Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Mon, 5 Mar 2018 11:31:27 -0600

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

-- 
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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System