Date: Wed, 05 Aug 2015 08:38:18 +0200 From: Hans Petter Selasky <hps@selasky.org> To: Garrett Cooper <yaneurabeya@gmail.com>, freebsd-hackers <freebsd-hackers@freebsd.org> Subject: Re: When and when not to use CTLFLAG_MPSAFE with the SYSCTL macros..? Message-ID: <55C1AF5A.1080601@selasky.org> In-Reply-To: <F4A56F9C-058B-4D91-B75D-92DEC16E8B2E@gmail.com> References: <F4A56F9C-058B-4D91-B75D-92DEC16E8B2E@gmail.com>
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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
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