From: Manfred Spraul <manfred@colorfullife.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: linux-kernel@vger.kernel.org,
Arjan van de Ven <arjan@fenrus.demon.nl>,
Doug Ledford <dledford@redhat.com>,
Linus Torvalds <torvalds@transmeta.com>
Subject: Re: [RFC] framework for fpu usage in kernel
Date: Sun, 11 Feb 2001 21:30:53 +0100 [thread overview]
Message-ID: <3A86F67D.53C1BD9B@colorfullife.com> (raw)
In-Reply-To: <E14S359-0004vi-00@the-village.bc.nu>
Alan Cox wrote:
>
> > memcopy is a really generic function, and calling it saves the current
> > fpu state into thread.i387.f{,x}save. IMHO that's wrong, memcopy must
> > save into a local buffer like raid5 checksumming.
>
> The mmx copy is only done in task context. There are a whole variety
> of _horrible_ problems doing it in interrupt space so based on the
> considerable number of problems with prior attempts to get it right on
> IRQ and copyuser cases I didnt bother
>
Even task context is dangerous:
What if a drm module wants to use the fpu and then uses memcpy() after
modifying the ftp registers?
--
Manfred
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next prev parent reply other threads:[~2001-02-11 20:33 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-02-11 19:03 Manfred Spraul
2001-02-11 20:26 ` Alan Cox
2001-02-11 20:30 ` Manfred Spraul [this message]
2001-02-11 20:37 ` Alan Cox
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