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Date: Wed, 10 Jun 2015 13:40:55 -0700
From: Peter Grehan <grehan@freebsd.org>
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To: Stefan Andritoiu <stefan.andritoiu@gmail.com>
CC: freebsd-virtualization@freebsd.org
Subject: Re: Gang scheduling implementation in the ULE scheduler
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Hi Stefan,

> When I start a Virtual Machine, during the guest's boot, IPIs are sent
> and received correctly between CPUs, but after a few seconds I get:
>      spin lock 0xffffffff8164c290 (smp rendezvous) held by
> 0xfffff8000296c000 (tid 100009) too long
>      panic: spin lock held too long

  Is this on a lightly loaded machine ? I've not looked at your diff in 
detail but it's possibly a code path where a spinlock wasn't unlocked, 
leaving another CPU spinning.

later,

Peter.