debugging in hardware

[Heaton, Eric D]

1. I think if you are doing some kind of interthread communication where one
thread is waiting for a signal from another, you could get into a situation
where the signal is missed and a microengine will hang forever if you start
getting your code out of sync.  Chances are it wouldn't happen with just one
(or perhaps many) stop/starts, but the possiblity goes up as you increase
breakpoint frequency.

2. This is more a problem of exceeding the capabilities of the reference
designs.  One example might be if there is packet loss for a gigabit port,
the gigabit code will loop forever waiting for the missing packet number.
Now you're in reset-city.  ;)

  -- Eric Heaton --

-----Original Message-----
From: Alok Kumar [mailto:alok at cs.utexas.edu]
Sent: Thursday, November 30, 2000 1:07 PM
To: Heaton, Eric D
Cc: ixp1200 at CS.Princeton.EDU; Brandewie, Dirk J
Subject: RE: debugging in hardware


Hi Eric,

Thanks a lot for the answers to my queries. 

1. The 1st reason you gave should not affect the behavior of the microcode
running. Anyway, microengines are running independentely of each other and
even if they stop at slightly different times and start at slightly
different time, it will not make changes in final outcome. This will not
at least make some thread to goto unwanted state and theoritically final
behaviour should be unchanged.

2. For the second reason, I was wondering whether this is a problem of
reference design or of the debugging environment?

Thanks
Alok

On Thu, 30 Nov 2000, Heaton, Eric D wrote:

> I know we've seen problems when inserting breakpoints in hardware.
> sometimes the Microengines get into an undefined state for reasons mostly
> related to either:
> 
> 1. Getting the Microengines out of sync with each other (i.e. when you set
a
> breakpoint in one Microengine, the other Microengines don't stop
> immediately, but only stop after their respective, currently running,
> threads swap out) or..
> 
> 2. Setting breakpoints while the IXP1200 is trying to receive or transmit
> packets.  This point is due to the fact that the reference designs aren't
as
> robust as one might like... they are, however, a very good starting point
to
> get a feel for the IXP1200 and to start developing your own applications.
> 
>   -- Eric Heaton --
> 
> -----Original Message-----
> From: Alok Kumar [mailto:alok at cs.utexas.edu]
> Sent: Wednesday, November 29, 2000 3:30 PM
> To: ixp1200 at CS.Princeton.EDU
> Subject: debugging in hardware
> 
> 
> Hi,
> 
> I have run the reference design pfwd8_1f_16rx_6tx on hardware. I am
> eventually successful in getting packets through it but here are some
> problems I am getting. If anyone has any thoughts or comments on it,
> please, let me know.
> 
> 1. When I use the Intel's latest release (version 1.1),  the packets
> greater than 64 bytes are not forwarded correctly. In version 1.0, there
> is no such problem. I downloaded pfwd8_1f_16rx_6tx in both the cases.
> 
> 2. When I try to debug code in hardware by inserting breakpoint to follow
> the execution of code, it does not forward any packet but rather go to
> some undesirable state. This problem happens in both the version.
> 
> If I use reference design of version 1.0 and do not insert any breakpoints
> in code, I get packets forwarded as expected.
> 
> If anyone has successfully run reference designs from version 1.1 or
> successfully followed code execution in hardware, please, let me know.
> 
> Thanks
> Alok
> 
>
____________________________________________________________________________
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> 
> Alok Kumar
> 
> Residence:
> 3401 Red River St #201
> Austin, TX 78705
> 
> Office:
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> ACES Building
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> Austin, TX 78712
> 
> Ph:  Home   - (512) 472-6443
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> 
> Homepage: http://www.cs.utexas.edu/~alok
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> 
> 

____________________________________________________________________________
___

Alok Kumar

Residence:
3401 Red River St #201
Austin, TX 78705

Office:
Dept of Computer Science
ACES Building
University of Texas
Austin, TX 78712

Ph:  Home   - (512) 472-6443
     Office - (512) 232-7883
Fax: (401) 679 8171

Homepage: http://www.cs.utexas.edu/~alok
____________________________________________________________________________
___