alpha/105134: 'panic: lockmgr: thread ... not exclusive lock owner' on SMP Alpha EV6 machine

[Kevin Thompson]

>Number:         105134
>Category:       alpha
>Synopsis:       'panic: lockmgr: thread ... not exclusive lock owner' on SMP Alpha EV6 machine
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-alpha
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Nov 04 07:20:20 GMT 2006
>Closed-Date:
>Last-Modified:
>Originator:     Kevin Thompson
>Release:        6.1-release, 6.2-beta3
>Organization:
Computer Science House at Rochester Institute of Technology
>Environment:
6.1-RELEASE ALPHA, 6.2-BETA3 ALPHA.
>Description:
Reproduced on FreeBSD 6.1-RELEASE, 6.2-BETA3 with SMP and PREEMPTION enabled.

Currently trying 6.2-PRERELEASE with preemption disabled, and if that doesn't work, turn off SMP.

Under heavy disk access and cpu load (eg make -j2 buildkernel), the machine deadlocks with the following message:
panic: lockmgr: thread 0xfffffc005f9a4000, not exclusive lock holder 0xfffffc00487e1500 unlocking cpuid = 1
It does not display anything more, it does not reboot, it just stops right there with that message. The machine is completely unresponsive from every interface - ethernet, serial console, vga console, etc.

The machine is a dual 500mhz alpha EV6 with 1.5GB of RAM, 

System disk:
   
   da0 at isp0 bus 0 target 0 lun 0
   da0: <IBM DDYS-T18350N S80D> Fixed Direct Access SCSI-3 device
   da0: 40.000MB/s transfers (20.000MHz, offset 8, 16bit), Tagged Queueing Enabled
   da0: 17501MB (35843670 512 byte sectors: 255H 63S/T 2231C)

Controller for system disk:
   isp0: <Qlogic ISP 1020/1040 PCI SCSI Adapter> port 0x1000-0x10ff mem 0x1010000-0x1010fff irq 47 at device 7.0 on pci1
   isp0: interrupting at TSUNAMI irq 47
   isp0: [GIANT-LOCKED]


The important bits of bootup:
   ST6600
   AlphaPC 264DP 500 MHz, 500MHz
   8192 byte page size, 2 processors.
   CPU: EV6 (21264) major=8 minor=7 extensions=0x303<BWX,FIX,MVI,PRECISE>
   OSF PAL rev: 0x2004500020157
   real memory  = 1607819264 (1533 MB)
   avail memory = 1567784960 (1495 MB)
   FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs
    cpu0 (BSP): PAL ID:  0
    cpu1 (AP): PAL ID:  1
   tsunami0: <21271 Core Logic chipset>
>How-To-Repeat:
Heavy disk i/o and cpu usage on alpha w/ SMP & PREEMPTION.
>Fix:

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