Re: [Chicken-users] mailbox: not working on 2.3?

[Thomas Chust]

On Wed, 12 Apr 2006, Graham Fawcett wrote:

> The mailbox egg does not work on my 2.3 build: it deadlocks on
> mailbox-wait! if the mailbox is empty. [...]

Hello,

I think this is not a bug, but rather a desired behaviour. When you 
execute mailbox-receive! and the message queue is empty, the calling 
thread suspends. But as there are no other threads running, the scheduler 
realizes that the calling thread will never become active again and thus 
signals a deadlock exception.

If you tried your example with a running background thread instead, you 
should get eternal blocking in mailbox-receive!. The scheduler has no way 
of checking whether or not another running thread might queue objects in 
the mailbox.

$ csi
[...]
Version 2, Build 308 - macosx-unix-gnu-ppc - [ libffi dload ptables ]
(c)2000-2006 Felix L. Winkelmann
; loading ./.csirc ...
#;1> (require-extension (srfi 18) mailbox)
; loading library srfi-18 ...
; loading /usr/local/lib/chicken/1/mailbox.so ...
#;2> (thread-start! (make-thread (rec (again) (thread-sleep! 3) (print "ping!") 
(again))))
#<thread: thread2>
#;3> (print "pong: " (mailbox-receive! (make-mailbox)))
ping!
ping!
ping!
[...]

cu,
Thomas