Experimental Physics and
Industrial Control System

Mark Rivers <[email protected]> · Fri, 19 Apr 2013 15:00:40 +0000

That is exactly the problem I fixed recently in the epics/extensions/src/ezcaIDL code.  ezcaIDL calls functions in 2 other libraries:

ezca
EzcaScan

ezca calls ca_context_create with preemptive callbacks.  EzcaScan does not call ca_context_create, it relies on automatic creation of a context.  The problem was that if a function in ezca was called first, everything was fine.  But if a function in EzcaScan was called first then the call to ca_context_create in ezca failed, and things did not work.  I fixed it by guaranteeing that a function in ezca was always called before any function in EzcaScan.

Mark

________________________________________
From: [email protected] [[email protected]] on behalf of Tim Mooney [[email protected]]
Sent: Friday, April 19, 2013 9:31 AM
To: michael abbott
Cc: [email protected]
Subject: Re: Calling ca_context_create(1) too late

Is there any chance you've made any CA calls before calling ca_context_create()?
If so, CA might have made a call to ca_context_create() for you, and may not have
enabled preemptive callbacks, which I understand that you have to enable on an ioc.

saveData calls ca_context_create() after iocInit, so I'm pretty sure that's not
the problem.

Tim
----- Original Message -----
> From: "michael abbott" <[email protected]>
> To: [email protected]
> Sent: Friday, April 19, 2013 8:44:09 AM
> Subject: Calling ca_context_create(1) too late
>
> I've just discovered that calling ca_context_create(1) after
> iocInit() appears to succeed (it returns ECA_NORMAL) ... but the
> resulting context is not very healthy!  In my particular case I find
> that ca_array_get_callback delivers zero length data, but I expect
> other deeper problems are to be found.
>
> I understand that I need to call ca_context_create() a good deal
> earlier, but I don't really understand why it appears to succeed --
> is it possible for an error code to be returned instead, please?
>  (In some future version of EPICS, I'm testing this on 3.14.11.)
>
> Alternatively, is there some reliable way I can test whether it has
> succeeded?  I don't have full control over when my library is
> initialised, so detecting an error immediately would be more
> friendly to the user.
>
> --
> This e-mail and any attachments may contain confidential, copyright
> and or privileged material, and are for the use of the intended
> addressee only. If you are not the intended addressee or an
> authorised recipient of the addressee please notify us of receipt by
> returning the e-mail and do not use, copy, retain, distribute or
> disclose the information in or attached to the e-mail.
> Any opinions expressed within this e-mail are those of the individual
> and not necessarily of Diamond Light Source Ltd.
> Diamond Light Source Ltd. cannot guarantee that this e-mail or any
> attachments are free from viruses and we cannot accept liability for
> any damage which you may sustain as a result of software viruses
> which may be transmitted in or with the message.
> Diamond Light Source Limited (company no. 4375679). Registered in
> England and Wales with its registered office at Diamond House,
> Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11
> 0DE, United Kingdom
>
>
>
>
>
>

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System