Blocking connection and timeout problem

Hi,

I managed to reproduce a locking problem, which is about blocking
transactions and dead connections. How can this be avoided?

What I did was:
1. Start a transaction on Client A
2. Execute a fcn doing an UPDATE on a certain record on client A
3. Execute a fcn doing an UPDATE on the same record on client B
/ as expected SQL on client B stalls untl client A's transaction ends/
4. disconnect client A's network cable
5. kill the psql on client A
/ C.A's transaction still runs since two hours, C.B's SQL lasts for equal
that time/
6. wait on client B's statement to finish...
7. kill -TERM client A's postmaster
/ client B's statement succeeds

Why is that? Why isn't client A's transaction detected as dead ? Yes,
because the socked wasn't closed due to a network error. But this can happen
all the time. What can I do?