Re: writing to aao crashes ioc

[Korhonen Timo <Timo.Korhonen@psi.ch>]

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


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