From owner-freebsd-current@FreeBSD.ORG Wed Jan 28 22:43:46 2009 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 923D7106566B; Wed, 28 Jan 2009 22:43:46 +0000 (UTC) (envelope-from rdivacky@vlk.vlakno.cz) Received: from vlakno.cz (77-93-215-190.static.masterinter.net [77.93.215.190]) by mx1.freebsd.org (Postfix) with ESMTP id 4AD0E8FC17; Wed, 28 Jan 2009 22:43:46 +0000 (UTC) (envelope-from rdivacky@vlk.vlakno.cz) Received: from localhost (localhost [127.0.0.1]) by vlakno.cz (Postfix) with ESMTP id 2E9959CB045; Wed, 28 Jan 2009 23:41:17 +0100 (CET) X-Virus-Scanned: amavisd-new at vlakno.cz Received: from vlakno.cz ([127.0.0.1]) by localhost (lev.vlakno.cz [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id WZbKGmXtEthW; Wed, 28 Jan 2009 23:41:14 +0100 (CET) Received: from vlk.vlakno.cz (localhost [127.0.0.1]) by vlakno.cz (Postfix) with ESMTP id 8E3C19CB0EC; Wed, 28 Jan 2009 23:41:14 +0100 (CET) Received: (from rdivacky@localhost) by vlk.vlakno.cz (8.14.3/8.14.3/Submit) id n0SMfEwg082900; Wed, 28 Jan 2009 23:41:14 +0100 (CET) (envelope-from rdivacky) Date: Wed, 28 Jan 2009 23:41:14 +0100 From: Roman Divacky To: John Baldwin Message-ID: <20090128224114.GA81550@freebsd.org> References: <20090128193318.GA42071@freebsd.org> <200901281521.17674.jhb@freebsd.org> <20090128220454.GA66961@freebsd.org> <200901281741.25021.jhb@freebsd.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200901281741.25021.jhb@freebsd.org> User-Agent: Mutt/1.4.2.3i Cc: freebsd-current@freebsd.org, scottl@freebsd.org Subject: Re: sysctl question X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 28 Jan 2009 22:43:47 -0000 On Wed, Jan 28, 2009 at 05:41:24PM -0500, John Baldwin wrote: > On Wednesday 28 January 2009 5:04:54 pm Roman Divacky wrote: > > On Wed, Jan 28, 2009 at 03:21:17PM -0500, John Baldwin wrote: > > > On Wednesday 28 January 2009 2:33:18 pm Roman Divacky wrote: > > > > hi > > > > > > > > we dont need Giant to be held for sysctl_ctx_init/SYSCTL_ADD_*, right? > > > > > > Ugh, it looks like the sysctl tree locking is woefully inadequate, so we > > > aren't quite ready for this yet. > > > > what do you mean? should all sysctl_ctx_init/SYSCTL_ADD_* consumers lock > > Giant? I didnt not find a single one (except the scsi stuff) that locks > > it... > > > > can you explain? thnx > > The supposed sysctl lock in kern_sysctl.c is actually worthless. None of the > routines that actually manipulate the sysctl tree to add and remove nodes use > it. Only sysctl itself uses it. It replaces an old 'memlock' hand-rolled > lock from 4.xBSD (in 1.1 of kern_sysctl.c) that I think has to do with > limiting the amount of wired memory, as it looks like sysctl used to always > wire the userland buffers. I've just submitted some changes to p4 to make > the sysctl lock actually protect the sysctl tree that I will test soon. Once > that stuff is done then Giant can be removed here and other places. cool! I found no other places where Giant is used for locking sysctl but please commit at least the patch I posted thnx! roman