[Info-vax] hung program location

[Stephen Hoffman]

On 2013-02-19 13:26:44 +0000, Tom Adams said:

> The PC is 80141918 (as shown on show proc/cont)  The process is in HIB 
> when it's at that address.
> 
> The code is well controlled in CMS so it's easy produce link maps.
> 
> I restarted the hung processes.  This hanging is a rare event that I
> don't know how to reproduce.  But the process does pause at that PC
> in HIB during a normal operation mode.

Build with full machine-code listings and with full maps, and start 
instrumenting the code.

As a guess directed at the error...

Look specifically at the handling of $hiber and $wake calls in the 
source code, as code that uses $hiber can easily be broken in various 
ways, and the end result is either a spurious $wake cycle — which the 
code should always expect — or the code gets stuck in a $hiber quite 
possibly because one or more $wake calls got coallesced into one $wake 
somewhere; it's not really a lost $wake call, but it seems like it.

The gloriously ugly work-around for these problems is adding a $schdwk 
call into the code, and deliberately inducing a periodic spurious $wake.

The best approach being figuring out where the $wake got lost, and 
reviewing the asynchronous portions of the code for errors.


-- 
Pure Personal Opinion | HoffmanLabs LLC