kern/85346: PREEMPTION causes unstability in Alpha4000 SMP kernel

[Pegasus McCleaft]

>Number:         85346
>Category:       kern
>Synopsis:       PREEMPTION causes unstability in Alpha4000 SMP kernel
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Aug 27 12:00:43 GMT 2005
>Closed-Date:
>Last-Modified:
>Originator:     Pegasus McCleaft
>Release:        FreeBSD 6.0-BETA3 alpha
>Organization:
>Environment:
System: FreeBSD poseidon.alicorntech.com 6.0-BETA3 FreeBSD 6.0-BETA3 #4: Sat Aug 27 01:51:20 BST 2005 ken at poseidon.alicorntech.com:/usr/obj/usr/src/sys/Poseidon alpha

>Description:
	The default option and build of a kernel for the 6.0 BETA3 is
to have preemption enabled. This option seems to still cause problems on my
machine after a few hours of running. The problems range between kernel traping
to hard locking. If a kernel trap is presented, the usual message is
a illegal address load within the syncer. (normally 0xffff....ff)

>How-To-Repeat:
	Build and load any kernel with PREEMPTION enabled. Do large amounts
of disk IO and ethernet, wait for the trap message (about 1 hour)

>Fix:

	Remove the "options PREEMPTION" from the config file, rebuild kernel.
I found that running the below script in another xterm keeps the machine
running long enough to build the new kernel:

	while true
	do
	sync
	echo -n "Sleeping.."
	sleep 5
	done

	
>Release-Note:
>Audit-Trail:
>Unformatted: