Kernel: Replace last CriticalScopes in kernel with SpinLocks

kernel/include/kernel/Scheduler.h

@@ -30,9 +30,12 @@ namespace Kernel
 		static pid_t current_tid();
 
 		[[noreturn]] void execute_current_thread();
-		[[noreturn]] void _execute_current_thread();
+		[[noreturn]] void execute_current_thread_locked();
 		[[noreturn]] void delete_current_process_and_thread();
 
+		// This is no return if called on current thread
+		void terminate_thread(Thread*);
+
 	private:
 		Scheduler() = default;
 
@@ -43,6 +46,8 @@ namespace Kernel
 		void remove_and_advance_current_thread();
 		void advance_current_thread();
 
+		[[noreturn]] void execute_current_thread_stack_loaded();
+
 		BAN::ErrorOr<void> add_thread(Thread*);
 
 	private:
@@ -57,6 +62,8 @@ namespace Kernel
 			Semaphore*	semaphore;
 		};
 
+		SpinLockUnsafe m_lock;
+
 		Thread* m_idle_thread { nullptr };
 		BAN::LinkedList<SchedulerThread> m_active_threads;
 		BAN::LinkedList<SchedulerThread> m_sleeping_threads;