Hi,
DMTCP does not put wrappers around read and write and thus no _real_
versions of these functions. In your application, are the _real function
defined in the binary or in some shared library?
A simple trick would be to use the function:
int dmtcp_is_running_state();
to check if the computation is in _RUNNING_ state or not. DMTCP uses
read/write only when it's _not_ in RUNNING state, i.e. during checkpoint
and restart.
Does this help?
Kapil
On Thu, Jun 27, 2013 at 3:44 AM, Cyrille Artho <[email protected]> wrote:
> Hi all,
> We are trying to use DMTCP for fault injection on sockets that are
> accessed via a file descriptor.
>
> The problem we ran into is that DMTCP sends its own data over existing
> application sockets. That data is used for internal bookkeeping in
> DMTCP, and not seen by the application.
>
> However, our wrapper for read sees this extra data, and we are thinking
> about how to ignore it or filter it out.
>
> Is it intentional that DMTCP uses "read" instead of "_real_read" for its
> own communication? If so, is there any chance for us to have internal
> use of "read" flagged somehow? It seems DMTCP now uses a lock for
> internal operations, so if DMTCP's internal use of "read" cannot be
> changed to "_real_read", the following may do the trick for us as well:
>
> lock
> set flag
> read
> clear flag
> unlock
>
> This way, we always know when the application uses read (the flag is not
> set).
>
> If there is no easy way for us to tell if DMTCP or the application calls
> "read", then we can try to filter the messages from DMTCP. They seem to
> use particular messages and port numbers. Is that documented somewhere?
> Is that expected to be stable?
> --
> Regards,
> Cyrille Artho - http://artho.com/
> Those who will not reason, are bigots, those who cannot,
> are fools, and those who dare not, are slaves.
> -- George Gordon Noel Byron
>
>
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