Experimental Physics and
Industrial Control System

Marty Kraimer <[email protected]> · Tue, 10 Jun 1997 12:55:23 -0500

Ralph Lange wrote:

> The periodic scan tasks ARE automatically restarted. (See line 539 +-20 of
> dbScan.c) Looks safe to me in that case. Generally I would agree with you.

In my version I see

near top of dbScan.c

int volatile scanRestart=FALSE;

Then later:

static void wdPeriodic(long ind)
{
    scan_list *psl;

    if(!scanRestart)return;

Thus tasks are not restarted. Many things could go wrong.
For example a task is likely to have records locked.
Restarting will merely hide original problem and cause
really strange behavior.

> > If you get a stack trace of crashed scanOnce task it should help.
>

Note that on ioc onceTask is given name scanOnce. This is confusing.

> We're trying to catch the task that is calling scanOnce() to see where the
> crap comes from. I think the onceTask itself doesn't do too much
> interesting things - it just reads from the ring buffer and calls
> dbScanLock without checking the validity of the precord it got from the
> buffer - then dies.

Note that onceTask scans a record. Since records can be linked,
this means an arbitrary number of records can process. This means
an arbitrary set of record/device/driver support can be executed.

Marty Kraimer

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System