[sensors](Linux) Fix tsan data race in sensor reader

device/generic_sensor/platform_sensor_provider_linux.h

 // Copyright 2016 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.
 
 #ifndef DEVICE_GENERIC_SENSOR_PUBLIC_PLATFORM_SENSOR_PROVIDER_LINUX_H_
 #define DEVICE_GENERIC_SENSOR_PUBLIC_PLATFORM_SENSOR_PROVIDER_LINUX_H_
 
 #include "device/generic_sensor/platform_sensor_provider.h"
 
 #include "device/generic_sensor/linux/sensor_device_manager.h"
 
 namespace base {
 template <typename T>
 struct DefaultSingletonTraits;
 class Thread;
 }
 
 namespace device {
 
+class SensorReader;
 struct SensorInfoLinux;
 
 class DEVICE_GENERIC_SENSOR_EXPORT PlatformSensorProviderLinux
     : public PlatformSensorProvider,
       public SensorDeviceManager::Delegate {
  public:
   static PlatformSensorProviderLinux* GetInstance();
 
   // Sets another service provided by tests.
   void SetSensorDeviceManagerForTesting(
@@ skipping 16 matching lines @@
       scoped_refptr<base::SingleThreadTaskRunner> file_task_runner) override;
 
  private:
   friend struct base::DefaultSingletonTraits<PlatformSensorProviderLinux>;
 
   using SensorDeviceMap =
       std::unordered_map<mojom::SensorType, std::unique_ptr<SensorInfoLinux>>;
 
   PlatformSensorProviderLinux();
 
-  void SensorDeviceFound(
+  // Creates a platform sensor using a sensor reader created on a different
+  // thread.

[Reilly Grant (use Gerrit), 2016/12/14 18:56:08]

*created on |polling_thread_|.

[maksims (do not use this acc), 2016/12/16 08:39:22]

comment removed

+  void SensorReaderCreated(
       mojom::SensorType type,
       mojo::ScopedSharedBufferMapping mapping,
       const PlatformSensorProviderBase::CreateSensorCallback& callback,
-      SensorInfoLinux* sensor_device);
+      SensorInfoLinux* const sensor_device,

[Reilly Grant (use Gerrit), 2016/12/14 18:56:08]

You mean const SensorInfoLinux*.

[maksims (do not use this acc), 2016/12/16 08:39:22]

Done.

+      std::unique_ptr<SensorReader> sensor_reader);
 
   bool StartPollingThread();
 
   // Stops a polling thread if there are no sensors left. Must be called on
   // a different than the polling thread which allows I/O.
   void StopPollingThread();
 
   // Shuts down a service that tracks events from iio subsystem.
   void Shutdown();
 
   // Returns SensorInfoLinux structure of a requested type.
   // If a request cannot be processed immediately, returns nullptr and
   // all the requests stored in |requests_map_| are processed after
   // enumeration is ready.
   SensorInfoLinux* GetSensorDevice(mojom::SensorType type);
 
   // Returns all found iio devices. Currently not implemented.
   void GetAllSensorDevices();
 
   // Processed stored requests in |request_map_|.
   void ProcessStoredRequests();
 
-  // Called when sensors are created asynchronously after enumeration is done.
-  void CreateSensorAndNotify(mojom::SensorType type,
-                             SensorInfoLinux* sensor_device);
-
   // SensorDeviceManager::Delegate implements:
   void OnSensorNodesEnumerated() override;
   void OnDeviceAdded(mojom::SensorType type,
                      std::unique_ptr<SensorInfoLinux> sensor_device) override;
   void OnDeviceRemoved(mojom::SensorType type,
                        const std::string& device_node) override;
 
   // Set to true when enumeration is ready.
   bool sensor_nodes_enumerated_;
 
@@ skipping 14 matching lines @@
   // provider to stop a polling thread and passed to a manager that
   // runs a linux device monitor service on this task runner.
   scoped_refptr<base::SingleThreadTaskRunner> file_task_runner_;
 
   DISALLOW_COPY_AND_ASSIGN(PlatformSensorProviderLinux);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_GENERIC_SENSOR_PUBLIC_PLATFORM_SENSOR_PROVIDER_LINUX_H_