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Re: [PATCH] fix cache coherency issues

To: yoichi_yuasa@tripeaks.co.jp
Subject: Re: [PATCH] fix cache coherency issues
From: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Date: Tue, 14 Feb 2006 19:12:15 +0900 (JST)
Cc: anemo@mba.ocn.ne.jp, linux-mips@linux-mips.org, ralf@linux-mips.org
In-reply-to: <200602140856.k1E8uvm1021728@mbox03.po.2iij.net>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <200602140707.k1E77Tah013064@mbox00.po.2iij.net> <20060214.164216.48797359.nemoto@toshiba-tops.co.jp> <200602140856.k1E8uvm1021728@mbox03.po.2iij.net>
Sender: linux-mips-bounce@linux-mips.org
>>>>> On Tue, 14 Feb 2006 17:56:57 +0900, Yoichi Yuasa 
>>>>> <yoichi_yuasa@tripeaks.co.jp> said:
yuasa> This patch fixed the boot problem, but the kernel still has
yuasa> cache coherency problem.

yuasa> ~# ./cachetest 
yuasa> Test separation: 4096 bytes: FAIL - cache not coherent

Thank you for testing.

As for the cachetest program, I think the test program is wrong.

It try to mmap offset 0 of a shared file to odd address page with
MAP_FIXED.  It means "I want non-coherent mapping if dcache alias
exists".  Currently the kernel surely gives what the program want.

The kernel might have to return EINVAL in such case, but I'm not sure
which is the right behavior.  Please look at David S. Miller's
comments, for example, http://lkml.org/lkml/2003/9/1/48

---
Atsushi Nemoto

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