[libcamera-devel] [PATCH 6/8] android: Guard access to the camera state

[Jacopo Mondi]

Guard access to the camera state and the start/stop sequences
with a mutex.

Currently only stop() and the first call to processCaptureRequest()
start and stop the camera, and they're not meant to race with each
other. With the introduction of flush() the camera can be stopped
concurrently to a processCaptureRequest() call, hence access to the
camera state will need to be protected.

Prepare for that by guarding the existing paths with a mutex.

Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
---
 src/android/camera_device.cpp | 23 ++++++++++++++---------
 src/android/camera_device.h   |  1 +
 2 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/src/android/camera_device.cpp b/src/android/camera_device.cpp
index ff965a1c8c86..14a3f79a7402 100644
--- a/src/android/camera_device.cpp
+++ b/src/android/camera_device.cpp
@@ -758,6 +758,7 @@ void CameraDevice::close()
 
 void CameraDevice::stop()
 {
+	MutexLocker cameraLock(cameraMutex_);
 	if (state_ == CameraStopped)
 		return;
 
@@ -1913,17 +1914,21 @@ int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
 	if (!isValidRequest(camera3Request))
 		return -EINVAL;
 
-	/* Start the camera if that's the first request we handle. */
-	if (state_ == CameraStopped) {
-		worker_.start();
+	{
+		MutexLocker cameraLock(cameraMutex_);
 
-		int ret = camera_->start();
-		if (ret) {
-			LOG(HAL, Error) << "Failed to start camera";
-			return ret;
-		}
+		/* Start the camera if that's the first request we handle. */
+		if (state_ == CameraStopped) {
+			worker_.start();
 
-		state_ = CameraRunning;
+			int ret = camera_->start();
+			if (ret) {
+				LOG(HAL, Error) << "Failed to start camera";
+				return ret;
+			}
+
+			state_ = CameraRunning;
+		}
 	}
 
 	/*
diff --git a/src/android/camera_device.h b/src/android/camera_device.h
index 30b364decaab..f263fdae472a 100644
--- a/src/android/camera_device.h
+++ b/src/android/camera_device.h
@@ -120,6 +120,7 @@ private:
 
 	CameraWorker worker_;
 
+	libcamera::Mutex cameraMutex_; /* Protects access to the camera state. */
 	State state_;
 
 	std::shared_ptr<libcamera::Camera> camera_;
-- 
2.31.1