Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Fri, 21 Jun 2013 10:24:29 -0500

Hi Benjamin,

On 2013-06-21 Benjamin Franksen wrote:
> On Friday, June 21, 2013 11:18:07 Benjamin Franksen wrote:
> > The errlog facility provides errlogAddListener, and errlogRemoveListener.
> > Unfortunately, the latter is broken, as there is no way to specify the
> > listener's private data. So if I have two listeners which differ only in
> > their private data (such as when using two instances of feller), then I
> > can only remove them all at once, not each one separately.

Actually errlogRemoveListener() will only delete the *first* listener in the 
list that matches (there's a 'break' which stops the loop once it finds a 
match).

WARNING: Kludge Ahead!  If feller keeps a list of its own registrations it 
could remove all its listeners up to the one it wants to delete and then add 
the others back again (but that would change their order in the list, so it 
would have to adjust its list accordingly; algorithm testing highly 
recommended!).

> > The attached patch file rectifies that by adding an
> > errlogRemoveSingleListener function to the API that allows to remove
> > single instances.

Thanks, I will consider this for the 3.15 branch.

> In the meantime, I wonder how to proceed with the feller module.
...
> Better ideas would be much appreciated.

You could just register one listener and keep your own list of clients which 
that listener traverses when it gets called.  Now you can delete specific 
entries at leisure because you own the list.

- Andrew
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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System