Setting a thread to a wait state using a wait instruction

A multi-thread processor includes a scheduler 216 to schedule thread execution. The scheduler includes a thread state register 218 and wait mask 220 which it uses to determine if any given thread is in a wait state. The wait states can include a halt state and an idle state. Threads enter the halt or idle state following the processing of a halt instruction or an idle instruction by the thread itself in the pipeline. A halted or idling thread can return to an active state for processing data when a resume instruction is processed. The wait state can be initiated in response to one of the temperature of the processor, the power consumption or the error rate of the thread. Initializing the processor involves placing a selected thread in a wait state whilst the operations of the processor are initialized.