Commit 661c21da authored Oct 22, 2014 by Eino-Ville Talvala

CameraService: Disconnect: Release mutex while waiting for joins.

The threads shutting down may have callpaths that require taking the
binder interface mutex, so waiting to join them with that mutex held
can lead to deadlocks.

A specific instance is StreamingProcessor calling dataCallbackTimestamp,
which can immediately lead to a Camera2Client::releaseRecordingFrame call,
which requires the binder interface mutex. If this call happens right when
shutdown is occurring, and Camera2Client::disconnect is holding the mutex,
deadlock ensues.

Bug: 17997578
Change-Id: I71253cd5542b5920ad205976d315110ca0043d94

parent 168799c3

services/camera/libcameraservice/api1/Camera2Client.cpp

+14 −6

Original line number	Diff line number	Diff line
		@@ -419,6 +419,11 @@ void Camera2Client::disconnect() {

		ALOGV("Camera %d: Waiting for threads", mCameraId);

		{
		// Don't wait with lock held, in case the other threads need to
		// complete callbacks that re-enter Camera2Client
		mBinderSerializationLock.unlock();

		mStreamingProcessor->join();
		mFrameProcessor->join();
		mCaptureSequencer->join();
		@@ -426,6 +431,9 @@ void Camera2Client::disconnect() {
		mZslProcessorThread->join();
		mCallbackProcessor->join();

		mBinderSerializationLock.lock();
		}

		ALOGV("Camera %d: Deleting streams", mCameraId);

		mStreamingProcessor->deletePreviewStream();