linux-kernel - Re: [PATCH v2 3/3] i387: support lazy restore of FPU state

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Date:	Mon, 20 Feb 2012 18:18:45 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Josh Boyer <jwboyer@...il.com>,
	Jongman Heo <jongman.heo@...sung.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/3] i387: support lazy restore of FPU state

On Mon, Feb 20, 2012 at 6:10 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> The attached trivial patch fixes it, I bet.

Actually, it doesn't fix it on x86-32, because we actually have an
#ifdef CONFIG_X86_64 around the "current_task" definition due to
pointless differences in how we do that on x86-64 and x86-32.

So much for the "common" part of "arch/x86/kernel/cpu/common.c"

> Although I do wonder if we should just make kernel_fpu_begin() be a
> real function instead of inlining it. I'm not sure it makes sense to
> inline that thing, and it might be better to export that one instead.

I do think that would be better in the long run, but for now here's an
updated "trivial" patch to fix it.

I want the fpu_owner_task to be declared next to the cache-hot
task-switching stuff, and since they are different on 32-bit and
64-bit (for no really good reason), that gets duplicated too. Sad.

                        Linus

                      Linus

View attachment "patch.diff" of type "text/x-patch" (897 bytes)