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Date: Fri, 02 Sep 2005 14:57:25 -0600
From: Scott Long <scottl@samsco.org>
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To: John Baldwin <jhb@FreeBSD.org>
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Cc: cvs-src@FreeBSD.org, src-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject: Re: cvs commit: src/sys/kern kern_mutex.c
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John Baldwin wrote:
> jhb         2005-09-02 20:21:49 UTC
> 
>   FreeBSD src repository
> 
>   Modified files:
>     sys/kern             kern_mutex.c 
>   Log:
>   - Add an assertion to panic if one tries to call mtx_trylock() on a spin
>     mutex.

Explaining exactly why this is bad, either in a commit log, in a
manpage, or in source code comments would be really nice.  The pitfalls
are not immediately obvious to the casual observer.

>   - Don't panic if a spin lock is held too long inside _mtx_lock_spin() if
>     panicstr is set (meaning that we are already in a panic).  Just keep
>     spinning forever instead.

If panicstr is set, shouldn't all CPUs have already been sent an NMI?
This seems like a step backwards in reliability.

Scott