Binder学习三 MediaServer -- 实例

Q&A

1.Multiple call of same binder object from 15 threads,will the binder service handle request in 15 threads?

Answer:  No.

Explain:The binder service may or may not handle in 15 threads.If threre's idle threads existed in thread pool , the binder service will re-use that thread to handle request.

In my test,only three threads created to handle the request when app query media DB from 15 threads

2.When app call binder service from one threads,does the binder service always use same thread to handle that?

Answer:No

Explain:If a thread in threadpool time out,it will exist automatically

3.Is there thread limitation in binder thread pool?

Answer:yes,the maximum thread nummber is set 15 in android implementation,see [e-mail].

在代码中加入调试语句，测试CameraService调用次序

测试步骤：

1.adb shell ps | | find "/system/bin/mediaserver",得到mediaserver对应pid my-pid

2adb logcat -c

3..adb shell kill my-pid

4.adb logcat > out

5.launch Camera

采集adb logcat的输出文本

由下面Log可知，mediaserver进程号为1771，启动时创建的工作线程为1777,此线程1777和主线程1771构成初始线程池，且此两个线程不会超时退出线程循环.

08-12 08:45:53.226  1771  1771 D ProcessState: enter open_driver

08-12 08:45:53.710  1771  1771 D IPCThreadState: enter IPCThreadState::joinThreadPool 1

08-12 08:45:53.710  1771  1771 D IPCThreadState: begin call ioctl(mProcess->mDriverFD, BINDER_WRITE_READ //block here

08-12 08:45:53.710  1771  1777 D IPCThreadState: enter IPCThreadState::joinThreadPool 1

08-12 08:45:53.710  1771  1777 D IPCThreadState: enter IPCThreadState::talkWithDriver 1

08-12 08:45:53.710  1771  1777 D IPCThreadState: bwr.write_size=4 bwr.read_size=256

08-12 08:45:53.710  1771  1777 D IPCThreadState: begin call ioctl(mProcess->mDriverFD, BINDER_WRITE_READ

08-12 08:45:53.710  1771  1777 D IPCThreadState: end call ioctl(mProcess->mDriverFD, BINDER_WRITE_READ

08-12 08:45:53.710  1771  1777 D IPCThreadState: leave IPCThreadState::talkWithDriver

08-12 08:45:53.710  1771  1777 D IPCThreadState: enter executeCommand cmd=29196

08-12 08:45:53.710  1771  1777 D IPCThreadState: leave executeCommands 29196

08-12 08:45:53.710  1771  1777 D IPCThreadState: enter IPCThreadState::talkWithDriver 1

08-12 08:45:53.710  1771  1777 D IPCThreadState: bwr.write_size=0 bwr.read_size=256

08-12 08:45:53.710  1771  1777 D IPCThreadState: begin call ioctl(mProcess->mDriverFD, BINDER_WRITE_READ  //block here

08-12 08:45:54.054  1771  1771 D IPCThreadState: end call ioctl(mProcess->mDriverFD, BINDER_WRITE_READ //主线程被唤醒

08-12 08:45:54.054  1771  1771 D IPCThreadState: leave IPCThreadState::talkWithDriver

08-12 08:45:54.054  1771  1771 D IPCThreadState: enter executeCommand cmd=29196

08-12 08:45:54.054  1771  1771 D IPCThreadState: leave executeCommands 29196

08-12 08:45:54.054  1771  1771 D IPCThreadState: enter IPCThreadState::talkWithDriver 1

08-12 08:45:54.054  1771  1771 D IPCThreadState: bwr.write_size=0 bwr.read_size=0

08-12 08:45:54.054  1771  1771 D IPCThreadState: enter executeCommand cmd=-2144833022

08-12 08:45:54.054  1771  1771 D IPCThreadState: BR_TRANSACTION

08-12 08:45:54.054  1771  1771 D IPCThreadState: call transact1 here
08-12 08:45:57.960  1771  1771 D IPCThreadState: end call ioctl(mProcess->mDriverFD, BINDER_WRITE_READ

08-12 08:45:57.960  1771  1771 D IPCThreadState: leave IPCThreadState::talkWithDriver

08-12 08:45:57.960  1771  1771 D IPCThreadState: enter executeCommand cmd=29196

08-12 08:45:57.960  1771  1771 D IPCThreadState: leave executeCommands 29196

08-12 08:45:57.960  1771  1771 D IPCThreadState: enter IPCThreadState::talkWithDriver 1

08-12 08:45:57.960  1771  1771 D IPCThreadState: bwr.write_size=0 bwr.read_size=0

08-12 08:45:57.960  1771  1771 D IPCThreadState: enter executeCommand cmd=-2144833022

