Date: Fri, 4 Dec 1998 18:34:11 +1100 From: Bruce Evans <bde@zeta.org.au> To: dfr@nlsystems.com, eivind@yes.no Cc: freebsd-current@FreeBSD.ORG, luigi@labinfo.iet.unipi.it, tinguely@plains.NoDak.edu Subject: Re: 3.0 and double operations in device drivers Message-ID: <199812040734.SAA09899@godzilla.zeta.org.au>
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>> > > > 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
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