A personality layer running above an operating system kernel puts any threads that the personality layer is responsible for into new states which the kernel does not know about. This prevents the kernel from performing operations on a thread which has been placed in one of these new states where these operations are sensitive to state of the thread itself (such as kill, suspend, change priority). Instead, the kernel redirects these thread operations to a handler in the personality layer which then handles the operation. The kernel is thus, in essence, extensible through the use of the added personality layers, and it can therefore be used to run legacy real-time applications written for other real-time operating systems.