linux-kernel - Re: unresoved symbol _gp

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Message-ID: <p73k5q268d4.fsf@bingen.suse.de>
Date:	04 Oct 2007 20:29:59 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	"Steven J. Hill" <sjhill@...litydiluted.com>
Cc:	veerasena reddy <veerasena_b@...oo.co.in>,
	linux-mips <linux-mips@...ux-mips.org>,
	"linux-kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: unresoved symbol _gp_disp

"Steven J. Hill" <sjhill@...litydiluted.com> writes:

> > I have written a loadble module ( which gets complied
> > along with kernel) which does some floating point
> > operation.
> >  
> NO FLOATING POINT in the kernel PERIOD. Either use integer
> operations, or redo your software architecture and do the
> floating point in userspace.

You can use floating point; you just have to make sure to 
save the FP context explicitely and disable preemption. Details
on how to do this vary by architecture.

The problem is that FP code typically takes often a lot of CPU time
and it is quite antisocial to disable preemption for a long time
because that impacts real time latency for everybody.

Besides many uses can be relatively easily rewritten to fixed
point.

-Andi
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