Re: recordGenerator record

[Dirk Zimoch <dirk.zimoch@psi.ch>]

Andrew Johnson wrote:

> Unfortunately there are major problems with doing this in a running IOC: we 
> don't have locks in all the database structures that need to be modified when 
> a new record instance is created, which makes this a precarious activity.  
> The current dbStaticLib design assumes that all record creation happens while 
> the IOC is running single-threaded before initialization of any scan or 
> server threads.  For example, the pdbbase->ppvd structure which is a hash 
> table of all the record instances has no locks, so one or more server threads 
> could be searching for PV names in the hash bucket linked list that your new 
> record instance gets added to.
>
> Looking at the code in base/src/dbStatic/dbPvdLib.c I can see several ways 
> that simultaneous calls to dbPvdFind() and dbPvdAdd() in different threads 
> could cause a segfault, because this code has not been written with that 
> possibility in mind.

It might be possible to make this thread-safe by disabling interrupts before 
calling dbPvdAdd().

Dirk

--
Dr. Dirk Zimoch
Paul Scherrer Institut, WBGB/006
5232 Villigen PSI, Switzerland
Phone +41 56 310 5182