From: Calvin Spealman <calvin@ironfroggy.com>
To: linux-kernel@vger.kernel.org
Subject: Re: How to use floating point in a module?
Date: Sun, 30 May 2004 22:39:02 +0000 [thread overview]
Message-ID: <1525857.l1LCNaafU7@ironfroggy.com> (raw)
In-Reply-To: <yw1xbrk5baq3.fsf@kth.se>
Måns Rullgård wrote:
> Floating point is forbidden in kernel code since the floating point
> registers (and other floating point context) is not saved/restored
> during system calls, for efficiency. I'm speculating here, but it
> might be possible to manually save the floating point context while
> doing some floating point operations. The problem arises if this code
> is interrupted midway. Using a preemptive 2.6 kernel would easily
> break here.
What about adding some functions such as enable_fpreg_syscalls() and
disable_fpreg_syscalls() that could be called before and after any floating
point operations? They could set a flag somewhere that would cause the
float registers to be saved/restored. Forgive me if this is somehow stupid.
I'm very much a kernel newbie.
next prev parent reply other threads:[~2004-05-31 2:44 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-05-31 1:52 ndiamond
2004-05-31 2:18 ` Måns Rullgård
2004-05-30 22:39 ` Calvin Spealman [this message]
2004-05-31 4:28 ` Linus Torvalds
2004-05-31 3:57 ` Calvin Spealman
2004-05-31 3:59 ` Matt Mackall
2004-05-31 4:11 ` Stephen Smoogen
2004-05-31 14:55 ` Scott Robert Ladd
2004-06-01 2:11 ` Richard B. Johnson
2004-05-31 2:50 ndiamond
2004-05-31 4:02 ` Chris Friesen
2004-05-31 5:44 ` Ian Kent
2004-05-31 6:13 ` Peter Williams
2004-05-31 13:39 ` Horst von Brand
2004-05-31 20:12 ` Michal Jaegermann
2004-05-31 20:23 ` Hugo Mills
2004-05-31 22:43 ` Peter Williams
2004-05-31 20:38 Manfred Spraul
2004-05-31 21:11 ` Horst von Brand
2004-06-01 0:38 ndiamond
2004-06-01 20:52 ` H. Peter Anvin
2004-06-01 2:27 ndiamond
2004-06-02 5:52 ndiamond
2004-06-02 19:31 ` Valdis.Kletnieks
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