digraph mutex_states {
	// States
	free;
	locked;
	unlocking;
	dead;

	// Valid transitions
	dead -> free		[ label="initialized" ];
	free -> locked		[ label="locked" ];
	locked -> unlocking	[ label="unlocked\nby owner" ];
	unlocking -> free	[ label="unlock completed" ];
	unlocking -> locked	[ label="lock changed owner" ];
	free -> dead		[ label="destroyed" ];

	// Bad transitions
	dead -> locked		[ style=dotted, label="locked\nafter destroy" ];
	dead -> free		[ style=dotted, label="unlocked\nafter destroy" ];
	
	locked -> free		[ style=dotted, label="unlocked\nby non-owner" ];
	locked -> dead		[ style=dotted, label="destroyed\nwhile locked" ];
}
