STREAMS/UX for the HP 9000 Reference Manual

175

Debugging STREAMS/UX Modules and Drivers

Using adb

occurred will be described later. These “panic time” register values enable

the user to examine the context of the process that was running at the time of

the system crash.

Debugging Hung Systems

If the system core dump is from a transfer of control (TOC) of a hung

system, adb will be unable to determine the “dump time” or “panic time”

contents of the kernel message buffer (see “Finding the Panic Message”),

and to examine kernel global variables (see “Obtaining Important Kernel

Global Variables”), but it will not be able to give you a stack trace or context

for the process that was running at the time of the system crash.

It is especially important, when looking at a dump from a system which

appeared to be hung, to check the kernel globals freemem, freemem_cnt, and

avenrun. These variables may indicate that your system was out of memory

or was overloaded. (See “Obtaining Important Kernel Global Variables” for

more information.)

It can also be helpful, before doing a TOC on a system which appears hung,

to determine how complete the system paralysis is. The following table

describes hang symptoms, from the least severe to the most severe. This

table may help you determine where your system ﬁts on this continuum.

Symptom Explanation

Some processes, like your shell or

your tests, do not run, but other

processes are running.

Your system is not hung, but there is some other problem

holding back your processes. If you have a terminal session

that is working, use strdb and adb to look at the kernel and the

STREAMS/UX subsystem state.

You cannot login, either locally or

remotely.

Your system may not be hung, its networking software state,

terminal I/O or getty processes may be deadlocked in some

way. If you have a terminal session that is working, use strdb

and adb to look at the kernel and the STREAMS/UX

subsystem state.