Experimental Physics and
Industrial Control System

Michael Davidsaver via Tech-talk <tech-talk at aps.anl.gov> · Wed, 16 Aug 2023 23:25:38 -0700

On 8/16/23 19:18, 김대영 via Tech-talk wrote:

Dear All

First of all, thank you for your help.

Please copy in text and not screenshots, which complicate quoting in replies.

I have the following question.

Before calling the iocsh (argv[1]) function that runs the st.cmd file, the ca_search or ca_create_channel function works normal.

However, if a ca_search or ca_create_channel function is called after the iocsh (argv[1]) function is called,

a Segmentation fault or dbContext preemptive callback problem occurs.

In other words, I made a driver called pv in st.cmd and made a thread on this driver to call ca_search

The error "preemptive callback required ..." means that a call to
`ca_context_create(ca_enable_preemptive_callback)` is needed.

"dbContext" is the code behind "local CA" links.  This is a shortcut
which allows the CA server and client of an IOC to talk to each other
without actually going over the network.

This code only supports libca in the newer preemptive mode.

I don't know the cause.

Our st.cmd file is as follows.

I would appreciate it if you could solve my curiosity.

Have a good day.

Thank you.

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System