## thread_activation_create

Function - Create a thread activation.

### SYNOPSIS

    kern_return_t   thread_activation_create
                    (task_t                                    task,
                     mach_port_name_t                      RPC_port,
                     vm_offset_t                         user_stack,
                     vm_size_t                           stack_size,
                     thread_act_t                      thread_act_t);

### PARAMETERS

task
  [in task send right] The port for the task that is to contain the new thread activation.

RPC_port
  [in receive right] A receive right held by the task, or a port set in the task.

user_stack
  [in scalar] The virtual address in the task to be used as the starting ad- dress of the user-level stack.

new_act
  [out thread send right] The kernel-assigned name for the new thread ac- tivation.

### DESCRIPTION

The thread_activation_create function creates a thread activation, or "empty thread", into which a client thread shuttle can migrate during RPC. The RPC_port must name ei- ther a receive right held by the task, or a port set in the task. The new thread activation will be added to a pool of activations attached to this port (or port set). Incoming RPC's targeted at the port (or one of the ports in the set) can use any of the activations in the pool. That is, the client thread shuttle will migrate into the specified server task, take one of the thread activations out of the pool, and join up with it for the duration of the RPC. The shuttle will migrate back to the original client activation at the end of the RPC. If no thread activations are in the pool, RPC will be blocked until one is created in the pool, or an existing one finishes its RPC and returns to the pool. The new thread activation will begin each RPC using the stack pointer specified by user_stack. The kernel neither knows nor cares how big the specified stack is. When a short-circuited RPC (or mach_rpc) is invoked on a port created with mach_port_allocate_subsystem, the RPC will begin execution in the subsystem server at the work function address specified by the port and routine number and looked up in the associated subsystem data.

### NOTES

The following calls targeted at a thread_act port may _not_ be called on an empty thread_act (and will return KERN_INVALID_ARGUMENT if they are called with one): thread_abort thread_abort_safely thread_depress_abort thread_info thread_wire In addition, if thread_switch is called with an empty thread_act as its first argument, the argument will be ignored (i.e., the function will behave as if a zero-valued argument had been given).

### RETURN VALUES

Only generic errors apply.

### RELATED INFORMATION

Functions: task_create, mach_port_allocate_subsystem,