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      1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include "base/threading/worker_pool_posix.h"
      6 
      7 #include "base/bind.h"
      8 #include "base/callback.h"
      9 #include "base/debug/trace_event.h"
     10 #include "base/lazy_instance.h"
     11 #include "base/logging.h"
     12 #include "base/memory/ref_counted.h"
     13 #include "base/strings/stringprintf.h"
     14 #include "base/threading/platform_thread.h"
     15 #include "base/threading/thread_local.h"
     16 #include "base/threading/worker_pool.h"
     17 #include "base/tracked_objects.h"
     18 
     19 using tracked_objects::TrackedTime;
     20 
     21 namespace base {
     22 
     23 namespace {
     24 
     25 base::LazyInstance<ThreadLocalBoolean>::Leaky
     26     g_worker_pool_running_on_this_thread = LAZY_INSTANCE_INITIALIZER;
     27 
     28 const int kIdleSecondsBeforeExit = 10 * 60;
     29 
     30 #ifdef ADDRESS_SANITIZER
     31 const int kWorkerThreadStackSize = 256 * 1024;
     32 #else
     33 // A stack size of 64 KB is too small for the CERT_PKIXVerifyCert
     34 // function of NSS because of NSS bug 439169.
     35 const int kWorkerThreadStackSize = 128 * 1024;
     36 #endif
     37 
     38 class WorkerPoolImpl {
     39  public:
     40   WorkerPoolImpl();
     41   ~WorkerPoolImpl();
     42 
     43   void PostTask(const tracked_objects::Location& from_here,
     44                 const base::Closure& task, bool task_is_slow);
     45 
     46  private:
     47   scoped_refptr<base::PosixDynamicThreadPool> pool_;
     48 };
     49 
     50 WorkerPoolImpl::WorkerPoolImpl()
     51     : pool_(new base::PosixDynamicThreadPool("WorkerPool",
     52                                              kIdleSecondsBeforeExit)) {
     53 }
     54 
     55 WorkerPoolImpl::~WorkerPoolImpl() {
     56   pool_->Terminate();
     57 }
     58 
     59 void WorkerPoolImpl::PostTask(const tracked_objects::Location& from_here,
     60                               const base::Closure& task, bool task_is_slow) {
     61   pool_->PostTask(from_here, task);
     62 }
     63 
     64 base::LazyInstance<WorkerPoolImpl> g_lazy_worker_pool =
     65     LAZY_INSTANCE_INITIALIZER;
     66 
     67 class WorkerThread : public PlatformThread::Delegate {
     68  public:
     69   WorkerThread(const std::string& name_prefix,
     70                base::PosixDynamicThreadPool* pool)
     71       : name_prefix_(name_prefix),
     72         pool_(pool) {}
     73 
     74   virtual void ThreadMain() OVERRIDE;
     75 
     76  private:
     77   const std::string name_prefix_;
     78   scoped_refptr<base::PosixDynamicThreadPool> pool_;
     79 
     80   DISALLOW_COPY_AND_ASSIGN(WorkerThread);
     81 };
     82 
     83 void WorkerThread::ThreadMain() {
     84   g_worker_pool_running_on_this_thread.Get().Set(true);
     85   const std::string name = base::StringPrintf(
     86       "%s/%d", name_prefix_.c_str(), PlatformThread::CurrentId());
     87   // Note |name.c_str()| must remain valid for for the whole life of the thread.
     88   PlatformThread::SetName(name.c_str());
     89 
     90   for (;;) {
     91     PendingTask pending_task = pool_->WaitForTask();
     92     if (pending_task.task.is_null())
     93       break;
     94     TRACE_EVENT2("toplevel", "WorkerThread::ThreadMain::Run",
     95         "src_file", pending_task.posted_from.file_name(),
     96         "src_func", pending_task.posted_from.function_name());
     97 
     98     TrackedTime start_time =
     99         tracked_objects::ThreadData::NowForStartOfRun(pending_task.birth_tally);
    100 
    101     pending_task.task.Run();
    102 
    103     tracked_objects::ThreadData::TallyRunOnWorkerThreadIfTracking(
    104         pending_task.birth_tally, TrackedTime(pending_task.time_posted),
    105         start_time, tracked_objects::ThreadData::NowForEndOfRun());
    106   }
    107 
    108   // The WorkerThread is non-joinable, so it deletes itself.
