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Date: Wed, 05 Aug 2015 08:38:18 +0200
From: Hans Petter Selasky <hps@selasky.org>
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To: Garrett Cooper <yaneurabeya@gmail.com>, 
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Subject: Re: When and when not to use CTLFLAG_MPSAFE with the SYSCTL macros..?
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On 08/05/15 00:47, Garrett Cooper wrote:
> Hi,
> 	I’ve been trying to figure out (because sysctl(9) is lacking) when to use CTLFLAG_MPSAFE. Is it strictly when dealing with SYSCTL_PROC handlers that do proper locking of shared resources, or are there other nuances that need to be handled?
> 	I’m also asking because SYSCTL_UQUAD, for instance, explicitly uses CTLFLAG_MPSAFE in the handler, which is a bit confusing.
> Thanks!
> -NGie

Hi,

This flag decides if you have Giant automatically locked or not around 
the sysctl proc. Your functions should have their own locks basically. I 
believe it is a leftover from many years ago, when the FreeBSD kernel 
was going multi threaded.

--HPS