error_msg;
stack_ = MemMap::MapAnonymous(name.c_str(),
stack_size,
PROT_READ | PROT_WRITE,
/*low_4gb=*/ false,
&error_msg);
CHECK(stack_.IsValid()) << error_msg;
CHECK_ALIGNED(stack_.Begin(), kPageSize);
CheckedCall(mprotect,
"mprotect bottom page of thread pool worker stack",
stack_.Begin(),
kPageSize,
PROT_NONE);
const char* reason = "new thread pool worker thread";
pthread_attr_t attr;
CHECK_PTHREAD_CALL(pthread_attr_init, (&attr), reason);
CHECK_PTHREAD_CALL(pthread_attr_setstack, (&attr, stack_.Begin(), stack_.Size()), reason);
CHECK_PTHREAD_CALL(pthread_create, (&pthread_, &attr, &Callback, this), reason);
CHECK_PTHREAD_CALL(pthread_attr_destroy, (&attr), reason);
}
ThreadPoolWorker::~ThreadPoolWorker() {
CHECK_PTHREAD_CALL(pthread_join, (pthread_, nullptr), "thread pool worker shutdown");
}
void ThreadPoolWorker::SetPthreadPriority(int priority) {
CHECK_GE(priority, PRIO_MIN);
CHECK_LE(priority, PRIO_MAX);
#if defined(ART_TARGET_ANDROID)
int result = setpriority(PRIO_PROCESS, pthread_gettid_np(pthread_), priority);
if (result != 0) {
PLOG(ERROR) << "Failed to setpriority to :" << priority;
}
#else
UNUSED(priority);
#endif
}
void ThreadPoolWorker::Run() {
Thread* self = Thread::Current();
Task* task = nullptr;
thread_pool_->creation_barier_.Pass(self);
while ((task = thread_pool_->GetTask(self)) != nullptr) {
task->Run(self);
task->Finalize();
}
}
void* ThreadPoolWorker::Callback(void* arg) {
ThreadPoolWorker* worker = reinterpret_cast<ThreadPoolWorker*>(arg);
Runtime* runtime = Runtime::Current();
CHECK(runtime->AttachCurrentThread(
worker->name_.c_str(),
true,
// Thread-groups are only tracked by the peer j.l.Thread objects. If we aren't creating peers
// we don't need to specify the thread group. We want to place these threads in the System
// thread group because that thread group is where important threads that debuggers and
// similar tools should not mess with are placed. As this is an internal-thread-pool we might
// rely on being able to (for example) wait for all threads to finish some task. If debuggers
// are suspending these threads that might not be possible.
worker->thread_pool_->create_peers_ ? runtime->GetSystemThreadGroup() : nullptr,
worker->thread_pool_->create_peers_));
worker->thread_ = Thread::Current();
// Mark thread pool workers as runtime-threads.
worker->thread_->SetIsRuntimeThread(true);
// Do work until its time to shut down.
worker->Run();
runtime->DetachCurrentThread();
return nullptr;
}
void ThreadPool::AddTask(Thread* self, Task* task) {
MutexLock mu(self, task_queue_lock_);
tasks_.push_back(task);
// If we have any waiters, signal one.
if (started_ && waiting_count_ != 0) {
task_queue_condition_.Signal(self);
}
}
void ThreadPool::RemoveAllTasks(Thread* self) {
// The ThreadPool is responsible for calling Finalize (which usually delete
// the task memory) on all the tasks.
Task* task = nullptr;
while ((task = TryGetTask(self)) != nullptr) {
task->Finalize();
}
MutexLock mu(self, task_queue_lock_);
tasks_.clear();
}
ThreadPool::ThreadPool(const char* name,
size_t num_threads,
bool create_peers,
size_t worker_stack_size)
: name_(name),
task_queue_lock_("task queue lock"),
task_queue_condition_("task queue condition", task_queue_lock_),
completion_condition_("task completion condition", task_queue_lock_),
started_(false),
shutting_down_(false),
waiting_count_(0),
start_time_(0),
total_wait_time_(0),
creation_barier_(0),
max_active_workers_(num_threads),
create_peers_(create_peers),
worker_stack_size_(worker_stack_size) {
CreateThreads();
}
void ThreadPool::CreateThreads() {
CHECK(threads_.empty());
Thread* self = Thread::Current();
{
MutexLock mu(self, task_queue_lock_);
shutting_down_ = false;
// Add one since the caller of constructor waits on the barrier too.
creation_barier_.Init(self, max_active_workers_);
while (GetThreadCount() < max_active_workers_) {
const std::string worker_name = StringPrintf("%s worker thread %zu", name_.c_str(),
GetThreadCount());
threads_.push_back(
new ThreadPoolWorker(this, worker_name, worker_stack_size_));
}
}
}
void ThreadPool::WaitForWorkersToBeCreated() {
creation_barier_.Increment(Thread::Current(), 0);
}
const std::vector<ThreadPoolWorker*>& ThreadPool::GetWorkers() {
// Wait for all the workers to be created before returning them.