    109   delete this;
    110 }
    111 
    112 }  // namespace
    113 
    114 // static
    115 bool WorkerPool::PostTask(const tracked_objects::Location& from_here,
    116                           const base::Closure& task, bool task_is_slow) {
    117   g_lazy_worker_pool.Pointer()->PostTask(from_here, task, task_is_slow);
    118   return true;
    119 }
    120 
    121 // static
    122 bool WorkerPool::RunsTasksOnCurrentThread() {
    123   return g_worker_pool_running_on_this_thread.Get().Get();
    124 }
    125 
    126 PosixDynamicThreadPool::PosixDynamicThreadPool(const std::string& name_prefix,
    127                                                int idle_seconds_before_exit)
    128     : name_prefix_(name_prefix),
    129       idle_seconds_before_exit_(idle_seconds_before_exit),
    130       pending_tasks_available_cv_(&lock_),
    131       num_idle_threads_(0),
    132       terminated_(false) {}
    133 
    134 PosixDynamicThreadPool::~PosixDynamicThreadPool() {
    135   while (!pending_tasks_.empty())
    136     pending_tasks_.pop();
    137 }
    138 
    139 void PosixDynamicThreadPool::Terminate() {
    140   {
    141     AutoLock locked(lock_);
    142     DCHECK(!terminated_) << "Thread pool is already terminated.";
    143     terminated_ = true;
    144   }
    145   pending_tasks_available_cv_.Broadcast();
    146 }
    147 
    148 void PosixDynamicThreadPool::PostTask(
    149     const tracked_objects::Location& from_here,
    150     const base::Closure& task) {
    151   PendingTask pending_task(from_here, task);
    152   AddTask(&pending_task);
    153 }
    154 
    155 void PosixDynamicThreadPool::AddTask(PendingTask* pending_task) {
    156   AutoLock locked(lock_);
    157   DCHECK(!terminated_) <<
    158       "This thread pool is already terminated.  Do not post new tasks.";
    159 
    160   pending_tasks_.push(*pending_task);
    161   pending_task->task.Reset();
    162 
    163   // We have enough worker threads.
    164   if (static_cast<size_t>(num_idle_threads_) >= pending_tasks_.size()) {
    165     pending_tasks_available_cv_.Signal();
    166   } else {
    167     // The new PlatformThread will take ownership of the WorkerThread object,
    168     // which will delete itself on exit.
    169     WorkerThread* worker =
    170         new WorkerThread(name_prefix_, this);
    171     PlatformThread::CreateNonJoinable(kWorkerThreadStackSize, worker);
    172   }
    173 }
    174 
    175 PendingTask PosixDynamicThreadPool::WaitForTask() {
    176   AutoLock locked(lock_);
    177 
    178   if (terminated_)
    179     return PendingTask(FROM_HERE, base::Closure());
    180 
    181   if (pending_tasks_.empty()) {  // No work available, wait for work.
    182     num_idle_threads_++;
    183     if (num_idle_threads_cv_.get())
    184       num_idle_threads_cv_->Signal();
    185     pending_tasks_available_cv_.TimedWait(
    186         TimeDelta::FromSeconds(idle_seconds_before_exit_));
    187     num_idle_threads_--;
    188     if (num_idle_threads_cv_.get())
    189       num_idle_threads_cv_->Signal();
    190     if (pending_tasks_.empty()) {
    191       // We waited for work, but there's still no work.  Return NULL to signal
    192       // the thread to terminate.
    193       return PendingTask(FROM_HERE, base::Closure());
    194     }
    195   }
    196 
    197   PendingTask pending_task = pending_tasks_.front();
    198   pending_tasks_.pop();
    199   return pending_task;
    200 }
    201 
    202 }  // namespace base
    203