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From: John Baldwin <jhb@freebsd.org>
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Date: Fri, 6 May 2011 16:19:38 -0400
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	(bigwig.baldwin.cx); Fri, 06 May 2011 16:19:42 -0400 (EDT)
Cc: Andriy Gapon <avg@freebsd.org>
Subject: Re: thread_lock vs panic/trap
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On Friday, May 06, 2011 5:11:57 am Andriy Gapon wrote:
> 
> Can a current thread panic or receive a trap while some other thread holds its
> thread_lock (the same lock as pointed to by the td_lock)?

I'm sure it's theoretically possible.  If the thread is running just about
anywhere and another thread is changing its cpuset for example, then you could
run into this.

> And a related question, can there be a reason for a thread in panic or kdb
> context to try to get the thread_lock?

I think it isn't safe to try to grab one's own thread lock in panic or kdb
for this reason.

-- 
John Baldwin