Experimental Physics and
Industrial Control System

Robert Soliday <[email protected]> · Tue, 20 Jul 2004 14:14:58 -0500

Thanks, this solved my problem.
--Bob
Chris Timossi wrote:

Robert,
I believe that you should replace ca_task_initialize with

> ca_context_create(ca_enable_preemptive_callback) in main. Then in the
> interrupt handler, you can call ca_current_context() to get the
> current context and finally join that context with
> ca_attach_context().


Chris Timossi
Robert Soliday wrote:
After upgrading to Epics/Base 3.14.6 from 3.13.10 I am having
difficulty handling signals. In one of our applications if the user
does a control-C it is suppose to trap the signal and restore the PVs
to their original values. Odds are the control-c will occur while in a
ca_pend_event call. When I go to do a ca_pend_io in the interrupt
handler I get the error:
pthread_mutex_unlock failed: error Not owner
fatal error: epicsMutexOsdUnlock
I have included a simple program that displays the same problem. If
anyone knows the proper way of doing CA calls after catching a signal
please let me know.
Thanks,
--Bob Soliday

#include <stdio.h>
#include <strings.h>
#include <cadef.h>
#include <signal.h>
void interrupt_handler(int);
chid channelID[1];
char names[1][40];
int main(int argc, char **argv)
{
  strcpy(names[0], "oag:H1:setCurrentC");
  ca_task_initialize();
  if (ca_search(names[0], &channelID[0])!=ECA_NORMAL) {
    fprintf(stderr, "error: search failed for PV\n");
    return(1);
  }
  if (ca_pend_io(10)!=ECA_NORMAL) {
    fprintf(stderr, "error: search failed for PV\n");
    return(1);
  }
  fprintf(stdout, "Found PV\n");
  signal(SIGINT, interrupt_handler);
  ca_pend_event(10);
  ca_task_exit();
  fprintf(stdout, "Done\n");
  return(0);
}
void interrupt_handler(int sig) {
  double value;
  fprintf(stdout, "Interrupt detected\n");
  if (ca_get(DBR_DOUBLE, channelID[0], &value)!=ECA_NORMAL) {
    fprintf(stderr, "Error: unable to get value for PV\n");
  }
  if (ca_pend_io(10)!=ECA_NORMAL) {
    fprintf(stderr, "Error: unable to get value for PV\n");
  }
  fprintf(stdout, "value = %lf\n", value);
}

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System