From mboxrd@z Thu Jan  1 00:00:00 1970
From: ben-linux@fluff.org (Ben Dooks)
Date: Thu, 22 Apr 2010 11:09:39 +0100
Subject: Can I use VFP in work queue context ?
In-Reply-To: <2A1038AD87AFFA4291065666737B4EAA08CB0BA1BC@dlee06.ent.ti.com>
References: <2A1038AD87AFFA4291065666737B4EAA08CB0BA1BC@dlee06.ent.ti.com>
Message-ID: <20100422100939.GG6684@trinity.fluff.org>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Wed, Apr 21, 2010 at 06:11:18PM -0500, Anbumony, Kasi Lakshman Karthi wrote:
> I have done some optimization in NEON (Neon/VFP sharing the same register set) and using it in my driver running in (Linux) kernel space. The neon optimized code will be used under a work queue context and not under any interrupt. Going by the design of Linux kernel, it looks like there is no context save and restore on VFP registers whenever there is a context switch from user mode to kernel mode, but Linux handles the same for user space processes.
> 
> Currently I am not seeing any issues (may be lucky) with my implementation (any exceptions) and was wondering whether it is safe to use of neon code in work queue context? My development platform is OMAP 3 (ARM cortex A-8) and using Android with Linux kernel: 2.6.29.

No FP in the kernel.

I expect this applies to NEON too.

If you're doing intensive processing in a work queue, you're probably
trying to solve the problem in the wrong place.

-- 
Ben

Q:      What's a light-year?
A:      One-third less calories than a regular year.