[PATCH v1] libcamera: camera_manager: Do not emit signals while holding lock

[Barnabás Pőcze]

Both `CameraManager::Private::{add,remove}Camera()` emit the
`camera{Added,Removed}` signals, respectively, while holding the
lock protecting the list of cameras.

This is problematic because if a callback tries to call `cameras()`,
then the same (non-recursive) lock would be locked again.

Furthermore, there is no real need to hold the lock while user code
is running, so release the lock as soon as possible.

Signed-off-by: Barnabás Pőcze <barnabas.pocze at ideasonboard.com>
---
 src/libcamera/camera_manager.cpp | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/src/libcamera/camera_manager.cpp b/src/libcamera/camera_manager.cpp
index 87e6717ec..d728ac44a 100644
--- a/src/libcamera/camera_manager.cpp
+++ b/src/libcamera/camera_manager.cpp
@@ -202,6 +202,7 @@ void CameraManager::Private::addCamera(std::shared_ptr<Camera> camera)
 {
 	ASSERT(Thread::current() == this);
 
+{
 	MutexLocker locker(mutex_);
 
 	for (const std::shared_ptr<Camera> &c : cameras_) {
@@ -213,13 +214,12 @@ void CameraManager::Private::addCamera(std::shared_ptr<Camera> camera)
 		}
 	}
 
-	cameras_.push_back(std::move(camera));
-
-	unsigned int index = cameras_.size() - 1;
+	cameras_.push_back(camera);
+}
 
 	/* Report the addition to the public signal */
 	CameraManager *const o = LIBCAMERA_O_PTR();
-	o->cameraAdded.emit(cameras_[index]);
+	o->cameraAdded.emit(std::move(camera));
 }
 
 /**
@@ -236,6 +236,7 @@ void CameraManager::Private::removeCamera(std::shared_ptr<Camera> camera)
 {
 	ASSERT(Thread::current() == this);
 
+{
 	MutexLocker locker(mutex_);
 
 	auto iter = std::find_if(cameras_.begin(), cameras_.end(),
@@ -245,14 +246,15 @@ void CameraManager::Private::removeCamera(std::shared_ptr<Camera> camera)
 	if (iter == cameras_.end())
 		return;
 
+	cameras_.erase(iter);
+}
+
 	LOG(Camera, Debug)
 		<< "Unregistering camera '" << camera->id() << "'";
 
-	cameras_.erase(iter);
-
 	/* Report the removal to the public signal */
 	CameraManager *const o = LIBCAMERA_O_PTR();
-	o->cameraRemoved.emit(camera);
+	o->cameraRemoved.emit(std::move(camera));
 }
 
 /**
-- 
2.48.1