libcamera: camera_manager: Construct CameraManager instances manually

The CameraManager class is not supposed to be instantiated multiple
times, which led to a singleton implementation. This requires a global
instance of the CameraManager, which is destroyed when the global
destructors are executed.

Relying on global instances causes issues with cleanup, as the order in
which the global destructors are run can't be controlled. In particular,
the Android camera HAL implementation ends up destroying the
CameraHalManager after the CameraManager, which leads to use-after-free
problems.

To solve this, remove the CameraManager::instance() method and make the
CameraManager class instantiable directly. Multiple instances are still
not allowed, and this is enforced by storing the instance pointer
internally to be checked when an instance is created.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>

include/libcamera/camera_manager.h

@@ -23,6 +23,11 @@ class PipelineHandler;
 class CameraManager : public Object
 {
 public:
+	CameraManager();
+	CameraManager(const CameraManager &) = delete;
+	CameraManager &operator=(const CameraManager &) = delete;
+	~CameraManager();
+
 	int start();
 	void stop();
 
@@ -32,23 +37,18 @@ public:
 	void addCamera(std::shared_ptr<Camera> camera);
 	void removeCamera(Camera *camera);
 
-	static CameraManager *instance();
 	static const std::string &version() { return version_; }
 
 	void setEventDispatcher(std::unique_ptr<EventDispatcher> dispatcher);
 	EventDispatcher *eventDispatcher();
 
 private:
-	CameraManager();
-	CameraManager(const CameraManager &) = delete;
-	CameraManager &operator=(const CameraManager &) = delete;
-	~CameraManager();
-
 	std::unique_ptr<DeviceEnumerator> enumerator_;
 	std::vector<std::shared_ptr<PipelineHandler>> pipes_;
 	std::vector<std::shared_ptr<Camera>> cameras_;
 
 	static const std::string version_;
+	static CameraManager *self_;
 };
 
 } /* namespace libcamera */