ART: Add ThreadPool mode that creates peers

Add a mode where worker threads in a thread pool will get a Java
peer. Add a test.

Bug: 29547798
Bug: 31684920
Test: m test-art-host-gtest-thread_pool_test
Change-Id: I3654cc2be1294a79881b6ac9f84445a1e7f24b70

3 files changed, 68 insertions, 4 deletions

diff --git a/runtime/thread_pool.cc b/runtime/thread_pool.cc
index d9179c3892..d24a5e5c4a 100644
--- a/runtime/thread_pool.cc
+++ b/runtime/thread_pool.cc
@@ -88,7 +88,10 @@ void ThreadPoolWorker::Run() {
 void* ThreadPoolWorker::Callback(void* arg) {
   ThreadPoolWorker* worker = reinterpret_cast<ThreadPoolWorker*>(arg);
   Runtime* runtime = Runtime::Current();
-  CHECK(runtime->AttachCurrentThread(worker->name_.c_str(), true, nullptr, false));
+  CHECK(runtime->AttachCurrentThread(worker->name_.c_str(),
+                                     true,
+                                     nullptr,
+                                     worker->thread_pool_->create_peers_));
   worker->thread_ = Thread::Current();
   // Thread pool workers cannot call into java.
   worker->thread_->SetCanCallIntoJava(false);
@@ -112,7 +115,7 @@ void ThreadPool::RemoveAllTasks(Thread* self) {
   tasks_.clear();
 }
 
-ThreadPool::ThreadPool(const char* name, size_t num_threads)
+ThreadPool::ThreadPool(const char* name, size_t num_threads, bool create_peers)
   : name_(name),
     task_queue_lock_("task queue lock"),
     task_queue_condition_("task queue condition", task_queue_lock_),
@@ -124,7 +127,8 @@ ThreadPool::ThreadPool(const char* name, size_t num_threads)
     total_wait_time_(0),
     // Add one since the caller of constructor waits on the barrier too.
     creation_barier_(num_threads + 1),
-    max_active_workers_(num_threads) {
+    max_active_workers_(num_threads),
+    create_peers_(create_peers) {
   Thread* self = Thread::Current();
   while (GetThreadCount() < num_threads) {
     const std::string worker_name = StringPrintf("%s worker thread %zu", name_.c_str(),
@@ -217,6 +221,7 @@ Task* ThreadPool::TryGetTaskLocked() {
 
 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);
diff --git a/runtime/thread_pool.h b/runtime/thread_pool.h
index 7ecfcd1289..a465e11055 100644
--- a/runtime/thread_pool.h
+++ b/runtime/thread_pool.h
@@ -105,11 +105,17 @@ class ThreadPool {
   // Remove all tasks in the queue.
   void RemoveAllTasks(Thread* self) REQUIRES(!task_queue_lock_);
 
-  ThreadPool(const char* name, size_t num_threads);
+  // Create a named thread pool with the given number of threads.
+  //
+  // If create_peers is true, all worker threads will have a Java peer object. Note that if the
+  // pool is asked to do work on the current thread (see Wait), a peer may not be available. Wait
+  // will conservatively abort if create_peers and do_work are true.
+  ThreadPool(const char* name, size_t num_threads, bool create_peers = false);
   virtual ~ThreadPool();
 
   // Wait for all tasks currently on queue to get completed. If the pool has been stopped, only
   // wait till all already running tasks are done.
+  // When the pool was created with peers for workers, do_work must not be true (see ThreadPool()).
   void Wait(Thread* self, bool do_work, bool may_hold_locks) REQUIRES(!task_queue_lock_);
 
   size_t GetTaskCount(Thread* self) REQUIRES(!task_queue_lock_);
@@ -159,6 +165,7 @@ class ThreadPool {
   uint64_t total_wait_time_;
   Barrier creation_barier_;
   size_t max_active_workers_ GUARDED_BY(task_queue_lock_);
+  const bool create_peers_;
 
  private:
   friend class ThreadPoolWorker;
diff --git a/runtime/thread_pool_test.cc b/runtime/thread_pool_test.cc
index 14c2c3bac8..28aa21f7a2 100644
--- a/runtime/thread_pool_test.cc
+++ b/runtime/thread_pool_test.cc
@@ -20,6 +20,7 @@
 
 #include "atomic.h"
 #include "common_runtime_test.h"
+#include "scoped_thread_state_change-inl.h"
 #include "thread-inl.h"
 
 namespace art {
@@ -159,4 +160,55 @@ TEST_F(ThreadPoolTest, RecursiveTest) {
   EXPECT_EQ((1 << depth) - 1, count.LoadSequentiallyConsistent());
 }
 
+class PeerTask : public Task {
+ public:
+  PeerTask() {}
+
+  void Run(Thread* self) {
+    ScopedObjectAccess soa(self);
+    CHECK(self->GetPeer() != nullptr);
+  }
+
+  void Finalize() {
+    delete this;
+  }
+};
+
+class NoPeerTask : public Task {
+ public:
+  NoPeerTask() {}
+
+  void Run(Thread* self) {
+    ScopedObjectAccess soa(self);
+    CHECK(self->GetPeer() == nullptr);
+  }
+
+  void Finalize() {
+    delete this;
+  }
+};
+
+// Tests for create_peer functionality.
+TEST_F(ThreadPoolTest, PeerTest) {
+  Thread* self = Thread::Current();
+  {
+    ThreadPool thread_pool("Thread pool test thread pool", 1);
+    thread_pool.AddTask(self, new NoPeerTask());
+    thread_pool.StartWorkers(self);
+    thread_pool.Wait(self, false, false);
+  }
+
+  {
+    // To create peers, the runtime needs to be started.
+    self->TransitionFromSuspendedToRunnable();
+    bool started = runtime_->Start();
+    ASSERT_TRUE(started);
+
+    ThreadPool thread_pool("Thread pool test thread pool", 1, true);
+    thread_pool.AddTask(self, new PeerTask());
+    thread_pool.StartWorkers(self);
+    thread_pool.Wait(self, false, false);
+  }
+}
+
 }  // namespace art