From owner-freebsd-current Fri Sep 27 14:22: 7 2002 Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.FreeBSD.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id AA00037B401 for ; Fri, 27 Sep 2002 14:22:06 -0700 (PDT) Received: from mail.speakeasy.net (mail17.speakeasy.net [216.254.0.217]) by mx1.FreeBSD.org (Postfix) with ESMTP id 433F743E65 for ; Fri, 27 Sep 2002 14:22:06 -0700 (PDT) (envelope-from jhb@FreeBSD.org) Received: (qmail 17032 invoked from network); 27 Sep 2002 21:22:07 -0000 Received: from unknown (HELO server.baldwin.cx) ([216.27.160.63]) (envelope-sender ) by mail17.speakeasy.net (qmail-ldap-1.03) with DES-CBC3-SHA encrypted SMTP for ; 27 Sep 2002 21:22:07 -0000 Received: from laptop.baldwin.cx (gw1.twc.weather.com [216.133.140.1]) by server.baldwin.cx (8.12.5/8.12.5) with ESMTP id g8RLM4Bv096195; Fri, 27 Sep 2002 17:22:04 -0400 (EDT) (envelope-from jhb@FreeBSD.org) Message-ID: X-Mailer: XFMail 1.5.2 on FreeBSD X-Priority: 3 (Normal) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8bit MIME-Version: 1.0 In-Reply-To: <18849.1033156603@critter.freebsd.dk> Date: Fri, 27 Sep 2002 17:20:27 -0400 (EDT) From: John Baldwin To: Poul-Henning Kamp Subject: RE: Freedom from Giant for (most^H^H^H^Hsome) driver writers! Cc: current@freebsd.org Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On 27-Sep-2002 Poul-Henning Kamp wrote: > 4. It may not even work at all in the first place. We havn't done > the VFS locking yet, so dropping giant in specfs may open a pathway > to the dungeon-dimensions (this is a bad thing). I actually implemented this very early on during SMPng (a flag in the cdevsw) but we ended up not committing it for this reason. You can only do this if you assume the calling code doesn't make any assumptions about interrupts being blocked. IOW, in 4.x terms, if cdevsw routines are always called at spl0 then this is safe. If they aren't, then, well, this isn't safe yet. :) -- John Baldwin <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message