Function kmap_alloc_wait

freebsd/vm/vm_kern.c:624–655

* kmap_alloc_wait: * * Allocates pageable memory from a sub-map of the kernel. If the submap * has no room, the caller sleeps waiting for more memory in the submap. * * This routine may block. */

 *	This routine may block.
 */
vm_offset_t
kmap_alloc_wait(vm_map_t map, vm_size_t size)
{
	vm_offset_t addr;

	size = round_page(size);
	if (!swap_reserve(size))
		return (0);

	for (;;) {
		/*
		 * To make this work for more than one map, use the map's lock
		 * to lock out sleepers/wakers.
		 */
		vm_map_lock(map);
		addr = vm_map_findspace(map, vm_map_min(map), size);
		if (addr + size <= vm_map_max(map))
			break;
		/* no space now; see if we can ever get space */
		if (vm_map_max(map) - vm_map_min(map) < size) {
			vm_map_unlock(map);
			swap_release(size);
			return (0);
		}
		map->needs_wakeup = TRUE;
		vm_map_unlock_and_wait(map, 0);
	}
	vm_map_insert(map, NULL, 0, addr, addr + size, VM_PROT_RW, VM_PROT_RW,
	    MAP_ACC_CHARGED);
	vm_map_unlock(map);
	return (addr);
}

/*
 *	kmap_free_wakeup: