Mailbox patch

[Christopher Cordahi]

Sorry I'm not replying to original message because I just joined the patches
mailing list, previously I was only reading the discuss list.

Nick Garnett wrote:

> This patch addresses some issues with the mailbox implementation
> raised by the following two threads:
>
> http://ecos.sourceware.org/ml/ecos-devel/2006-08/msg00004.html
> http://ecos.sourceware.org/ml/ecos-discuss/2006-08/msg00170.html
>
> The second raised some problems with the use of mailboxes in LWIP. It
> is not clear what the issue there was, I cannot see any obvious
> problems with the mailbox implementation.

>From my understanding of David's problem described in
http://ecos.sourceware.org/ml/ecos-discuss/2006-08/msg00200.html

when the queue contains an item, the following line is executed
to return the next item from the queue
       ritem = itemqueue[ (count--, base++) ];

but when the queue is empty the thread sleeps and there is no corresponding
line when the thread resumes execution, thus an invalid item is returned

> However: switching from mboxt2 to mboxt does introduce a slight change
> in semantics for mailboxes.

What is the change in semantics?

-- 
Chris