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Subject: ca_search() and "preemptive callback"
From: Michael Westfall <mwestfal@gemini.edu>
To: "tech-talk@aps.anl.gov Talk" <tech-talk@aps.anl.gov>
Date: Thu, 5 Jan 2017 15:33:14 -0300
We are converting our legacy systems from EPICS 3.13/vxWorks to EPICS 3.14/RTEMS,

I have an IOC that calls
SEVCHK( ca_search(buf, &id), "ca_search failed\n");

but it results in the following error:
dbContext: preemptive callback required for direct in
memory interfacing of CA channels to the DB.
CA.Client.Exception...............................................
    Warning: "Not supported by attached service"
    Context: "ca_search failed
"
    Source File: ../caLogDataDriver.c line 119
    Current Time: Thu Jan 05 2017 18:02:41.367850828


OK, so I insert this first:
SEVCHK(ca_context_create(ca_enable_preemptive_callback), "caInitLogSetup() calling ca_context_create()");

But now I get this
CA.Client.Exception...............................................
    Error: "Preemptive callback not enabled - additional threads may not join context"
    Context: "caInitLogSetup() calling ca_context_create()"
    Source File: ../caLogDataDriver.c line 106
    Current Time: Thu Jan 05 2017 17:41:58.248806684


What am I missing? Do I need to supply a callback function first? The Channel Access documentation seems a bit sparse in this regard...

--
Mike Westfall
Control Systems Software Engineer



Replies:
Re: ca_search() and "preemptive callback" Andrew Johnson

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