Experimental Physics and
Industrial Control System

I am not sure what versions of Epics base/vxWorks this applies to, we noticed it on R3.14.7/VxWorks 5.5.1.

 

We looked at taskwd because we saw it bus-error out and leave the IOC unable to accept new connections.  I don’t think what I am reporting necessarily has anything to do with the current problem; I just noticed that it might be a bug.

 

As I understand it, taskwd, is supposed to monitor registered tasks so that when one of them gets unexpectedly into a suspended state some action can be taken.  In our case, taskwd was suspended and no other task appeared in the list as suspended.  Looking at source code, I see that on vxWorks the taskwd main loop calls epicsThreadIsSuspended() which in turn calls taskIsSuspended() in the vxWorks kernel.  Looking there, to see if there might be a cause for the bus error, I noticed that the logic of the routine might not match the semantics that the taskwd is expecting.

 

Here is the problem, if the task is suspended, the function returns TRUE to taskwd, if the task is not suspended or is non-existent, deleted,  the function returns FALSE.

 

Seems to me that taskwd would want to know the difference between “running” and “dead”.  Maybe the loss of connectivity lies in a dead task that no longer shows up in the task list.

 

Just an observation.