From owner-freebsd-current Thu Dec 3 23:35:11 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id XAA02455 for freebsd-current-outgoing; Thu, 3 Dec 1998 23:35:11 -0800 (PST) (envelope-from owner-freebsd-current@FreeBSD.ORG) Received: from godzilla.zeta.org.au (godzilla.zeta.org.au [203.15.68.22]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id XAA02252 for ; Thu, 3 Dec 1998 23:35:03 -0800 (PST) (envelope-from bde@godzilla.zeta.org.au) Received: (from bde@localhost) by godzilla.zeta.org.au (8.8.7/8.8.7) id SAA09899; Fri, 4 Dec 1998 18:34:11 +1100 Date: Fri, 4 Dec 1998 18:34:11 +1100 From: Bruce Evans Message-Id: <199812040734.SAA09899@godzilla.zeta.org.au> To: dfr@nlsystems.com, eivind@yes.no Subject: Re: 3.0 and double operations in device drivers Cc: freebsd-current@FreeBSD.ORG, luigi@labinfo.iet.unipi.it, tinguely@plains.NoDak.edu Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG >> > > > My question is: "Is floating point math now taboo in the kernel?" >> > > >> > > it has always been! >> > >> > I asked for that one :). remove taboo and replace with "forbidden". >> >> It always has been. >> >> (Ie, it has never worked reliably, and this has been a known property >> of the design). What design? Most implementations don't support floating point in the kernel because supporting would slow down interrupt handling and context switching. Since some implementations don't support it, it should never be used. >On the alpha, any floating point instructions executed by the kernel >(except some very careful ones during task switching) should cause a >panic. Same for all versions of FreeBSD on i386's, except there are also some very careful ones in some versions of bcopy() and bzero(). Actually, not so careful. The panic for unexepected ones went away, apparently to support unexpected ones in bcopy() or bzero(). See trap.c rev.1.78. Bruce To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message