fatal double fault (spinlock)

[Duane Hill]

We have a Dell PowerEdge 6850 with four 3ghz Intel dual core Xeon 
processors and 12 gig ram. It is running FreeBSD 5.5-RELEASE-p15 amd64. 
SMP has been compiled into the kernel. However, 
machdep.hyperthreading_allowed has been set to zero(0) in 
/etc/sysctrl.conf.

Once about every 1.5 to 2 weeks, the server throws the error:

   fatal double fault
   cpuid=15
   spinlock sched lock held by 0xffffff032f3c1500 > 5 seconds

This server is located in a colo many miles away. I had to have a person 
at the colo facility read off the message that was on the screen. I hope 
it is exact (or at least close).

This server is one of our main spam filter servers. It use to have an MTA 
installed on it that required FreeBSD 5.5. That software does not run on 
the server anymore.

I've been meaning to upgrade the server to 6.2 release, but have been 
procrastinating. Would upgrading the server to 6.2 release correct this 
issue?

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