On Mittwoch, 27. Oktober 2010, Tim Mooney wrote:
> One point that is probably obvious to you guys, but was obvious to me
> only in retrospect,
> is that it matters *where* in the processing chain the asynchronous
> record occurs.
It was not obvious to me, thanks for pointing it out.
> If the only asynchronous record in the chain is the first one, you
> can get good behavior
> from a sequence of ca_put_callbacks and be fooled into thinking that
> server-side code
> is more aware of putNotify than it actually is. This is because the
> first record's PACT field
> will be True all the while the putNotify is active, so server-side
> code, which only honors
> record locks and PACT fields, will accidentally be honoring putNotify
> as well.
>
> To make a good ca_put_callback test, you have to write to a
> synchronous record that links
> to an asynchronous record. In this case, when the first record has
> written to the asynchronous
> record, and that record has gone into its asynchronous wait, both the
> lockset and the
> first record's PACT field will look ready for another
> ca_put_callback, but the putNotify
> fields will not be ready, and you'll be able to see the problem you
> need to defend against.
Jeff, can you confirm this, i.e. does the server only look at PACT, and
not at the putNotify fields? If yes, do we treat this as a CA bug (to
be fixed in the next base release)?
(I may offer a work-around in any case, but I'd still like to know what
the specified behaviour is, so that work-arounds can be marked as such
and phased out when implementation and spec cease to differ.)
Cheers
Ben
- References:
- Some Channel Access Questions Ben Franksen
- RE: Some Channel Access Questions Jeff Hill
- Re: Some Channel Access Questions Tim Mooney
- Navigate by Date:
- Prev:
Re: OMS MAXv announces fix Kurt Goetze
- Next:
EPICS Base 3.14.12-pre2 Andrew Johnson
- Index:
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
<2010>
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
- Navigate by Thread:
- Prev:
Re: Some Channel Access Questions Tim Mooney
- Next:
Re: Some Channel Access Questions Ben Franksen
- Index:
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
<2010>
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
|