Experimental Physics and
Industrial Control System

Michael Davidsaver <[email protected]> · Mon, 5 Mar 2018 13:30:51 -0500

> This looks like a bug in the sscan module.

FYI, I had a report last week of problems with sscan and epics 7.0.2
which I haven't had time to investigate.  The symptom was positioners
not being updated.  So the recDyn code is probably involved.

On 03/05/2018 12:31 PM, Andrew Johnson wrote:
> Hi Mark,
> 
> On 03/04/2018 01:40 PM, Mark Rivers wrote:
>> My IOC application is crashing on exit with an access violation.
>>  
>> spinnakerApp: caught exception 0xC0000005 "Access violation"...
>>  
>> Base 7.0.1 (master)
>> Windows 7
>> Visual Studio 2015, debug, static
>>  
>> I have appended the debugger screen shot. It tells me that pParm->pName
>> is a bad pointer.
>>  
>> When I run the application without the debug build I see this on
>> application exit:
>>  
>> Thread recDynInp (000000000D7F4DB0) suspended
>> Thread recDynOut (000000000D7F4E10) suspended
>>  
>> This leads me to suspect that the crash is happening when it attempts to
>> get the name of the recDynInp or recDynOut task?
> 
> This looks like a bug in the sscan module.
> 
> We have added quite a lot of proper shut-down code to other parts of
> Base in recent years. If threads from other modules don't register an
> appropriate epicsAtExit() routine and stop trying to call the IOC APIs
> while shutdown is occurring, they can end up trying to access memory
> that has been freed.
> 
> In this case it seems that in sscanApp/src/recDynLink.c both recDynLink
> threads register themselves with the task watchdog, but don't remove
> themselves from it before they exit. That would agree with the error
> messages you're seeing from the debug build, which almost certainly come
> from taskwd. In the stack-trace you posted the taskwd subsystem is
> trying to use a hanging pointer presumably to one of those threads. If
> you add the line
>     taskwdRemove(0);
> immediately before the closing brace of both the recDynLinkInp() and
> recDynLinkOut() functions this should remove those threads from the
> watchdog and stop it from trying to display those "suspended" messages.
> 
> HTH,
> 
> - Andrew
> 

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System