Make SharedMemoryDataConsumerHandle thread-safe.

content/child/shared_memory_data_consumer_handle.cc

 // Copyright 2015 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 "content/child/shared_memory_data_consumer_handle.h"
 
 #include <algorithm>
 #include <deque>
 #include <vector>
 
+#include "base/bind.h"
+#include "base/message_loop/message_loop.h"
+#include "base/single_thread_task_runner.h"
+#include "base/synchronization/lock.h"
 #include "content/public/child/fixed_received_data.h"
 
 namespace content {
 
+namespace {
+
+class DelegateThreadSafeReceivedData final
+    : public RequestPeer::ThreadSafeReceivedData {
+ public:
+  explicit DelegateThreadSafeReceivedData(
+      scoped_ptr<RequestPeer::ReceivedData> data)
+      : data_(data.Pass()),
+        task_runner_(base::MessageLoop::current()->task_runner()) {}
+  ~DelegateThreadSafeReceivedData() override {
+    if (!task_runner_->BelongsToCurrentThread()) {
+      // Delete the data on the original thread.
+      task_runner_->DeleteSoon(FROM_HERE, data_.release());
+    }
+  }
+
+  const char* payload() const override { return data_->payload(); }
+  int length() const override { return data_->length(); }
+  int encoded_length() const override { return data_->encoded_length(); }
+
+ private:
+  scoped_ptr<RequestPeer::ReceivedData> data_;
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+
+  DISALLOW_COPY_AND_ASSIGN(DelegateThreadSafeReceivedData);
+};
+
+}  // namespace
+
 using Result = blink::WebDataConsumerHandle::Result;
 
 class SharedMemoryDataConsumerHandle::Context final
     : public base::RefCountedThreadSafe<Context> {
  public:
   Context()
       : result_(Ok),
         first_offset_(0),
         client_(nullptr),
         is_reader_active_(true) {}
 
   bool IsEmpty() const { return queue_.empty(); }
   void Clear() {
-    for (RequestPeer::ReceivedData* data : queue_) {
+    for (auto& data : queue_) {
       delete data;
     }
     queue_.clear();
     first_offset_ = 0;
     client_ = nullptr;
   }
-  RequestPeer::ReceivedData* Top() { return queue_.front(); }
-  void Push(scoped_ptr<RequestPeer::ReceivedData> data) {
+  void Notify() {
+    // Note that this function is not protected by |lock_| (actually it
+    // shouldn't be) but |notification_task_runner_| is thread-safe.
+
+    if (notification_task_runner_->BelongsToCurrentThread()) {
+      NotifyImmediately();
+    } else {
+      notification_task_runner_->PostTask(
+          FROM_HERE, base::Bind(&Context::NotifyImmediately, this));
+    }
+  }
+
+  RequestPeer::ThreadSafeReceivedData* Top() { return queue_.front(); }
+  void Push(scoped_ptr<RequestPeer::ThreadSafeReceivedData> data) {
     queue_.push_back(data.release());
   }
   size_t first_offset() const { return first_offset_; }
   Result result() const { return result_; }
   void set_result(Result r) { result_ = r; }
   Client* client() { return client_; }
-  void set_client(Client* client) { client_ = client; }
+  void SetClient(Client* client) {
+    if (client) {
+      notification_task_runner_ = base::MessageLoop::current()->task_runner();
+      client_ = client;
+    } else {
+      notification_task_runner_ = nullptr;
+      client_ = nullptr;
+    }
+  }
   bool is_reader_active() const { return is_reader_active_; }
   void set_is_reader_active(bool b) { is_reader_active_ = b; }
   void Consume(size_t s) {
     first_offset_ += s;
-    RequestPeer::ReceivedData* top = Top();
+    auto top = Top();
     if (static_cast<size_t>(top->length()) <= first_offset_) {
       delete top;
       queue_.pop_front();
       first_offset_ = 0;
     }
   }
+  base::Lock& lock() { return lock_; }
 
  private:
   friend class base::RefCountedThreadSafe<Context>;
   ~Context() {
     // This is necessary because the queue stores raw pointers.
     Clear();
   }
 
+  void NotifyImmediately() {
+    // As we can assume that all reader-side methods are called on this
+    // thread (see WebDataConsumerHandle comments), we don't need to lock.
+    if (client_)
+      client_->didGetReadable();
+  }
+
+  base::Lock lock_;
   // |result_| stores the ultimate state of this handle if it has. Otherwise,
   // |Ok| is set.
   Result result_;
-  // TODO(yhirano): Use std::deque<scoped_ptr<ReceivedData>> once it is allowed.
-  std::deque<RequestPeer::ReceivedData*> queue_;
+  // TODO(yhirano): Use std::deque<scoped_ptr<ThreadSafeReceivedData>>
+  // once it is allowed.
+  std::deque<RequestPeer::ThreadSafeReceivedData*> queue_;
   size_t first_offset_;
   Client* client_;
+  scoped_refptr<base::SingleThreadTaskRunner> notification_task_runner_;
   bool is_reader_active_;
 
   DISALLOW_COPY_AND_ASSIGN(Context);
 };
 
 SharedMemoryDataConsumerHandle::Writer::Writer(
     const scoped_refptr<Context>& context,
     BackpressureMode mode)
     : context_(context), mode_(mode) {
 }
 
