EPICS Controls Argonne National Laboratory

Experimental Physics and
Industrial Control System

1994  1995  1996  1997  1998  <19992000  2001  2002  2003  2004  2005  2006  2007  2008  2009  2010  2011  2012  2013  2014  2015  2016  2017  2018  2019  2020  2021  2022  2023  2024  Index 1994  1995  1996  1997  1998  <19992000  2001  2002  2003  2004  2005  2006  2007  2008  2009  2010  2011  2012  2013  2014  2015  2016  2017  2018  2019  2020  2021  2022  2023  2024 
<== Date ==> <== Thread ==>

Subject: Re: database race condition?
From: Marty Kraimer <[email protected]>
To: Till Straumann <[email protected]>
Cc: "[email protected]" <[email protected]>
Date: Mon, 22 Mar 1999 12:55:19 -0600
Till Straumann wrote:
> 
> Hi Marty.
> 
> Thanks for your response. Because I like discussions I appended some
> more ideas that just crossed my mind...

> The only thing I didn't know was that there's nothing implemented like
> `atomic field access' in EPICS, so if I need mutual exclusion I have to
> put the whole records in one lock set.
> BTW, knowing this, there's nothing too bad about it (except maybe
> efficiency;
> a finer grained or `one writer, many readers' type locking scheme could
> maybe
> proposed for version 5.0 :-) ...) since the database designer usually
> can hack
> around this by reading DBF_STRING typed links MS if necessary.
> Still - the idea of having atomic access to record fields without
> needing to
> lock a whole set of records would be nice.

The Application Developer's Guide states:

"Lock sets prevent two different tasks from simultaneously modifying records in
the same lock set."

This allows algorithms to be developed via linked records with the guarantee
that outside tasks, e.g. a CA server, will not modify something in the lock set
while the algorithm is being executed. Fine grained locks do not provide this
guarantee.


Marty Kraimer

Replies:
Re: database race condition? Till Straumann
References:
database race condition? Till Straumann
Re: database race condition? Marty Kraimer
Re: database race condition? Till Straumann

Navigate by Date:
Prev: Re: EPICS web pages at LANL Bill McDowell
Next: Re: Scan Record Tim Mooney
Index: 1994  1995  1996  1997  1998  <19992000  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: database race condition? Till Straumann
Next: Re: database race condition? Till Straumann
Index: 1994  1995  1996  1997  1998  <19992000  2001  2002  2003  2004  2005  2006  2007  2008  2009  2010  2011  2012  2013  2014  2015  2016  2017  2018  2019  2020  2021  2022  2023  2024 
ANJ, 10 Aug 2010 Valid HTML 4.01! · Home · News · About · Base · Modules · Extensions · Distributions · Download ·
· Search · EPICS V4 · IRMIS · Talk · Bugs · Documents · Links · Licensing ·