amd64/116620: Ifconfig spins when creating carp(4) device on amd64/SMP

[Chris Chen]

>Number:         116620
>Category:       amd64
>Synopsis:       Ifconfig spins when creating carp(4) device on amd64/SMP
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    freebsd-amd64
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Sep 24 23:50:01 GMT 2007
>Closed-Date:
>Last-Modified:
>Originator:     Chris Chen
>Release:        6.2 RELEASE with Patch from PR kern/92776
>Organization:
>Environment:
FreeBSD ear.bennett.laika.com 6.2-RELEASE FreeBSD 6.2-RELEASE #1: Mon Sep 24 16:20:21 PDT 2007     root at ear.bennett.laika.com:/usr/src/sys/amd64/compile/DELL_PE860_AMD64  amd64
>Description:
After startup, run ifconfig carp0 create.

The process will spin. It is impossible to kill the spinning ifconfig process. The rest of the system remains operational, however, so you can reboot it.

Here are the last lines of a ktrace of ifconfig carp0 create:

  944 ifconfig CALL  modstat(0x10a,0x7fffffffe280)
  944 ifconfig RET   modstat 0
  944 ifconfig CALL  modfnext(0x10a)
  944 ifconfig RET   modfnext 267/0x10b
  944 ifconfig CALL  modstat(0x10b,0x7fffffffe280)
  944 ifconfig RET   modstat 0
  944 ifconfig CALL  socket(0x2,0x2,0)
  944 ifconfig RET   socket 3
  944 ifconfig CALL  ioctl(0x3,SIOCIFCREATE,0x514ce0)

After this point, the process take up 100% cpu, and just spins.
>How-To-Repeat:
Run ifconfig carp0 create.
>Fix:


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