Re: writing to aao crashes ioc

[Eric Bjorklund <bjorklund@lanl.gov>]

On Apr 20, 2010, at 5:21 AM, Korhonen Timo wrote:

> Hi Dirk,
>
> Now that Ben pointed this out, it rang a bell.
> This probably does not help in any way, but almost exactly ten years
> ago there was a discussion thread about aao record in tech-talk,  
> starting from:
>
> http://www.aps.anl.gov/epics/tech-talk/2000/msg00310.php
>
> I thought however that these issues (memory allocation, etc) would  
> have been solved already
> a long time ago....
> If I remember correctly, at that time I assumed Eric (Bjorklund)  
> would do the changes,
> he probably expected that I do and we never cross-checked. :-(
>
> best regards,
>
> Timo

Wow.  Now that was a blast from the past.  The last post in that chain  
was on May 4, 2000.  On May 5, the Cerro Grande fire went out of  
control and Los Alamos was evacuated shortly thereafter.   We didn't  
really get back to productive work here until early June -- by which  
time I obviously had completely forgotten about the aai/aao issue (but  
at least I have a good excuse ;-}

We have a grand total of 9 aao records in our system (two device  
support modules), so I don't think we would be terribly inconvenienced  
by having to modify device support.  This is not a particularly good  
time for me to be taking on any new projects, however, so I won't be  
the one to "step up".  Could be a good codeathon project  though....

-Eric Bj.

> Benjamin Franksen wrote:
> > On Tuesday 20 April 2010, Dirk Zimoch wrote:
> >
> > > Tim Mooney wrote:
> > >
> > > > Dirk,  I was seeing something similar (though in 3.14.11),
> > > > and "dbpr <recordname>,5" showed "DTYP: <nil>",
> > > > until I added the line
> > > > device(aao,CONSTANT,devAaoSoft,"Soft Channel")
> > > > to the .dbd file.
> > > Hi Tim.
> > >
> > > That is not the problem:
> > > DTYP: Soft Channel
> > >
> > > The ioc also crashes when the aao record is not processed! Thus DTYP
> > > cannot be the problem.
> >
> > I believe the aao record support is at fault.
> >
> > The problem is that it does not allocate bptr itself but leaves  
> > this to device support. However, when device support's init_record  
> > method is called, it is too late. Because by then links have  
> > already been initialized, thus cvt_db_addr has been called, which  
> > sets the field address to bptr, i.e. NULL.
> >
> > This explains why regular puts work but puts via db links lead to a  
> > crash. If you dbpf from the ioc shell or do caput, the cvt_db_addr  
> > gets called and since this is after device support init, bptr will  
> > contain a valid pointer to the array.
> >
> > You could verify my theory by issuing a 'caput aao1.OUT aao2'.  
> > After this, the IOC should not crash when processing aao1. It  
> > shoudl still crash when processing ao1, until you re-initialize  
> > thits OUT link, too.
> >
> > Solution: Fix aao (and probably aai) record support to either  
> > allocate bptr itself or else call device support's init_record  
> > during the first pass of record support initialization.
> >
> > Cheers
> > Ben
>
>
> --
> Timo Korhonen  PSI (Paul Scherrer Institut, http:// 
> www.psi.ch)               CH-5232 Villigen PSI               tel +  
> 41- 56 3103262  fax + 41 - 56 310 5090 e-mail:	       timo.korhonen@psi.ch



<><><><><><><><><><><><><><><><><><><><><><><><><><><><>
Eric Björklund
Los Alamos Neutron Science Center (LANSCE)

phone:  
505-667-6031                                                      
email:  bjo@lanl.gov
<><><><><><><><><><><><><><><><><><><><><><><><><><><><>
"The universe is full of magical things,
patiently waiting for our wits to grow sharper"
 -- Eden  
Phillpotts 
                                                                   
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