08-12 08:45:57.960  1771  1771 D IPCThreadState: BR_TRANSACTION

08-12 08:45:57.960  1771  1771 D IPCThreadState: call transact1 here

08-12 08:45:57.960  1771  1771 D CameraService: enter CameraService::onTransact code=3      //code=BnCameraService::CONNECT,new CameraService::Client()

08-12 08:45:58.609  1771  1777 D IPCThreadState: end call ioctl(mProcess->mDriverFD, BINDER_WRITE_READ
08-12 08:45:58.609  1771  1777 D IPCThreadState: BR_SPAWN_LOOPER:                 //这里新的Thread被binder要求创建出来,应该是由于CameraService需要创建新的binder对象 ICameraClient从而需要额外的线程来处理
08-12 08:45:58.609  1771  1777 D ProcessState: enter ProcessState::spawnPooledThread isMain=0
08-12 08:45:58.609  1771  1777 D ProcessState: create PoolThread 0xaa880
08-12 08:45:58.609  1771  1777 D ProcessState: leave ProcessState::spawnPooledThread isMain=0
08-12 08:45:58.609  1771  1814 D libutils.threads: enter Thread::_threadLoop //新线程创建成功
08-12 08:45:58.609  1771  1814 D IPCThreadState: enter IPCThreadState::joinThreadPool 0
08-12 08:45:58.609  1771  1777 D IPCThreadState: BR_TRANSACTION
08-12 08:45:58.609  1771  1777 D IPCThreadState: call transact1 here
08-12 08:45:58.609  1771  1777 D ICamera : enter BnCamera::onTransact code=2            //调用到了ICamera::onTransact,code=SET_PREVIEW_DISPLAY
08-12 08:45:58.609  1771  1813 V MediaPlayerService: player type = 4
08-12 08:45:58.609  1771  1771 D CameraService: enter CameraService::onTransact code=2 //code=GET_CAMERA_INFO
08-12 08:45:58.617  1771  1777 D IPCThreadState: BR_TRANSACTION
08-12 08:45:58.617  1771  1777 D ICamera : enter BnCamera::onTransact code=11 //code=SEND_COMMAND
08-12 08:45:58.617  1771  1777 D IPCThreadState: finish call transact
08-12 08:45:58.617  1792  1801 D IPCThreadState: begin call ioctl(mProcess->mDriverFD, BINDER_WRITE_READ

08-12 08:45:58.617  1771  1771 D ICamera : enter BnCamera::onTransact code=21 //code=GET_CUSTOM_PARAMETERS
08-12 08:45:58.625  1771  1771 D OMXCameraAdapter: hardware/ti/omap4/omap3/camera-omap4/src/OMXCameraAdapter/OMXCameraAdapter.cpp:2824 getParameters - OMXCameraAdapter - getParametersOMX - exposure.nShutterSpeedMsec = 60

08-12 08:45:58.625  1771  1771 D OMXCameraAdapter: hardware/ti/omap4/omap3/camera-omap4/src/OMXCameraAdapter/OMXCameraAdapter.cpp:2825 getParameters - OMXCameraAdapter - getParametersOMX - exposure.nSensitivity = 100

08-12 08:45:58.656  1771  1814 D ICamera : enter BnCamera::onTransact code=20 //code=SET_CUSTOM_PARAMETERS

08-12 08:45:58.687  1771  1777 D ICamera : enter BnCamera::onTransact code=21

08-12 08:45:58.695  1771  1771 D CameraService: enter CameraService::onTransact code=1

08-12 08:45:58.710  1771  1814 D CameraService: enter CameraService::onTransact code=2

08-12 08:45:58.757  1771  1814 D ICamera : enter BnCamera::onTransact code=20

08-12 08:45:58.757  1771  1814 E CameraService: Invalid Burst Count setting burst count to 1
08-12 08:45:58.796  1771  1777 D ICamera : enter BnCamera::onTransact code=20
08-12 08:45:58.796  1771  1777 E CameraService: Invalid Burst Count setting burst count to 1
08-12 08:45:58.820  1771  1771 D ICamera : enter BnCamera::onTransact code=21

08-12 08:45:58.882  1771  1814 D ICamera : enter BnCamera::onTransact code=20

08-12 08:45:58.906  1771  1777 D ICamera : enter BnCamera::onTransact code=4

08-12 08:45:59.843  1771  1814 D ICamera : enter BnCamera::onTransact code=2

08-12 08:46:00.515  1771  1777 D ICamera : enter BnCamera::onTransact code=6

结论：mediaserver中，共3个线程被创建出来处理CameraService及CameraClient Binder的处理，tid=1771,1777,1814。