4.3 hangs

[chris at umcp-cs.UUCP]

In article <2836 at brl-smoke.ARPA> dlu%tektools.tek.csnet at CSNET-RELAY.arpa writes:
>The problem you describe has not shown up, to my recolection, on the
>785 here.  But I do know how to get a dump from the console [...] :
>
>	^P
>	HALT
>	START <address of doadump()>

This does indeed provide a crash dump.  However, it is almost always
preferable to force an actual crash:

	^P
	H
	D PC -1		! N.B.: `@crash' does these three commands for you
	D PSL -1	! (and perhaps the HALT as well).  But this works
	CO		! even if you have no file `crash' on your floppy.

or, on a 750,

	D/G F FFFFFFFF
	D P FFFFFFFF
	C

This invalidates the PC, sets the PSL to kernel mode, IPL 31, and
continues, causing an immediate trap and a `panic: Segmentation
fault'.  The advantage this has over simply starting the CPU at
doadump() is that disk buffers are written, leaving the file systems
in a much more recoverable state.

(On the other hand, sometimes the disk syncing leads to another
hang.  A second trap invokes a crash dump without attempting to
sync, so you still need not know the address of doadump().)
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 1516)
UUCP:	seismo!umcp-cs!chris
CSNet:	chris at umcp-cs		ARPA:	chris at mimsy.umd.edu