 SharedMemoryDataConsumerHandle::Writer::~Writer() {
   Close();
 }
 
 void SharedMemoryDataConsumerHandle::Writer::AddData(
     scoped_ptr<RequestPeer::ReceivedData> data) {
   if (!data->length()) {
     // We omit empty data.
     return;
   }
 
-  if (!context_->is_reader_active()) {
-    // No one is interested in the data.
-    return;
+  bool needs_notification = false;
+  {
+    base::AutoLock lock(context_->lock());
+    if (!context_->is_reader_active()) {
+      // No one is interested in the data.
+      return;
+    }
+
+    needs_notification = context_->client() && context_->IsEmpty();
+    scoped_ptr<RequestPeer::ThreadSafeReceivedData> data_to_pass;
+    if (mode_ == kApplyBackpressure) {
+      data_to_pass =
+          make_scoped_ptr(new DelegateThreadSafeReceivedData(data.Pass()));
+    } else {
+      data_to_pass = make_scoped_ptr(new FixedReceivedData(data.get()));
+    }
+    context_->Push(data_to_pass.Pass());
   }
 
-  bool needs_notification = context_->client() && context_->IsEmpty();
-  scoped_ptr<RequestPeer::ReceivedData> data_to_pass;
-  if (mode_ == kApplyBackpressure) {
-    data_to_pass = data.Pass();
-  } else {
-    data_to_pass = make_scoped_ptr(new FixedReceivedData(data.get()));
-  }
-  context_->Push(data_to_pass.Pass());
-
   if (needs_notification)
-    context_->client()->didGetReadable();
+    context_->Notify();
 }
 
 void SharedMemoryDataConsumerHandle::Writer::Close() {
-  if (context_->result() == Ok) {
-    context_->set_result(Done);
-    if (context_->client() && context_->IsEmpty())
-      context_->client()->didGetReadable();
+  bool needs_notification = false;
+
+  {
+    base::AutoLock lock(context_->lock());
+    if (context_->result() == Ok) {
+      context_->set_result(Done);
+      needs_notification = context_->client() && context_->IsEmpty();
+    }
   }
+  if (needs_notification)
+    context_->Notify();
 }
 
 SharedMemoryDataConsumerHandle::SharedMemoryDataConsumerHandle(
     BackpressureMode mode,
     scoped_ptr<Writer>* writer)
     : context_(new Context) {
   writer->reset(new Writer(context_, mode));
 }
 
 SharedMemoryDataConsumerHandle::~SharedMemoryDataConsumerHandle() {
+  base::AutoLock lock(context_->lock());
   context_->set_is_reader_active(false);
   context_->Clear();
 }
 
 Result SharedMemoryDataConsumerHandle::read(void* data,
                                             size_t size,
                                             Flags flags,
                                             size_t* read_size_to_return) {
+  base::AutoLock lock(context_->lock());
+
   size_t total_read_size = 0;
   *read_size_to_return = 0;
   if (context_->result() != Ok && context_->result() != Done)
     return context_->result();
 
   while (!context_->IsEmpty() && total_read_size < size) {
     const auto& top = context_->Top();
     size_t readable = top->length() - context_->first_offset();
     size_t writable = size - total_read_size;
     size_t read_size = std::min(readable, writable);
     const char* begin = top->payload() + context_->first_offset();
     std::copy(begin, begin + read_size,
               static_cast<char*>(data) + total_read_size);
     total_read_size += read_size;
     context_->Consume(read_size);
   }
   *read_size_to_return = total_read_size;
   return total_read_size ? Ok : context_->result() == Done ? Done : ShouldWait;
 }
 
 Result SharedMemoryDataConsumerHandle::beginRead(const void** buffer,
                                                  Flags flags,
                                                  size_t* available) {
   *buffer = nullptr;
   *available = 0;
 
+  base::AutoLock lock(context_->lock());
+
   if (context_->result() != Ok && context_->result() != Done)
     return context_->result();
 
   if (context_->IsEmpty())
     return context_->result() == Done ? Done : ShouldWait;
 
   const auto& top = context_->Top();
   *buffer = top->payload() + context_->first_offset();
   *available = top->length() - context_->first_offset();
 
   return Ok;
 }
 
 Result SharedMemoryDataConsumerHandle::endRead(size_t read_size) {
+  base::AutoLock lock(context_->lock());
+
   if (context_->IsEmpty())
     return UnexpectedError;
 
   context_->Consume(read_size);
   return Ok;
 }
 
 void SharedMemoryDataConsumerHandle::registerClient(Client* client) {
-  context_->set_client(client);
+  bool needs_notification = false;
+  {
+    base::AutoLock lock(context_->lock());
 
-  if (!context_->IsEmpty())
-    client->didGetReadable();
+    context_->SetClient(client);
+    needs_notification = !context_->IsEmpty();
+  }
+  if (needs_notification)
+    context_->Notify();
 }
 
 void SharedMemoryDataConsumerHandle::unregisterClient() {
-  context_->set_client(nullptr);
+  base::AutoLock lock(context_->lock());
+
+  context_->SetClient(nullptr);
 }
 
 }  // namespace content