STREAMS/UX for the HP 9000 Reference Manual

168

Debugging STREAMS/UX Modules and Drivers

HP-UX Kernel Debugging Tools and strdb

The strdb tool can be used in conjunction with other standard HP-UX kernel

debugging tools to provide STREAMS/UX-speciﬁc information and data

formatting. Generally, if your system is running normally except for

STREAMS/UX, it is recommended that you use strdb to debug the problem.

If your system panics or hangs, strdb can be used on the resulting system

core dump, along with adb to diagnose the problem. strdb is documented

earlier in this chapter, and examples of using adb and strdb together are

given at the end of this chapter.

What Is a System Panic?

Unlike user code, programming errors in kernel code can cause system

panics. A system panic will result in a panic message to the console. Also,

a system core dump will be generated. This is a copy of physical memory at

the time of the panic. The panic message and core dump can be examined

using adb and strdb to determine the cause of the panic.

There are three main categories of panics. The ﬁrst category is when a

kernel routine calls panic() because of a system inconsistency from which it

cannot recover. In this case, the panic message contains a string from the

routine that called panic(), explaining why panic was called. In the example

below, the panic string is “ifree: freeing free inode.” A hexadecimal stack

trace will also be printed. Interpreting the stack trace will be described later.

System Panic:

@(#)9245XA HP-UX (A.10.00) #1: Wed Sep 28 15:47:13 PDT 1994

panic: (display==0xb000, flags==0x0) ifree: freeing free inode

PC-Offset Stack Trace (read across, most recent is 1st):

0x0014766c 0x001480b0 0x000b3a38 0x000b411c 0x000b3b78 0x000b76

0x000b10d8 0x000aefd0 0x0001c500

End Of Stack

The second category is the occurrence of a kernel level trap or exception

condition. These usually involve virtual memory and are described below.

A hexadecimal stack trace is also printed.