WaitForWorkersToBeCreated();
return threads_;
}
void ThreadPool::DeleteThreads() {
{
Thread* self = Thread::Current();
MutexLock mu(self, task_queue_lock_);
// Tell any remaining workers to shut down.
shutting_down_ = true;
// Broadcast to everyone waiting.
task_queue_condition_.Broadcast(self);
completion_condition_.Broadcast(self);
}
// Wait for the threads to finish. We expect the user of the pool
// not to run multi-threaded calls to `CreateThreads` and `DeleteThreads`,
// so we don't guard the field here.
STLDeleteElements(&threads_);
}
void ThreadPool::SetMaxActiveWorkers(size_t max_workers) {
MutexLock mu(Thread::Current(), task_queue_lock_);
CHECK_LE(max_workers, GetThreadCount());
max_active_workers_ = max_workers;
}
ThreadPool::~ThreadPool() {
DeleteThreads();
RemoveAllTasks(Thread::Current());
}
void ThreadPool::StartWorkers(Thread* self) {
MutexLock mu(self, task_queue_lock_);
started_ = true;
task_queue_condition_.Broadcast(self);
start_time_ = NanoTime();
total_wait_time_ = 0;
}
void ThreadPool::StopWorkers(Thread* self) {
MutexLock mu(self, task_queue_lock_);
started_ = false;
}
Task* ThreadPool::GetTask(Thread* self) {
MutexLock mu(self, task_queue_lock_);
while (!IsShuttingDown()) {
const size_t thread_count = GetThreadCount();
// Ensure that we don't use more threads than the maximum active workers.
const size_t active_threads = thread_count - waiting_count_;
// <= since self is considered an active worker.
if (active_threads <= max_active_workers_) {
Task* task = TryGetTaskLocked();
if (task != nullptr) {
return task;
}
}
++waiting_count_;
if (waiting_count_ == GetThreadCount() && !HasOutstandingTasks()) {
// We may be done, lets broadcast to the completion condition.
completion_condition_.Broadcast(self);
}
const uint64_t wait_start = kMeasureWaitTime ? NanoTime() : 0;
task_queue_condition_.Wait(self);
if (kMeasureWaitTime) {
const uint64_t wait_end = NanoTime();
total_wait_time_ += wait_end - std::max(wait_start, start_time_);
}
--waiting_count_;
}
// We are shutting down, return null to tell the worker thread to stop looping.
return nullptr;
}
Task* ThreadPool::TryGetTask(Thread* self) {
MutexLock mu(self, task_queue_lock_);
return TryGetTaskLocked();
}
Task* ThreadPool::TryGetTaskLocked() {
if (HasOutstandingTasks()) {
Task* task = tasks_.front();
tasks_.pop_front();
return task;
}
return nullptr;
}
void ThreadPool::Wait(Thread* self, bool do_work, bool may_hold_locks) {
if (do_work) {
CHECK(!create_peers_);
Task* task = nullptr;
while ((task = TryGetTask(self)) != nullptr) {
task->Run(self);
task->Finalize();
}
}
// Wait until each thread is waiting and the task list is empty.
MutexLock mu(self, task_queue_lock_);
while (!shutting_down_ && (waiting_count_ != GetThreadCount() || HasOutstandingTasks())) {
if (!may_hold_locks) {
completion_condition_.Wait(self);
} else {
completion_condition_.WaitHoldingLocks(self);
}
}
}
size_t ThreadPool::GetTaskCount(Thread* self) {
MutexLock mu(self, task_queue_lock_);
return tasks_.size();
}
void ThreadPool::SetPthreadPriority(int priority) {
for (ThreadPoolWorker* worker : threads_) {
worker->SetPthreadPriority(priority);
}
}
} // namespace art