Re: [patch][rfa] Multi core debugging with GDB

Approved by fche and committed with the attached modification to ensure 
that all data gets flushed.

Dave Brolley wrote:

> Hi,
>
> Debugging multiple cores with multiple instances of GDB within a 
> simulation is currently possible by specifying a separate --gdb option 
> after each --board and specifying a different port for each GDB 
> instance. The simulation ends (as it does without GDB) when the first 
> core exits. However, the other GDB instances all report "Watchdog 
> expired.  Target disconnected". This was because of three problems:
>
> 1) The "enabled?", "enable-threshold",  "yield-host-time?" and 
> "yield-host-time-threshold" of the host scheduler were not being set. 
> This caused the host scheduler to yield host time after the first GDB 
> stub exited.
>
> 2) The other GDB stubs were not properly notifying their GDB clients 
> that they were exiting
>
> 3) Even after proper notfication and yielding were implemented, the 
> packets never reached their GDB clients because their socket 
> components were never polled again which was because the host 
> scheduler was never advanced again which was because the whole shut 
> down process was initiated when the first GDB stub drove main's 
> "stop!" pin. This problem is corrected by having the sockets do one 
> final transmit when their "fini" pins are driven by shutdown-sequence.
>
> The result is an orderly shutdown of the GDB stubs and their clients.
>
> OK to commit?
>
> Dave