Is it guaranteed that tasks in the same thread group can always send signals to each other, irrespective of their respective credentials structs? It's not clear to me whether this is always possible based on the security_task_kill implementations I've examined. I want to support per-thread setresuid/setresgid, but we also use signals for inter-thread communication. This is mainly for thread cancellation; the setxgid stuff isn't needed for threads with private credentials. I wonder if I need to disable cancellation for threads with such credentials. Thanks, Florian
