Function vmspace_switch_aio

freebsd/vm/vm_map.c:501–525

* Switch between vmspaces in an AIO kernel process. * * The new vmspace is either the vmspace of a user process obtained * from an active AIO request or the initial vmspace of the AIO kernel * process (when it is idling). Because user processes will block to * drain any active AIO requests before proceeding in exit() or * execve(), the reference count for vmspaces from AIO requests can * n

 * vmspace_acquire_ref() above.
 */
void
vmspace_switch_aio(struct vmspace *newvm)
{
	struct vmspace *oldvm;

	/* XXX: Need some way to assert that this is an aio daemon. */

	KASSERT(refcount_load(&newvm->vm_refcnt) > 0,
	    ("vmspace_switch_aio: newvm unreferenced"));

	oldvm = curproc->p_vmspace;
	if (oldvm == newvm)
		return;

	/*
	 * Point to the new address space and refer to it.
	 */
	curproc->p_vmspace = newvm;
	refcount_acquire(&newvm->vm_refcnt);

	/* Activate the new mapping. */
	pmap_activate(curthread);

	vmspace_free(oldvm);
}

void
_vm_map_lock(vm_map_t map, const char *file, int line)