libcamera: object: Add and use thread-bound assertion

Several functions in libcamera classes are marked as thread-bound,
restricting the contexts in which those functions can be called. There
is no infrastructure to enforce these restrictions, causing difficult to
debug race conditions when they are not met by callers.

As a first step to solve this, add an assertThreadBound() protected
function to the Object class to test if the calling thread context is
valid, and use it in member functions of Object subclasses marked as
thread-bound. This replaces manual tests in a few locations.

The thread-bound member functions of classes that do not inherit from
Object are not checked, and neither are the functions of classes marked
as thread-bound at the class level. These issue should be addressed in
the future.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Milan Zamazal <mzamazal@redhat.com>

include/libcamera/base/object.h

@@ -49,6 +49,8 @@ public:
 protected:
 	virtual void message(Message *msg);
 
+	bool assertThreadBound(const char *message);
+
 private:
 	friend class SignalBase;
 	friend class Thread;