locking/concurrency question.

I have an app  that does essentially the following query:

SELECT host(netblock),masklen(netblock),netblock,netmask(netblock)
FROM networks 
WHERE status=get_status_code('available') AND parent_asn=4278      AND masklen(netblock)=xx -- where xx is a legit mask
size
FOR UPDATE
LIMIT 1;

inside a BEGIN TRANSACTION block.

My question is:

if a 2nd copy of this query runs with the same size, will it skip the
locked row, or wait for commit? 

-- 
Larry Rosenman                     http://www.lerctr.org/~ler
Phone: +1 972-414-9812                 E-Mail: ler@lerctr.org
US Mail: 1905 Steamboat Springs Drive, Garland, TX 75044-6749